The discovery of an exoplanet nearly 13,000 light years away, one of the most distant ever detected, could pave the way for improved planet searchers in the future, astronomers say.

The detections of the gas giant planet about half the size of Jupiter, by NASA's Spitzer Space telescope working in tandem with a ground-based instrument in Chile, shows Spitzer can help solve the question of how planets are distributed around our home Milky Way galaxy, they say.

Astronomers have long debated whether planets are more likely to be concentrated in the central hub of our spiral galaxy or evenly distributed around its outer "suburbs."

"We don't know if planets are more common in our galaxy's central bulge or the disk of the galaxy, which is why these observations are so important," says Jennifer Yee of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

The newly detected planet goes by the rather unwieldy name of OGLE-2014-BLG-0124, and it is truly distant, Yee says.

"For context, most of the planets we do know about are a factor of 10-100 times closer than OGLE-2014-BLG-0124," she says.

The planet was detected through the phenomenon knows as "microlensing," in which gravity from one star bends the light coming from a more distant one.

If the nearer star has a planet orbiting it, that planet can create a "blip" in the microlensing — exactly as happened with the new exoplanet, the astronomers report in The Astrophysical Journal.

It marked the first time Spitzer was used to measure the microlensing shift for a planet, Yee says.

From our location in the Milky Way "suburbs" — around two-thirds of the distance out from our galaxy's center — microlensing has been used to detect around 30 exoplanets so far, the researchers say.

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

Other planet-hunting instruments, including NASA's Kepler mission, have detected more than a thousand planets closer to Earth, but determining their precise distances has proved difficult.

That's where Spitzer comes in; trailing Earth in the same orbit, but more than 120 million miles behind us, it can observe a microlensing occurrence also captured by telescopes on Earth.

The observations from two widely separated vantage points, much farther apart than any two telescopes on Earth, allows a precise measure of the distance to a distant planet through a technique known as parallax.

"Spitzer is the first space telescope to make a microlens parallax measurement for a planet," Yee says.

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