Astronomers have discovered five planets, including one potentially habitable, with the famous star Tau Ceti is that scientists are still half a century ago "listened" in the search for signals from extraterrestrial civilizations, according to a paper accepted for publication in the journal Astronomy & Astrophysics.

The position of the star Tau Ceti in the sky

The star Tau in the constellation of China (HD 10700) visible in the sky like a star of the third magnitude. It is located at 11.9 light years from Earth and is very similar in its characteristics to our Sun. It has the same spectral class (G) and roughly the same age (Tau kita - 5,8 billion years, the Sun of 4.57 billion years), its weight is 78.3% of the sun. Therefore, in 1960, American astronomer Frank Drake (Frank Drake) made this star and the star Epsilon Eridan first order "Project Ozma", in which scientists listened to radio signals from these stars in the calculation to detect traces of extraterrestrial intelligence.

Tau Ceti is widely mentioned in the press, as well as in science fiction and fantasy literature, and the journey to "Taukina" has become a subject of one of the songs of Vladimir Vysotsky.

A group of astronomers from Britain, Chile, USA and Australia, under the leadership Mikko Twomey (Mikko Tuomi) from the University Hertfordshire (UK) decided to try out the observations of this star new high-precision method for measuring the radial-velocity - the speed star of the observer and from it.

The radial velocity measurements by fixing the Doppler shifts in the spectrum of a star allows to measure very weak motion caused by the gravity of the planets. Astronomers have developed a new high-accuracy method "cleanup" data from interference and distortion by "subtracting" modulirovannogo noise, which will allow you to find the very lungs of the planet, by fixing the radial velocities below 1 meter per second.

"We chose the Tau Ceti for this study, because I thought that from it there will be no signal. In addition, this star so bright and so similar to our Sun that it ideal as a calibration target to test our method of detecting planets", says study co-author Hugh Jones (Hugh Jones) from Hertfordshire.

The astronomers used the data about the Tau Ceti three spectrographs - HARPS spectrograph installed on the 3.6-m telescope at the European southern Observatory in Chile, UCLES on the Anglo-Australian telescope at Siding spring, Australia and HIRES mounted on a 10-meter telescope, the Keck Observatory in Hawaii.

The researchers analyzed data and found periodic oscillations radial velocities of stars, which testified to the presence of planetary systems.

"This frequency can be interpreted as a manifestation of the presence of planets on stable approximately circular orbits with periods of treatment 13.9, 35,4, 94, 168 and 640 days, and the minimum mass of 2, 3.1, 3.6, 4.3 and 6.6 Earth masses, respectively", - the article reads.

If these data are confirmed, the system Tau China will become the second planetary system, the nearest to the Sun after the planetary system from one of the stars of the triple alpha Centauri system.

In addition, one of the five planets Tau kita - the period of circulation of which is 168 days, and the weight of 4.3 earth is proved in "zone of life" - areas where water can exist in liquid form, it means that there are conditions for the existence of living organisms.

However, scientists emphasize that additional independent measurements to confirm the presence of planets in the star Tau Ceti.