On February 27, the team of astronomers involved with NASA’s spacecraft Kepler published their most recent catalog of exoplanets (short for extrasolar planets, which are planets beyond our solar system) that Kepler has detected.

Data from the newest catalog is cumulative and includes information from the two catalogues created in June 2010 and February 2011. As of now, the total number of exoplanets Kepler has detected is 2,321, which orbit 1,790 stars. A full 93% are smaller than Neptune, the smallest of the gas giants in the solar system. Over 200 are Earth-sized and more than 900 are smaller than twice the size of the Earth’s diameter. There are 46 exoplanets located in the habitable zone, 10 of which are Earth-sized.

“With each new catalog release a clear progression toward smaller planets at longer orbital periods is emerging,” Natalie Batalha, Kepler deputy science team lead at San Jose State University in California, states in NASA’s press release. “This suggests that Earth-size planets in the habitable zone are forthcoming if, indeed, such planets are abundant.”

Furthermore, the percent for more than one planet orbiting a star has increased to 20 percent from last year’s 17 percent (many other planets are rogue, unattached to a parent star, twirling alone in space). More and detailed statistics can be found here.

Three methods can be utilized to find exoplanets: gravitational lensing, radial-velocity, and transiting. Kepler largely uses the latter method, using the software Transiting Planet Search (TPS) pipeline module, because it has proven to produce more results compared to the former two. Transiting works as thus: one measures a star’s periodic drop in brightness due to an object – in the most hopeful scenario, a planet – passing in front of the star.

Sifting through 150,000 stars, Kepler detected around 5,000 transit signals, through which the spacecraft had more to sort. One can easily misidentify an object to be an exoplanet when using the transiting method; one may instead find a binary star system, which contains two stars that orbit and eclipse one another. To confirm its detection of a planet, Kepler has to record the transit at least three times.

Kepler was launched in mid-2009 to find Earth-like exoplanets that are able to sustain water and life. These planets would have to be located in the habitable zone, an area in which a planet must orbit a star in order for liquid water to exist on its surface. Kepler goes about attempting to detect exoplanets by looking at their parent stars first, largely searching for G-type stars, or Sun-like stars (or at least stars a part of the Main Sequence), which astronomers believe to be ideal parent stars.

For much of the time Kepler began exploring, it mostly detected gas giants tens of times larger than Jupiter. As the spacecraft endured, it began, recently, to find numerous smaller rocky planets. Soon after, astronomers working with Kepler have calculated that there are more of these kinds of planets than there are gas giants.

Kepler’s latest milestone includes Kepler-20e and Kepler-20f, which were detected this January and are the first Earth-sized planets known to exist. Another milestone occurred in December 2011, when Kepler discovered super-Earth Kepler-22b, the first known exoplanet in the habitable zone.

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A team of astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA), using NASA’s Hubble Space Telescope, has discovered a “waterworld” planet beyond the solar system.

This exoplanet (i.e. extrasolar planet), dubbed GJ1214b, is located in the constellation Opphiuchus, 40 light-years away from the Earth. It is 2.7 times the size of the Earth and roughly seven times Earth’s weight. At a distance of 1.3 million miles, the watery exoplanet orbits a red dwarf every 38 hours and has a surface temperature of 450º F (230º C).

GJ1214B was first discovered in 2009 by a team of astronomers, led by David Charbonneau of CfA, with the groudbased project MEarth (pronounced “mirth”). Charbonneau and his team were able to detect GJ2124b through transiting, a widely-used method used to search for exoplanets in which one looks to see if a star’s light slightly drops periodically. If it does, a planetary body has traveled in front of the star.

A year later, in 2010, astrophysicist Jacob Bean and his colleagues (also working at CfA) learned that GJ1214b’s atmosphere was chiefly composed of gaseous water. And in 2012, the current group of astronomers working at CfA has confirmed that GJ1214b is indeed veiled in a watery haze.

“GJ1214b is like no planet we know of,” Zachary Berta – an astronomer who is the head of the team – states in CfA’s press release.

Using the parent star’s light, he and his colleagues learned which gases comprise the larger exoplanet’s atmosphere, through which the light passed. With that knowledge, they concluded the GJ1214b and its atmosphere were not mostly made of water, but also hazy – and quite steamy.

The team of was also able to calculate the density of GJ1214b, knowing its size and mass: 2g/cm3. In comparison, Earth’s density = 5.5 g/cm3, and water on Earth 1 gm/cm3. GJ1214b’s larger density suggests that it has more water and less solid material.

