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Earth II?

A broken space telescope continues to expand our view of the universe.

by
Rand Simberg

Bio

April 21, 2014 - 11:02 pm
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Ever since the realization that our sun was a star amidst uncountable others in the universe, astronomers and philosophers have speculated about the possibility of extrasolar planets, or “exoplanets” — planets that orbit other stars — and whether or not they could harbor life or intelligence. The modern era has given us tools to allow us to answer that question, and the answer turns out to be, yes, at least in terms of the existence of exoplanets, though there is still no evidence of extraterrestrial life or intelligence.

The initial, and vast majority of such discoveries were made not by directly viewing them with powerful telescopes (though there have been some of those), but by indirect methods that require inference. The first such discovery was confirmed in the early 1990s, when telescopes observed a slight regular wobble in a distant star, that was likely caused by a very large planet (perhaps like Jupiter) pulling it from side to side as the massive body orbited it. But a more powerful means of detection has been by observing so-called transits — when a planet passes between us and its star and slightly, momentarily dims its light. Though we can’t see the planet itself because there is no light coming from its night side, its size can be calculated by measuring the degree to which the starlight is dimmed by it.

So promising was the technique in fact that, five years ago, in March 2009, after multiple failed attempts to get it funded, NASA finally launched a space telescope specifically designed to look for such events. It was named after the astronomer Johannes Kepler, who first described planetary orbits as ellipses, a result which helped Isaac Newton come up with his universal law of gravitation.

Unlike the Hubble Space Telescope, which is in low earth orbit, Kepler is in a heliocentric (or sun-centered) orbit, far from earth, to prevent it from being dazzled by earthlight and moonlight as it gazes deep into the galaxy. In order to stare at a star well enough to see transits, it has to have very precise pointing capability, akin to “pinpointing a soccer ball in Central Park as seen from San Francisco.” To do this smoothly, it has four gyroscopic devices called reaction wheels. By rotating the axes of these small spinning flywheels, the attitude of the spacecraft can be moved and held in a very precise controlled manner.

For the past half decade Kepler has been observing and sending back data, but in the summer of 2012, a little over three years into its mission, it started to run into problems when one of its reaction wheels started to fail, with friction buildup in the bearing, slowing the wheel. Last May, almost a year ago, another one started to display similar symptoms. With too much friction in half of its redundant devices, it was no longer able to point sufficiently accurately to perform its primary mission of star staring. Last August, NASA engineers despaired of fixing it, and were searching for ways to repurpose it for other missions.

But last fall, some engineers at Ball Aerospace, its prime contractor, came up with a clever fix. Our own nearby star puts out so-called “radiation pressure,” resulting from photons of sunlight bouncing off spacecraft surfaces. They figured out how to maintain an attitude almost as precisely as with the reaction wheels by changing the angle of the telescope’s solar arrays to vary the resulting force on the vehicle. While it’s not as good as when originally launched, it is still returning data, and may now continue to do so until its successor, the Transiting Exoplanet Survey Satellite (TESS), is launched in 2017. A few weeks ago, in fact, by using a new more efficient technique to verify the discoveries, NASA reported a doubling of the number of detected planets, and potentially quadruple the number of earth-sized ones, and it may be that as many as one in five stars have such bodies.

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All Comments   (10)
All Comments   (10)
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In a galaxy 100,000 light-years across, that makes it a relatively close neighbor. But in terms of our current propulsion technology, it might as well be on the other side of the universe.

Propulsion technology is the single biggest limiting factor we face. We're not going very far or very fast on chemical rockets. Until we overcome that fundamental problem, we're consigned to crawling around the immediate vicinity.
26 weeks ago
26 weeks ago Link To Comment
While discovering planets by telescope is nice, it would be even better if we can go out and space and explore them personally. Of course, that requires us to get over our angst that using Earth's resources destroys our own planet.
26 weeks ago
26 weeks ago Link To Comment
I just noticed that I made an error in writing this. Planets don't cast shadows on their stars. I should have written "...by measuring the degree to which the starlight is dimmed."
26 weeks ago
26 weeks ago Link To Comment
Are they only finding planets whose ecliptic planes closely align with a line of sight from us to the other star? If so what number of exoplanets should we presume are out there?

Do you know of anyone but Dr. Woodward (Mach Effect) working a theoretically plausible interstellar drive? I'm discounting Eagleworks for now.
26 weeks ago
26 weeks ago Link To Comment
How are they confirming these observations? It's not like they haven't lied before to justify continued funding.
26 weeks ago
26 weeks ago Link To Comment
They lied? Can you help me with some examples? Skip any lies about climate change though; that is a political not a scientific observation issue.
26 weeks ago
26 weeks ago Link To Comment
OK, so they're essentially sailing Kepler now...
26 weeks ago
26 weeks ago Link To Comment
Riding the solar wind. I'mna liking that. And why don't we have a space tug tethered to ISS? Something that could go out and do things, like, oh, I don't know, repair Kepler?
26 weeks ago
26 weeks ago Link To Comment
Actually, it's not the solar wind, which is particles streaming out from the sun. Radiation pressure comes from the light itself.
26 weeks ago
26 weeks ago Link To Comment
Kepler is heliocentric, not earth centric. It's too far away. And the ISS's "space tug" is simply an escape and return to earth if things go seriously wrong on the space station. It's not a motor boat that you can use to flit about near earth. We could probably build something like that, but there's the whole expensive problem.
26 weeks ago
26 weeks ago Link To Comment
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