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Space telescope would turn Earth into a giant magnifying lens
When it is finished sometime next decade, Europe's Extremely Large Telescope will be the largest in the world, with a mirror nearly 40 meters across. But one astronomer has proposed an even more powerful space telescope—one with the equivalent of a 150-meter mirror—that would use Earth's atmosphere itself as a natural lens to gather and focus light. Astronomer David Kipping of Columbia University has worked out that a 1-meter space telescope, positioned beyond the moon, could use the focusing power of the ring of atmosphere seen around the edge of the planet to amplify the brightness of dim objects by tens of thousands of times.
The atmosphere is too variable for a Terrascope, as Kipping calls it, to produce beautiful images to rival those from the Hubble Space Telescope. But it could discover much fainter objects than is now possible, including small exoplanets or Earth-threatening asteroids. Kipping acknowledges that more work is needed to prove the idea, but the necessary technology already exists. "None of this is reinventing the wheel, it just needs to be pushed a bit harder," he says.
Astronomers who read the paper Kipping posted last week on arXiv were both delighted and cautious. Matt Kenworthy, of Leiden University in the Netherlands, says he was "blown away by how much work and thought he had put into it" but wants more evidence that it will work. "I'd want to sit down and do a more realistic model," he says. Bruce Macintosh of Stanford University in Palo Alto, California, adds: "It's an interesting thought experiment, but there are a lot of details to think through."
A telescope could be put on the surface of the Moon facing the Earth (thus making both sides of the Moon attractive places to put telescopes), or at another location such as the L1 Lagrange point.
Also at Scientific American.
The "Terrascope": On the Possibility of Using the Earth as an Atmospheric Lens (arXiv:1908.00490)
Related: Sun Could be Used as a Gravitational Lens by a Spacecraft 550 AU Away
Halo Drive
(Score: 1, Interesting) by Anonymous Coward on Thursday August 22 2019, @09:23PM (1 child)
While I'm skeptical it could obtain high-quality images, taking the spectrum of an exoplanet might be right up its alley.
(Score: 3, Interesting) by takyon on Thursday August 22 2019, @10:53PM
This is a concept that is a lot easier to test than the solar gravitational lens telescope at 550+ AU. This could be done within the next 5 years on a low budget if NASA or others get serious about it. This could also be more versatile than a telescope at 550+ AU which could take years to aim at desired targets.
The Kipping paper assumes a 1 meter telescope, but we could put up a much bigger one with Starship.
I watched a YouTube video about this that said it would be limited to stars near the ecliptic plane [wikipedia.org], but I would think you could get around that by using an extreme orbital inclination around Earth or have it "orbit" the L1 point at a distance.
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