A Book About the Mostly Invisible Universe

I assert that "Your Ticket to the Universe" by Kim Arcand and Megan Watzke is an outstanding book and you should consider buying it.

I'll give some reasons why, in no particular order (and I'll also discuss two of my favorite topics, the dark universe and multi-wavelength images):

• It's beautiful. It pulls together many iconic astronomical images: Saturn, the Cats-Eye nebula, the Bullet Cluster, the Hubble Ultra Deep Field and, just as importantly, many other beautiful images that are less familiar.

Top: Saturn, as seen by Cassini. Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
Bottom: the Bullet Cluster, from Chandra, HST, Magellan and ESO WFI data. Credit: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

• It covers the Universe, ranging from bacteria on Earth up to the cosmological mysteries of dark matter and dark energy.

• It has a tongue-in-cheek trailer:

• There was a press release.

• The authors have done some great projects in astronomy outreach, including the award winning "From Earth to the Universe" project, the inspiration for this book, and the "Here, There, and Everywhere" project.

• Well-regarded writers and astronomers said very complimentary things about the book:

 "This is the "Goldilocks" book for a reader who wants more than pretty pictures, but less than a treatise on astrophysics. It's a great "ticket" to that space in-between the coffee table book and the text book. Just enough extra information to understand why these beautiful images of the Universe matter, to us all."

- Dr. Alyssa Goodman, Harvard professor of astronomy

"A delightful jaunt through space and time, equal parts knowing verve and dazzling views.”

- Dan Vergano, USA TODAY 

"The Universe is the ultimate ride, and this book is your ticket to get on. Arcand and Watzke use gorgeous images as well as clear, easy-to-understand prose, so you'll really enjoy the view as you travel from Earth to infinity."
- Dr. Phil Plait, Astronomer and author (badastronomy.com)

• Astrophysicist Mario Livio, an accomplished author himself, wrote a very positive foreword.

• Other science writers gave positive reviews, including this one by Jason Major and this one by Amy Shira Teitel.

The Cats-Eye nebula (aka NGC 6543), as seen with Chandra and HST. Credit: X-ray: NASA/CXC/RIT/J.Kastner et al.; Optical: NASA/STScI

Reasons not to buy the book:

• You cannot afford the (US) $24.95.

• You're a troll, crank or conspiracy theorist who harbors deep distrust about all the invisible things astronomers love to study, like black holes, dark matter and dark energy, topics that are covered in "Your Ticket to the Universe" in some detail. I give more comments about this below.

• You're a troll, crank or conspiracy theorist who is suspicious about images that show the electromagnetic spectrum beyond the optical range. "I've got to see it to believe it", they might say, but this is radiation that we cannot see. "Your Ticket to the Universe" is full of multi-wavelength images. Again, I give more comments below.

There may be other reasons not to buy the book, but I can't think of any (full disclosure: Kim Arcand and Megan Watzke are friends and colleagues of mine). So here it is on Amazon.

Authors Kim Arcand (left) and Megan Watzke (right). Credit: Adeline and Grace Photography

As promised, I'll elaborate on two of the points raised above, about the dark universe and multi-wavelength images.

The Dark Universe

When I think about people who don't believe in black holes, dark matter or dark energy I'm mostly referring to self-trained "scientists" who have read a few popular science books, have developed an unhealthy dose of skepticism and like to concoct their own theories. These people are difficult to argue with and usually aren't interested in hearing about evidence that contradicts their suspicions. They can be found lurking in the darker corners of the internet and sometimes contact astronomers to share their research.

There are also real scientists who are skeptical about the darker side of astronomy. In researching this post I was reminded that Lawrence Krauss has argued that black holes might not be able to form. He's not the only scientist who is skeptical. For example, another physicist has argued that the objects astronomers think are black holes are really dark energy stars. (Physicist and science writer Matthew Francis has argued against this idea.) However, the majority of astronomers do think that black holes exist. In some cases the evidence is very strong, including one that involved a bet between Stephen Hawking and Kip Thorne about whether a black hole really exists in Cygnus X-1.

A Digitized Sky Survey (DSS) optical image showing the black hole Cygnus X-1 (left) and an artist's illustration (right) showing a close-up of the black hole. Credit: Optical: DSS; Illustration: NASA/CXC/M.Weiss

There are also some professional scientists who are skeptical about the existence of dark matter and dark energy, as Charles Choi has written about here and here. "Your Ticket to the Universe" does not attempt to cover all of the different pieces of evidence for dark matter and dark energy, but it mentions a few.

Although most astronomers are comfortable with the "standard" model of cosmology, with dark energy and dark matter dominating the mass-energy of the Universe, modifications to gravity are taken seriously as a possible explanation of the accelerating expansion of the Universe and an alternative to dark energy. The Nobel Committee were careful in awarding their 2011 Physics prize to Adam Riess, Brian Schmidt and Saul Perlmutter "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae", not for discovering dark energy. Attempts to explain away dark matter by modifying gravity aren't nearly as well motivated, but that's a subject for another blog post. As Jim Peebles, a leading cosmologist, says in a recent paper: "The evidence for the dark matter of the hot big bang cosmology is about as good as it gets in natural science." 

Multi-wavelength images

Besides multi-wavelength images, another red flag for some skeptics are images that have been processed with Photoshop. If this program can make models look skinnier, or correct blemishes, maybe it can do the same with galaxies. Scandalous! Photoshop was used in many of the images in "Your Ticket to the Universe" and it's the tool of choice for combining different wavelengths. The only "touching up" that occurs is repairing image artifacts, equivalent to fixing the red eye in photos that use a flash. The crucial tool in Photoshop is being able to overlay multiple images with different wavelengths.

Earlier this year, MIT Professor Tom Levenson wrote a blog post about a couple of people who believe that the coloring used in multi-wavelength images is "propaganda with which NASA and space scientists in general trick us into paying for the observatories in space and on earth that generate the data behind the fibs." Judging from their comments, this pair qualify as trolls and cranks and conspiracy theorists. Levenson gave an excellent defense of the power of multi-wavelength astronomy and used a Chandra and Hubble image of Eta Carinae that appears in "Your Ticket to the Universe".

A composite image of Eta Carinae combining data from Chandra and Hubble. Credit: X-ray: NASA/CXC/GSFC/M.Corcoran et al.; Optical: NASA/STScI 

One minor criticism of Levenson's article is that he uses the term "false color" to describe images outside the optical spectrum. This is a term that's commonly used by scientists, but the astronomers who are image experts tend to avoid it. As astrophysicist and image expert Robert Hurt from JPL said in a blog post "I personally dislike that term a lot because it implies something is being misrepresented." Another astrophysicist and image expert, Travis Rector, from University of Alaska, noted in a paper in The Astronomical Journal:

"Terms such as "false color" and "pseudocolor" are often used to describe images assembled with other methods, implying that such images are fabricated. However, the goal of these images is data visualization, not a portrayal of reality as defined by human vision. Color and intensity scaling therefore serve a different role."

