from the a-lens-that-blinds-you dept.
The Sun could be used as a gravitational lens to magnify normally hard-to-image targets such as exoplanets. The catch? The equipment needs to be 550 AU away from the Sun:
Now Leon Alkalai from the Jet Propulsion Lab and his co-authors have picked up an earlier suggestion from Italian physicist Claudio Maccone to use our Sun, rather than a distant star, to create what might be the ultimate telescope based on the microlensing principle. Alkalai's team has investigated the viability of the method in detail as a breakthrough mission concept. They also presented their findings at NASA's recent Planetary Science Vision 2050 workshop in Washington, D.C.
To build such a "telescope," detecting instruments would be placed at a point in space where the Sun's gravity focuses lensed light from distant stars. Not only is the idea viable, according to the Alkalai team, it would produce images that separate the distant star from its exoplanet, a critical observation that is the goal of future space telescopes equipped with Starshades. And using the Sun as a lens would result in much greater magnification. Instead of a single pixel or two, astronomers would get images of 1,000 x 1,000 pixels from exoplanets 30 parsecs, or about 100 light years, away. That translates to a resolution of about 10 kilometers on the planet's surface, better than what the Hubble Space Telescope can see on Mars, which would allow us to make out continents and other surface features.
[...] There is a downside, however. The telescope's focal plane instruments would have to be at least 550 AU from the Sun (1 AU, or astronomical unit, is the distance from the Sun to Earth), which is well into interstellar space. The only spacecraft that has reached interstellar space so far is Voyager 1, which covered approximately 137 AUs in 39 years. So we would need a spacecraft that is at least 10 times faster, but Alkalai and his colleagues say this is within the reach of current technology.
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.
Phys.org reports on the bold plan to take pictures of an exoplanet so sharp that oceans, continents and even clouds would be discernible.
Right now, it's impossible. From our vantage point, exoplanets—planets orbiting other stars—look like fireflies next to spotlights. In the few images we've managed to take of them, the exoplanets are mere dots. Even as the next generation of space telescopes comes online, this won't change—you'd need a 90-kilometer-wide telescope to see surface features on a planet 100 light years away.
A group of researchers has an audacious plan to overcome these difficulties. It involves using solar sail spacecraft—possibly an entire fleet of them—to fly faster and farther away from Earth than any previous space probe, turn around, and use our distant Sun's gravity as a giant magnifying glass. If it works, we'll capture an image of an exoplanet so sharp that we can see features just 10 kilometers across.
Recently awarded a $2 million grant by NASA's Innovative Advanced Concepts (NIAC) program, and spearheaded by JPL physicist Slava Turyshev, the project,
called the Solar Gravity Lens, or SGL, sounds like something straight out of science fiction. NASA and a collection of universities, aerospace companies and other organizations are involved, as well as Planetary Society co-founder Lou Friedman, the original solar sailing guru.
According to Turyshev
The needed technologies do already exist, but the challenge is how to make use of that technology, how to accelerate their development, and then how to best put them to use. I think we are at the beginning of an exciting period in the space industry, where getting to SGL would be practical, and scientifically exciting."
I wonder if it will come with an EF mount.