Working with the Palomar Observatory near San Diego and the W.M. Keck Observatory in Hawaii and using NASA’s spacecraft Kepler, astronomers from the California Institute of Technology have found three teeny, rocky, extrasolar planets (otherwise known as exoplanets, which lie beyond our solar system).

NASA launched Kepler in 2009 to search for Earth-like planets that orbit stars in the habitable zone, a region colloquially called the “Goldilocks Zone”, in which a planet must not be too close or too far from a star, so that its temperature would be just right to be habitable for life. Kepler uses a method called transiting to accomplish its mission: it sees if any stars have slight dips in brightness caused by a planet, which eventually eclipses its parent star sometime during its orbit.

The freshly discovered planetary system’s star is named KOI-961 (KOI is an acronym for Kepler Object in Question). Approximately 130 light-years from the Earth, KOI-961 is a red dwarf – a pipsqueak of a star compared to the Sun, which is six times larger. KOI-961 is similar to a nearby star, Barnard’s Star, which is also a red dwarf. Astronomers used information about Barnard’s Star to determine KOI-961′s characteristics, which were then used to calculate its companion planets’ sizes.

The planets’ names are KOI-961.01, KOI-961.02, and KOI-961.03 and have the radii of 0.78, 0.73, and 0.57 times that of the Earth, respectively. The smallest, KOI-961.03, is about the size of Mars, and the other two are about the size of Venus. All three do not lie in habitable zones; they orbit their parent star too closely, and one year equals two days.

Due to their incredibly close orbits, they are too hot to form liquid, let alone for life to thrive. Temperatures are hundreds of degrees, with the closest, KOI-961.01, having a surface temperature of nearly 1,000 degrees Fahrenheit (500°C).

This planetary system is the tiniest known to astronomers. John Johnson, assistant professor of astronomy at Caltech and co-author of the team’s paper, states in the Caltech press release, “It’s actually more similar to Jupiter and its moons in scale than any other planetary system. The discovery is further proof of the diversity of planetary systems in our galaxy.”

Red dwarfs are the most common type of star in our home galaxy, the Milky Way, making up eight out of every ten stars. Because of their ubiquity, Kepler may find more planetary systems with red dwarfs as parent stars. “That boosts the chances of other life being in the universe – that’s the ultimate result here,” Johnson says.

In the past, Kepler has found numerous gas giants around the sizes of Jupiter and Neptune. Its most recent discoveries occurred in December 2011, when it detected Kepler-22b, the first planet discovered to orbit in the habitable zone, and Kepler-20e and Kepler-20f, the first Earth-sized exoplanets detected.

The more planets Kepler detects nowadays, the more they become smaller and rockier, it seems. Kepler’s last two discoveries increases the probability that there may be more rocky exoplanets than astronomers thought, thereby, boosting the chance of the existence of extraterrestrial life.

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In 2009, NASA launched Kepler to search for planets outside the solar system – called extrasolar planets, or exoplanets – that are Earth-sized and have a chance of harboring life. As of December 2011, the spacecraft has discovered 2,326 exoplanets, over a hundred of which are likely candidates to meet the requirements.

A team of astronomers at NASA decided in early January to give Kepler an additional mission of hunting for extrasolar moons, or exomoons. The team believes in the potential existence of exomoons. Natural satellites only survive half the time when they and their companion planets are still undergoing evolution, though the many moons in our solar system increase the possibility.

With this new mission, titled Hunt of Exomoons with Kepler (HEK), Kepler may find life on these moons as well as on exoplanets and help astronomers understand planetary evolution and the formation of natural satellites. Kepler will first look at the exoplanets cataloged thus far to see if any of them have any such natural satellites. The exomoons would have to be similar in size, or larger, than our Moon because they would be easiest for the spacecraft to detect.

It is also possible that exomoons are capable of harboring life. In our solar system, Jupiter’s Europa and Saturn’s Enceladus have liquid water beneath their surfaces. It is not known for sure if these two large moons contain life, though the presence of water heightens the probability as well as the probability that exomoons may be habitable.

Kepler will attempt to search for exomoons through two means: dynamical effects and eclipses features. With dynamical effects, the spacecraft would observe and measure the gravitational effect between the exoplanet and the exomoon (i.e. how much they tug on each other).

The amount of gravitational effects on the two bodies would determine whether or not the system would be a planet-moon system or a binary-planet system (it would be easy for the former to be mistaken with the latter). With eclipse features, Kepler would be on the lookout for solar and lunar eclipses, involving the exomoon, its companion planet, and their star. Kepler would see if the exomoon may make subtle changes in a star’s brightness through eclipsing the star, which would drop a bit in brightness.

Once Kepler finds an exomoon, it would be able to determine its size and mass based on the gravitational effect and eclipse features. Upon discovering the size and mass, it would then calculate the density. Thereafter, the exomoon’s composition can be determined, giving insight as to how to the exomoon formed and, ultimately, revealing the process of planetary evolution.

“Extrasolar moons represent an outstanding challenge in modern observational astronomy,” writes head author David Kipping in the team’s paper. Kipping,  a member of the team at NASA, is an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

“Their detection and study would yield a revolution in the understanding of planet/moon formation and evolution, but perhaps most provocatively, they could be frequent seats for life in the Galaxy.”

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