February 27, 2014

The number of known exoplanets in the Milky Way Galaxy has nearly doubled, thanks to a new method of confirming planet candidates discovered by the Kepler space telescope. Mission control officials at NASA‘s Ames Research Center in Moffett Field, California, announced that they had identified 715 new planets, which raises the total number of alien planets to some 1,700. The research has also significantly increased the number of smaller exoplanets. About 95 percent of the new planets are smaller than Neptune, which is about 17 times as massive as Earth. Many exoplanets found previously were at least as massive as Jupiter, which is 318 times as massive as Earth. All of the newly discovered planets orbit one of 305 stars in a multiplanet system like the solar system.

Although Kepler’s original planet-hunting days are over–the telescope has been nonoperational since May 2013–mission scientists are still on the job. The new exoplanets were found in data collected during the telescope’s first two years in orbit, from 2009 to 2011. Kepler’s main mission was to search one section of the Milky Way for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Although Kepler searched over 150,000 stars for signs of orbiting planets, its search zone was actually quite small. Scientists estimate that the Milky Way alone has up to 200 billion stars.

All of the newly identified planets orbit a star in a multiplanet system, like the solar system. (NASA)

The new method of identifying planets is called validation by multiplicity. This method, which relies on the logic of probability, allows scientists to identify exoplanets in groups, rather than one by one. NASA officials compared the technique to the behavior of lions and lionesses living on the savannah. “In our imaginary savannah, the lions are the Kepler stars and the lionesses are the planet candidates,” the agency explained in a press release. “If you see two of the big cats it could be a lion (star) and a lioness (planet) or two lions. But if more than two large felines are gathered, then it is very likely to be a lion and his pride (star and its planets).”

Additional World Book articles:

• Binary star
• In Search of Other Worlds (a special report)
• Space exploration (2011) (a Back in Time article)

June 20, 2013

Kepler space telescope has turned up another 503 potential exoplanets, mission control officials at NASA‘s Ames Research Center in Moffett Field, California, announced recently. This brings to 3,216 the number of planet candidates detected by the orbiting probe since its launch in March 2009. Further investigation has confirmed that 132 of those objects are, in fact, extrasolar planets.

Unfortunately, Kepler’s planet-hunting days may be over. Since mid-May, Kepler has been nonoperational because of an equipment malfunction. At that time, mission controllers discovered that one of the craft’s reaction wheels was not working. These devices keep the craft aimed precisely in the right direction. Kepler, which needs three reaction wheels to operate properly, now has only two. Originally, the telescope carried a spare, but that device was put into service when another of the reaction wheels quit working in 2012.

A planet about the size of Saturn, known as Kepler-35b, orbits a binary star (pair of stars) in an artist's illustration of a planetary system discovered by Kepler.

Kepler’s main mission is to search one section of the Milky Way Galaxy for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Kepler has searched over 150,000 stars for signs of orbiting planets.

Additional World Book articles:

• Binary star
• Planet
• In Search of Other Worlds (a special report)
• Space exploration (2011) (a Back in Time article)

Dec. 21, 2011

The Kepler space telescope has spotted two Earth-sized planets orbiting a star about 1,000 light-years from Earth. The two planets are the smallest yet found orbiting a sun-like star. The smaller of the planets, named Kepler-20e, is about 0.87 times as large as Earth–about the size of Venus. Kepler-20e is the first extrasolar planet smaller than Earth to be discovered. The other, named Kepler-20f, is 1.03 times as large as Earth–slightly larger than Earth. Astronomers believe that the two planets orbit too close to the star to support life. The surface temperatures were reported to be about 800 °F (426 °C) on Kepler-20f and about 1,400 °F (760 °C) on Kepler-20e.

Kepler-20e is the first planet smaller than Earth to be discovered outside the solar system. It orbits its star in only six days. NASA/Ames/JPL-Caltech

The Kepler telescope was launched in March 2009. Its main mission is to search one section of our galaxy for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Kepler has searched over 150,000 stars for signs of orbiting planets. Earlier in December, the Kepler team announced the discovery of the first confirmed Earth-like planet in the habitable zone of another star. Scientists believe this planet is too large to have a solid rocky surface.

Although the three planets may not support life, the discoveries mark important steps in Kepler’s mission. Kepler’s ultimate goal is to spot a planet of similar size and temperature as Earth. At that point, scientists can study the planet with other instruments and techniques to determine if the planet does indeed have liquid water and, possibly, indications of life.

Additional World Book articles:

• COROT
• Kepler, Johannes
• Planet (Planets in other solar systems)
• Transit

Dec. 14, 2011

The Kepler space telescope has found the first confirmed Earth-like planet orbiting in the “habitable zone” of a distant star. The planet, named Kepler 22b, is about 2 ½ times as large as Earth. The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Kepler’s sole mission, since the spacecraft’s launch in 2009, has been to spot planets circling distant stars.

Since the first extrasolar planet was discovered in the mid-1990′s, scientists have uncovered thousands of planets orbiting stars other than the sun. Because larger objects are easier to spot, most of the planets discovered so far are giants, many times larger than Jupiter, the largest planet in the solar system. Scientists have no way of knowing at this point if Kepler 22b has life. They think it is more likely that the planet is rocky, like Earth, rather than gaseous, like Neptune. It could even be an ocean world. They have calculated that if the planet has an atmosphere, the temperature there could be a pleasant 72 °F (22 °C).

The discovery comes just as the Allen Telescope Array (ATA) operated by the SETI Institute is back in operation. The 42 telescopes in the ATA, which were shut down early in 2011 because of budgetary problems, scan the sky for radio signals that could be signals from extraterrestrial beings. Over the next two years, SETI plans to focus the ATA at the top 1,000 habitable planets found by Kepler.

Additional World Book articles:

• COROT
• Kepler, Johannes
• Planet (Planets in other solar systems)