An artist’s conception portrays the first planet discovered by the Kepler spacecraft during its K2 mission. A transit of the planet was teased out of K2’s noisier data using ingenious computer algorithms. The newfound planet, HIP 116454b, has a diameter of 20,000 miles (2.5 times the width of Earth).

In may 2013 we saw the end of an era. NASA’s Kepler Space Telescope, which was responsible for discovering nearly 1,000 alien worlds (and another 3,200 that are awaiting confirmation) stopped working. Before Kepler, we conceived of the universe as a place with an indeterminate number of planets. Indeed, 20 years ago we didn’t know of any exoplanets (planets that orbit alien suns). Now we know of thousands. And although we can’t be sure of the exact number of alien worlds, we now believe that nearly every star has at least one planet (probably more).

All thanks to Kepler. And now, it’s back.

NASA announced that Kepler had been revived, thanks to a bit of scientific ingenuity. And yesterday they stated that it had discovered another planet. This beauty is called HIP 116454b, and it is a “super Earth.” These planets are worlds that are rocky bodies (like our own) that are simply massive. This one in particular is about 2.5 times larger than our home planet. It lies 180 light-years from Earth, in the constellation Pisces — which is close enough to be studied by other instruments.

And the dicovery made a few at NASA wax poetic. “Like a phoenix rising from the ashes, Kepler has been reborn and is continuing to make discoveries. Even better, the planet it found is ripe for follow-up studies.” lead author Andrew Vanderburg, of the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement.

HIP 116454b is about 20,000 miles wide (32,000 km) and is 12 times more massive than Earth, scientists said. For comparison, Earth’s equatorial diameter is 7,926 miles (12,756 kilometers). The density of the alien world suggests that it is either primarily covered by water or is a “mini Neptune” with a large, thick atmosphere. This means that it obviously would be a good place for our kind of life.

Moreover, HIP 116454b lies just 8.4 million miles from its host star (13.5 million km), an “orange dwarf” slightly smaller and cooler than the sun, and completes one orbit every 9.1 Earth-days. So this planet is really uninhabitable for our kind of life. We all know how hostile Mercury is, the closest planet to our own Sun. But Mercury is 35.9 million miles from the Sun (57.9 million km). That’s leagues away when compared to HIP.

Kepler is able to locate planets by use of the “transit method,” which means that the little craft watches for the telltale dimming that is caused when a planet crossed in front of its parent star (this crossing is known as a “transit”). In order to accomplish this, Kepler needs to keep a steady eye on a very precise point, and this is an ability that the spacecraft lost in 2013, when the second of its four orientation-maintaining reaction wheels failed.

However, the Kepler team devised a way to increase Kepler’s stability by using the subtle pressure of sunlight, then proposed a new mission called K2, which would continue Kepler’s exoplanet hunt in a limited fashion. But “limited” is a subjective term.

Kepler K2 mission. Image credit: NASA

“The Kepler mission showed us that planets larger in size than Earth and smaller than Neptune are common in the galaxy, yet they are absent in our solar system,” said Steve Howell, Kepler/K2 project scientist at NASA’s Ames Research Center in Moffett Field, California. “K2 is uniquely positioned to dramatically refine our understanding of these alien worlds and further define the boundary between rocky worlds like Earth and ice giants like Neptune.”

Since the K2 mission officially began in May 2014, it has observed more than 35,000 stars and collected data on star clusters, dense star-forming regions, and several planetary objects within our own solar system. It is currently in its third campaign.

The research paper reporting this discovery has been accepted for publication in The Astrophysical Journal.


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