Kepler finds Earth-sized planet in habitable zone 500ly away

[Borgholio]

https://www.nasa.gov/ames/kepler/nasas- ... other-star

Using NASA's Kepler Space Telescope, astronomers have discovered the first Earth-size planet orbiting a star in the "habitable zone" -- the range of distance from a star where liquid water might pool on the surface of an orbiting planet. The discovery of Kepler-186f confirms that planets the size of Earth exist in the habitable zone of stars other than our sun.

While planets have previously been found in the habitable zone, they are all at least 40 percent larger in size than Earth and understanding their makeup is challenging. Kepler-186f is more reminiscent of Earth.

The diagram compares the planets of our inner solar system to Kepler-186, a five-planet star system about 500 light-years from Earth in the constellation Cygnus. The five planets of Kepler-186 orbit an M dwarf, a star that is is half the size and mass of the sun.

"The discovery of Kepler-186f is a significant step toward finding worlds like our planet Earth," said Paul Hertz, NASA's Astrophysics Division director at the agency's headquarters in Washington. "Future NASA missions, like the Transiting Exoplanet Survey Satellite and the James Webb Space Telescope, will discover the nearest rocky exoplanets and determine their composition and atmospheric conditions, continuing humankind's quest to find truly Earth-like worlds."

Although the size of Kepler-186f is known, its mass and composition are not. Previous research, however, suggests that a planet the size of Kepler-186f is likely to be rocky.

"We know of just one planet where life exists -- Earth. When we search for life outside our solar system we focus on finding planets with characteristics that mimic that of Earth," said Elisa Quintana, research scientist at the SETI Institute at NASA's Ames Research Center in Moffett Field, Calif., and lead author of the paper published today in the journal Science. "Finding a habitable zone planet comparable to Earth in size is a major step forward."

Kepler-186f resides in the Kepler-186 system, about 500 light-years from Earth in the constellation Cygnus. The system is also home to four companion planets, which orbit a star half the size and mass of our sun. The star is classified as an M dwarf, or red dwarf, a class of stars that makes up 70 percent of the stars in the Milky Way galaxy.

"M dwarfs are the most numerous stars," said Quintana. "The first signs of other life in the galaxy may well come from planets orbiting an M dwarf."

Kepler-186f orbits its star once every 130-days and receives one-third the energy from its star that Earth gets from the sun, placing it nearer the outer edge of the habitable zone. On the surface of Kepler-186f, the brightness of its star at high noon is only as bright as our sun appears to us about an hour before sunset.

"Being in the habitable zone does not mean we know this planet is habitable. The temperature on the planet is strongly dependent on what kind of atmosphere the planet has," said Thomas Barclay, research scientist at the Bay Area Environmental Research Institute at Ames, and co-author of the paper. "Kepler-186f can be thought of as an Earth-cousin rather than an Earth-twin. It has many properties that resemble Earth."

The four companion planets, Kepler-186b, Kepler-186c, Kepler-186d, and Kepler-186e, whiz around their sun every four, seven, 13, and 22 days, respectively, making them too hot for life as we know it. These four inner planets all measure less than 1.5 times the size of Earth.

The next steps in the search for distant life include looking for true Earth-twins -- Earth-size planets orbiting within the habitable zone of a sun-like star -- and measuring the their chemical compositions. The Kepler Space Telescope, which simultaneously and continuously measured the brightness of more than 150,000 stars, is NASA's first mission capable of detecting Earth-size planets around stars like our sun.

Ames is responsible for Kepler's ground system development, mission operations, and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and was funded by the agency's Science Mission Directorate.

The SETI Institute is a private, nonprofit organization dedicated to scientific research, education and public outreach. The mission of the SETI Institute is to explore, understand and explain the origin, nature and prevalence of life in the universe.

For more information about the Kepler mission, visit:

http://www.nasa.gov/kepler

Very cool!

[Iroscato]

That article is over a year old. Did you mean this one old chap?

http://www.nasa.gov/press-release/nasa- ... n-to-earth

NASA's Kepler mission has confirmed the first near-Earth-size planet in the “habitable zone” around a sun-like star. This discovery and the introduction of 11 other new small habitable zone candidate planets mark another milestone in the journey to finding another “Earth.”

The newly discovered Kepler-452b is the smallest planet to date discovered orbiting in the habitable zone -- the area around a star where liquid water could pool on the surface of an orbiting planet -- of a G2-type star, like our sun. The confirmation of Kepler-452b brings the total number of confirmed planets to 1,030.

"On the 20th anniversary year of the discovery that proved other suns host planets, the Kepler exoplanet explorer has discovered a planet and star which most closely resemble the Earth and our Sun," said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate at the agency’s headquarters in Washington. “This exciting result brings us one step closer to finding an Earth 2.0."

Kepler-452b is 60 percent larger in diameter than Earth and is considered a super-Earth-size planet. While its mass and composition are not yet determined, previous research suggests that planets the size of Kepler-452b have a good chance of being rocky.

While Kepler-452b is larger than Earth, its 385-day orbit is only 5 percent longer. The planet is 5 percent farther from its parent star Kepler-452 than Earth is from the Sun. Kepler-452 is 6 billion years old, 1.5 billion years older than our sun, has the same temperature, and is 20 percent brighter and has a diameter 10 percent larger.

“We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment," said Jon Jenkins, Kepler data analysis lead at NASA's Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b. "It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”

To help confirm the finding and better determine the properties of the Kepler-452 system, the team conducted ground-based observations at the University of Texas at Austin's McDonald Observatory, the Fred Lawrence Whipple Observatory on Mt. Hopkins, Arizona, and the W. M. Keck Observatory atop Mauna Kea in Hawaii. These measurements were key for the researchers to confirm the planetary nature of Kepler-452b, to refine the size and brightness of its host star and to better pin down the size of the planet and its orbit.

