What Color is the Sky in Your World?

That used to be my favorite expression to tell someone I thought they were full of it. Turns out it's a scientifically valid question after all. Only instead of the sky, astronomers are interested in determining the color of the entire Universe. This may seem like asking what does the Moon taste like, but I can assure you that the collective astronomy community has not spontaneously developed a case of synesthesia.

The medium astronomers work with most is light. In fact, it's pretty much the only medium we have to work with. Everything in the Universe emits some form of electromagnetic radiation and some of that radiation makes it way to Earth and is detected by our telescopes. In addition to the stars in the night sky, there are an unfathomable number of other astronomical objects out there that we have detected and observed in some detail - most notably hundreds of thousands of galaxies, made up themselves of billions of stars and numerous conglomerations of gas and dust known as nebulae.

On a bit of a lark, astronomers decided to take a representative sample of 200,000 galaxies to determine the dominant wavelength of their composite light. The phenomenon we call light comes in a wide range of frequencies known as the electromagnetic spectrum. It runs the gauntlet from low energy, long wavelength radio waves through the canonical rainbow to gamma rays, the highest form of energy currently detectable. However, color is a property unique to optical wavelengths.

So to determine the color of the Universe, astronomers looked at this sample of galaxies through just the narrow window of the visible spectrum and obtained an aggregate signal that can be represented by either a plot of the spectral energy distribution, or by the crowd favorite: a rainbow.



Astronomers prefer the former, but we definitely appreciate the appeal and the accessibility of the latter.

However, rainbows can be misleading. If your eyes were to take in all the light from these 200,000 galaxies at once, you would not see a rainbow, but rather the sum of its constituent wavelengths. It's like how we view sunlight; it appears essentially white as it pours in through a window, but place a prism in just the right spot on the window sill and you can extract its signature rainbow.

Now, imagine a room where the light of the Universe shines through the window. Your eyes would most likely interpret the color of the Universe as white as well, but us astronomers prefer to be more specific. Calculating the exact location of the color in a CIE chromaticity diagram, an international standard for primary colors, prescribes the color of the Universe to be...

...........drumroll please...........

BEIGE! Beige? Yes, beige.


I admit I was hoping for a color with a bit more pizzazz. But then again, the pizzazz is that I no longer ask the question in jest. The sky in my world is beige, thank you very much.

(Image credits:http://www.pha.jhu.edu/~kgb/cosspec/)

Lunar Splashdown

Three different spacecraft have independently detected the presence of water on the moon. And tomorrow morning, a fourth will attempt to make a big splash.

The Moon was thought to be a dry, barren place after the days of Apollo when astronauts returned, mission after mission, with samples of powdered lunar soil and rocks. The latest results from India's Chandrayaan-1 lunar probe indicate that the Moon is still a dry, barren place, but with a little bit of water hiding in the mix. And when I say a little bit of water, I really mean a tiny, minute, miniscule bit. If you could compile a ton of lunar soil, you would only amass about 32 ounces of water. However, that's still a nontrivial amount.

So how do we know this? As astronomers observing objects at such great distances, the only physical thing we have to measure is light. Lucky for us, we can learn a heck of a lot from light. One of the scientific instruments aboard Chandrayaan-1 was a spectrometer. Astronomers rely on spectrometers to detect the distribution of wavelengths of light coming from an object, in this case the Moon. While the Moon doesn't produce its own light, it reflects the sunlight that hits it in a way that is specific to its composition, i.e. the molecules that make up the lunar surface either scatter incoming sunlight or selectively absorb and/or re-radiate it. Thanks to laboratories here on Earth, we've gotten very good at identifying the exact wavelengths associated with known molecules. The spectra captured by Chandrayaan-1 show signs of absorption features that we associate with the presence of water.


But that's just scratching the surface. The next question is whether or not there is more water hidden deeper, underneath the Moon's dusty veneer.

