Making dreams reality

Posted by Korey Haynes
on Wednesday, January 07, 2015

Artist's rendition of Gaia in space, measuring its billion stars. // ESA

One of the coolest things about being at the American Astronomical Society (AAS) meeting is hearing about the future of space science straight from the source. Last night I got to hear about the far future of space observatories — what comes after the James Webb Space Telescope (JWST), set to launch in 2018. The next, next big project, currently dubbed the High Definition Space Telescope (if you don't like it, the name will almost certainly change before launch), imagines the world's leading ground-based telescopes of today, but in space.

The idea is for a 10- to 12-meter segmented mirror, which is similar to the currently existing Keck telescopes. It would fly, like JWST, at an Earth-Sun Lagranian point, and it would have capabilities from the ultraviolet to the infrared. In most ways, it would represent at least an order of magnitude improvement over JWST's abilities.

Why do we need an order of magnitude improvement over the most cutting-edge telescope we're currently able to produce? Think of it this way: There only will be a handful of rocky planets close enough and bright enough for JWST to search for signs of life. It's just not precise enough to study the farther, dimmer candidates satisfactorily. If the odds are only 1 in 10 that an Earth "twin" actually supports life (a reasonable fraction), do you want to take your chances and only able to study five planets? Better by far to study 50. That's one of the many drivers to keep pushing for bigger, better telescopes for the future.

While it may seem a bit premature to start thinking beyond JWST, it takes decades to walk a giant project like this from first concept to first light. JWST began its planning just after the launch of Hubble, so we're actually right on track to start thinking about the succeeding generation, which would launch in the mid 2030s. By then, perhaps we even could fly servicing missions to such an observatory.

Tuesday morning, we heard updates from the European Space Agency (ESA) on the Gaia mission, whose slogan is "a billion pixels for a billion stars." Gaia is a space telescope with a gigapixel detector and two mirrors that fly in close formation. Its main purpose is astrometry, or measuring the positional change of stars on the sky, which Gaia accomplishes by observing them repeatedly as the spacecraft orbits. It can measure positions to such an accuracy that from Astronomy's offices near Milwaukee, Wisconsin, it could measure the width of a human hair in Washington, D.C.

Gaia is the successor to a mission called Hipparcos that operated between 1989 and 1993. Hipparcos was a revolutionary project, and its catalog consists of 120,000 stars. Gaia will measure more than one thousand million stars when its survey is complete. With a catalog that enormous and precise, it will find thousands of exoplanets through radial velocity searches. It will tell us unprecedented detail about stellar populations and even deliver detailed information about near-Earth objects.  

Gaia was launched back in 2013 and started collecting data in July. It will take almost two more years before it returns its first big results in astrometry, but it's already found its first supernova and is working just as expected.

Gaia will return the data set of a lifetime. It's the manifestation of a dream when astronomers looked at Hipparcos and said, "Yes, but we can do even better." Now astronomers right here, right now, are looking at JWST, the pinnacle of space observatories, and thinking the same thing. Imagine what we'll be imagining in twenty more years.

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