His footnote to the first sentence described above is:

"In reality no astronomical image accurately represents the appearance of an object, as the human eye's sensitivity to color is very complex and nonlinear. Ultimately such arguments are rhetorical, as the purpose of a telescope is to show what the eye cannot see."

What observatories like Chandra, Hubble, the Spitzer Space Telescope, and the Very Large Array give us is a type of *superhuman* vision, containing rich scientific detail and often dazzling beauty. It's churlish and ignorant to describe it as propaganda. As for being a trick, the image experts at the Space Telescope Science Institute have been very open about how they make their images and the same applies to our Chandra image expert Joe Depasquale who wrote a blog post a few months ago about how he made an image. There is also an excellent article in Slate by Daniel Engber giving a detailed explanation about how astronomical images are made. I like everything about this article except the title and subtitle, which plays on the popular notion that Photoshop is about fakery. Advice for it was provided by Robert Hurt and astrophysicist Frank Summers from Space Telescope Science Institute.

Kim and Megan have also written at Huffington Post about the meaning of color in astronomical images, and you won't see any mention of "false color"in their blog post.

If you're so inclined, there are also detailed instructions on how to make your own color images using the processed data. Here are the instructions provided by the Hubble image experts, and those from the Chandra image experts. This recent video also includes Hubble image expert Zolt Levay discussing how their images are made.

You might think I'm reacting strongly to the criticism of only two trolls, but I did some research and found a broader mistrust of images, including science journalists and astronomers. I'll leave the details to a follow-up blog post, where I'll give some examples of these complaints and explain the production of a few classic images.

A composite image of W49B containing Chandra data (blue and green), VLA data (pink) and Palomar Observatory data (yellow). Credit: X-ray: NASA/CXC/MIT/L.Lopez et al.; Infrared: Palomar; Radio: NSF/NRAO/VLA

I'll end on a positive note, by showing an image that's too new to be included in "Your Ticket to the Universe". The subject of Joe Depasquale's blog post, W49B, provides another powerful demonstration of the benefits of multi-wavelength observations. The X-ray, infrared and radio data combine to make a beautiful image with exciting science, but the optical image, as Joe explains, shows nothing. The universe is a much more interesting and beautiful place when we observe it with everything we've got. This is the spirit of "Your Ticket to the Universe".

Kepler, Exoplanets and Dark Matter in the News

NASA's Kepler mission is not doing well.  Its planet-hunting days are probably over because one of its reaction wheels failed and it cannot point accurately anymore. The research isn't finished because the data in the archive still has to be analyzed and follow-up observations from ground-based telescopes will carry on for years, but this problem is obviously disappointing news.

Here, I'll discuss the strong public interest in Kepler's planet results and the widespread media coverage that's been generated. It's like the scientists have been playing a game to one-up each other, as more and more records have been broken for the smallest planet, or the planet that's most likely to be hospitable to life, and so on. These gains occurred naturally, as the length of the mission increased and the ability to detect small planets in the habitable zone improved (later in the article I'll comment about the difficulties with the term "habitable zone").

The results released in April are a good example of this. The release was about planets in the habitable zone, where liquid water may exist. Because at least three transits are needed to identify a planet, and objects in the habitable zone of stars similar to the Sun can have periods of hundreds of days, these results could not have been obtained early in the mission.

The artist's concept depicts Kepler-62f, a super-Earth-size planet in the habitable zone of a star smaller and cooler than the sun, located about 1,200 light-years from Earth in the constellation Lyra. Kepler-62f orbits it's host star every 267 days and is roughly 40 percent larger than Earth in size. The size of Kepler-62f is known, but its mass and composition are not. However, based on previous exoplanet discoveries of similar size that are rocky, scientists are able to determine its mass by association. Caption from Kepler web-site.
Credit: NASA/Kepler Mission.

This work, led by the Kepler PI Bill Borucki, is excellent for publicity. The Science paper, titled "Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone" contains strong claims and superlatives:

"Therefore Kepler-62e and -62f are Kepler’s first HZ planets that could plausibly be composed of condensable compounds and be solid, either as a dry, rocky super-Earth or one composed of a significant amount of water (most of which would be in a solid phase due to the high internal pressure) surrounding a silicate-iron core."

and

"With radii of 1.61 and 1.41 [solar radii] respectively, Kepler-62e and -62f are the smallest transiting planets detected by the Kepler Mission that orbit within the HZ of any star other than the Sun."

With statements like this, it's easy to see that the title of the press release, "NASA'S Kepler Discovers its Smallest 'Habitable Zone' Planets to Date" is justified by the paper.

Dark Matter Hints?

Sometimes there can be a big difference between the claims in the science paper and those in the press release, leading to problematic media reports. Jumping from exoplanets to cosmology, here's a recent example concerning results from the Alpha Magnetic Spectrometer (AMS). Concerning their detection of an excess of positrons with AMS, the press release says:

"These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations."

AMS in orbit on the Space Station photographed on July 12, 2011. Credit: NASA/AMS-02 collaboration.

Even saying they might have detected dark matter is a strong claim. So, what does the science paper say about dark matter? Explicitly, nothing. That's not completely true because reference [2] mentions "Proceedings of the Tenth Symposium on Sources and Detection of Dark Matter and Dark Energy in the Universe, Los Angeles (to be published)", but that hardly counts. The closest the text of the paper comes to mentioning dark matter is in the final sentence before the acknowledgements:

"These observations show the existence of new physical phenomena, whether from a particle physics or an astrophysical origin."

That's a vague statement, and the resulting press coverage was not terrific. Dark matter expert Katie Mack gave an excellent summary in her article "Space Station's Detector Has Not Found Dark Matter, Despite What Some Media Reports Say" at the new blog Physics Focus. One article I spotted
starts with this sentence:

"Physicists announced on Wednesday that they have discovered the most convincing evidence yet of the existence of dark matter – the particles that are thought to make up a quarter of the universe but whose presence has never been confirmed."

This sentence is problematic because much better pieces of evidence have been found for dark matter, including cosmic microwave background observations (CMB) by WMAP released in 2003, Planck CMB results released earlier this year, and observations of the Bullet Cluster with Chandra, HST and other telescopes.

