The weird system of star CVSO 30: two planets at extreme distances
A direct image has been taken of a planet so far away from his star that it takes twenty-seven thousand years for completing one orbit, and it shares the system with another planet which completes its orbit in just eleven hours.
Calar Alto Observatory (CAHA, MPG/CSIC) 2.2m Telescope and the Astralux camera has been used on this observation campaign.
An international observation campaign has allowed to photograph a planet around CVSO 30 star which is part of a curious system: the newly found CVSO 30c orbits the star at a extreme distance (more than twenty times the distance between Neptune and the Sun), and contrasts with its partner CVSO 30b, found in 2012, that is only at 1.2 million kilometers from the star (Mercury, the planet closest to the Sun, is 58 million kilometers away from it). It is the first system found with these characteristics, and their weird orbits could be due to the fact that both planets interacted to each other in the past and there was a dispersion process.
Up to now, most of the more than two thousand found planets orbiting other stars have been detected thanks to indirect methods, which study the influence of the planets on their stars. Barely sixty have been found with direct imaging, a very instrumental demanding method, but allowing exploring remote regions of the star where indirect methods are less effective.
The confirmation that the little dot on the images was indeed a planet has been possible thanks to the combined use of Keck (Hawaii), VLT (Chile) and Calar Alto Observatory telescopes. “CVSO 30c has been a surprise as it is at 660 Astronomical Units - an Astronomical Unit, or AU, is equivalent to hundred and fifty million kilometers, the distance between the Earth and the Sun -. Neptune is the most external planet of our Solar System, and it is at 30 AUs” , Jesús Aceituno, Calar Alto Observatory (CAHA, MPG/CSIC) Deputy Director points.
A unique system
Besides, this planet shares system with another one found in 2012 through indirect methods. Although both planets have a similar mass (between one and four times the mass of Jupiter), both of them have a relative distance never saw in the planetary system found up to now: while one is as close to its star that it completes its orbit in barely eleven hours, the other takes about twenty-seven thousand years for finishing it.
Researchers think about several possibilities in order to explain this distance disparity, but the most probable explanation points to the fact that both planets were formed within the internal regions of the system, and a gravitational interaction, happened in the past, resulted in the dispersion. This is a mechanism invoked to explain what are known as “Hot Jupiters”, gas giants very close to its star and which its detection constituted a surprise: in so short distances, the temperature prevents condensation of volatile ice to form gaseous planets, so they should have migrated to the inner regions by orbital resonances with other bodies.
This planetary system is a suitable object for studying these planetary dispersion theories, as well as for inquire on the first planet development phases: CVSO 30 star is a very young one, with only 2.5 million years (our Sun has five thousand million years), and researchers are studying how it could form planets so quickly.
The German-Spanish Calar Alto Observatory is located at Sierra de los Filabres, north of Almería (Andalucía, Spain). It is jointly operated by the Instituto Max Planck de Astronomía in Heidelberg, Germany, and the Instituto de Astrofísica de Andalucía (CSIC) in Granada, Spain. Calar Alto has three telescopes with apertures of 1.23m, 2.2m and 3.5m. A 1.5m aperture telescope, also located at the mountain, is operated under control of the Observatorio de Madrid.
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