The Kepler-452 system is located 1,400 light-years away in the constellation Cygnus. The research paper reporting this finding has been accepted for publication in The Astronomical Journal.

In addition to confirming Kepler-452b, the Kepler team has increased the number of new exoplanet candidates by 521 from their analysis of observations conducted from May 2009 to May 2013, raising the number of planet candidates detected by the Kepler mission to 4,696. Candidates require follow-up observations and analysis to verify they are actual planets.

Twelve of the new planet candidates have diameters between one to two times that of Earth, and orbit in their star's habitable zone. Of these, nine orbit stars that are similar to our sun in size and temperature.

“We've been able to fully automate our process of identifying planet candidates, which means we can finally assess every transit signal in the entire Kepler dataset quickly and uniformly,” said Jeff Coughlin, Kepler scientist at the SETI Institute in Mountain View, California, who led the analysis of a new candidate catalog. “This gives astronomers a statistically sound population of planet candidates to accurately determine the number of small, possibly rocky planets like Earth in our Milky Way galaxy.”

These findings, presented in the seventh Kepler Candidate Catalog, will be submitted for publication in the Astrophysical Journal. These findings are derived from data publicly available on the NASA Exoplanet Archive.

Scientists now are producing the last catalog based on the original Kepler mission’s four-year data set. The final analysis will be conducted using sophisticated software that is increasingly sensitive to the tiny telltale signatures of Earth-size planets.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

[Simon_Jester]

I really wish someone would do estimates of whether our instruments are good enough to arrive at negative conclusions. For instance, "yes, we are pretty sure Alpha Centauri doesn't have any planets larger than X or closer to the star(s) than Y."

Because as it stands we keep spotting exoplanets at varying ranges, but it would almost as useful, perhaps in the long run vastly more useful, to know whether the star systems immediately around us have any planets or not.

[Irbis]

I really wish someone would do estimates of whether our instruments are good enough to arrive at negative conclusions. For instance, "yes, we are pretty sure Alpha Centauri doesn't have any planets larger than X or closer to the star(s) than Y."

Because as it stands we keep spotting exoplanets at varying ranges, but it would almost as useful, perhaps in the long run vastly more useful, to know whether the star systems immediately around us have any planets or not.

Oh, people do that. In fact, last 50 years of observation of Barnard's Star was spent doing just that:

https://en.wikipedia.org/wiki/Barnard%2 ... ary_system

The problem is, Barnard's Star is second closest star system to Earth with by far smallest star in our neighbourhood. Doing that with larger, farther away stars is not so conclusive because even if we note say Wolf 359 or Lalande 21185 don't have any Jupiters around, excluding Earth sized targets is far more difficult. Much like proving existence is easier than proving not existence.

[Borgholio]

That article is over a year old. Did you mean this one old chap?

Oh frakking hell. Thanks. :-/

[SpottedKitty]

For instance, "yes, we are pretty sure Alpha Centauri doesn't have any planets larger than X or closer to the star(s) than Y."

I'm not sure it would ever be possible to make a firm statement like that with current detection techniques. The most reliable methods include detecting a pattern of red/blue shift in the light from a star, because orbiting planets tug it very slightly back and forth, and detecting the very slight reduction in light when a planet passes in front of a star.

How well this works, or even whether it works at all, depends on which way round the planets' orbits are aligned, relative to our viewing position here on Earth. The first method I described doesn't work well if we're looking down onto the plane of the planet's orbit, since red/blue shift only happens if the star's wobble is towards/away from us; wobbling sideways makes precisely zero light shift.

The other method only works if the planet's orbit is perfectly aligned so it passes in front of the star. The mere fact that we've detected quite a few planets like this can only mean there are a lot more planets that will never be detectable this way.

There are other methods, of varying efficiency, but they all have similar limitations. This means there are a lot of planets that can never be detected unless we go there and look (method left as an exercise for the student), or unless some better long range detection techniques come along.

[Guardsman Bass]

I really wish someone would do estimates of whether our instruments are good enough to arrive at negative conclusions. For instance, "yes, we are pretty sure Alpha Centauri doesn't have any planets larger than X or closer to the star(s) than Y."

Because as it stands we keep spotting exoplanets at varying ranges, but it would almost as useful, perhaps in the long run vastly more useful, to know whether the star systems immediately around us have any planets or not.

We're getting to that with new telescopes and better use of the existing ones. Kepler has been excellent, but it's ultimately limited to a particular patch of the sky and systems that it sees edge-on. TESS is supposed to be able to see in all directions, surveying thousands of the nearest stars to see if they have any planets (presumably including the Alpha Centauri binary).

As for Kepler-452b, I'm skeptical that it's habitable. It's on the wrong side of the 1.5 Earth radius threshold for rocky planets, and it gets higher than Earth-level solar flux. Even NASA's been qualifying it with the remark "higher chance of being rocky than not", because there's a not insignificant chance that it's a lifeless rock with a thick, hot hydrogen-helium atmosphere.

[wautd]

It's been a good month for space exploration.

[Starglider]

The New Worlds Mission i.e. a precision starshade for the James Webb Space Telescope is AFAIK the most credible near-term concept for direct imaging of (a decent number of) extrasolar planets.

[Guardsman Bass]

One of the scientists involved with the StarShade project has a very good TED talk on the proposal, and why it would help.

Even without it, JWST might be able to direct image some nearby plants. It's supposedly getting fit with a coronagraph.