MOFFET FIELD, Calif. — NASA’s Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet’s surface, but they are the smallest exoplanets ever confirmed around a star like our sun.

The discovery marks the next important milestone in the ultimate search for planets like Earth. The new planets are thought to be rocky. Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth. Kepler-20f is a bit larger than Earth, measuring 1.03 times its radius. Both planets reside in a five-planet system called Kepler-20, approximately 1,000 light-years away in the constellation Lyra.

Kepler-20e orbits its parent star every 6.1 days and Kepler-20f every 19.6 days. These short orbital periods mean very hot, inhospitable worlds. Kepler-20f, at 800 degrees Fahrenheit, is similar to an average day on the planet Mercury. The surface temperature of Kepler-20e, at more than 1,400 degrees Fahrenheit, would melt glass.

“The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone,” said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a new study published in the journal Nature. “This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.”

The Kepler-20 system includes three other planets that are larger than Earth but smaller than Neptune. Kepler-20b, the closest planet, Kepler-20c, the third planet, and Kepler-20d, the fifth planet, orbit their star every 3.7, 10.9 and 77.6 days. All five planets have orbits lying roughly within Mercury’s orbit in our solar system. The host star belongs to the same G-type class as our sun, although it is slightly smaller and cooler.

The system has an unexpected arrangement. In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large.

“The Kepler data are showing us some planetary systems have arrangements of planets very different from that seen in our solar system,” said Jack Lissauer, planetary scientist and Kepler science team member at NASA’s Ames Research Center in Moffett Field, Calif. “The analysis of Kepler data continue to reveal new insights about the diversity of planets and planetary systems within our galaxy.”

Scientists are not certain how the system evolved but they do not think the planets formed in their existing locations. They theorize the planets formed farther from their star and then migrated inward, likely through interactions with the disk of material from which they originated. This allowed the worlds to maintain their regular spacing despite alternating sizes.

The Kepler space telescope detects planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets crossing in front, or transiting, their stars. The Kepler science team requires at least three transits to verify a signal as a planet.

The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field Kepler observes in the constellations Cygnus and Lyra can be seen only from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

To validate Kepler-20e and Kepler-20f, astronomers used a computer program called Blender, which runs simulations to help rule out other astrophysical phenomena masquerading as a planet.

On Dec. 5 the team announced the discovery of Kepler-22b in the habitable zone of its parent star. It is likely to be too large to have a rocky surface. While Kepler-20e and Kepler-20f are Earth-size, they are too close to their parent star to have liquid water on the surface.

“In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time,” said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University. “We are on the edge of our seats knowing that Kepler’s most anticipated discoveries are still to come.”

NASA’s Ames Research Center in Moffett Field, Calif., manages Kepler’s ground system development, mission operations and science data analysis. JPL managed the Kepler mission’s development.

Ball Aerospace and 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 is funded by NASA’s Science Mission Directorate at the agency’s headquarters in Washington.

For more information about the Kepler mission and to view the digital press kit, visit: http://www.nasa.gov/kepler

A mission recap and lots of planets to view.

Planets on parade as we prepare for Curiosity Rover launch

Trajectory of Asteroid 2005 YU55 - November 8-9, 2011
Click on image for animation

Near-Earth asteroid 2005 YU55 will pass within 0.85 lunar distances from the Earth on November 8, 2011. The upcoming close approach by this relatively large 400 meter-sized, C-type asteroid presents an excellent opportunity for synergistic ground-based observations including optical, near infrared and radar data. The attached animated illustration shows the Earth and moon flyby geometry for November 8th and 9th when the object will reach a visual brightness of 11th magnitude and should be easily visible to observers in the northern and southern hemispheres. The closest approach to Earth and the Moon will be respectively 0.00217 AU and 0.00160 AU on 2011 November 8 at 23:28 and November 9 at 07:13 UT.

Discovered December 28, 2005 by Robert McMillan of the Spacewatch Program near Tucson Arizona, the object has been previously observed by Mike Nolan, Ellen Howell and colleagues with the Arecibo radar on April 19-21, 2010 and shown to be a very dark, nearly spherical object 400 meters in diameter. Because of its approximate 20-hour rotation period, ideal radar observations should include tracks that are 8 hours or longer on multiple dates at Goldstone (November 3-11) and when the object enters Arecibo’s observing window on November 8th.

Using the Goldstone radar operating in a relatively new “chirp” mode, the November 2011 radar opportunity could result in a shape model reconstruction with a resolution of as fine as 4 meters. Several days of high resolution imaging (about 7.5 meters) are also planned at Arecibo. As well as aiding the interpretation of the radar observations, collaborative visual and near infrared observations could define the object’s rotation characteristics and provide constraints upon the nature of the object’s surface roughness and mineral composition.

Since the asteroid will approach the Earth from the sunward direction, it will be a daylight object until the time of closest approach. The best time for new ground-based optical and infrared observations will be late in the day on November 8, after 21:00 hours UT from the eastern Atlantic and western Africa zone. A few hours after its close Earth approach, it will become generally accessible for optical and near-IR observations but will provide a challenging target because of its rapid motion across the sky.