This composite image shows the galaxy cluster 1E 0657-56, also known as the "bullet cluster", formed after the collision of two large clusters of galaxies. Hot gas detected by Chandra is seen as two pink clumps in the image and contains most of the "normal" matter in the two clusters. An optical image from Magellan and the Hubble Space Telescope shows galaxies in orange and white. The blue clumps show where most of the mass in the clusters is found, using a technique known as gravitational lensing. Most of the matter in the clusters (blue) is clearly separate from the normal matter (pink), giving direct evidence that nearly all of the matter in the clusters is dark. This result cannot be explained by modifying the laws of gravity. Caption taken from this web-site.
Credit: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

Use of "but whose presence has never been confirmed" can also be a problem because some people might infer that it has now been confirmed.

I think a substantial amount of the responsibility for articles like this lies with the AMS publicity effort and the large disparity between the paper and the press release. Use of the term "consistent with" in the release is especially problematic, because the scientific use of this term (not inconsistent with) differs from the use that most people assume (agrees with). To use an extreme example, one could also say that the observations are consistent with invisible fairy dust or alien exhaust fumes. It's a term that's best avoided.

Astrophysicist and writer Ethan Siegel gave a detailed explanation of the AMS result and a forceful critique of the publicity effort, arguing that the press release and press conference were misleading and even deceitful.

This is not easy work to explain. The results from the various attempts to detect dark matter directly are very complicated and often seemingly contradictory, as Katie Mack points out in another excellent blog post. With their large workloads, science writers need all the help they can, especially the ones who don't specialize in astronomy.

The Three S's

The contrast with Kepler research is stark. Kepler has three great strengths regarding publicity: simplicity, success and sexiness. The way Kepler works - finding transits - is simple and easy to understand. Clearly, Kepler been very successful at finding planets, or more specifically planet candidates. Finally, the search for planets is, in my opinion, sexy science, in part because of the connection to finding life. So, Kepler has some clear advantages over dark matter detection work.

These light curves of Kepler's first five planet discoveries show not only drop in star brightness as the planet transits the star, but an indication of the planet's inclination--how far from the center the planet is passing across the star. Caption taken from this web-site. Credit: NASA/Kepler Mission

Although astronomy publicity is renowned for beautiful images, Kepler hasn't had them and hasn't needed them. However, it has inspired some outstanding animations, visualizations and illustrations. Examples are these videos from the Kepler team available here and here and this graphic from the New York Times.

But, there have been some challenges. Kepler has been so popular with the media that it has led to discussion about whether there has been too much exoplanet news. Here's a very interesting blog post by John Rennie titled "Exoplanets bore me (and what that means for science news)", with some particularly good discussion between Rennie and astrophysicist August Muench.

There are also challenges involved with reasonable use of "habitable zone" and "Earth-like planets". I've already used "habitable zone" freely in this article but the concept involves many subtle details. An audience member during "The Great Exoplanet Debate" mentioned that it would be great if astronomers could keep discovering habitable planets and MIT astrophysicist Sara Seager interrupted to say:

"Hold on. Let me just interrupt. There's a correction involved here. That is: people keep claiming the first habitable planet, and as far as exoplanet astronomers go, there's no agreement that there's any habitable planets."

If the experts can't agree on whether there are any habitable planets then you know it's a term to approach with caution. Earlier, Seager advocated use of "potentially habitable" to make it clear that they are making educated guesses.

Astrophysicist John Johnson describes the challenge nicely by explaining that its almost impossible to know if a planet is truly habitable. This is because "we don't even know the conditions for habitability on our own planet!". He then gives a long list of factors or questions that may or may not have been significant for the development of life on Earth, following a discussion with fellow exoplanet expert Jason Wright.

As astrophysicist and writer Matthew Francis explains in a blog post:

"Habitability is a complex and fascinating notion, and of course until/unless we discover life on another world, we can’t be absolutely certain what conditions are truly “just right”."

Then there's the issue of "Earth-size" vs "Earth-like" planets. As Seager explains,

"Those are two very different concepts. And its almost impossible to communicate that. Even professionals slip up. Earth-like means it’s like Earth, with oceans and land and trees and everything great. Earth-size could be anything. It could be hotter than anything that you could imagine and be Earth-size."

Science writer Lee Billings has also written about the challenges of defining Earth-like planets, and astrophysicist and writer Caleb Scharf has asked whether we should expect other Earth-like planets at all.

Kepler hasn't been the only observatory to make major contributions in exoplanet research. The early work was dominated by radial velocity studies - the "wobble" method - and more recently there have been notable observations using this technique. However, Kepler has inspired much of the debate and discussion described above. This discussion will continue as new results are pulled out of the Kepler archive and astronomers keep using ground-based facilities to search for exoplanets. The next dedicated effort from NASA will be the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope (JWST) should also make big advances.

Sizes of planet candidates found with Kepler. The percentages in yellow show the changes in the numbers of planet candidates in different categories, when comparing the January 2013 and February 2012 catalogs.
Credit: NASA/Kepler mission

The exoplanet field has been active for less than 20 years, but has expanded enormously in that period, especially in the Kepler era. Astronomers have been surprised by what they've found many times. The detection of planets around pulsars was a surprise as was the early detection of hot Jupiters. More recently the detection of large numbers of "super Earths", with masses sizes between Earth and Neptune, has been surprising, along with the large diversity in planet characteristics. It will be fascinating to see what else can be found with Kepler and with future observations.

Exoplanet Publicity in the Future

It's difficult to predict where exoplanet science will go in the future, but I'm confident that public interest will increase. Although some writers might feel that planet news reached saturation levels, I think there's room for growth. As an informal demonstration, I've played around with Google Trends showing how terms used in Google web searches have changed with time. The numbers here should be treated with caution, as there can be multiple uses of the same search term, and I haven't spent a long time experimenting with this tool.

The first plot here shows the recent increase in searches containing "exoplanet" and "habitable zone", compared with a flat curve for "black hole galaxy". (I include "galaxy" to place limits on the results for "black hole". I found that other variations are also flat, but with different normalizations. I also excluded terms for "exoplanet" because of searches unrelated to planets).

In the next plot I kept the same search term for "exoplanet" but searched for "black hole" by itself, without "galaxy". I replaced "habitable zone" with "new planet" and I added two other search terms, the fictitious planet "Nibiru" and "Pluto planet". I restricted this search just to the US, so that the results for "Nibiru" are not exaggerated because the term is used in different languages. You can see the blue line for "exoplanet" now almost disappears because it is so small. Part of the issue is that the Kepler results are still relatively new and the terminology may not have sunk in.

What are all the peaks? The peak for "Pluto planet" occurred in August 2006 when the IAU voted to reclassify Pluto into a dwarf planet and the peak for Nibiru occurred at the end of 2012 because it was identified as a potential culprit for the end of the world. The peak for "black hole" occurred in September 2008 when the Large Hadron Collider (LHC) turned on and some people were concerned that a black hole would be created and destroy the Earth. One conclusion is that fanciful threats to the Earth and votes that cause changes in textbooks generate a lot of interest. (*)

The peaks in "new planet" correspond to announcements for the discovery of the dwarf planet Sedna in March 2004, Xena and other dwarf planets in July 2005, the exoplanet Gliese 581c in April 2007, the exoplanet Gliese 581g in October 2010, and the exoplanet Kepler-22b in December 2011.

