Yale finds a low-density planet that won’t stick to a schedule

Yale finds a low-density planet that won’t stick to a schedule

ober 29, 2014

(Illustration by Michael S. Helfenbein)

For their latest discovery, Yale astronomers and the Planet Hunter program have found a low-mass, low-density planet with a punctuality problem.

The new planet, called PH3c, is located 2,300 light years from Earth and has an atmosphere loaded with hydrogen and helium. It is described in the Oct. 29 online edition of The Astrophysical Journal.

The elusive orb nearly avoided detection. This is because PH3c has a highly inconsistent orbit time around its sun, due to the gravitational influence of other planets in its system. “On Earth, these effects are very small, only on the scale of one second or so,” said Joseph Schmitt, a Yale graduate student and first author of the paper. “PH3c’s orbital period changed by 10.5 hours in just 10 orbits.”

That inconsistency kept it from being picked up by automated computer algorithms that search stellar light curves and identify regular dips caused by objects passing in front of stars.

Luckily, Planet Hunters came to the rescue. The program, which has found more than 60 planet candidates since 2010, enlists citizen scientists to check survey data from the Kepler spacecraft. Planet Hunters recently unveiled a new website and an expanded scientific mission.

“It harnesses the human dimension of science,” said Debra Fischer, who leads the exoplanets group at Yale and is a co-author of the paper. “Computers can’t find the unexpected, but people can, when they eyeball the data.”

More than 300,000 volunteers are part of Planet Hunters, which is coordinated by Yale and the University of Oxford. The program’s revamped website will allow Planet Hunters to analyze data more quickly than before, Fischer said. In addition, Planet Hunters is launching an effort to see if there is a correlation between types of stars and the planets that form around them.

“I think we’ll be able to contribute some really unique science this way,” Fischer said.

Not only did Planet Hunters spot PH3c, but the discovery also enabled astronomers to better characterize two other planets — one on each side of PH3c. An outer planet, PH3d, is slightly larger and heavier than Saturn, for example. An inner planet, PH3b, may have a rocky composition, like Earth.

“Finding the middle planet was key to confirming the others and allowing us to find their masses,” Schmitt said. “The outer planet’s orbital period also changes slightly, by about 10 minutes. You need to see both planets’ changing orbital periods in order to find out the masses of the planets. One planet doesn’t give enough information.”

There’s also a quirky aspect of the planetary trio, Schmitt added. The outer planet’s year is 1.91 times longer than the middle planet’s year, and the middle planet’s year is 1.91 times longer than the inner planet’s year.

“We’re not sure if this is just a coincidence or whether this might tell us something about how the planets were formed,” Schmitt said.

For more information about Planet Hunters, visit the website.

(Photo via Shutterstock)

Earth-Size Planet Found In The 'Habitable Zone' of Another Star

April 17, 2014: Using NASA's Kepler Space Telescope, astronomers have discovered the first Earth-size planet orbiting in the "habitable zone" of another star. The planet, named "Kepler-186f" orbits an M dwarf, or red dwarf, a class of stars that makes up 70 percent of the stars in the Milky Way galaxy. The discovery of Kepler-186f confirms that planets the size of Earth exist in the habitable zone of stars other than our sun.

The "habitable zone" is defined as the range of distances from a star where liquid water might pool on the surface of an orbiting planet. While planets have previously been found in the habitable zone, the previous finds 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 artist's concept depicts Kepler-186f , the first validated Earth-size planet to orbit a distant star in the habitable zone.  More

Kepler-186f orbits its parent M dwarf star once every 130-days and receives one-third the energy 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.

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

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

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: 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 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.  More

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.

"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.

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.

Looking ahead, Hertz said, "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."

Credits:

Production editor: Dr. Tony Phillips | Credit: Science@NASA

More information:

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