Thursday, May 30, 2013

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):
Top: Saturn, as seen by Cassini. CreditCassini Imaging TeamSSIJPLESANASA
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:

  • 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.
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 ChandraHubble, 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".

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