Spitzer telescope finds one of the most distant planets ever

Chuck Bednar for redOrbit.com – @BednarChuck

Thanks to NASA’s Spitzer Space Telescope and a technique known as microlensing, a team of astronomers has located one of the most distant exoplanets ever discovered – a remote gas planet located approximately 13,000 light-years from Earth.

The location of this far-off new world demonstrates how Spitzer can be used to help determine how planets are distributed throughout the Milky Way, according to NASA. The discovery is the topic of three new studies published recently in The Astrophysical Journal.

Using microlensing to discover new worlds

Jennifer Yee, a NASA Sagan research fellow and a member of the Harvard-Smithsonian Center for Astrophysics in Massachusetts, and her colleagues used both the space-based instrument and the Optical Gravitational Lensing Experiment (OGLE) Warsaw Telescope in Chile to search for new planets by taking advantage of a phenomenon known as microlensing.

Microlensing, the US space agency explains, occurs when one star passes in front of another. Its gravity acts like a lens to magnify and brighten the light of the more distant star, and if the star in the foreground has a planet it orbit around it, it can cause a blip in the magnification.

Those blips can be used by astronomers to locate and characterize planets tens of thousands of light-years away in our galaxy’s central bulge, where these star-crossing events tend to be more common. To date, the process has led to the discovery of nearly 30 new planets, with the farthest of the new worlds resting approximately 25,000 light years away, the agency noted.

“Microlensing experiments are already detecting planets from the solar neighborhood to almost the center of the Milky Way,” explained co-author Andrew Gould of the Ohio State University in Columbus . “And so they can, in principle, tell us the relative efficiency of planet formation across this huge expanse of our galaxy.”

Monitoring a microlensing event

While the microlensing technique can be used to complement other planet-hunting tools such as the Kepler mission, it has one major drawback: it cannot always precisely determine the distance of the planets and stars that are being observed. In fact, of the nearly 30 planets that have been located to date using this method, about half cannot be placed at an exact location.

To help out, researchers use Spitzer and take advantage of the telescope’s remote Earth-trailing orbit. The instrument monitors a microlensing event at a distance of about 128 million miles (207 million kilometers) away at the same time as a telescope on the surface, but it sees the brightness at a different time due to the distance between the two telescopes. This is known as parallax.

Yee said that Spitzer is “the first space telescope to make a microlens parallax measurement for a planet,” and that typically, parallax techniques use multiple ground-based telescopes. The length of the microlensing event used to discover the newfound exoplanet was unusually long (a period of about 150 days), with Spitzer seeing it 20 days after OGLE, NASA said.

The time delay between OGLE’s viewing of the event and Spitzer’s was used to calculate how far away the star and its planet were, and knowing that also enabled the researchers to figure out the mass of the planet, which is approximately half that of Jupiter. It was the 23rd microlensing collaboration between Ogle and Spitzer, and the space-based telescope is currently scheduled to observe an additional 120 microlensing events over the course of the summer.

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Source: http://www.redorbit.com/news/space/1113372606/spitzer-telescope-finds-one-of-most-distant-planets-ever-041615/