That's where NASA comes in. Tomorrow morning at approximately 7:30am EDT, the used upper stage of a Centaur rocket that propelled the LCROSS (Lunar CRater Observing and Sensing Satellite) spacecraft to the Moon over the last three and a half months will crash into a pre-existing crater at the South Pole of the Moon. Why you ask? To create a large enough impact that the ejected material will come from not only the lunar surface, but from previously unexposed layers many meters below. The LCROSS spacecraft has a spectrometer of its own that will study the resulting plume of lunar debris and search for that telltale signature of water.

The Starry Messenger

The universality of the sky was revealed to me last night.

It started simply enough. Dinner in the valley with my godparents, a typical Saturday evening in August. Given the size of the valley and the small social circles, it's common to run into several friends and families at any given event, and this time was no different. The couples at the table outside, the family at the table next to us and the one next to that, and the neighbors at the table in the far corner, all known to my godparents and after tonight known to me as well. But one of these introductions was to mean more than the others.

The house up the hill from my godparents belongs to a couple who open their home to most of the valley each year when they honor their patriarch. I have vague memories of attending these fetes as a young child and sporadic ones as an adolescent, which came flooding back to me as I was walking into the house for this year's celebration. This particular summer I had come to know two of the three now full grown children in the family so I was especially excited to attend. In between the cocktail chaos and the bustling buffet though, I never came across the third and eldest daughter and her husband...until Saturday night.

As I am introduced to the husband I find myself volunteered and volunteering to set up a telescope for the family, which the aforementioned patriarch has just purchased for their mountain house. I worry a little to myself that my academic qualifications may not translate directly into telescopic proficiency, but being an engineer in a former life and a tinkerer by birth, I can't wait to get my hands on the shiny new toy.

Late Sunday afternoon, I head up the hill to report for duty. Within an hour the hardware is assembled, but due to a lack of batteries, we cannot test the AutoStar function which is where all the fun is - once the telescope is calibrated to a location, it can automatically slew to any number of celestial targets. Instead, I am made an offer that I cannot refuse: drinks and dinner on the porch on a future and hopefully clear night in exchange for returning to help with the remaining set-up. I return home and immediately look up the weather forecast; it's my last week in the valley and I pray that there will be at least one clear night. Tuesday jumps out at me. I check multiple weather websites, and they corroborate the first - Tuesday looks perfect.

Tuesday morning I awake to blue skies and bright sunshine, just the kind of day that makes you never want to leave the valley. As I am going about the online portion of my day, a friend tells me to check out Google's home page - it's familiar logo is composed of telescopes in honor of Galileo Galilei. Unbeknownst to me, it is exactly 400 years to the day after Galileo first unveiled his telescope to Venetian lawmakers. His intention at the time may have been to sell the instrument to merchants for use at sea or in trade, but I have no doubt he had already turned his to the sky. Less than six months later, he would publish his first telescopic astronomical observations in a brief treatise he titled Sidereus Nuncius, or Starry Messenger.

Now across time and space, from a stone patio on the side of a mountain, I find myself looking at the very same sky that Galileo first explored, low those many years ago. The telescope has been calibrated and aligned and it is asking us to choose an object. The Milky Way brilliantly spills across the sky directly overhead with the Summer Triangle practically at the zenith. The Big Dipper is hiding behind the pine trees lining the driveway. An occasional shooting star flashes in and out of view. Unanimously, the dinner party demands a closer look at the exceptionally bright object rising in the southeast from behind the house: Jupiter. Upon acquiring its target, the telescope reveals the exact picture that Galileo once set his sights on. His discovery of four small satellites orbiting Jupiter was what prompted him to question to the principles of Aristotelian Cosmology that required the orbits of all heavenly bodies to be centered on the Earth.

The telescope we are using is not terribly more powerful than Galileo's original one. And the sky has only changed imperceptibly since his time. Standing there with my eye glued to the eyepiece and Jupiter and its four Galilean Moons sliding across my field of view, I feel a sense of connection to Galileo, the Earth, and the cosmos stronger than I've ever felt before. Contrary to many people's reaction to the vastness of space and time, I feel all the more special and privileged to be a part of something universal, in all senses of the word.

And We Have A Winner!

