Luminary HD 40307 from the constellation of the Painter, member of the spectral type K2,5V, since 2008 it is known as the owner of three "supertall" with the masses 4.2, 6,7 and 9.4 times bigger than earth and astronomical year 4.3, 9.6 20,4 earth days. But subordinate to the star, the planet could hardly be candidates in the life carriers of the earth type. The orbits of all three removed from the parent star for no more than is 0.135 and. that is, For comparison, note that mercury and the Sun shares of 0.3 a. that is, Even with the smaller one quarter of the mass and luminosity orange stars temperature of these supersemar" too high for the development of complex earth-life.

If the surface of the new "supersample" there is water, the planet may not be less suitable for life than our Earth. (Illustration J. Pinfield, for the RoPACS network at the University of Hertfordshire.)

A group of astronomers under the leadership Mikko Twomey from the University of Hertfordshire (UK) re-analysis of data of the HARPS spectrograph, using new methods of analysis. And opened three new planets, which were not able to identify its predecessors in 2008.

"We found two more clear signal with the period 34 and 51 days, corresponding to candidates with a minimum mass in several earth - scientists say. - The sixth planet... has a circulation period of around 200 days... and weight about seven mass of the Earth." Although mass 7.1 earth, strictly speaking, the minimum possible this planet, the practice shows that the minimum weight is most often true. That's why astronomers and generalize it to "about seven mass of the Earth."

Given the mass of an object, you cannot say whether it is a planet with a hard surface or a reduced copy of Neptune, which would make it habitability less likely. Mr. Twomey believes that the chances are almost equal, but "the truth is that we simply do not know if this planet is big Land or a little warm Neptune without a solid surface". Caution scientist can understand: in the Solar system, there's nothing like a planet seven times heavier than our own, and the smallest of the local giants 14.5 times heavier than Earth.

Well, in the habitable zone of its star was HD 40307 g, the sixth planet, weighing approximately seven earth. For the parent stars such an area on the surface of earth-like planets may be liquid water is 0,43-0,85. E., and HD 40307 g is almost exactly in the middle, with a large radius of the orbit, equal to 0.6. that is, the Year of the planet lasts 320 earth days. Although the current orbit of new candidate receives only 62% of terrestrial solar radiation, it is rather a plus. Because the atmosphere at seven times more massive planet definitely thicker and has a much more effective greenhouse effect. Keep it the same dose of radiation, and low-mass Land on its surface would be much hotter.



According to the astronomers, most likely, in the system of the star, there is no huge bodies, which leaves the possibility for the existence there of a few low-mass exoplanets. In addition, around the "supersample" in habitable zone may exist massive satellites...


Even at zero percent cloud cover HD 40307 g is located deep in the habitable zone. By the way, when theoretically achievable absolute clouds the same applies to the HD 40307 f. (Illustration M.Tuomi et al.)

Unfortunately, direct observation of the transit HD 40307 g disk stars excluded: plane Ecliptic closer to the sun the planets do not coincide with ours, and the planet is located farther from the star. However, with introduction in operation of fundamentally new space-based telescopes further study of the planet is the second remoteness "supersample" in the habitable zone is likely to bring more information.

Report on the study accepted for publication in the journal Astronomy & Astrophysics, and with its Preprint available here.
http://arxiv.org/abs/1211.1617

Based on the materials of the University of Puerto Rico at Arecibo.