“The high temperatures and high pressures would form exotic materials like ‘hot ice’ or ‘superfluid water’ – substances that are completely alien to our everyday experience,” Berta explains. Furthermore, GJ1214b cannot harbor any bodies of liquid water due its temperature and proximity to its parent star.

He and his colleagues utilized Hubble to measure GJ1214b’s light spectrum. The spectrum is apparently not restricted to any particular wavelengths, which indicates and further proves the state of the atmosphere. The team is also currently attempting to study the exoplanet’s sunsets through infrared using the Hubble; they can see through the atmosphere more easily with infrared than if they used visible light, which is shorter in wavelength and, hence, cannot traverse thick mediums readily.

According to CfA, theorists have predicted GJ1214b’s formation:

“GJ1214b formed farther out from its star, where water ice was plentiful, and migrated inward early in the system’s history. In the process, it would have passed through the star’s habitable zone. How long it lingered there is unknown.”

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This week, the National Aeronautics and Space Administration’s (NASA) spacecraft, Kepler, detected eleven planetary systems, which, overall, contain 26 new exoplanets (short for extrasolar planets, which exist beyond out solar system). Located in the Lyra and Cygnus constellations, each system contains two to five planets. The systems have been dubbed Kepler-23, Kepler-24, Kepler-25, Kepler-26, Kepler-27, Kepler-28, Kepler-29, Kepler-30, Kepler-31, Kepler-32, and Kepler-33.

The sizes of the exoplanets range from 1.5 to 5 times the size of Earth to larger than Jupiter. All of them orbit their parent stars closely; none of them lie in the habitable zone, an area in which a planet is not too close or too far away from a star so that it can sustain water and life. Each of their orbits is closer than that of Venus. The farthest exoplanet has years that last fewer than 200 days and the surface temperature of hundreds of degrees.

Kepler primarily detects planets through a process known as transiting, in which it measures a star’s periodic change in brightness generated by a planet crossing its parent star, causing the star’s light to drop a bit in brightness.

The NASA spacecraft was able to find these newer exoplanets by means of measuring Transit Timing Variations (TTVs). With this method, Kepler calculates changes in the acceleration of planets due to the gravitational pull on one another from being so close together. TTVs help Kepler find the more distant – hence fainter – star systems.

“Prior to the Kepler mission, we knew of perhaps 500 exoplanets across the whole sky,” said Doug Hudgins, Kepler program scientist at NASA Headquarters in Washington, in the press release on NASA’s Kepler website.

“Now,” Hudgins continues, “in just two years staring at a patch of sky not much bigger than your fist, Kepler has discovered more than 60 planets and more than 2,300 planet candidates. This tells us that our galaxy is positively loaded with planets of all sizes and orbits.”

Kepler has been in space for nearly three years. Its mission is to search for Earth-like exoplanets that orbit stars in the habitable zone. Ever since its launch in March 2009, Kepler has made numerous momentous findings, especially in the last couple of months.

On December 5, the spacecraft detected Kepler-22b, the first planet to be found in a habitable zone, and on December 20, it discovered the first two Earth-sized exoplanets, Kepler-20e and Kepler-20f. Kepler’s most recent significant detection occurred earlier this month: exoplanets KOI-961.01, KOI-961.02, and KOI-961.03, the tiniest exoplanets thus far.

Based on the diversity of the types of exoplanets, astronomers believe they will attain a better understanding of how planets form.

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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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An international research team of astronomers and astrophysicists were originally trying to find and study pulsars with the Kepler space telescope and the Kitt Peak Earth observatory in Arizona. However, the team got more than they bargained for. Later last week, they detected a star with a unusual pulsating rate: intervallic modulations, which occurred every 5.76 and 8.23 hours, caused the star to faintly flicker. Upon further studying, the team found out that these modulations were not produced by the star, and that is when they discovered two earth-sized exoplanets rotating around a red giant star well within its outer envelopes of gas.

“Having migrated so close, they probably plunged deep into the star’s envelope during the red giant phase, but survived,” says Stéphane Charpinet, who is the leader of the team and an astronomer at the University of Toulouse in France.

Before this finding, scientists in general assumed that planets engulfed by a red giant’s outer layers would be incinerated, and it is believed that this is to happen to the Earth since the Sun is fated to become a red giant. Now that these two exoplanets have been discovered, though, it seems that planets are able to endure stars’ transition to a red giant.

