Translated material
Two salt planet
American astronomers at a press conference on September 15 reported the opening of a planet with two suns. It was found by the NASA “Kepler” orbital telescope, launched in 2009 for a photometric search for off -based planets (it monitors periodic changes in brightness caused by the passage of the planet in front of the star). The star system, remote from us at a distance of 200 light years, consists of orange and red dwarfs, which are circulated around the General Center for the masses with a period of 41 days.
The mass of the Kepler-16B planet is comparable to the mass of Saturn. The radius of its circular orbit is almost equal to the radius of the orbit of Venus - 105 million km; The year is also almost Venusian, 229 days. However, the temperature of its surface most likely does not exceed 170-200 kelvins, since both stars by thousands of degrees are colder than the sun.
This news was instantly replicated by the media, because the opening of exoplanets in the double star system is quite drawn to the sensation (especially since such a planet appears in the film epic "Star Wars" and is called tatuin). In the 2010s, several candidates were already found for the role of Tatuin-according to indirect data. There was also an unconfirmed “planet of the three suns” HD 188753 AB). Here, periodic transit eclipses are very reliable information.
Some important points have slipped away from the attention of journalists. Firstly, the orbital plane of the Double Ealvipation Star System KIC 12644769, to which the planet belongs, almost accurately lies on the ray connecting it with the Sun, so that earthly devices see it “from the rib”. This circumstance has just made it possible to identify the planet, which periodically partially shields the light coming from each star. But the inclination of the orbital plane of the planet varies with an amplitude of 0.2 ° over time, due to which the photometric registration of the planet is not always possible. The passage of the planet on the disk of the orange dwarf for earth's astronomers will stop in early 2018 and will resume only in 2042. Transits through the Red Dwarf will become unbatient in May 2014 and will remain 35 years old. So the discoverers were very lucky.
In double star systems, two types of planetary orbits are possible:
1) The planet turns at a distance significantly superior to the size of the orbit of a star pair, immediately around both stars. It is such a planet that was discovered in this case. The gas -pale discs on such orbits have already opened, and the fact that the planets in such a configuration “on the way”, almost no one doubted (but strictly speaking the presence of a gas -fiber disk still does not mean that when it is dispersed, the finished planets in stable orbites will remain).
2) The planet is spinning around one of the stars of the double system at a distance, noticeably inferior to the size of the star orbit. Formally, this is also a planet in the system of two suns, and such planets have long been known.
Another nuance associated with two -star planets. From the most general considerations it follows that it is easier for them to arise on the periphery of the protoplanetary disk, where the disturbances of the gravitational field caused by the movement of stars are not so felt. It follows that among them planets with large periods should prevail - at least about a dozen earthly years. On the other hand, for reliable photometric registration of the planet, you need to observe at least two of its passages along the star disk. So, perhaps, we do not yet notice them just because such observations have been conducted only a few years. And you just have to wait.
The second interesting point is that the presence of the planet made it possible to extremely accurately measure the masses and radii of both stars. In particular, the red dwarf turned out to be the lightest star of the main sequence to date, for which these data are known with so many signs after aim (its mass is 0.202-0.203 of the sun, the radius is 0.226-0.227 of the solar radius). The mass of the orange dwarf is 69% of the mass of the sun, the radius is 65%.
The orbit of the Kepler-16B planet is almost a compliance with star orbit (lies with it in almost one plane), the angle between them does not exceed 0.4 °. It follows that the planet was formed from the same gas -fluid cloud as the stars themselves, and they were not captured at a later stage. Theoretical models for the formation of planets in the vicinity of double stars are still developed much worse than similar models for single star. If the distances between the stars are not too large (which is exactly the case in this case), gravitational perturbations caused by their mutual movement are not too felt on the periphery of the protoplanetary disk and therefore do not particularly prevent the birth of planetosimals (planetary “embryos”) and their subsequent sticking. However, the details of this evolution so far serve as the subject of disputes, so that a further study of the newly open triple system promises a lot of interesting things.
The initiator of this project and the first author of the publication in Science Lawrence Doyle told me that his team was only the cataloging of double tagging stars discovered by the equipment of the telescope during the first two years after the launch of Kepler. Only in the third year did they began to look for candidates for the possession of planets among them, and the Kepler-16B became the first success. Doyle expressed confidence that other similar discoveries will follow over the next few months.
Alexey Levin
1. Laurance R. Doyle et al, Kepler-16: a transiting circumbinary Planet-http: //sciencemag.org/content/333/6049/1602.Abstractraact