Six on a prank

Astronomers fascinate six small planets surrounding a sonorous star

The Kepler mission of NASA has discovered a remarkable planetary system, in which six planets circle around a sungloth star – five of them in close orgates. Astronomers of the University of California (Santa Cruz) and their cooolers have analyzed the circulation dynamics of the system that calculates coarse and masses of the planets and determines their likely composition – everything based on Kepler’s quantities of changing brightness of their central star (Kepler-11), During the planets at this before moving.

"This is not blob a fascinating planetary system," says Daniel Fabrycky, Hubble Postdoc-Fellow at the UC Santa Cruz, who led the circulation dynamic analyzes, "It also saves a new, powerful method for the mass calculation of planets". Fabrycky and Jack Lissauer, a scientist at the NASA-Ames Research Center in Mountain View, are the feather-proof authors of an article about Kepler-11 in the Nature Edition of 3. February.

Six on a prank

Kepler-Telescope. Image: NASA / Kepler Mission / Wendy Stenzel

The five internal planets of the Kepler 11 system have masses of 2.3 to 13.5 times our earth. The round periods amount to all less than 50 days, so their orbits are within a region that was fit into the orbit of Mercury. The sixth planet is gross and further away from the central star with a circulation period of 118 days and so far still indefinite mass.

"From the six planets, the most massive is probably our Neptune and Uranus similar. The three mass-poor planets do nothing, which there was also in our solar system, "says Jonathan Fortney, lecturer for astronomy and astrophysics at the UCSC, which, together with his graduated Eric Lopez and Neil Miller, conducts the working group with the structure and composition the planned.

The Kepler Space-Telescope is looking for planets that attribute to their central retirement in advance and cause recurring brightness fluctuations that can then be measured with the sensitive photometers of the telescope. The coarse of this brightness differences betrayed the scientists, how rough the planet is or. Which radius he has. From the time passing between his transits in front of the sun, the scientists derive his roundout time. To determine the masses of the planets, Fabrycky has analyzed lightweight deviations in the rounding times that arise through gravitational interactions.

Llustration of the transit method. Image: NASA

"The duration of the transits are not absolutely equal and that is a sign for the gravitational interactions of the planets," explores Fabrycky. "The fact that we have developed a model for the circulation speeds, we were able to calculate the masses of the planets and have found that the solar system has existed for several million years in a stable state."

Previously, after the discovery of transient planets, even strong earth-based telescopes were used to confirm planet finding and determine its mass by means of Doppler spectroscopy. In the Kepler-11 system, however, the planets are too small and the (2000 light-years removed) star to light sweat to watch the typical swirl of the star at the pre-return of a planet. This is the case with many exoplanet systems, which were discovered during the Kepler mission. Their main goal is to search small, earth-rough planets within the "habitable" zone of your star.

Doppler shift when "wobbling". Image: NASA

More than 100 transit planets have been observed from Kepler and other telescopes so far, but the majority of them are Jupiter-like gas giants, and almost all of them are in one-planet solar system. The Kepler-11 system is therefore remarkable due to the amount of his trabants, their small coarse and close oriented. Astronomers knew only three systems in front of his discovery, in which planets smaller than Neptune circle around their sun. Now you know a single planetary system with five other such planets. The sixth planet in Kepler-11, however, is too far away from the floating trabants than that interactions could be observed, the back closing remains on its mass, so Fabrycky.

As well as in our solar system, all planets Kepler-11 circle more or less on the same level. This discovery puts the thesis that planets of flat gas slices and dust circling around the sun shaped. Fabrycky says: "The Komplanar orbit in our solar system has delivered the first ideas for this theory; Now we have another good example. This and the similarity of Kepler-11 with our sun are the only similarities with our solar system."

The density of the planets (derived from their mass and their radius) allow jerk to their composition. All six planets have densities lower than that of the earth. "It looks like the inner two mostly made of water, perhaps with a dun Hull made of hydrogen and helium – like mini-Neptune," suspects Fortney. "The further dubs have densities that are lower than those of water, which gives a significant indication that they have hydrogen helium atmosphere."

Six on a prank

Kepler search box. Image: NASA, Carter Roberts

That’s surprisingly because a small, heather planet should actually have difficulty holding such a light atmosphere. "These planets are pretty hot due to their near orbit. And the chatter of them are, the more gravitational they need to keep their atmosphere, "says Fortney. "My students and I still work on this problem, but we believe that all these planets have emerged with a denser hydrogen helium atmosphere. And we see residues of such atmosphere in the wide planet. Those who are closer to the sun have probably lost more of their atmosphere."

Another reason why a six-planet system is so interesting is that it is the scientists to make such comparisons between the planets of the system. "In this way, we can derive what happened to the system as a whole in the past," says Fortney. "Such comparative planet science has helped us to understand our own solar system. That is why the current find is so much more interesting than the discoveries of some cheering Jupiter, which circle around other stars."

For example, the presence of small planets with hydrogen helium atmosphere suggests that this system has formed very quickly. Other studies have shown that stellar slices lose their hydrogen and helium prirdhead within about 5 million years. "This can be read on how fast planet forms", willing Fortney.

The inner planets are so close to each other that their formation in this state seems unlikely, he adds. "At least some of them have to continue to have formed outside of the system and then hiked inwards. When a planet is enclosed in a gas disc, the resistor gradually calls him to the center of spirally. So such formations and hikes have already taken place very early."

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