Kepler-186f ~ The first known Earth-size planet to lie within the habitable zone of a star beyond the Sun. Discovered using data from the prolific planet-hunting Kepler spacecraft, the distant world orbits its parent star, a cool, dim, M dwarf star about half the size and mass of the Sun, some 500 light-years away from us, in the constellation Cygnus. While the size and orbit of Kepler-186f are known, its mass and composition are not, and can’t be determined by Kepler’s transit technique. (NASA)

An Exo-What...?

Simply put, an exoplanet is a planet that orbits another star. That said, just because a planet orbits a star (like Earth) does not mean that it is automatically stable for life. The planet must be within the habitable zone, which is the area around a star in which water has the potential to be liquid…aka not so close that all the water would evaporate, and not too far away where all the water would freeze.

Recently, with the help of our Kepler spacecraft, scientists have discovered the most Earth-like exoplanet ever, Kepler-452b. Pretty cool! This chart shows 12 other exoplanet discoveries that are less than twice the size of Earth, and live in the habitable zone of their host star. Kepler-452b is special because all previous findings have orbited stars that are smaller and cooler than Earth’s.

You may be thinking, “Okay, so what? There’s an Earth-like planet that spins around a similar sized sun.” Well, Kepler-452b orbits its sun at nearly the same distance from its star as Earth does from our sun, which means that conditions on the plant could be similar to those here on Earth!

We can already guess your next question…”When are we going to Kepler-452b?!” Well, this planet is located in the constellation Cygnus which is 1,400 light-years away, so not anytime soon. However, our Kepler spacecraft continues to search for Earth-like exoplanets and gather important scientific information about them.

Here’s an artist’s comparison of Earth and the newly discovered Earth-like planet Kepler-452b. Kepler-452b is a real dud of a name, so I’m going to refer to the planet as Henrietta* for the rest of this post.

Here’s what we know:

  • Henrietta is 60% larger than Earth, so its gravity is twice as strong
  • A year on Henrietta is 385 earth days
  • It’s a bit farther away from its sun, but its sun is larger and hotter. That means Henrietta orbits in a sweet spot – a region of space that is not too hot and not too cold – the kind of place that could foster life.
  • Henrietta’s star is in the Cygnus constellation, about about 1,400 light years away from Earth

“Exoplanets, especially small Earth-size worlds, belonged within the realm of science fiction just 21 years ago,” the NASA statement says. “Today, and thousands of discoveries later, astronomers are on the cusp of finding something people have dreamed about for thousands of years — another Earth.”

Scientists don’t know if [Henrietta] could be habitable. Aside from not knowing what the planet’s composition is, they also don’t know what its atmosphere might be like.

“This is the beginning of a very long journey,” said Didier Queloz, a professor of astrophysics at Cambridge University.

*There’s no official approval of this name, but if you know someone at the IAU, pass it along.



This very interesting planet discovered in January of this year is thought to be the most likely planet to contain alien life. It scores a 0.88 on the earth similarity index with a maximum of 1.00 being identical to earth. As well as this it its orbit around the sun is in what is known as the Goldilocks zone. This is the zone where it is just the right temperature for water to exist in its liquid form. This makes it highly likely to contain alien life.

Readings in NASA’s Kepler Telescope Data Show Strange Megastructures That Has Serious Exoplanetary Scientists Baffled

In the Northern hemisphere’s sky, hovering above the Milky Way, there are two constellations—Cygnus the swan, her wings outstretched in full flight, and Lyra, the harp that accompanied poetry in ancient Greece, from which we take our word “lyric.”

Between these constellations sits an unusual star, invisible to the naked eye, but visible to the Kepler Space Telescope, which stared at it for more than four years, beginning in 2009.

“We’d never seen anything like this star,” says Tabetha Boyajian, a postdoc at Yale. “It was really weird. We thought it might be bad data or movement on the spacecraft, but everything checked out.”

Kepler was looking for tiny dips in the light emitted by this star. Indeed, it was looking for these dips in more than 150,000 stars, simultaneously, because these dips are often shadows cast by transiting planets. Especially when they repeat, periodically, as you’d expect if they were caused by orbiting objects.

