The Fourth Brother’s Quest

Newt Barnes is an informed and enthusiastic speaker in Cathleen’s “IR, Spitzer and the Universe” memorial symposium. Unfortunately Al interrupts him by bustling in to refresh the coffee urn.

After the noise subsides, Newt picks up his story. “As I was saying, it’s time for the Spitzer‘s inspirational life story. Mind you, Spitzer was designed to inspect very faint infra-red sources, which means that it looks at heat, which means that its telescope and all of its instruments have to be kept cold. Very cold. At lift-off time, Spitzer was loaded with 360 liters of liquid helium coolant, enough to keep it below five Kelvins for 2½ years.”

“Kelvins?”

“Absolute temperature. That’d be -268°C or -450°F. Very cold. The good news was that clever NASA engineers managed to stretch that coolant supply an extra 2½ years so Spitzer gave us more than five years of full-spectrum IR data.”

<mild applause>

“Running out of coolant would have been the end for Spitzer, except it really marked a mid-life transition. Even without the liquid helium, Spitzer is far enough from Earth’s heat that the engineers could use the craft’s solar arrays as a built-in sunshield. That kept everything down to about 30 Kelvins. Too warm for Spitzer‘s long-wavelength instruments but not too warm for its two cameras that handle near infra-red. They chugged along just fine for another eleven years and a fraction. During its 17-year life Spitzer produced pictures like this shot of a star-forming region in the constellation Aquila…”

NASA/JPL-Caltech/Milky Way Project.

The maybe-an-Art-major goes nuts, you can’t even make out the words, but Newt barrels on. “Here’s where I let you in on a secret. The image covers an area about twice as wide as the Moon so you shouldn’t need a telescope to spot it in our Summertime sky. However, even on a good night you won’t see anything like this and there are several reasons why. First, the light’s very faint. Each of those color-dense regions represents a collection of hundreds or thousands of young stars. They give off tons of visible light but nearly all of that is blocked by their dusty environment. Our nervous system’s timescale just isn’t designed for capturing really faint images. Your eye acts on photons it collects during the past tenth of a second or so. An astronomical sensor can focus on a target for minutes or hours while it accumulates enough photons for an image of this quality.”

“But you told us that Spitzer can see through dust.”

“That it can, but not in visible colors. Spitzer‘s cameras ignored the visible range. Instead, they gathered the incoming infrared light and separated it into three wavelength bands. Let’s call them long, medium and short. In effect, Spitzer gave us three separate black-and-white photos, one for each band. Back here on Earth, the post-processing team colorcoded each of those photos — red for long, green for medium and blue for short. Then they laid the three on top of each other to produce the final image. It’s what’s called ‘a falsecolor image’ and it can be very informative if you know what to look for. Most published astronomical images are in fact enhanced or colorcoded like this in some way to highlight structure or indicate chemical composition or temperature.”

“What happened after the extra extra years?”

“Problems had just built up. Spitzer doesn’t orbit the Earth, it orbits the Sun a little bit slower than Earth does. It gets further away from us every minute. It used to be able to send us its data almost real-time, but now it’s so far away a 2hour squirt-cast drains its batteries. Recharging the batteries using Spitzer‘s solar arrays tilts the craft’s antenna away from Earth — not good. Spitzer‘s about 120° behind Earth now and there’ll come a time when it’ll be behind the Sun from us, completely out of communication. Meanwhile back on Earth, the people and resources devoted to Spitzer will be needed to run the James Webb Space Telescope. NASA decided that January 30 was time to pull the plug.”

Cathleen takes the mic. “Euge, serve bone et fidélis. Well done, thou good and faithful servant.”

~~ Rich Olcott

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