An Infrared Glimpse of What’s to Come - by Amy Mainzer

The image on the left shows a picture of the constellation Orion taken in the visible light that humans see.
On the left, a picture of the constellation Orion taken in the visible light that humans see. On the right, an infrared view of Orion reveals a swirling mass of glowing gas and newly formed stars, which are invisible to the human eye.› Larger image

Almost everyone has had the frustrating experience of getting lost. To avoid this problem, the savvy traveler carries a map. Similarly, astronomers need maps of the sky to know where to look, allowing us to make the best use of precious time on large telescopes. A map of the entire sky also helps scientists find the most rare and unusual types of objects, such as the nearest star to our sun and the most luminous galaxies in the universe. Our team (lead by our principal investigator, Dr. Ned Wright of UCLA) is building a new space telescope called the Wide-field Infrared Survey Explorer that will make a map of the entire sky at four infrared wavelengths. Infrared is a type of electromagnetic radiation with a wavelength about ten or more times longer than that of visible light; humans perceive it as heat.

Why do we want to map the sky in the infrared? Three reasons: First, since infrared is heat, we can use it to search for the faint heat generated by some of the coldest objects in the universe, such as dusty planetary debris discs around other stars, asteroids and ultra-cold brown dwarfs, which straddle the boundary between planets and stars. Second, we can use it to look for very distant (and therefore very old) objects, such as galaxies that formed only a billion years after the Big Bang. Since light is redshifted by the expansion of the universe, the most distant quasars and galaxies will have their visible light shifted into infrared wavelengths. And finally, infrared light has the remarkable property of passing through dust. Just as firefighters use infrared goggles to find people through the smoke in burning buildings, astronomers can use infrared to peer through dense, dusty clouds to see things like newborn stars, or the dust-enshrouded cores of galaxies.


This animation shows the Sombrero galaxy, first in visible
light and then in infrared. The infrared view shows a bright,
smooth ring of dust circling the galaxy, and stars that are
hidden by dust in the visible-light view.
› Full caption

So how does one go about building an infrared space telescope? And why does it need to be in space in the first place? Since infrared is heat, you can imagine that trying to observe the faint heat signatures of distant astronomical sources from our nice warm Earth would be very difficult. A colleague of mine compares ground-based infrared astronomy to observing in visible light during the middle of the day, using a telescope made out of fluorescent light bulbs! Putting your infrared telescope in the deep freeze of space, well away from the warmth of Earth, improves its sensitivity by orders of magnitude over a much larger ground-based infrared telescope.

On the Wide-field Infrared Survey Explorer project, our team is in the middle of one of the most exciting phases of building a spacecraft — we’re assembling and testing the payload. Right now, the major pieces of the observatory have been designed and manufactured, and we’re in the process of integrating all these pieces together. The payload is elegantly simple. It has only one moving part — a small scan mirror designed to “freeze-frame” the sky for each approximately 10 second exposure as the spacecraft slowly scans. After six months, we will have imaged the entire sky. The telescope is flying the latest generation of megapixel infrared detector arrays, along with an off-axis telescope that gives us the wide field of view that we need to cover the whole sky so quickly. In the next few months, we’ll be setting the focus on our telescope, characterizing our detector arrays, and verifying the thermal performance of our cryostat. The observatory’s cryostat is essentially a giant thermos containing the cryogenic solid hydrogen that we use to keep our telescope and detectors at their operating temperatures near absolute zero.

telescope
Engineers install the telescope optics into the observatory’s
cryostat. The top dome of the cryostat can be seen in the
foreground. This cover will be ejected approximately two
weeks after launch, allowing the observatory an unfettered
view of the sky. Image courtesy of Space Dynamics
Lab/Utah State University. › Larger image

We are also in the midst of making detailed plans for verifying that the spacecraft is working properly once we launch. This is called the “in-orbit checkout” phase. For this mission, checkout is fast — only 30 days! The checkout commences right after our November 2009 launch, when we wake the spacecraft up and begin switching on its various subsystems: Power generation and distribution, communications, attitude control and momentum management, and the main computer system. We’ll also power on the payload electronics and detectors. Next, we will begin the calibration observations that we need to start the survey, such as verifying the telescope’s image quality and the way our detector arrays respond to light. Once these steps are completed, we’ll be ready to extend our gaze across the universe using the observatory’s infrared eyes.