These peaks are reasonably large. For example, they are comparable to the size of peaks for "climate change" and, for the last couple of years, to "global warming", a term that's declining in use. In the plot shown here they are the only strong peaks corresponding to new scientific results, showing the high public interest in planets. It's notable that all five of these popular stories correspond either to new objects in our solar system or the discovery of new exoplanets that may harbor life. A discovery like the possible planet around Alpha Centauri B - announced in October 2012 - received less attention, perhaps because that exoplanet is much too close to its star to be habitable.

To place these results in perspective, I replaced "pluto planet" with "beer" and this time the other search terms are so small they almost disappear. I'm not sure interest in exoplanets will ever consistently rival interest in beer, but as I said earlier, there's room for growth. Interest in planets is high when discoveries are made, but it's not obvious that this level is sustained.

There are many exciting fields in astronomy, including black holes, supernovas and cosmology, but exoplanet work has the potential to capture public interest in an unprecedented way. Astronomers are already starting to predict that biosignatures may be detected in exoplanets not too many years into the future, and such a discovery would surely surpass the interest shown in far-fetched speculation about mini-black holes in the LHC. If we find life outside the Earth it would change our view of life on Earth for ever.



(*) One interesting aspect of the results is that the terms for "exoplanet" and "habitable zone" have high search rates in just a few populous states like California and New York. For the other more popular terms there are high search rates across almost all of the US.

Spinning Black Holes Are a Drag

When you release a lot of black hole results to the public, you can sometimes forget how weird these objects are. We focus on the significance and the novelty of the result, rather than the exotic features that are common to many black holes. A recent paper reminded me about the latter and highlighted one of the curiosities of General Relativity, concerning the distortion of spacetime near these extreme objects. This post discusses some of the physics of spinning black holes.

In late February, NASA released a new result where the authors "measure definitively, for the first time, the spin rate of a black hole with a mass 2 million times that of our sun." In their press release, written by Whitney Clavin and her JPL colleagues, they say that the supermassive black hole is "spinning almost as fast as Einstein's theory of gravity will allow". These are results from NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), the new X-ray kid on the space block, and the European Space Agency's XMM-Newton. The 1st author of the paper is Guido Risaliti from the Harvard-Smithsonian Center for Astrophysics (my home institution) in Cambridge, Mass., and the Italian National Institute for Astrophysics. The supermassive black hole is located in the middle of a beautiful galaxy called NGC 1365.

Guided by the press release, a NASA press conference, the science paper and a News and View article in Nature, science writers tackled the story. There are details about how the data enabled the authors to reach their conclusions, but I will focus on the basic result, the rapid spin of the black hole and how it was described. I'll also give some thoughts on how it should be described, given the luxury of time.

This artist's concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. (Smaller black holes also exist throughout galaxies.) In this illustration, the supermassive black hole at the center is surrounded by matter flowing onto the black hole in what is termed an accretion disk. This disk forms as the dust and gas in the galaxy falls onto the hole, attracted by its gravity. Also shown is an outflowing jet of energetic particles, believed to be powered by the black hole's spin. The regions near black holes contain compact sources of high energy X-ray radiation thought, in some scenarios, to originate from the base of these jets. This high energy X-radiation lights up the disk, which reflects it, making the disk a source of X-rays. The reflected light enables astronomers to see how fast matter is swirling in the inner region of the disk, and ultimately to measure the black hole's spin rate. [Caption reproduced from this NASA site] Credit: NASA/JPL-Caltech

The Bad Astronomer, Phil Plait, wrote at his Slate blog about the author's observations of the black hole and how they "were surprised to find out it's spinning so fast that the outer edge is moving at very nearly the speed of light!"

An LA Times article by Amina Khan has a headline of "X-rays show galactic black hole spinning near speed of light" and says the black hole "is spinning at 84% of the maximum possible rate" following the paper and the News and Views article. It also says:

"If you were standing near the event horizon of this particular black hole, you would have to turn around because your space-time is twisting," NuSTAR lead scientist Fiona Harrison, a Caltech astrophysicist, said at a news conference. "You would be turning around once every four minutes just to stand still."

An article in Physics World by Hamish Johnston says:

"The study confirms that the SMBH is spinning at a rate close to the limit defined by the general theory of relativity. While the rotational properties of a spinning gravitational singularity are difficult to describe in a simple way, Risaliti explains that the rotational energy of the SMBH at the heart of NGC1365 is about the same as the energy that is given off by a billion stars burning for a billion years."

That's three different stories giving different ways to describe the spin. I think Johnston explains the challenge well. How do you describe the properties of a spinning singularity in a simple way? To answer this question well I think it's useful to explain what is doing the spinning. Plait discusses the "very edge of the black hole" and he's presumably talking about the event horizon, the region surrounding the black hole that light cannot escape beyond. The event horizon is an important boundary, but it isn't a physical object, like a wall (unless some recent speculation about black hole firewalls is correct, as explained in this article by Jennifer Ouellette). If material makes it to the event horizon, as must occur regularly for some supermassive black holes, including the one in NGC 1365, it won't last there for long.

I looked back at how we have previously described black hole spin with Chandra results. We did a press release for Cygnus X-1, a black hole in our galaxy that is about 15 times as massive as the Sun, and a different press release for a group of nine supermassive black holes.

For Cygnus X-1 we said:

"the black hole is spinning at very close to its maximum rate. Its event horizon -- the point of no return for material falling towards a black hole -- is spinning around more than 800 times a second." 

That's a very impressive number and it's accurate, but it doesn't explain what is spinning.

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets. [Caption reproduced from this Chandra website] Credit: Optical: DSS; Illustration: NASA/CXC/M.Weiss

For the sample of nine black holes we include a quote from astrophysicist Rodrigo Nemmen:

"We think these monster black holes are spinning close to the limit set by Einstein's theory of relativity, which means that they can drag material around them at close to the speed of light".

That's very close to the best answer. It's spacetime itself that is rotating at almost the speed of light in one of these black holes, and this is what drags material around with it at the same speed. (The technical term for this is "frame-dragging", as Matthew Francis explains in his Ars Technica article in more detail.) I checked with Robert Penna, a local expert on General Relativity and black holes, who confirmed this explanation. Here's the description he gave:

"A good mental picture is to think of the spacetime around a spinning black hole as a whirlpool. Objects are dragged around by spacetime as they fall towards the hole. At the horizon they are forced to rotate at the angular velocity of the whirlpool."

