Never pass up a chance to sit down or relieve yourself. -old Apache saying

Sunday, April 19, 2015

Beyond the Hubble

Few things get me off like astronomy and science....and my wife, of course.

From the Daily Kos:

Beyond the Hubble

The Cat's Eye Nebula as seen by the Hubble Space Telescope in the constellation Draco.
Ask anyone to name a telescope and odds are one answer will come up every time: Hubble. Not as many know it was named after Edwin Hubble, the father of modern cosmology, who found the universe wasn't just far larger than we dared imagine, its very fabric was expanding in all directions at warp speeds every second of every day. Hubble the man expanded our appreciation of the universe and our place in it much the same way Hubble the telescope has blown our minds with thousands of images since.

For 25 years the Hubble Space Telescope has graced our textbooks and computer monitors with a seemingly endless procession of jaw-dropping beauty hidden far away, in tiny spaces—from our perspective. It stares at a hunk of sky the size of a dust grain once thought totally empty and finds hundreds of primeval galaxies, each an island universe, each one made of billions of stars. It glances briefly at a distant supernova remnant and we fall into infinitely recursive filaments and sheets of star-stuff. You could spend hours and hours scrolling through Hubble space porn and not see the half of it. Not a bad rebound for an instrument that first went up half-blind, needing corrective glasses.
Of course like all man-made devices, Hubble's days were always numbered. It is nearing the end of its operational life. There is a successor slated for launch as early as 2018. It's big, it's bad, it's even a little risky. But boy howdy, if it works as designed, we will all be the richer. Come on down below the fold and meet the James Webb Space Telescope.

The JWST is named after James Webb, an important NASA administrator during the space race heyday. Webb the telescope is the size of a tennis court and designed to provide far greater resolution than Hubble, at least 10 to 20 times better, and as much as 100 times or more as it comes completely online—never underestimate the ability of clever astronomers to tweak and tease out every last photon! But the tech upgrades don't stop there.

Webb sees in both visible light and the near infrared: it has something akin to night vision goggles. It can even peer inside and through vast cosmic clouds of dust and debris that are completely opaque to other telescopes. This ability opens up whole new vistas of observation. Webb will be able to image objects so distant, so small and so dim—and in some cases so well concealed—that purely optical instruments could never see them no matter how powerful they might be. This infrared vision is the whole point of building a device like Webb and the reason it has to be in deep space. Those wavelengths are stopped cold by our atmosphere.

Since we've never had a super-duper infrared hyper-scope in interplanetary orbit before, it's hard to say exactly what this will mean in terms of observational astronomy. But to get the idea across with a little creative license, if we could somehow point Webb exclusively at the night side of Jupiter, even all the way from Earth it could probably produce a moving image from residual heat of the cyclones and bands in that turbulent atmosphere comparable in resolution and quality to what the Voyagers saw close up when they visited these many space years ago.

It will be able to see individual stars and small galaxies at the beginning of space and time so red-shifted by Big Bang expansion that no optical telescope would have a prayer of ever seeing them. If it performs at the very high end of its expected range, and given ideal conditions in a target star system, Webb could eventually, directly image exosolar planets many light years away.

Well, some experts might go along with those exact examples, others would quibble, we'll have to wait and see. But the point is, given that kind of jump in both power and perception, Webb is intended to see lots and lots of things that we just flat out can't see now and don't know anything about.

We can only guess: If there's an icy super-Earth or modest little gas dwarf out way past Pluto in a long, lazy orbit around our sun, Webb could eventually find it. If there are swarms of Jovian-mass rogue worlds with retinues of rings and moons that were ejected from ancient, long vanished solar systems, sentenced to wander the galaxy alone forever, Webb will probably be able see some of them. It will be able peer inside proto-planetary disks and observe embryonic planets as hot knots of accruing matter, and it is expected to be able to shoot spectra of transiting exo-planets identified by NASA's Kepler telescope.

And now for the downside: giant, super-duper interplanetary infrared/optical telescopes are expensive, not to mention terribly tricky to build and operate. Webb has been subject to incessant cost overruns and scheduling delays year after year. That comes at a direct cost to other, worthy programs. Congress came damn close to killing it in 2011. That 2018 launch date is by no means certain.

To see in the near infrared, the collecting surface (what passes for the mirror in an optical telescope) must be kept really cold, around 50 degrees above absolute zero. To see with high resolution means that chilly collecting surface must be large—that weird-looking mirror is huge, brittle, and made out of gold-coated beryllium. It's a sitting duck for even a small meteor strike. It must be completely isolated from the heat and light of the sun, so the collector will sit on a multi-layer insulating sunshade. The telescope is so sensitive to thermal pollution that even the reflected energy from a nearby Earth or moon could screw up performance, so the whole contraption will be sequestered far, far away.

Webb won't be in Low Earth Orbit like Hubble. It will spend its days a million miles farther out, at a semi-stable orbital anomaly called L2. If the slightest little thing goes wrong, if a panel or sunshade doesn't unfurl all the way, if it happens to get hit by a grain of dust in the right spot, God forbid if a mirror or lens is off like that embarrassing Hubble incident, there's no way to retrieve it for repair and there's no chance to visit and fix it onsite any time soon. Not until we either develop 1) manned interplanetary space travel or 2) awfully agile remotely-operated deep space robots that do not exist, yet.

Is that all worth the risk? Given the money NASA and other institutions have already sunk into JWST, we're probably going to find out. It's close enough to completion now that the smart money would bet on it going up sooner or later. So hopefully, in the next five years or less, we'll all be changing our wallpaper and screensavers over to brilliant new images delivered on the gossamer wings of invisible light, courtesy of the James Webb Space Telescope.


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