The public has spoken. Over 140,000 votes were cast for the next celestial object that the Hubble Space Telescope should observe, and nearly half of them went to the interacting galaxy system known as Arp 274 (also known as NGC 5679). The result is a stunningly beautiful picture of not just two, but three, galaxies roughly 400 million light-years away from Earth in the constellation Virgo. The image is dominated by two face-on spiral galaxies with a third compact galaxy in the bottom left. The two bright spots above the right most galaxy are actually foreground stars in the Milky Way. The colors in the image represent the distribution of hydrogen gas, which is the dominant element of stars and of the Universe as a whole. Younger, hotter stars in the spiral arms appear blue, while new star forming nebulae are pink. Older, cooler, yellower stars are located in the center bulges of each galaxy. You can also clearly see the dust lanes lining the spiral arms where new stars are likely to form in the future.


While I personally voted for the edge-on galaxy, I always love a good interacting galaxy system. Even though you can still clearly see the strong spiral structures in the two larger galaxies, it's a safe bet that it won't last for long (at least on galactic time scales - a.k.a. millions of years). Gravity is already hard at work choreographing their cosmic tango.

Colbert in Space

Stephen Colbert has set his sights on the International Space Station.

On February 20th, NASA asked the public to help name the next module to be launched and mated to the International Space Station (ISS). In addition to providing additional room for the vital life support systems on-board the station, the new module will serve as coolest observation deck ever. One end of the module is essentially a cupola surrounded by windows on all sides to allow astronauts to observe and photograph the Earth from the ISS like never before.


Naturally, such an amazing module deserves an amazing name, right? NASA thinks so.

"Individuals can vote for the module's name online, choosing one of four NASA suggestions -- Earthrise, Legacy, Serenity or Venture -- or writing in a name. Submissions will be accepted Feb. 19 through March 20. The name should reflect the spirit of exploration and cooperation embodied by the space station and follow in the tradition set by Node 1, named 'Unity,' and Node 2, named 'Harmony.' "

As you may have noticed, NASA has conveniently allowed for write-in votes. They clearly aren't familiar with the power of Colbert Nation. Stephen Colbert has previously mobilized his fan base to get a minor-league hockey team mascot, a bald eagle, a leatherback turtle, a new species of spider, a Ben & Jerry's ice cream flavor, a Virgin American airplane, and a bridge in Hungary named after him. Can you see where I going with this...?

Hubble Space Telescope - People's Choice

In the spirit of the International Year of Astronomy 2009 and presumably to commemorate that magical day in history when Galileo first turned his telescope to the sky, the Hubble Space Telescope is letting the public decide what celestial object it should peer at next.

This is not to say that the public now gets to point Hubble capriciously at whatever strikes its collective fancy. Rather the scientists at the Space Telescope Science Institute, who oversee Hubble, have put together a list of six interesting objects that the telescope has never observed. And as you can see there is a good range of objects: galaxies, star forming regions, and planetary nebulae. I personally voted for the edge-on galaxy (NGC 4289) because we don't observe galaxies at that angle very often. And planetary nebulae are so passe, don't you agree?


If you prefer to make your choice based on more than looks alone, there is even a short video describing what we currently know about each object and what a much longer look might tell us about them.

As the infomercials often say, this is a limited offer, quite limited it turns out. You have until Sunday, March 1st to cast your vote. So act now! There nothing like having the power to control a 25,000 lb machine in space.

J'Adore Le Report

I am madly in love with Stephen Colbert and his writers. 

"In the Milky Way of punditry, there are white dwarfs (photo of George Stephanopoulos) and there are flaming balls of gas (photo of Rush Limbaugh)." - Feb. 11, 2009.

Happy Birthday, Galileo

Four hundred and forty-five years ago today, Galileo Galilei was born in Pisa, Italy. Without this amazingly curious mind, we would not have the Galilean moons of Jupiter, this plush little Galileo doll from the Unemployed Philosopers Guild, and the fabulous sing-a-long lyrics to Queen's "Bohemian Rhapsody."

Most importantly though thanks to this day in history we have the International Year of Astronomy to celebrate the 400th anniversary of Galileo turning the first telescope on the heavens. This is cause for celebration indeed.

Watch this space.