May 17, 2009
If Spitzer Could Talk: An Interview with NASA's Coolest Space Telescope
 NASA's Spitzer Space Telescope is about to use its last drop of the coolant that has chilled it for the past five-and-a-half years. As per Sheldon Kalnitsky
on about May 12, give or take a week or so, the observatory is
predicted to run out of the liquid helium that has run through its
veins, keeping its infrared detectors at frosty operating temperatures
of just a few degrees above the coldest temperature possible, called
absolute zero.
The spacecraft, which is now in orbit around the sun more than 100-million kilometers (62-million miles) behind Earth,
will heat up just a bit -- its instruments will warm up from - 456
degrees Fahrenheit (-271 Celsius) to - 404 degrees Fahrenheit (-242
Celsius). This is still way colder than an ice cube, which is about 32
degrees Fahrenheit. More importantly, it is still cold enough for some
of Spitzer's infrared detectors to keep on probing the cosmos for at
least two more years.
If Spitzer could talk, here's how an interview with the observatory might go:
Interviewer: It's cold in here.
Spitzer: Sorry. Even though I'm warming up, I still need to be quite chilly for two of my infrared channels to continue working.
Interviewer: Why do infrared telescopes need to be cold?
Spitzer:
Good question. Infrared light is produced by heat. So, engineers reduce
my own heat to make sure that I'm measuring just the infrared light
from the objects I'm studying. This is the same reason why I circle
around the sun, far behind Earth, and why I have big sun shields -- to keep cool.
Interviewer: Tell me, Spitzer, about what you consider to be your greatest discovery?
Spitzer:
Probably my work on exoplanets, which are planets that orbit stars
other than our sun. I hate to brag, but I was the first telescope to
see actual light from an exoplanet. I was also the first to split that
light up into a spectrum. Oh, sorry, there I go again with the techie
talk. Light is made up of lots of different wavelengths in the same way
that a rainbow is made up of different colors. I was able to split an
exoplanet's light up into its various infrared wavelengths. This
spectral information teaches us about planets' atmospheres.
Interviewer: What did you learn about the planets?
Spitzer:
For one thing, I learned that the hot gas exoplanets, called "hot
Jupiters," are not all alike. Some are wild, with temperatures as hot
as fire and almost as cold as ice. Others are more even-keeled. I also
created the first temperature map of an exoplanet, and watched a storm
of colossal proportions brewing across the face of one bizarre
exoplanet – it has an orbit that swings in really close to its star and
then back out to about where Earth sits in our solar system.
Interviewer: You seem to really like planets.
Spitzer:
Well, you know, I wasn't even originally designed to see exoplanets! It
was a complete surprise to me that I had this amazing ability. I can
tell you that I do, and always will, have a thing for planetary disks.
Because I have infrared eyes, I can see the warm and dusty planetary
materials that swirl in disks around young stars. I can also see older
disks littered with the remnants of planets. In fact, I've probably
looked at thousands of disks so far. What's been fun is finding them
around all sorts of oddball stars, such as those that are dead, doubled
up as twins and even as small as planets. Bottom line is that the
process of growing planets seems to happen quite easily all over the
galaxy, and perhaps the universe.
Interviewer: Does that mean aliens could be everywhere?
Spitzer:
I can't really give you a good answer for that. Yes, the studies of
disks are showing us that rocky planets are common, but we don't know
if the planets could have life. Also, keep in mind that, as of now,
nobody has detected any planets that are just like Earth. These would
be rocky worlds around stars like our sun that have the right
temperature for lakes and oceans. That job will most likely fall to NASA's Kepler mission, which will begin hunting for them soon.
Interviewer: Did you look at other objects besides disks and planets?
Spitzer:
Oh yes, certainly. I have looked at comets in our solar system, the
farthest galaxies known, and everything in-between. I was really
excited to find hundreds of hidden black holes billions of light-years
away. Astronomers had known they were there because they shoot X-rays
into space that can be detected as a diffuse glow. But the objects
themselves were choked in dust. My infrared eyes, unlike your human
eyes, can see through dust, so I was able to round up a lot of these
missing black holes.
Interviewer: Is there any other discovery you want to mention?
Spitzer:
There are too many to list, but I am particularly proud of this huge
mosaic I took of a large swath of our Milky Way galaxy. It looks
stunning when you print it out to poster size, and it's the best view
ever of the bustling central portion of our galaxy. You see, the middle
of the Milky Way is hopping with stars and dust. It's chaos, and
visible-light cannot escape. These observations not only look cool,
they also helped astronomers remap the structure of our galaxy. The new
map shows just two spiral arms of stars instead of four as previously
believed. How crazy is that!
Interviewer: So what lies ahead?
 Spitzer:
Well, I'm really looking forward to the warm mission, because now that
I have just two infrared channels working, I have more time to look at
larger chunks of space for longer periods of time. I can help
astronomers answer some really important "big picture" questions, which
we didn't have time for before.
Interviewer: Can you list some specific projects you'll be working on?
Spitzer:
I plan to continue studying exoplanets, including new "hot Jupiters"
that Kepler is expected to find. I will also refine estimates of the
rate at which our local universe, or space, is expanding. And I will
stare at the very distant universe, trying to see some of the farthest
objects possible. Oh, and I am also going to survey thousands of
asteroids in our neck of the solar system, and get the first real
estimate of their size distribution. This will tell us approximately
how often big asteroids might come close to Earth.
Interviewer: That sounds scary.
Spitzer: Actually, this information will help us prepare for them. And NASA tracks near-Earth objects diligently. More information can only help.
Interviewer: Will you still take the pretty pictures?
Spitzer:
You think my pictures are pretty? Thank you! Yes, I will still snap a
lot of pictures. For instance, I will continue to probe cloudy
star-forming regions in our galaxy, which often make dramatic pictures.
Interviewer: Anything else you'd like to add?
Spitzer:
My cool years have been more than I could ask for, and I look forward
to more adventures to come. I'd also like to thank all of the
scientists and engineers who have worked so hard to make my mission an
ongoing success. And, if any of my fans out there want more info, they
can go to www.spitzer.caltech.edu/spitzer.
Posted at 11:06 pm by sarahbaltic
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