Friday, September 30, 2016

2016: The Year of the Black Hole (1)

The 2016 Nobel Prize in physics will be announced in only 4 days, on Tuesday October 4th. Ronald Drever, Kip Thorne and Rainer Weiss, three founders of the Laser Interferometer Gravitational-Wave Observatory (LIGO), are hot favorites to win the award this year or soon after for their direct − and ground-breaking − detection of gravitational waves (2). They have already won multiple awards for this discovery including the Kavli Prize in Astrophysics, the Gruber Cosmology Prize, a Special Breakthrough Prize in Fundamental Physics and the Shaw Prize in Astronomy. (Kudos to those behind the Gruber Cosmology Prize and the Special Breakthrough Prize for explicitly naming the LIGO team in their awards, something the Nobel Prize award likely won’t do.)
Ronald Drever, Kip Thorne and Rainer Weiss (left to right). Credit: The Kavli Foundation.
A Nobel Prize in physics for this work will celebrate more than the first direct detection of gravitational waves, astonishing as this feat is. It also celebrates a breakthrough in black hole research, as it will be the first Nobel Prize involving definitive evidence for black holes. It also involves the clearest evidence yet for the existence of black holes, as my colleagues Daniel Eisenstein and Avi Loeb from the Harvard-Smithsonian Center for Astrophysics pointed out soon after the LIGO announcement in February.

The LIGO Hanford Observatory. Credit: Caltech/MIT/LIGO Observatory.

So, leading the way in astrophysics Nobel Prizes are 2 awards for pulsar work, 2 for work on the CMB and 2 for work on cosmic radiation. Black holes have never been explicitly mentioned in an award, though it’s important to note that the Nobel Prize awarded to Riccardo Giacconi "for pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources" was a crucial step in finding evidence for black holes. Giacconi’s work established a whole new field of astrophysics, eventually leading to the development of NASA’s Chandra X-ray Observatory, and indirectly to my job helping to publicize Chandra science. Note that Chandra has been involved in a number of results relating to gravitational waves (4).

Jocelyn Bell Burnell with the radio telescope she used to discover pulsars. CreditJocelyn Bell Burnell.
Although there are limitations in interpreting a single prize, I think it’s reasonable to argue that research done with pulsars has, until this year, taught us more about physics than research done with black holes. For example decades ago neutron star work enabled the indirect detection of gravitational waves, a key test of General Relativity resulting in one of the Nobel Prizes mentioned earlier. It has also allowed other tests of General Relativity. Neutron stars have also taught us a great deal of astrophysics, as I wrote back in 2013.

In the case of black holes, I think we have learned a lot about astrophysics but less about physics. For example, here are many examples of important astrophysics we have learned from Chandra observations of black holes. From my perspective, black hole work hasn’t taught us as much about physics. For example, scientists will sometimes assume that General Relativity holds to make inferences about the properties of black holes, such as their spins. This is important work for understanding the astrophysics of black holes, but not for understanding fundamental physics.

With the detection by LIGO of gravitational radiation from two and perhaps three different black hole mergers, and the prospect of many more to come, the value of physics research using black holes may soon catch up with and surpass that of research using neutron stars. A wild card here is how many events involving neutron stars will be detected using gravitational waves and what we’ll learn from such observations.

A simulation showing two black holes that are close to merging, as their orbital separation decreases via the emission of gravitational waves. The distortion of light from background stars is from gravitational lensing caused by the warping of spacetime by the black holes' strong gravity. Credit: SXS, the Simulating eXtreme Spacetimes project.
For popular interest there isn’t much of a contest: research with black holes gets a lot more attention than research with neutron stars. Though neutron stars are remarkable and exotic objects, it’s hard to compete for public attention with a thing that pulls material in until it disappears from view forever. Black holes are so popular that the term is regularly used outside astrophysics for describing dire situations, such as a recent example about the economy edging closer to a black hole.

Despite the renown and familiarity of black holes, news about them has been eclipsed over the last few years by another field. The hottest news topic in astronomy recently has been exoplanets, especially with all the results coming from NASA’s Kepler satellite and other results such as the exciting discovery of a planet found in the habitable zone of the nearest star to our Sun. However, with the excellent prospects for new gravitational wave detections, especially from mergers between black holes, this situation could change. We may look back to 2016 as the year when black hole work regularly started challenging exoplanet work for the biggest news stories in astronomy.

End notes:

(1) The title of this blog post was inspired by a smart tweet from astrophysicist JJ Eldridge.

(2)  The LIGO press conference announcing the detection of gravitational waves was superb, as I wrote earlier this year, one of the best I’ve seen. It did full justice to the outstanding science.

