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NASA’s Spitzer’s Space Telescope: Shaping Scientific Careers of Researchers and Future Space Telescopes
Sajina blog rec

By Anna Sajina | September 4th, 2019

This year we celebrate the 15-year legacy of NASA’s Spitzer Space Telescope. I was happy to be asked to write about the role of Spitzer in my career. Indeed, I am one of the many scientists whose career has been shaped by Spitzer and the fantastic data it provided us with during its long lifespan.

I was one of the very first groups of visiting graduate students at the Spitzer Science Center—a program that continues to this day. I arrived in Pasadena in September 2003, just after Spitzer launched. It was amazing to be part of all the activity and excitement at the Spitzer Science Center at that point! I got to work on predictions for what Spitzer would see, including techniques for finding dust-obscured, accreting supermassive black holes—the kind that had eluded astronomers prior to Spitzer.

My PhD thesis, completed a year and a half after Spitzer’s launch, ended up weaving together data from the Infrared Space Observatory (ISO), an earlier infrared mission, and from Spitzer. In the final year of my PhD, I also did my first public talk. At the Vancouver planetarium, I talked about the infrared Universe, covering both the history of infrared astronomy and all the exciting science the then-new Spitzer Space Telescope was going to do. I didn’t anticipate even half of it!

Upon graduation, I was lucky enough to be able to return to the Spitzer Science Center as a postdoc, where I worked on Spitzer IRS mid-IR spectra of galaxies located billions of light years away-- science that was completely unachievable with the earlier generation of infrared facilities like ISO. But, in interpreting these spectra, we were building upon the legacy of those earlier missions, just as future missions like the James Webb Space Telescope (JWST) mid-IR spectrograph will build upon the knowledge gained from NASA’s Spitzer Space Telescope.

In analyzing the Spitzer mid-IR spectra, some of our key results involved (again) finding dust-obscured, accreting supermassive black holes and finding that this kind of activity is much more common than previously thought. One of my favorite memories is a project I led where we detected the presence of water ice in galaxies nearly 10 billion years in the past. This water is likely part of the icy mantles of interstellar dust grains. Combined with the ubiquity of complex hydrocarbons, again seen in the mid-IR spectra, this finding makes it clear the raw ingredients for the development of life are already commonly found throughout the Universe, and only a few billion years after the Big Bang!

Running out of cryogen put an end to the mid-IR spectrograph on Spitzer five years after its launch. Spitzer then shifted to the warm mission, where it kept using only its shortest wavelength instrument, IRAC. I have been involved in several large-area IRAC surveys and indeed led such a survey in the last general observer cycle in 2018/2019. IRAC data provides coverage in a part of the spectrum critical for constraining the physical characteristics of distant galaxies and is unmatched in sensitivity and its ability to map large areas in this regime. The archival Spitzer IRAC data will continue to give us scientific return for at least the next decade— well past the end of Spitzer observing.

Lastly, like all scientists who were involved with the Spitzer mid-IR spectrograph, I am looking forward to its successor, the mid-IR spectrograph on the James Webb Space Telescope. Just as I did for my thesis more than a decade ago, I applied the lessons of ISO to Spitzer. I am looking forward to writing papers that apply the lessons from Spitzer to JWST.