A super Earth, made of diamonds

A super Earth, made of diamonds.

Astronomers also thought 55 Cancri e contained a substantial amount of super-heated water, based on the assumption that its chemical makeup was similar to Earth’s, Madhusudhan said. But the new research suggests the planet has no water at all, and appears to be composed primarily of carbon (as graphite and diamond), iron, silicon carbide, and, possibly, some silicates. The study estimates that at least a third of the planet’s mass — the equivalent of about three Earth masses — could be diamond. “By contrast, Earth’s interior is rich in oxygen, but extremely poor in carbon — less than a part in thousand by mass,” says co-author and Yale geophysicist Kanani Lee.

Another planet has been found in the habitable zone

Planets without end: Another planet has been found in the habitable zone.

Gliese 163c could have a size between 1.8 to 2.4 Earth radii, depending if it is composed mostly of rock or water, respectively. It receives on average 40% more light from its parent star than Earth from the Sun, making it hotter. In comparison, Venus receives 90% more light from the Sun than Earth. We do not know the properties of the atmosphere of Gliese 163c but, if we assume that it is a scaled up version of Earth’s atmosphere, then its surface temperature might be around 60°C [140°F]. Most complex life on Earth (plants, animals, and even humans) are not able to survive at temperatures above 50°C [122°F], however, plenty of extremophilic microbial life forms can thrive at those temperatures or higher.

Astronomers have now confirmed 41 new exoplanets, first pinpointed by the Kepler space telescope

Astronomers have now confirmed 41 new exoplanets, first pinpointed by the Kepler space telescope.

One paper, by Jiwei Xie at the University of Toronto, confirms 24 new planets in 12 systems. Another study, by Steffen and his colleagues, confirms 27 planets in 13 systems. Five of the systems, and 10 of the planets, are the same in both papers. All in all, the new research adds 20 new planetary systems to the 47 that Kepler had previously confirmed, marking a more than 40 percent increase.

Among the Kepler candidates are five Earth-sized planets in the habitable zone, according to the vidoe at the link. However, this announcement does not tell us if any of those candidates were confirmed by these two papers.

One of Kepler’s reaction wheels — used to orient the space telescope — has failed.

Bad news: One of Kepler’s four reaction wheels — used to orient the space telescope — has failed.

Kepler only needs three wheels to function – one to control the probe’s motion along each axis – and the probe resumed its observations on 20 July. “Kepler is functioning very well on three reaction wheels,” says mission manager Roger Hunter of NASA’s Ames Research Center in Moffett Field, California. If the glitch can’t be fixed, though, Kepler will be left without a backup wheel. “This is reducing the odds of making the mission go as long as we can,” says Kepler chief scientist William Borucki of NASA Ames, who doubts that Kepler could point accurately enough to look for transiting planets if reduced to two reaction wheels. “It was a disappointing surprise to find this wheel stopped so early.”

Two exoplanets in a tight orbital dance.

Two exoplanets in a tight orbital dance.

“These are the closest two planets to one another that have ever been found,” Agol said. “The bigger planet is pushing the smaller planet around more, so the smaller planet was harder to find.”

Orbiting a star in the Cygnus constellation referred to as Kepler-36a, the planets are designated Kepler-36b and Kepler-36c. Planet b is a rocky planet like Earth, though 4.5 times more massive and with a radius 1.5 times greater. Kepler-36c, which could be either gaseous like Jupiter or watery, is 8.1 times more massive than Earth and has a radius 3.7 times greater.

But wait, there’s more!

The fact that the two planets are so close to each other and exhibit specific orbital patterns allowed the scientists to make fairly precise estimates of each planet’s characteristics, based on their gravitational effects on each other and the resulting variations in the orbits. To date, this is the best-characterized system with small planets, the researchers said.

They believe the smaller planet is 30 percent iron, less than 1 percent atmospheric hydrogen and helium and probably no more than 15 percent water. The larger planet, on the other hand, likely has a rocky core surrounded by a substantial amount of atmospheric hydrogen and helium.

One astronomer has found that the habitable zone around some smaller stars is smaller than first calculated because of tidal heating.

One astronomer has found that the inner edge of the habitable zone around some dwarf stars is smaller than first calculated because tidal forces overheat planets close to the star.

Then again, this heating might expand the habitable zone in other directions. Stars might overheat when close to the star, but get a boost of needed heat when they would normally be too far away.

The blistering hot exoplanet where it snows

The blistering hot exoplanet where it snows.

These results have led to a suggestion that [HD 189733b] could continually experience silicate snow. In the lower atmosphere of [the exoplanet], magnesium silicate sublimates, that is, it passes directly from a solid into a gas. But we know there are small silicate particulates in the upper atmosphere. Formation of these particulates requires that the temperature be lowered, and so must have been formed at a temperature inversion in the atmosphere. The generally windy conditions would help some of the tiny particulates grow into respectable snow crystals.

smaller planets are preferentially found in low-eccentricity orbits.

More Kepler results: From the abstract of a preprint paper published today on the Los Alamos astro-ph website:

The mean eccentricity of the Kepler candidates decreases with decreasing planet size indicating that smaller planets are preferentially found in low-eccentricity orbits.

In other words, the smaller a planet is, the more likely its orbit will be circular like the Earth’s. This result is encouraging news for the search for life on other worlds. Before Kepler, astronomers had found that the orbits of most exoplanets were far more eccentric than the orbits of the planets in our solar system, a condition that scientists thought was unfriendly for the development of life. These new results counter that conclusion. The orbits of the planets in our solar system might not be as unusual as first thought.