Trajectory of Asteroid 2005 YU55 - November 9, 2011

Although classified as a potentially hazardous object, 2005 YU55 poses no threat of an Earth collision over at least the next 100 years. However, this will be the closest approach to date by an object this large that we know about in advance and an event of this type will not happen again until 2028 when asteroid (153814) 2001 WN5 will pass to within 0.6 lunar distances.

Join a live conversation with Brian Greene, exploring how scientists are piecing together the most complete picture yet of space, time, and the Universe.

Held at at Columbia University’s Miller Theatre, the event begins at 9 PM with the premiere broadcast of the first episode of NOVA’s The Fabric of the Cosmos, followed immediately by a live Q&A hosted by Greene, with special guests including renowned theoretical physicist Leonard Susskind and Saul Perlmutter, winner of the 2011 Nobel Prize in Physics.

The Q&A will also be streamed live as an interactive webcast at 10PM ET/9PM CT at www.worldsciencefestival.com:

•Get the conversation going now and ask your questions via Twitter (using hashtag #WSFforum), or submit questions on the World Science Festival Facebook wall

•Tune in to the live webcast at worldsciencefestival.com on Nov. 2 at 10pm ET and submit your questions live during the webcast »

The Fabric of the Cosmos
Acclaimed physicist Brian Greene reveals a mind-boggling reality beneath the surface of our everyday world. Airing 11/2, 11/9, 11/16 and 11/23, at 9pm on PBS

Program Description
“The Fabric of the Cosmos,” a four-hour series based on the book by renowned physicist and author Brian Greene, takes us to the frontiers of physics to see how scientists are piecing together the most complete picture yet of space, time, and the universe. With each step, audiences will discover that just beneath the surface of our everyday experience lies a world we’d hardly recognize—a startling world far stranger and more wondrous than anyone expected.

Brian Greene is going to let you in on a secret: We’ve all been deceived. Our perceptions of time and space have led us astray. Much of what we thought we knew about our universe—that the past has already happened and the future is yet to be, that space is just an empty void, that our universe is the only universe that exists—just might be wrong.

Interweaving provocative theories, experiments, and stories with crystal-clear explanations and imaginative metaphors like those that defined the groundbreaking and highly acclaimed series “The Elegant Universe,” “The Fabric of the Cosmos” aims to be the most compelling, visual, and comprehensive picture of modern physics ever seen on television.

A map of the morning sky on Saturday, Oct. 22nd at 5:30 a.m. local time, viewed facing southeast.

Weekend Meteor Shower Oct. 20, 2011: Earth is about to pass through a stream of debris from Halley’s comet, source of the annual Orionid meteor shower. Forecasters expect more than 15 meteors per hour to fly across the sky on Saturday morning, Oct. 22nd, when the shower peaks.

Orionids are most easily seen during the dark hours before sunrise. Twilight Orionids, however, are the most beautiful of all. “Although this isn’t the biggest meteor shower of the year, it’s definitely worth waking up for,” says Bill Cooke of the NASA Meteoroid Environment Office. “The setting is dynamite.”

Orionids are framed by some of the brightest and most beautiful constellations in the night sky. The meteors emerge from mighty Orion, the shower’s glittering namesake. From there they streak through Taurus the Bull, the twins of Gemini, Leo the Lion, and Canis Major–home to Sirius, the most brilliant star of all.

This year, the Moon and Mars are part of the show. They’ll form two vertices of a celestial triangle in the eastern sky on Saturday morning while the shower is most active; Regulus is the third vertex. Blue Regulus and red Mars are both approximately of 1st magnitude, so they are easy to see alongside the 35% crescent Moon. Many Orionids will be diving through the triangle in the hours before dawn.

Cooke’s team at the Meteoroid Environment Office will be watching for Orionids that actually hit the Moon.

Cometary debris streams like Halley’s are so wide, the whole Earth-Moon system fits inside. So when there is a meteor shower on Earth, there’s usually one on the Moon, too. Unlike Earth, however, the Moon has no atmosphere to intercept meteoroids. Pieces of debris fall all the way to the surface and explode where they hit. Flashes of light caused by thermal heating of lunar rocks and moondust are so bright, they can sometimes be seen through backyard-class telescopes.

“Since we began our monitoring program in 2005, our group has detected more than 250 lunar meteors,” says Cooke. “Some explode with energies exceeding hundreds of pounds of TNT.”

So far, they’ve seen 15 Orionids hitting the Moon–”two in 2007, four in 2008, and nine in 2009,” recalls Cooke. This year they hope to add to the haul. About 25% of the Moon’s dark terrain will be exposed to Halley’s debris stream, giving the team millions of square miles to scan for explosions.

Watching meteoroids hit the Moon is a good way to learn about the structure of comet debris streams and the energy of the particles therein. It also allows Cooke and colleagues to calculate risk factors for astronauts who, someday, will walk on the lunar surface again.

“Going outside to watch the Orionids might not be a good idea for a moonwalker,” says Cooke.

But it is a good idea for the rest of us. Set your alarm for a few hours before dawn on Saturday morning and enjoy the show.

Author: Dr. Tony Phillips | Credit: Science@NASA

Look for moons and meteors this month!

Enjoy a tour of lunar landing sites as NASA’s GRAIL mission launches to the moon this month.