A subset of a sample of nine large galaxies is seen on the left of this graphic. These Chandra images show pairs of bubbles created in the gaseous atmospheres of the galaxies that were created by jets produced by giant central black holes. These data were used to help determine that the supermassive black holes are likely to be spinning very rapidly. The artist’s illustration (right) depicts how material very near the black hole falls inward and joins a rapidly spinning disk of matter. Most of this material is swallowed by the black hole, but some of it is swept outward in jets (colored blue) by quickly spinning magnetic fields close to the black hole. [Caption reproduced from this Chandra website] Credit: NASA/CXC/UFRGS/R.Nemmen et al.; Illustration: NASA/CXC/M.Weiss

Other explanations are useful, but they're not as clear. For example, the one by Risaliti gives a good explanation of the energy a spinning supermassive black hole has, but this is more useful for stories explaining the black hole's effect on their host galaxy. It also doesn't explain how fast the spin is or what is spinning. The answer by Harrison explains how fast the event horizon is spinning but it does not mention that an infinitely powerful rocket would be required to stand still near the event horizon of a spinning black hole, both to prevent infall and rapid spin.

There is a subtlety regarding the 84% number quoted above. This refers to the quantity a* used by astronomers that is a measure of the angular momentum of the black hole, which itself depends on its mass and speed. This quantity a* is defined so that its maximum value is 1.0 for a black hole with an event horizon rotating at the fastest speed allowed, the speed of light. For no spin a*=0. For the black hole in NGC 1365, a* was estimated to be at least 0.84. However, this does not mean that the black hole's speed is at least 84% of the speed of light. The speed is given by this formula:

speed = (a*/(1+sqrt(1-a*^2))) c

provided by Robert Penna, where "c" is the speed of light. So, when a*=0.84 the speed is 0.54c, or just over half the speed of light.

This point is more pedantic than interesting, but it helps set up a related issue. Let's return to the stellar-mass black hole Cygnus X-1. The rate of spin given above for this black hole comes from a spin frequency estimate. The spin frequency of a black hole measured at the event horizon depends only on a* and the black hole's mass. For Cygnus X-1, if a*=1 then the spin frequency is 1091 Hz, that is spacetime at the event horizon would spin around 1091 times a second. That's mind-bogglingly fast, but it isn't the interesting numerical point that I want to make.

What happens when you double-check that the speed of the event horizon - in this extreme case of a*=1 - is the speed of light? The radius of the event horizon for Cygnux X-1 is 21.9 km. So, the speed of the horizon should be the circumference of the event horizon multiplied by the spin frequency, ie 2*pi*21.9*1091 km/s. But this only equals ~150,000 km/s, which is half the speed of light. What's going on here?

The answer is that our assumption about the geometry was wrong. Near a black hole the normal geometry that we learned in school doesn't apply and the circumference of a circle is less than 2*pi times the radius, because of the severe distortion of spacetime. When you use the correct geometry you find that that the speed of the event horizon for a black hole with a*=1 is the speed of light, as expected (I was assured that this is the case but I didn't do the calculation myself, since my General Relativity skills are a little rusty).

For some explanations and more details about how geometry is distorted near a black hole, you can check the illustrations and descriptions in "Black Holes and Time Warps: Einstein's Outrageous Legacy" by Kip Thorne given here and in "The Physical Universe: An Introduction to Astronomy" by Frank Shu given here.

General Relativity and black hole expert Robert Penna. Credit: Robert Penna.

I asked Penna what happens to the velocity of spacetime inside the black hole's event horizon, but we don't even have a useful definition of velocity in this region. In Penna's words:

"The velocity makes sense outside the horizon because there is a standard observer, the fixed observer at infinity [someone who is a very long distance away where the gravitational effects of the black hole are negligible]. This observer is not available inside the horizon, because an observer at infinity can't see across the horizon. And an observer inside the horizon can't be at rest: the severe gravity causes everything inside the horizon to fall towards the singularity. Different observers will measure different velocities, so there isn't a standard velocity inside the horizon."

With black holes you have objects where normal geometry and physics do not apply and where material can be pulled along at almost the speed of light just before it disappears from the observable universe for ever. These points about geometry and physics are well established but can sometimes be neglected by astronomers and science communicators. Black holes should not be taken for granted just because a lot of papers are published on them.


End-note: I would like to thank Robert Penna for his thoughtful comments and also black hole expert Jeff McClintock, from Harvard Smithsonian Center for Astrophysics, who directed my questions to Robert.

The Remarkable Properties of Neutron Stars

The collapse of a massive star in a supernova explosion is an epic event. In less than a second a neutron star (or in some cases a black hole) is formed and the implosion is reversed, releasing prodigious amounts of light that can outshine billions of Suns. That is a spectacular way to be born. Here, I'll explain that the properties of neutron stars are no less spectacular, even though they are not as famous as their collapsed cousins, black holes.

Because of the incredible pressures involved in core collapse, the density of neutron stars is astounding: all of humanity could be squashed down to a sugar cube-sized piece of neutron star. The escape velocity from their surface is over half the speed of light but an approaching rocket ship would be stretched, then crushed and assimilated into the surface of the star in a moment. Resistance would be futile.

If this cricket ball were made of neutron star material it would weigh about 20 trillion kg, or about 40 times the estimated weight of the entire human population.

Another remarkable property is that neutron stars generate the most extreme magnetic fields known in the universe, up to a quadrillion times the strength of Earth's magnetic field. If one of these ultra-magnetic neutron stars, called a magnetar, flew past Earth within 100,000 miles, its magnetic field would destroy the data on every credit card on Earth. Luckily for our economy none are that close, but the distant ones can put on spectacular shows. In 2004 a magnetar underwent an extraordinary outburst and become one of the brightest objects ever observed in the sky, causing a disturbance in the Earth's ionosphere that was recorded around the globe, as described in this paper by astrophysicist Bryan Gaensler (@SciBry on Twitter) from the University of Sydney (my alma mater). That's impressive for an object about the size of a city that is located around 50 thousand light years away.

An artist's conception of the spectacular outburst from the magnetar SGR 1806-20, including magnetic field lines. After the initial flash, smaller pulsations in the data suggest hot spots on the rotating magnetar’s surface.  This animation contains no audio, because "in space no-one can hear you scream".  Credit: NASA

Neutron star behavior can be so odd and distinctive that their discovery was initially greeted as the possible discovery of extraterrestrial intelligence. The real explanation is that a pulsar, a rotating neutron star, was discovered. Pulsars have become such an important tool for physics research that two different Nobel Prizes have been awarded in their name, the first for their discovery by Antony Hewish. Many people - including myself - have argued that Jocelyn Bell Burnell should have been awarded part of the Nobel prize with Hewish, since she made the discovery, but in an expression of modesty or Imposter Syndrome, Bell Burnell later commented that she did not deserve the award. However, this does not diminish the significance of her discovery, and of the outstanding research that it enabled.

