NASA’s Kepler detects first Earth-size planets 1,000 light years away

21 Dec 2011

Today is Winter Solstice and NASA has added another cosmic treat to 21 December as its Kepler mission has just discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The discovery signals the next important milestone in the ultimate search for planets like planet Earth, believes the space-exploration agency.

NASA has confirmed that the planets, which it is naming 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 it believes they are the smallest planets ever confirmed around a star like our sun.

Computer programme Blender to validate the planets

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

NASA has been making some newsworthy planetary discoveries of late. Just on 5 December, the Kepler mission, which launched from Cape Canaveral Air Force Station in Florida on 6 March 2009, discovered a new planet (Kepler 22-b), which could potentially offer the best scope yet for a new human abode, other than planet Earth, giving much people hope we can one day branch out into our galaxy.

But back to the new planets NASA has just discovered: Kepler-20e and Kepler-20f. The new planets are thought to be rocky at this point.

According to NASA:

  • Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth, while Kepler-20f is slightly larger than Earth, measuring 1.03 times its radius.
  • Both planets reside in a five-planet system called Kepler-20, about 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,” said NASA last night.

“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, Massachusetts, the lead author of a new study published in the journal Nature, in response to NASA’s planetary discoveries.

“This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.”

  • 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, according to NASA’s Kepler data.

Kepler 22-b a new planet discovered by NASA on 5 December 2011. This planet could potentially host humans

Kepler 22-b, depicted above by an artist, is a new planet discovered by NASA on 5 December 2011. This planet could potentially host humans. NASA believes this planet is too large to have a rocky surface. It is 600 light years away from planet Earth

Unusual arrangement of the planets

NASA said 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 organised in alternating size: large, small, large, small and large,” a NASA spokesperson said last night.

“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, California. “The analysis of Kepler data continue to reveal new insights about the diversity of planets and planetary systems within our galaxy.”

How the planets evolved …

Scientists are not yet certain how the system evolved but they do not think the planets formed in their existing locations.

NASA explained that scientists theorise 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 autumn. The data from these other observations help determine which candidates can be validated as planets, according to NASA.

The Kepler planetary discoveries this December

The discovery of Kepler-22b in the habitable zone of its parent star is likely to be too large to have a rocky surface, said NASA yesterday.

“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.”

Carmel Doyle was a long-time reporter with Silicon Republic