Mapping the surface of an extrasolar planet light years away.

Mapping the surface of an extrasolar planet light years away. From the paper’s abstract [pdf]:

We use archived Spitzer [Space Telescope] data of [the star] HD189733 … encompassing six transits, eight secondary eclipses, and a phase curve in a two-step analysis. The first step derives the planet-star system parameters. The second step investigates the structure found in eclipse scanning, using the previous planet-star system parameter derivation as Gaussian priors.

We find a 5-sigma deviation from the expected occultation ingress/egress shape for a uniform brightness disk, and demonstrate that this is dominated by large-scale brightness structure and not an occultation timing offset due to a non-zero eccentricity. Our analysis yields a 2D brightness temperature distribution showing a large-scale asymmetric hot spot whose finer structure is limited by the data quality and planet orbit geometry. [emphasis mine]

The Kepler team today announced the discovery of eleven new solar systems holding twenty-six planets.

Planets galore! The Kepler team today announced the discovery of eleven new solar systems holding twenty-six planets.

The planets orbit close to their host stars and range in size from 1.5 times the radius of Earth to larger than Jupiter. Fifteen of them are between Earth and Neptune in size, and further observations will be required to determine which are rocky like Earth and which have thick gaseous atmospheres like Neptune. The planets orbit their host star once every six to 143 days. All are closer to their host star than Venus is to our sun.

No Earths in the habitable zone quite yet, but we are circling in on our prey.

It doesn’t exist

Fomalhaut b

In a preprint paper published today on the Los Alamos astro-ph website, astronomers have concluded that the exoplanet orbiting the star Formalhaut might not exist. This planet, the first exoplanet ever thought to be directly imaged in visible light, was first described in a paper published in 2008, and was actually tracked in its orbit over several years, as shown in the image on the right.

The new research used the Spitzer Space Telescope to see if the planet’s heat could be detected in infrared wavelengths. Unfortunately, the scientists found nothing.
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Astronomers have concluded that the stars in the Milky Way must average at least one planet per star.

Billions and billions! Astronomers have concluded that the stars in the Milky Way must average at least one planet per star. More importantly, the data says the galaxy should have billions of habitable planets.

[According to astronomer Uffe Gråe Jørgensen], a statistical analysis … shows that out of the Milky Way’s 100 billion stars, there are about 10 billion stars with planets in the habitable zone. This means that there may be billions of habitable planets in the Milky Way.

A Sun-like Star with Three Sub-Neptune Exoplanets and Two Earth-size Candidates

Want to read the actual paper, “A Sun-like star with three sub-Neptune exoplanets and two Earth-size candidates,” describing the discovery announced yesterday of two Earth-sized planet? You can download it here.

The paper’s closing paragraph sums the discovery up nicely:

A striking feature of the Kepler-20 planetary system is the presence of Earth-size rocky planet candidates interspersed between volatile-rich sub-Neptunes at smaller and larger orbital semi-major axes, as also seen in Kepler candidate multi-planet systems. Assuming that both [Kepler-20e] and [Kepler-20f] are planets, the distribution of the Kepler-20 planets in orbital order is as follows: Kepler-20b (3.7 days, 1.9 Earth radii), [Kepler-20e] (6.1 days, 0.9 Earth radii), Kepler-20c (10.9 days, 3.1 Earth radii), [Kepler-20f] (19.6 days, 1.0 Earth radii), and Kepler-20d (77.6 days, 2.8 Earth radii). Given the radii and irradiation fluxes of the two Earth-size planet candidates, they would not retain gas envelopes. The first, second, and fourth planets have high densities indicative of solid planets, while the other two planets have low densities requiring significant volatile content. The volatile-rich third planet, Kepler-20c dominates the inner part of the Kepler-20 system, by holding much more mass than the other three inner planets put together. In the Solar System, the terrestrial planets, gas-giants, and ice giants are neatly segregated in regions with increasing distance from the sun. Planet formation theories were developed to retrodict these Solar System composition trends. In the Kepler-20 system, the locations of the low-density sub-Neptunes that are rich in water and/or gas, and the Earth-size planet candidates does not exhibit a clean ordering with orbital period, challenging the conventional planet formation paradigm. In situ assembly may form multi-planet systems with close-in hot-Neptunes and super-Earths, provided the initial protoplanetary disk contained massive amounts of solids (∼ 50–100 Earth masses) within 1AU of the star.

First Earth-sized planets found

Big news: The first Earth-sized planets have been found by Kepler.

The two planets, dubbed Kepler-20e and 20f, are the smallest planets found to date. They have diameters of 6,900 miles and 8,200 miles – equivalent to 0.87 times Earth (slightly smaller than Venus) and 1.03 times Earth. These worlds are expected to have rocky compositions, so their masses should be less than 1.7 and 3 times Earth’s.

Both worlds circle Kepler-20: a G-type star slightly cooler than the Sun and located 950 light-years from Earth. (It would take the space shuttle 36 million years to travel to Kepler-20.) Kepler-20e orbits every 6.1 days at a distance of 4.7 million miles. Kepler-20f orbits every 19.6 days at a distance of 10.3 million miles. Due to their tight orbits, they are heated to temperatures of 1,400 degrees Fahrenheit and 800 degrees F.

Once again, this is only the beginning. The announcement of an Earth in the habitable zone is only a matter of months away.

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