Jocelyn Bell Burnell with the radio telescope she used to discover pulsars. Credit: Jocelyn Bell Burnell.

The second Nobel prize was for Russell Hulse and Joseph Taylor, who discovered the first known binary pulsar, PSR1913+16, which has become extremely valuable for testing Einstein's Theory of General Relativity (GR). Since then other important objects have been discovered, including a double pulsar system known as PSR J0737-3039A/B that is one of the best objects available for testing GR and alternative theories of gravity, as explained in this paper by Michael Kramer from the University of Manchester.

Looking ahead in pulsar work, there is an exciting and ingenious project called the North American Nanohertz Observatory (NANOGrav) that is attempting a direct detection of gravitational waves, ripples in the fabric of space-time, using pulsars. Like several of the topics covered here this project deserves a dedicated blog post, but for now I'll just say that exotic objects like black hole binaries are expected to produce gravitational waves. Two of the pulsar experts leading this project are Scott Ransom from NRAO, whose enthusiasm for pulsars is well explained by the papers he writes, like this one: "Pulsars are cool. Seriously" and Victoria Kaspi, from McGill University, seen here speculating about some possible applications of pulsar research.

So far I've emphasized spectacular features of neutron stars and some famous results. These stories capture a lot of attention and do an excellent job at promoting astrophysics, but most research occurs in the gaps between catchy headlines and Nobel prizes. These gaps contain plenty of room for excellent research, much of it about understanding the nature of neutron stars, rather than testing fundamental physics with them.

Some of the most important open questions about neutron stars concern their size and structure. How large are they? What makes up their atmosphere? What is their core like?

One key advantage that neutron stars have over black holes is that their surface is visible to us, enabling much to be be learned about their atmospheres and interior structure. For example, in 2009, Wynn Ho from the University of Southampton and Craig Heinke from the University of Alberta, found evidence for a carbon atmosphere on the neutron star in the Cassiopeia A supernova remnant, using NASA's Chandra X-ray Observatory (note: I work at the Chandra X-ray Center in the Education and Public Outreach Group). This resolved a mystery about the nature of the neutron star, as the press release and Nature paper explain. An interesting side-note: the researchers calculate that the carbon atmosphere is only about 4 inches thick, as shown in the figure, because it has been compressed by a surface gravity that is 100 billion times stronger than on Earth. We're used to talking about massive scales and distances in astronomy, not small ones.

The properties of the carbon atmosphere on the neutron star in the Cassiopeia A supernova remnant are remarkable. It is only about four inches thick, has a density similar to diamond and a pressure more than ten times that found at the center of the Earth. As with the Earth's atmosphere, the extent of an atmosphere on a neutron star is proportional to the atmospheric temperature and inversely proportional to the surface gravity. The temperature is estimated to be almost two million degrees, much hotter than the Earth's atmosphere. However, the surface gravity on Cas A is 100 billion times stronger than on Earth, resulting in an incredibly thin atmosphere. Caption taken from Chandra web-site. Credit: NASA/CXC/M.Weiss

Heinke and Ho followed up this work with an even more interesting result, the first direct evidence for a superfluid, a bizarre, friction-free state of matter, at the center of a neutron star. First, a 4% drop in the temperature of the Cas A neutron star over 10 years was observed with Chandra and reported by Heinke et al. Then, two different papers, one in Physics Review Letters led by Dany Page from the National Autonomous University in Mexico and another in Monthly Notices of the Royal Astronomical Society led by Peter Shternin from the Ioffe Institute in St Petersburg, Russia independently came up with the same explanation. When the temperature of the neutron star fell below a critical level, a superfluid formed in the core of the star, forming neutrinos which travel outwards, taking energy with them. This causes the star to cool rapidly as observed with Chandra.

This image shows a composite of X-rays from Chandra (red, green, and blue) and optical data from the Hubble Space telescope (gold) of Cassiopeia A, the remains of a massive star that exploded in a supernova. The artist’s illustration in the inset shows a cutout of the interior of the neutron star where densities increase from the crust (orange) to the core (red) and finally to the part of the core where evidence for a superfluid has been found (inner red ball). The blue rays emanating from the center of the star represent the copious numbers of neutrinos -- nearly massless, weakly interacting particles -- that are created as the core temperature falls below a critical level and a neutron superfluid is formed, a process that began about 100 years ago as observed from Earth. These neutrinos escape from the star, taking energy with them and causing the star to cool much more rapidly. Credit: X-ray: NASA/CXC/UNAM/Ioffe/D.Page,P.Shternin et al; Optical: NASA/STScI; Illustration: NASA/CXC/M.Weiss

Other important information about the structure of neutron stars comes from studying the relationship between their size and mass. For a given mass, the size of a neutron star will depend on how stiff or soft the structure is. These are all relative terms, since by Earthly standards, nothing about neutron stars is soft.

Old neutron stars are typically faint objects, but when they pull material away from companion stars they can become much brighter, allowing good studies of their atmospheres. Observations of the amount of X-rays at different wavelengths, combined with theoretical models for their atmospheres, can allow the relationship between the radius and mass of the neutron star to be estimated. This work has been performed by Heinke, by Natalie Webb and Didier Barret (both from the Institut de Recherche en Astrophysique et Planétologie) as explained in this paper, and by Sebastien Guillot (Seb_Guillot on Twitter) from McGill University, in this paper. All of these observations were of neutron star binaries in globular clusters.

Neutron stars pulling material away from companions have also been observed to undergo bursts of X-rays, caused by thermonuclear explosions on their surfaces. These explosion can cause the atmosphere of the neutron star to expand. If observers catch one of these bursts they can follow as the star cools and calculate its surface area. When this area is combined with independent estimates of the distance to the neutron star, the relationship between the mass and radius of this object can be estimated. Two researchers who have applied this technique with great success are Feryal Ozel from the University of Arizona and Tolga Guver from Sabanci University, as described in this set of papers here, here, here, and here.

Each of the papers quoted in the previous two paragraphs provide information about the mass and radius of the neutron star and about their structure. However, there may be problems with relying too much on a single technique or a single object. A very good new paper by Andrew Steiner, from the University of Washington, avoids this problem by combining all of the papers mentioned above: 4 neutron stars in globular clusters quietly pulling material from a companion and 4 undergoing X-ray bursts.

A Chandra X-ray Observatory image of 47 Tucanae, my favorite globular cluster. One of the neutron star binaries from Steiner et al. (2013), called X7, is labeled. Credit: NASA/CXC/Michigan State/A.Steiner et al.

