Here’s How NASA Discovers Potentially Habitable Exoplanets

Image courtesy of Kanijoman via Flickr.

NASA has discovered batches of potentially habitable exoplanets among hundreds of others similar to our own. What are the planets outside of our solar system like, and how are they discovered?

As designer Josh Worth’s “tediously accurate” scale model of the solar system demonstrates, our solar system’s planets are extremely far apart.

But as barely-graspable the hugeness of our own set-up is, beyond Pluto are more suns like ours, orbited by planets like ours: scattered gaseous dots in the incomprehensible expanse that is the universe.

The first planet discovered orbiting another sun (called an exoplanet) was announced in 1995, since which time more and more have been identified.

The Kepler Mission

NASA’s Kepler Mission was launched in 2009 to search a portion of the Milky Way Galaxy for exoplanets, specifically those around the size of Earth in habitable conditions.

As of January 2015, the confirmed amount of planets is nearly 1,795, with over 3,000 other exoplanet candidates.


As NASA’s chart demonstrates, discoveries in 2014 were remarkably substantial: almost as great as the last two decades combined.

How are the planets discovered and verified?

When a planet passes in front of the star it orbits, the light dips. Kepler looks at stars in the constellations Cygnus and Lyra and studies their brightness to detect these winks, measuring the variations of 100,000 stars every 30 minutes. This is called the “transit method” of exoplanet discovery.

Once detected, the planet’s orbit, mass, size, and even temperature can be determined depending on the time and depth of the orbit, as well as the characteristics of the sun. From these factors, scientists can determine if they are habitable exoplanets, NASA says.

All of these observations are made using the Kepler telescope, an instrument that measures star variation over the course of its mission.

The planets are confirmed through verification by multiplicity, which takes observations of stars with “planet candidates,” studies the hundreds with multiple candidates, and verifies planets from this sample using probability.

Habitable exoplanets

715 new planets were discovered in February of 2014 orbit 305 stars, an announcement by NASA stated, revealing many multi-planet solar systems much like our own.

While there has been previous evidence of gas giants, hot super-earths, and ice giants, 95 percent of planets discovered by the Kepler mission were smaller than Neptune, less than four times the size of Earth.

But four of these planets were less than 2.5 times the size of earth, as well as being in their sun’s habitable orbit zone — a place where there could feasibly be life-giving water.

In January of 2015, the discovery of 8 new potentially habitable exoplanets less than 2.7 times the size of earth were announced. Two of these appear to be the most Earth-like yet.

So, aliens? Or, even better — space colonies? It’s really impossible to say. But considering this is only within one small portion of the Milky Way, and billions of other galaxies have been located as far as 12 light years away, can we really rule out the possibility?

Originally published on March 19, 2014. 

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