(3) In 2013 I discussed other good candidates for future Nobel Prizes in Physics, including work on exoplanets, dark matter and several other important topics in cosmology.

(4) The Chandra X-ray Observatory was named after Nobel Laureate Subrahmanyan Chandrasekhar, shown in the figure below, who did important theoretical work on gravitational waves, beginning in 1970 and extending right up until he passed away in 1995. It’s apt that the observatory named after him has gone on to observe so many objects that are producing – or will produce – gravitational waves. Theorists like Chandrasekhar laid the foundation, now observers can surge forward with them to do more groundbreaking science.

Subrahmanyan Chandrasekhar. Credit: AIP

Thursday, June 23, 2016

Astronomy is Exciting: Here’s Where You Can Learn More

Astronomy is a fascinating and vibrant field, with important discoveries occurring at an astonishing rate. Although these discoveries are widely reported in the press, even well informed readers may want more background than can be given in a typical newspaper or online article, or may be overwhelmed by the huge amount of information available on the Internet. Where can they start? How can they find reliable information? How can students consider whether a career in astronomy may be right for them?

To answer these questions I’ve collected the information and links given below. There's a lot here but it represents only a small part of the information that’s publicly available. I'm sure I've missed important resources, so please send me suggestions for additions to this list, along with any corrections or updates that might be needed for any URLs. 

As a roadmap, here are the different sections:

Observatory news
Astronomy news websites
Astronomy blogs
Online videos about astronomy
Astronomers on Twitter
Astronomy books
Experimenting with images
Visual observing
Exploring the sky with your computer
Citizen science projects
Career advice

Observatory news

For the latest press and image releases in astronomy you can go to websites for various observatories in space and on the ground. Here’s a selection, beginning with the observatory that I work for, Chandra:

Figure 1: A screen capture of the Chandra webpage, taken just after our 15th anniversary in 2014. Credit: NASA/CXC.

These websites contain a lot of background information, e.g. there’s a field guide to X-ray astronomy on the Chandra website and an Explore Astronomy feature on the Hubble website.

Astronomy news websites

Here are a few websites devoted to astronomy news:

More generally you can use Google News to search for new results in "astronomy" or "black holes" or countless other topics of interest. I check the Google News science section regularly.

Astronomy blogs

Here is a small sample of the many excellent astronomy-related blogs that are available:

Brian Koberlein has a blog about different topics in astronomy and maintains an active Google+ account.

Phil Plait, otherwise known as the "Bad Astronomer", has a blog at Slate about science, with a lot of astronomy discussion.

Amanda Bauer, aka astropixie, has a blog about astronomy and life as a scientist.

Emily Lakdawalla has a blog about planetary science. Also check out the other Planetary Society blogs.

Ethan Siegel has a blog, also found at Forbes, focusing on astronomy, with beautiful graphics and detailed explanations. It’s one of my favorite astronomy blogs.

Sabine Hossenfelder has a blog about science, concentrating on physics but with some astrophysics.

Matthew Francis has a blog about science, especially physics, astronomy and science communication.

John Johnson has a blog covering a range of topics including exoplanet research and diversity in science.

Peter Coles has a blog "about the Universe, and all that surrounds it".

Sean Carroll has a blog covering a range of topics in physics and astrophysics, including cosmology. Warning, some equations have been spotted.

Astronomy Picture of the Day (APOD) has a new image and description, with good background information and links, every day.

Online videos about astronomy

Phil Plait is compiling a set of astronomy videos as part of the CrashCourse series.

The PBS program NOVA has a large set of videos about space.

Coursera has over a dozen educational videos on astronomy, and many other fields of science.

David Kipping from Columbia has an impressive set of videos on exoplanets and related research in his Cool Worlds series.

Katie Frey from Wolbach Library at the Harvard-Smithsonian Center for Astrophysics has curated an extensive set of astronomy videos.

Many other videos can be found by searching YouTube.

Astronomers on Twitter

Here’s a list of astronomers and astronomy organizations I follow on Twitter and here are their tweets. Some astronomy communicators are included on this list and there are a bunch of astronomy writers included in my Twitter lists of science writers and science journalists.

Astronomy books

All the above info is free and you're welcome to stick with that, of course. These books are not free unless you find them in a library, so I'll just give a short list:

Your Ticket to the Universe: A Guide to Exploring the Cosmos” is a book by two colleagues of mine, Chandra’s science visualization lead Kim Arcand and Chandra press officer Megan Watzke. I reviewed the book’s science content and wrote a blog post about it.

For people interested in how astronomical data is collected and beautiful images are made, I highly recommend the book “Coloring the Universe: An Insider's Look at Making Spectacular Images of Space”, by astronomy professor and image expert Travis Rector, Kim Arcand and Megan Watzke. For more details you can read my blog post review of this book.