Steiner et al. take these results and apply the latest neutron star models to estimate that the radius of a neutron star with a mass that is 1.4 times the mass of the Sun - a typical value - is between 10.4 and 12.9 km (6.5 to 8.0 miles), as we reported recently in a Chandra image release. They also estimate that the density at the center of a neutron star is almost ten times that of nuclear matter found in Earth-like conditions. This is equivalent to a pressure that is over ten trillion trillion times the pressure required for diamonds to form inside the Earth.

Using their results, Steiner et al. are able to compare their results with values derived from nuclear physics experiments performed on Earth, such as the distance between protons and neutrons in atomic nuclei. A larger neutron star radius implies that, on average, neutrons and protons in a heavy nucleus like Uranium are farther apart.

What is the core of a neutron star made of? It could be neutrons or it could be free quarks, the fundamental particles that combine to form protons and neutrons but which are not usually found in isolation. The paper by Steiner et al. cannot distinguish between these two possibilities, but there is potential to do so with future neutron star work.

There are many other interesting and important results about neutron stars. Regarding their structure, there are the very strong constraints that have come from pulsar work, such as the mass measurement of (1.97+/-0.04) solar masses by Demorest et al. (2010), with Scott Ransom as a co-author, that has already accumulated over 400 citations! An even larger neutron star mass might have been found by Romani et al. (2012). Then there are the astonishing spin rates that these incredibly massive, city-sized objects can reach, such as PSR J1748-2446ad which spins around 716 times a second, as reported by Hessels et al. (2006), with Ransom and Victoria Kaspi as co-authors.

I will continue to follow developments in neutron star research closely, as part of my job with Chandra but also because of my excellent location at Harvard-Smithsonian Center for Astrophysics (CfA), which has a regular stream of visitors covering a wide range of astrophysics. For example, Bryan Gaensler is giving the CfA colloquium next week, on a topic that is yet to be announced, and Scott Ransom is giving a talk in early April about NANOGrav.

In the meantime, I may write a blog post or two on black holes, which are rumored to be interesting objects.

What Does a Progressive Scientific Society Look Like?

In principle, scientific societies can play an important role in helping scientists perform, discuss and publicize their research. If they are progressive and open-minded, rather than old-fashioned and elitist, these societies can be very effective at enabling science and science communication.

The question I'll address in this blog post is how progressive and open-minded is my scientific society, the American Astronomical Society (AAS)?

The AAS is over 110 years old and was once dominated by people who looked like this:

Some astronomers at the AAS meeting in 1910. Credit: University of Chicago Photographic Archive, [apf digital item number, e.g., apf12345], Special Collections Research Center, University of Chicago Library.

and this:

The AAS meeting in 1910. Credit: University of Chicago Photographic Archive, [apf digital item number, e.g., apf12345], Special Collections Research Center, University of Chicago Library.

[As an aside, when I look at pictures like the ones shown above I imagine someone whispering "carpe", which gives me an excuse to show a clip from one of my favorite movies, Dead Poets Society:

]

Enough with the movie-watching digression. Here's a recent movie from real life showing what AAS members look like now:

based on a party held recently at the 221st meeting of the AAS, in Long Beach, California.

The people attending the AAS have changed a lot in appearance, but how well has the AAS kept up with these changes? How representative is the AAS membership of the general population and where are the disparities? What is the AAS doing right and where is there room for improvement?

Diversity

Those early photos show that AAS meetings were once male-dominated. That's not a huge surprise. This domination began with the leadership, as the AAS presidents were all men from 1899 until Margaret Burbidge took on the role between 1976 and 1978. Another lull followed until Andrea Dupree became president between 1996 and 1998. Since then three women have been president, not including Meg Urry (@UrryM on Twitter), from Yale University, who was recently announced as the latest AAS member to take on this role, beginning next year. This is a great development because Urry has made exceptional efforts to enhance the participation of women in astronomy, and received an award last year from the AAS for this service.

Of the 16 plenary, or keynote, sessions held during the day at the recent AAS meeting, 5 were given by women. That's not terrible, but it could be better. For the press briefings the number was lower: only 4 out of 45 speakers. So, there's definitely room for improvement there. [I decided to check back over our own publicity with Chandra X-ray Observatory to see how we're doing with including women and our numbers aren't very different. We also have room for improvement.]

What about broader statistics for women in astronomy and the AAS? An article by Joan Schmelz, chair of the AAS Committee on the Status of Women, pointed out that women make up only about 15% of the tenured faculty members of PhD astronomy departments in the US. This is higher than the 7% figure that applied in 2001 but it's still pathetic, as pointed out by Ann Finkbeiner in an interesting blog post at the excellent blog The Last Word on Nothing.

I tweeted about these statistics and the AAS quickly gave a response on their Facebook page:

"A tweet today by @peterdedmonds, points out that only about 15% of tenured astronomy faculty are women. This graph helps explain why. The demography of the American Astronomical Society is not uniform with age. 

The oldest astronomers have roughly a 15 to 20 percent fraction of women (or less), while the youngest age brackets are nearly at parity. This has not always been the case. In the 1970s, the Society had roughly 15% women in all age categories. 

Progress is being made, but it takes time, policy changes that welcome women into our field and support them during their career as well as engaged women interested in pursuing a career in astronomy. 

We don't know if women are being disadvantaged in other ways from our data, but are working on a longitudinal survey with the help of the American Institute of Physics to find out."

Here's the graph mentioned by the AAS correspondent on Facebook:

Blue bars are the fraction of women in that age group, and yellow is the fraction of men. Credit: AAS.

Similar graphs were produced for 1995 and 2003. A good discussion followed on the AAS Facebook page about whether a disproportionately high percentage of women drop out of the AAS as they get older. The Facebook correspondent from the AAS stated that this wasn't occurring. Michael Merrifield attempted a quick test of this claim by taking the 1995 data, then moving it forward 15 years and overplotting it on the 2010 graph (astronomers like playing with numbers). The resulting figure gives a hint of systematic drop-outs in the youngest of the age bins where a comparison is possible. However, it's unclear whether these differences are significant because the raw numbers are not given and error bars cannot be estimated. The youngest and oldest age bins contain relatively few members, as mentioned by the AAS in the Facebook discussion, so the errors bars could be large.

A comparison between the gender balance of the 2010 AAS and the 1995 AAS shifted by 15 years. Credit: AAS and Michael Merrifield. 

Although the data presented here are inconclusive, it's certainly plausible that a higher fraction of women than men drop out of astronomy as they get older. A recent article in the Guardian noted that the fraction of women in biomedical science drops off as one goes to higher professional levels. One possible explanation given for these trends is that women are treated less fairly than men, as suggested by a paper led by Corinne Moss-Racusin from Yale University. Astrophysicist John Johnson has written about this very interesting study and the effects of unconscious bias, and Meg Urry also wrote about the Moss-Racusin paper for CNN.

