Saturday, November 30, 2013

Second Planetary System Like Ours Discovered



A comparison between our solar system and a second planetary system: KOI-351. Image Credit: DLR Press Release

A team of European astronomers has discovered a second planetary system, the closest parallel to our own solar system yet found. It includes seven exoplanets orbiting a star with the small rocky planets close to their host star and the gas giant planets further away. The system was hidden within the wealth of data from the Kepler Space Telescope.

KOI-351 is “the first system with a significant number of planets (not just two or three, where random fluctuations can play a role) that shows a clear hierarchy like the solar system — with small, probably rocky, planets in the interior and gas giants in the (exterior),” Dr. Juan Cabrera, of the Institute of Planetary Research at the German Aerospace Center, told Universe Today.

Three of the seven planets orbiting KOI-351 were detected earlier this year, and have periods of 59, 210 and 331 days — similar to the periods of Mercury, Venus and Earth.

But the orbital periods of these planets vary by as much as 25.7 hours. This is the highest variation detected in an exoplanet’s orbital period so far, hinting that there are more planets than meets the eye.

For the entire article:

The Planetary System to KIC 11442793: A Compact Analogue to the Solar System

We announce the discovery of a planetary system with 7 transiting planets around a Kepler target, a current record for transiting systems. Planets b, c, e and f are reported for the first time in this work. Planets d, g and h were previously reported in the literature (Batalha et al. 2013), although here we revise their orbital parameters and validate their planetary nature. Planets h and g are gas giants and show strong dynamical interactions. The orbit of planet g is perturbed in such way that its orbital period changes by 25.7h between two consecutive transits during the length of the observations, which is the largest such perturbation found so far. The rest of the planets also show mutual interactions: planets d, e and f are super-Earths close to a mean motion resonance chain (2:3:4), and planets b and c, with sizes below 2 Earth radii, are within 0.5% of the 4:5 mean motion resonance. This complex system presents some similarities to our Solar System, with small planets in inner orbits and gas giants in outer orbits. It is, however, more compact. The outer planet has an orbital distance around 1 AU, and the relative position of the gas giants is opposite to that of Jupiter and Saturn, which is closer to the expected result of planet formation theories. The dynamical interactions between planets are also much richer.
Kepler-90 (also KOI-351) is a main-sequence star with a planetary system that has the largest number of observed exoplanets in the Milky Way. It is approximately 2,500 light years away from Earth. Kepler-90 has seven planets, with rocky planets nearer and gas giants further away. This is similar to our Solar System. The five inner planets are either super-Earths or mini- Neptunes due to their size. The two outer planets are gas giants. The outermost of the seven previously discovered planet orbits the star at about the same distance as the earth the sun. Kepler-90 is designated as KOI-351. During its observation from 2008-2013 it provided evidence for the existence of exoplanets using the transit method which shows the size of a planet but not its mass. The planets are named based on their distance to the star. Kepler-90 b is the innermost and Kepler-90 h the outermost of the seven known planets.

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