May 1, 2014

The first Earthlike planet orbiting in the “Goldilocks zone” of a star other than the sun has been found by scientists analyzing data from the Kepler space telescope. The Goldilocks zone is the region around a star in which liquid water can exist. That is, the planet, called Kepler-186f, is not too hot to cause water to evaporate or too cold to cause it to freeze. Scientists believe the most likely place to find life as we know it is on planets or moons that can support liquid water.

“Being in the habitable zone does not mean we know this planet is habitable,” commented 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.”

The newly discovered extrasolar planet is just 10 percent larger than Earth. It orbits a type of star called a red dwarf. Smaller and cooler than the sun, red dwarfs are also the most abundant type of star in our galaxy, the Milky Way. The star, called Kepler-186, is about half the size and mass of the sun. It is about 500 light-years from Earth in the constellation Cygnus. Four other planets orbit Kepler-186.

Extrasolar planets orbit stars other than the sun. This infrared image of the star HR 8799 and its three orbiting planets was taken in 2008. The arrows indicate the directions of the planets’ orbits. (C. Marois et. al/NCR Canada)

Since the first planets outside the solar system were discovered in the 1990′s, scientists have hoped to find a planet that could support life. Because of the limited ability of the instruments used to search for extrasolar planets, almost all of the early planets discovered were very large and orbited very close to their host star. However, Kepler, which was constructed specifically to hunt for exoplanets, expanded the number of known extrasolar planets from just a few hundred to thousands.

To find extrasolar planets, Kepler examined some 150,000 stars in one small section of the galaxy using a technique called the transit method. Away from the distorting interference of Earth’s atmosphere, almost all stars shine at a consistent brightness. But a planet or other body passing in front of star will block some of the star’s light. Kepler looked for this dip in brightness. Unlike most of the first exoplanets discovered, the planets spotted by Kepler are of many sizes and distances from their home star.

Additional World Book articles:

• Kepler, Johannes
• Life (The search for life on other planets)
• In Search of Other Worlds (a Special Report)

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. 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)