Another considerable challenge involves work-life balance. As pointed out by Mary Mason from Berkeley in a longitudinal study:

"family formation—most importantly marriage and childbirth—accounts for the largest leaks in the pipeline between Ph.D. receipt and the acquisition of tenure for women in the sciences."

A related issue is unreasonable travel workloads for Principal Investigators, as explained by astrophysicist Sara Seager from MIT.

These problems are difficult to counter. The Moss-Racusin paper and the Mason study both present some suggestions and I encourage you to read them. Regarding work-like balance, astrophysicist David Charbonneau from Harvard University has argued that improved access to childcare should be provided. I expect that the AAS Committee on the Status of Women is working on some possible solutions. With Meg Urry as president elect and with responsive AAS officers and councilors, I'm hopeful that real progress can be made.

I'm encouraged by the AAS's attempts to be inclusive with members of the lesbian, gay, bisexual, transgender, intersex, and questioning (LGBTIQ) communities. There is a AAS Working Group on LGBTIQ equality (WGLE) and at the recent AAS meeting there was a workshop on "How to Be a Better Professor or Teaching Assistant for your LGBT Students". There was also a reception held by WGLE and a LGBTIQ networking dinner. I haven't seen reports about the effectiveness of these workshops and networking opportunities, but it's good to see that attempts are being made to be inclusive.

I'm less encouraged by the possibility that the number of African Americans in astronomy will rise significantly above the current number, which is very small. Kevin Marvel, Executive Officer of the AAS, admits this is a considerable challenge. There are limits to the influence that a scientific society can have. We're lucky to have one of the most famous scientists in the world in our ranks - Neil Tyson - but strong role models can only help so much. Also, Tyson is still relatively young for a renowned scientist, so many children inspired by him will not have graduated yet from school or university. This important topic is appropriate for a separate discussion, preferably led by astrophysicists like Neil Tyson and John Johnson.

Meeting Etiquette

The winter and summer meetings held by the AAS are the "largest and most logistically complex astronomy meetings in the world". To help with this complexity, the AAS included a "Guide to AAS Meeting Etiquette"in the handbook for the recent meeting. A cynic might argue that his guide is just common-sense advice for nerds with poor social skills. But, I think it's more than that, as it includes discussion of several important and subtle issues. It also acts as compensation for the lack of professional development that many scientists experience, beyond standard research skills.

The guide begins with a general statement that

"It is AAS policy that all participants in Society activities will enjoy an environment free from all forms of discrimination, harassment, and retaliation."

It provides a link to the anti-harassment policy of the AAS and a few pages later gives the text for this policy, following a letter from the current AAS president, David Helfand, titled "Harassment Will Not be Tolerated at AAS Meetings". Helfand's letter ends with:

"We must all work together to ensure an environment free of harassment so that our scholarly and collegial interactions are focused on our common mission: to enhance and share humanity’s scientific understanding of the Universe. We can only accomplish this mission fully when we respect each other as professionals, and I call on each of you to help us in this regard."

The guide later gives some tips about asking questions during meetings:

"When asking questions of speakers, please be professional, courteous, and polite. This is especially important when questioning students presenting their dissertation research."

I think this is useful advice, especially for any older astronomers who were "broken-in" as students by aggressive questioning at talks, and who might think behavior like this is professional. Of course, it's up to the session chair to control and, if necessary, stop this sort of behavior.

The issue of "astronomical bullying" has been discussed in at least two different venues by Joan Schmelz, including a previous AAS meeting, as reported in this blog post and a talk at my institution, the Harvard-Smithsonian Center for Astrophysics. A pdf of the presentation is included here. I'm sure various forms of academic bullying occur in other scientific disciplines, and it's important for them to be addressed.

Journalists & Embargoes

The next section in the conference handbook is about journalists and embargoes. Because it isn't very long and it overlaps with my professional interests, I'll include the complete text from this section:

"If your presentation covers results that have been, or will be, submitted to Nature or Science or any other journal with a strict embargo policy, be sure you understand how that policy applies to scientific meetings. No journal wishes to hinder communication between scientists. For example, both Science and Nature state explicitly that conference presentations do not violate their embargo policies. 

But both journals also state that if your presentation covers work that has been, or will be, submitted to them, you should limit your interaction with reporters to clarifying the specifics of your presentation. As Science puts it, "We ask that you do not expand beyond the content of your talk or give copies of the paper, data, overheads, or slides to reporters." That does not mean you should be rude if a reporter asks you for such materials or poses a questions that you do not want to answer - just explain that your results are under embargo at Science or Nature, and the reporter will understand why you cannot be more forthcoming."

This is good advice, which isn't surprising considering that the AAS press officer Rick Fienberg managed to get onto Ivan Oransky's Embargo Watch honor roll, and to maintain this status by smart handling of an embargo break.

I've noticed there is sometimes confusion about Nature and Science embargoes among astronomers, and presumably other scientists as well. Some astronomers are surprised to hear they can talk about their Nature or Science papers at conferences, and post their papers to the arXiv before publication.

Blogging & Tweeting

Another section of the etiquette guide concerns blogging and tweeting, and again I'll include their text because it isn't very long and because it overlaps with my interests:

"If you blog, tweet, or otherwise post near-real-time material from the meeting online, you must follow the guidelines above concerning the use of computers, tablets, mobile phones, and AAS wireless bandwidth. 

Please do not publicly report private conversations — only scheduled presentations and public comments are fair game for blogging, tweeting, etc. 

Remember that many presentations at AAS meetings concern work that has not yet been peer-reviewed. So think twice before posting a blog entry or tweet that is critical of such work. It is helpful to receive constructive criticism during the Q&A after your talk or while standing next to your poster, but it is hurtful to be raked over the coals online before your session is even over and with no easy way to respond.

New York Times editor Bill Keller said it well. When it comes to meetings among colleagues, he explained, "We need a zone of trust, where people can say what's on their minds without fear of having an unscripted remark or a partially baked idea zapped into cyberspace. Think of it as common courtesy." "

I think their advice here is well-intentioned, even if it might give the impression to uninitiated readers that Twitter and blogs are dominated by critical and hasty commentary. I'm interested to hear if other scientific societies have guidelines for blogging and tweeting.

Conclusion

My conclusion is that the AAS is progressive and open-minded and is serving its members well. Feel free to add comments if I've missed some key problem areas or if you have suggestions for improvements. I am happy to pass these comments along to the AAS.

For scientists who aren't astronomers, how is your scientific society doing? For non-scientists, I hope you've enjoyed this small window into the thinking of a modern scientific society.