Tuesday, November 15, 2016

Scientists are building a telescope to seek another Earth — and you can help

On Valentine’s Day 1990, from a dark and frozen spot on the outer edges of our solar system, the spacecraft Voyager 1 turned around to take one last photo of the world it left behind.

Viewed from a distance of almost 4 billion miles, Earth was little more than a pixel, a “mote of dust suspended in a sunbeam,” in the words of Carl Sagan. Although the space program has produced countless gorgeous photographs of our planet — exquisite images of deep blue oceans and swirling clouds, of the incandescent spider web that is human civilization at night — nothing else has captured so starkly the profound loneliness of this precious, pale blue dot we call home.

Now scientists want to find a companion for that dot.

On Tuesday, a consortium of private research institutions launched a crowdfunding campaign to help build a new space telescope capable of searching for and photographing planets in the star system Alpha Centauri — which holds the closest stars to our sun. They call the mission “Project Blue.”

“We are seeking to take another pale blue-dot image,” said Jon Morse, former director of NASA’s astrophysics division and current chief executive of the BoldlyGo Institute, a research organization that is co-leading Project Blue. “This is the holy grail of exoplanet research.”

Before Dec. 20, Morse and his partner Brett Marty, executive director of the nonprofit Mission Centaur, aim to raise $1 million via Kickstarter — enough seed funding to get their project going. The rest of their budget will likely come from foundations and wealthy donors. The telescope, which they hope to launch into low Earth orbit in 2019, would be about the size of a dishwasher; its half-meter main mirror could fit on a coffee table.

Because their hardware is small and relatively modest in scope, Morse and Marty believe they can achieve their entire mission for $50 million or less.

The project is the kind of high-risk, high-reward mission that NASA is typically unwilling to pursue. Focusing solely on Alpha Centauri will keep costs low, but there's no guarantee that the system contains planets, let alone rocky bodies in the habitable zone. There is a chance that scientists will spend millions of dollars lofting the telescope into space, only to find it has nothing to look at. Previous discoveries of possible planets in the Alpha Centauri system have turned out to be flukes in data or objects that lie beyond Neptune in our own solar system.

NASA once considered building an observatory capable of directly imaging large numbers of exoplanets, which scientists currently detect by measuring small fluctuations in the light coming from the stars they orbit. But the project was deemed too expensive.

The intervening years have substantially changed the stakes for an exoplanet imaging project. The Kepler telescope has discovered thousands of exoplanets years after its mission was planned to end, and some estimates now suggest that as many as half of all stars could host a rocky planet. The proliferation of private aerospace companies has made it easier to launch instruments like the Project Blue telescope into low Earth orbit.

Just this August, astronomers announced that they'd found a small, rocky planet orbiting in the habitable zone of Proxima Centauri, a star in the Alpha Centauri system that is 4.22 light years away.

The Project Blue telescope wouldn't be able to image the new planet, dubbed Proxima b. It is too close to its star, making it impossible to distinguish the planet's faint glow from the brilliant blaze of its sun. Besides which, Proxima b is an unlikely candidate for “Earth 2.0.” It orbits its star every 11 days and is likely tidally locked, meaning that one half constantly faces the sun while the other is cloaked in endless night.

But the discovery of Proxima b makes Marty even more optimistic that more terrestrial planets could orbit Alpha Centauri A and B — the two other stars that make up that system. He noted that our own solar system has three rocky planets in the habitable zone of a single star.

“It's an old saying that if you can do it once, you can do it more than once,” he said. “Where there’s one there’s usually others because the process for forming these planets is common.”

Several of the technologies necessary for the telescope have already been on various NASA missions, according to Project Blue's lead scientist Supriya Chakrabarti, an astronomer at the University of Massachusetts Lowell. The project's most important and most expensive challenge will be developing a high-performance coronagraph — a device capable of blocking light from the two stars so that scientists can detect the much fainter reflections of their nearby planets. If those planets exist, that is.

In theory, this can be done with a deformable mirror that manipulates and refocuses light from the center of an image, so that the doubled reflections from a star cancel each other out. But such a coronagraph is incredibly difficult to build on Earth and has never been tried in space.

The telescope also must be able to remain focused on Alpha Centauri even as it whizzes around Earth at a speed of 5 miles per second.

“Think of a lighthouse which is illuminating a marble, where the lighthouse is at Cape Cod and you are trying to image it from San Francisco,” Chakrabarti said. “That will give you an idea of how challenging it is.”

Once aloft, the telescope would image blue wavelengths of light coming from Alpha Centauri; this region of the visible spectrum is most likely to indicate whether a planet has liquid water and an atmosphere. If the Project Blue telescope finds anything, Morse and Marty are certain that NASA or other research organizations will leap to develop instruments and telescopes capable of investigating the planet further.

That said, it's well within the realm of possibility that the project never gets to that point. The telescope is barely a concept yet — it may be thwarted by funding or engineering problems before it ever reaches a launchpad or derailed by an instrument malfunction once it reaches space. Environmental factors — for example, clouds of dust surrounding the Alpha Centauri system — could make any planets hard to image. And it may well be that the stars have no planets at all.

“It’s pretty ambitious,” Steve Howell, a member of NASA’s Kepler science team who is not involved with the effort, told Popular Science when Project Blue was first announced last month. “But that’s okay, we should do ambitious things.”

Project Blue is the not the only space exploration effort to seek funding from the masses. The U.K.-based Lunar Mission One, which aims to send a lander to the moon in 2024, raised roughly $900,000 on Kickstarter in 2014. Bill Nye and the Planetary Society have garnered more than $1 million via crowdfunding for the LightSail project aimed at a solar-sail spacecraft.

Nor are Morse, Marty and Chakrabarti the only scientists with their eyes set on Alpha Centauri. NASA recently considered and rejected a proposal from astronomers Ruslan Belikov and Eduardo Bendek at Ames Research Center in Silicon Valley that would have built a similar telescope for $175 million. Stephen Hawking and Yuri Milner's Breakthrough Starshot project wants to send light-powered probes to the nearby system, but the effort will take at least 20 years to launch and another generation to reach its target. NASA's Wide Field Infrared Survey Telescope, which will include a coronagraph capable of directly imaging exoplanets, was officially designated as a mission this year. Yet it, too, is a long way from completion.

Were it to make it into orbit, the Project Blue telescope would spend two years imaging the system and tracking whatever planets it finds. By 2020, they the team says, we could be marveling at another pale blue dot in a sea of black.

Until then, all we've got is our own.

Source: https://www.washingtonpost.com/news/speaking-of-science/wp/2016/11/15/scientists-are-building-a-telescope-to-seek-another-earth-and-you-can-help/