Figure 2: The cover of Coloring the Universe, showing an optical image from the NSF’s Mayall 4-meter telescope at Kitt Peak National Observatory of IC 1396A, a dark nebula more commonly known as the Elephant Trunk Nebula. Credit: T.A. Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOAO/AURA/NSF).

For an acclaimed account of exoplanet work, one of the hottest fields of research at the moment, you can read “Five Billion Years of Solitude: The Search for Life Among the Stars” by Lee Billings. It’s had excellent reviews at many places, like one by Dennis Overbye at the New York Times.

Another exciting and fascinating field is cosmology. Harvard professor Bob Kirshner wrote an engaging account of the discovery that the expansion of the universe is accelerating, in “The Extravagant Universe: Exploding Stars, Dark Energy, and the Accelerating Cosmos”. Here’s a sample chapter.

For a fascinating account of the science and history of black hole research, I recommend “Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved” by Marcia Bartusiak.

The hottest field in astrophysics right now involves detecting and interpreting gravitational waves, thanks to LIGO’s ground-breaking and well-described detection of these ripples in space-time. Janna Levin has written an interesting and well-timed account of the work leading up to this discovery, called Black Hole Blue and Other Songs from Outer Space.

For more comprehensive but also expensive books about astronomy, there are several introductions to astronomy for non-science majors beginning college. One of them is “Cosmic Perspective” by Jeffrey Bennett, Megan Donahue, Nicholas Schneider, and Mark Voit. I haven't read it but I know several of the authors are very good.

You can use Google to search for other popular books on astronomy.

Experimenting with images

If you're interested in playing around with astronomical images, there are guides on accessing images, viewing them and using software to combine them into color images. Here’s a guide to creating images from raw data at the Chandra website. See the tutorial at the top. You can create your own color Hubble images, with this extensive guide.

You can collect images of any part of the sky using the Digitized Sky Survey and then follow the instructions given above to make color images. These images are lower in quality than specialized ones from Hubble, for example, but the unlimited field of view is an advantage for large objects.

Figure 3: An image of the Flame Nebula by Chandra image processor Joe DePasquale, using data from the Digitized Sky Survey. Credit: DSS.

Visual observing

For tips on observing the skies, along with a bunch of excellent articles about news and research, you can check out Astronomy magazine and Sky and Telescope magazine. Only a subset of the magazine’s content is available online.

If you have access to a smart-phone or iPad, there are plenty of apps that help in observing the sky, including use of GPS to give a star map of any region you're looking at. Some apps are free and others are not, depending on the sophistication and depth of the database, etc. Several lists of the top apps can be found with Google.

Depending on your location, there may be astronomy clubs nearby. Also, physics and astronomy departments at Universities sometimes hold Open Houses or public talks. Use Google to check for both.

Exploring the sky from a computer

If the skies are cloudy, or if it’s too cold or there are too many mosquitoes, you can explore the sky using your computer. One option is Google sky, either in the web-based application or as part of the desktop program Google Earth. For the latter you have to download Google Earth but it’s more fun to use than the web-based program.

Another excellent program is the World Wide Telescope from Microsoft. This also has a web-based application, but the desktop program is more powerful.

Citizen science projects

Citizen science projects involve voluntary work contributing to active science programs. One motivation is to “help researchers deal with the flood of data that confronts them”. Here are a few of the more popular projects:

Galaxy zoo, involving classifying galaxies. This project was a trendsetter in citizen science for astronomy.

Planet hunters, helping astronomers look for planets using data from NASA’s Kepler mission.

Spacewarps, involving looking for distortion in images caused by gravitational lensing.

Planet Four, involving classifying features on the surface of Mars.

Gravity Spy will help LIGO improve their search for gravitational waves. At the time of writing it’s still in beta test mode.

Those are just a few of the individual projects that are available. The Planetary Society has an excellent web-page summary of different citizen science projects.

Figure 4: A screen capture of the Galaxy Zoo webpage. Credit: Galaxy Zoo.

Career advice

I’ve pulled together some career advice about becoming an astronomer:

Here are a collection of tweets by and responses to astrophysicist Katie Mack on "Advice for Aspiring Astrophysicists" with some tips for aspiring astronomers/astrophysicists in preparing for a possible career in the field.

Duncan Forbes wrote a paper called “So you want to be a professional astronomer” (click on “PDF only” in the upper right).

The Royal Museums Greenwich explains “How to become an astronomer”.

Here is advice from the National Optical Astronomy Observatory on “Being an astronomer”.

Here’s a brief explanation from Caltech about “How can I become an astronomer?”. Note there is a problem with the link to the AAS career brochure at the end. This is the correct link (