The star in question is named KIC 05807616 (also KOI 55, with “KOI” being the acronym for “Kepler Object of Interest”), formerly a main sequence star on the Hertzsprung-Russell Diagram, like our Sun. The two exoplanets, KOI 55-01 and KOI 55-02, revolve around KIC 05807616 less than approximately 900,000 kilometers and approximately one million kilometers, orbiting KIC 05807616 closer than Mercury orbits the Sun. They have the radii of .76 and .87 times the Earth’s respectively, making them the smallest exoplanets detected thus far.

According to another member of the team, Elizabeth ‘Betsy’ Green, an associate astronomer at the University of Arizona’s Steward Observatory, “The friction with the star’s envelope also strips the gaseous and liquid layers off the planet, leaving behind only some part of the solid core, scorched but still there.” This would account for KOI 55-01 and KOI 55-02′s small sizes.

The research team studied KIC 05807616 and found out that it had been transitioning to become a typical red giant, but since the nuclear reactions began occurring in the outer shells rather than in the core, it expanded, shedding its outer layers and jettisoning much of its mass. Due to the fact that KOI 55-01 and KOI 55-02 orbit KIC 05807616 closer than Mercury orbits the Sun, they may have may have helped KIC 05807616 with its transition, causing it to lose mass more rapidly by stripping its outer shells of gas.

The exoplanets ultimately affected KIC 05807616 enough to become a subdwarf B, which, entirely stripped of its outer layers, has the core of a red giant and the luminosity of a main sequence star, but smaller in mass. Upon finishing their research, the team concluded that planets can affect stellar evolution. “We think this is the first documented case of planets influencing a star’s evolution,” Charpinet states.

“We thought we had a pretty good understanding of what solar systems were like as long as we only knew one – ours,” says Green. “Now we are discovering a huge variety of solar systems that are nothing like ours, including, for the first time, remnant planets around a stellar core like this one.”

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Earlier this week, the spacecraft, Kepler, discovered two exoplanets around the size of the earth – the first of their kind – orbiting a sun-like star. Named Kepler-20e and Kepler-20f, these exoplanets are a part of the star system, Kepler-20, which lies 950 light years away from Earth near the constellation, Lyra.

“This discovery demonstrates for the first time that Earth-size planets exist around other stars and that we are able to detect them,” says Dr. Francois Fressin, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

Launched in 2009, Kepler is a space telescope built and sent by NASA to detect Earth-like exoplanets (also known as extrasolar planets, which are planets that exist outside our solar system) orbiting stars in habitable zones. Its most recent, significant discovery occurred in early December, when it detected the Neptune-sized Kepler-22b, the first of its kind that has been seen orbiting in the “Goldilocks zone” and that might possibly have water and life.

Kepler took a step closer in accomplishing its mission when it detected Kepler-20, Kepler-20e, and Kepler-20f. Kepler-20 is similar to the sun, in that it is a G-type star. It is yellowish, though a bit smaller and cooler. The star contains five planets in total, all of which orbit it closer than Mercury orbits the sun. The three other planets are gas giants, which are about the size of Neptune, and each planet orbits alternating in size.

These newly discovered exoplanets are only Earth-like in their sizes and rocky composition. Kepler-20e orbits its star every 6.1 days, and its temperature is 1400° F. Its diameter, 6900 miles, is 0.87 times the diameter of the Earth’s. Kepler-20f has an orbit of 19.6 days. It has the temperature of 800° F, and it is 1.03 times Earth’s diameter, being 8,200 miles.

Because of their close orbits and high temperatures, these two exoplanets are not able to sustain water, let alone life. For them to have water and life, they have to lie in the “Goldilocks zone,” or the habitable zone, in which a planet cannot be too close or too far (hence, too hot or too cold) from the star it orbits.

Ever since its launch in 2009, Kepler has been detecting hundreds of exoplanets, many of which are not Earth-like, being hostile and sometimes lonely, not orbiting any stars. With its most recent detection of Kepler-22b and of Kepler-20′s two Earth-like planets, Kepler has reached a new landmark, not just in its journey, but in our knowledge of the various kinds of planets that exist in the observable universe.

“This could be an important milestone,” Dr. Fressin states. “I think 10 years, or maybe even 100 years, from now people will look back and ask when was the first Earth-sized planet found. It is very exciting.”

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