This amazing map shows just how little of our galaxy we’ve explored so far

This amazing map shows just how little of our galaxy we’ve explored so far
Using NASA’s Spitzer Space Telescope and the Optical Gravitational Lensing Experiment (OLGE), astronomers have discovered a planet that’s roughly 13,000 light-years from Earth — one of the furthest ever such exoplanets ever discovered.

Using NASA’s Spitzer Space Telescope and the Optical Gravitational Lensing Experiment (OLGE), astronomers have discovered a planet that’s roughly 13,000 light-years from Earth — one of the furthest ever such exoplanets ever discovered. The official name for it is OGLE-2014-BLG-0124L, which like most of these, rolls right off the tongue. Not much is known about this planet other than the fact that it’s a gas giant.

Coinciding with the discovery, NASA/JPL has released an artist’s rendering of a map showing exactly where we’ve found exoplanets to date. It’s amazing: We’ve barely scratched the surface of our own galaxy, which is 100,000 light-years across, even after finding more than 1,800 exoplanets so far (and 4,600 other possible suspects). Each time we get a little push or bump in technology or search methods, we’re able to push our search that much further out.

There are many methods scientists use to find exoplanets, and nearly all of them are indirect in some way (i.e. not visibly observed). Let’s review three of the most common ones.

The ‘transit’ method: Scientists discovered the first exoplanets using ground telescopes and what’s called pulsar timing and radial velocity, but a more common method used since the turn of the century is the ‘transit’ method. It’s pretty simple; when a planet crosses in front of a star, that star dims ever so slightly. So going by the distance to that star, and the relative sizes of the star and planet, you can confirm a planet is orbiting a star by the regular, very small dips in brightness.

In the map below (click it for a larger version), most of the planets found this way are in the orange-pink circle around our Solar System. More recently, scientists are sifting through data from NASA’s Kepler space telescope, using the transit method and others to find possible candidates. Exoplanets found with Kepler are shown with the orange-pink “cone” that extends outward, representing the space telescope’s field of view.

Gravitational microlensing: Astronomers are also working with a technique called microlensing (illustrated below) to reach these further-out exoplanets, like the one that’s 13,000 light-years away. The gravitational field of the star acts like a lens that magnifies the light from a distant background star. If there’s a planet present, that will affect the results in an extremely tiny, but still detectable way. Exoplanets found with microlensing are in yellow. The furthest-out one we found so far is about 25,000 light years away, and sits just near the center of our galaxy.

Direct observation and imaging: This one is extremely tough with our current level of technology, and only relatively recently (2008) was it confirmed that the first exoplanet was found in this manner. In these cases, usually the planet is very young, emits infrared light, and is far enough from the glare of the star that you can pick it out.

We’re finding everything from so-called “super Earths” to hot Jupiters and massive gas giants. But all of this is not just about finding other worlds. There’s the search for exoplanets (and exomoons) in general, and then specifically the search for planets that could harbor alien life. For the latter, scientists have been looking in what’s called the ‘Goldilocks’ zone. And of course, we’re still looking within our own Solar System for alien lifeas well.

(Map image credit: NASA/JPL)