The great thing about the mission’s all-sky dataset is that it will be accessible to everyone in the entire world via a Web interface. So you will literally be able to access some of the coldest, most distant and dustiest parts of the universe from the comfort of your couch. Stay tuned to explore the universe with us!

    12 Responses to “An Infrared Glimpse of What’s to Come - by Amy Mainzer”

  1. ms Says:
    July 23rd, 2008 at 2:33 pm

    Saying “infrared is heat” is highly misleading. Better would be to say that warm things emit infrared and things (or people) that absorb infrared get warmer. Might also add that our atmosphere absorbs most infrared, although there is a window of frequencies that get through.

  2. dn Says:
    July 24th, 2008 at 5:04 am

    Things (or people) that absorb any “color” of light get warmer. Infrared is perceived by humans as heat. Probably what Amy was trying to say is that objects do not have to be as energetic to emit infrared as they do to emit, say, gamma rays, and there should be far more lower-energy objects that could be seen by the infrared instrument. There is also of course the redshift explanation which makes sense.

  3. johnny Says:
    July 28th, 2008 at 1:29 pm

    come on 2009!!!, and 30 days checkout. the waiting is the hardest part. lol.

  4. johnny Says:
    July 29th, 2008 at 6:37 pm

    question is if we are looking from the outside in, on the possibility of other worlds point of view of our galaxy, what would they see, and then will we be looking into the mirror from the inside of our own galaxy. In other wor”l”ds, what will we see when we are looking in from the outside. This is how one must perceive and conceive in order to get a clear picture of the universe.

  5. johnny Says:
    July 29th, 2008 at 6:47 pm

    we must look at the hospitable zone within which conditions are “ripe” for life sustaining elements. How will this telescope help in the search for alien worlds, in far and near galaxies, such as recently discovered zones using Spitzer, or “organic zones”?

  6. johnny Says:
    August 2nd, 2008 at 10:55 pm

    the answer is both near and far and in between! its all “plane” and simple and the the temperate zone. In other words, avg temp must be similiar to earths temp, and maybe plus or minus some temp. within certain limitations. can we study temps of other objects, such as temps of brown dwarfs once we find them?

  7. johnny Says:
    August 2nd, 2008 at 11:03 pm

    what does blog mean. i all new to this thing called blog, why do i feel like im conversing with myself? lol

  8. Space Star Wars Episode 3 Planet Mars Says:
    August 7th, 2008 at 5:54 pm

    Space Star Wars Episode 3 Planet Mars…

    I didn’t agree with you first, but last paragraph makes sense for me…

  9. guvenlik sistemleri Says:
    August 8th, 2008 at 8:51 pm

    You have excellent analysis. thanks for writting

  10. johnny Says:
    August 12th, 2008 at 2:55 pm

    If it is hospitable, and it is “forgiveable” to life, then the ingredients are present, such as hydro-carbons and polycycic carbons, then time will only take care of itself, which in turn is inevitable, that we become educated from the evidence available or not availble yet omnipotent, then one can see the ultimate truth of existence of the universe and the very begining of time. what do you think?

  11. johnny Says:
    August 12th, 2008 at 2:56 pm

    please forgive my misspellings, for my typing is less than perfect. lol

  12. Derek Says:
    August 14th, 2008 at 12:16 pm

    I am totally stoked for WISE. I think it is going to provide an amazing picture of our galaxy… far better than previous wide-survey infrared telescopes.