The Kepler Space Telescope collected a great deal of light from all of those stars it watched. So much light that Kepler’s science team couldn’t process it all with algorithms. They needed the human eye, and human cognition, which remains unsurpassed in certain sorts of pattern recognition. Kepler’s astronomers decided to found Planet Hunters, a program that asked “citizen scientists” to examine light patterns emitted by the stars, from the comfort of their own homes.

In 2011, several citizen scientists flagged one particular star as “interesting” and “bizarre.” The star was emitting a light pattern that looked stranger than any of the others Kepler was watching.

The light pattern suggests there is a big mess of matter circling the star, in tight formation. That would be expected if the star were young. When our solar system first formed, four and a half billion years ago, a messy disk of dust and debris surrounded the sun, before gravity organized it into planets, and rings of rock and ice.

But this unusual star isn’t young. If it were young, it would be surrounded by dust that would give off extra infrared light. There doesn’t seem to be an excess of infrared light around this star.

It appears to be mature.  

And yet, there is this mess of objects circling it. A mess big enough to block a substantial number of photons that would have otherwise beamed into the tube of the Kepler Space Telescope. If blind nature deposited this mess around the star, it must have done so recently. Otherwise, it would be gone by now. Gravity would have consolidated it, or it would have been sucked into the star and swallowed, after a brief fiery splash.

Boyajian, the Yale Postdoc who oversees Planet Hunters, recently published a paper describing the star’s bizarre light pattern. Several of the citizen scientists are named as co-authors. The paper explores a number of scenarios that might explain the pattern—instrument defects; the shrapnel from an asteroid belt pileup; an impact of planetary scale, like the one that created our moon.

The paper finds each explanation wanting, save for one. If another star had passed through the unusual star’s system, it could have yanked a sea of comets inward. Provided there were enough of them, the comets could have made the dimming pattern.

But that would be an extraordinary coincidence, if that happened so recently, only a few millennia before humans developed the tech to loft a telescope into space. That’s a narrow band of time, cosmically speaking.

And yet, the explanation has to be rare or coincidental. After all, this light pattern doesn’t show up anywhere else, across 150,000 stars. We know that somethingstrange is going on out there.

When I spoke to Boyajian on the phone, she explained that her recent paper only reviews “natural” scenarios. “But,” she said, there were “other scenarios” she was considering.

Jason Wright, an astronomer from Penn State University, is set to publish an alternative interpretation of the light pattern. SETI researchers have long suggested that we might be able to detect distant extraterrestrial civilizations, by looking for enormous technological artifacts orbiting other stars. Wright and his co-authors say the unusual star’s light pattern is consistent with a “swarm of megastructures,” perhaps stellar-light collectors, technology designed to catch energy from the star.

“When [Boyajian] showed me the data, I was fascinated by how crazy it looked,” Wright told me. “Aliens should always be the very last hypothesis you consider, but this looked like something you would expect an alien civilization to build.”

Boyajian is now working with Wright and Andrew Siemion, the Director of the SETI Research Center at the University of California, Berkeley. The three of them are writing up a proposal. They want to point a massive radio dish at the unusual star, to see if it emits radio waves at frequencies associated with technological activity.

If they see a sizable amount of radio waves, they’ll follow up with the Very Large Array (VLA) in New Mexico, which may be able to say whether the radio waves were emitted by a technological source, like those that waft out into the universe from Earth’s network of radio stations.

Assuming all goes well, the first observation would take place in January, with the follow-up coming next fall. If things go really well, the follow-up could happen sooner. “If we saw something exciting, we could ask the director for special allotted time on the VLA,” Wright told me. “And in that case, we’d be asking to go on right away.”

Recommended Further Reading: Phil Plait’s Take on The Findings


The Kepler Space Telescope has discovered the first planet similar in size to the Earth that is also in the potentially habitable zone of a star like the sun, NASA announced today. Kepler-452b rotates once around its star every 385 days some 1,400 light-years away from Earth in the constellation Cygnus. 

The planet, scientists say, has a better than even chance of being rocky and has an orbit the right distance from its star for liquid water to exist on the surface, a necessary prerequisite for life as we know it. See image captions below. Learn more here. 

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