Binary star: the new target for the search for extraterrestrial life
A team of researchers from the University of Copenhagen in Denmark has just published in Nature the results of its research on binary stars. The formation of these planetary systems could take place in a different way from those around single stars. They represent new opportunities to discover, perhaps, forms of life.
A very young binary star in the molecular cloud of Perseus
A binary star is a system made up of two stars that orbit around the same center of gravity. Almost half of the stars the size of the Sun are binary stars. Researchers at the University of Copenhagen have just discovered that the formation of planets in these binary solar systems is peculiar.
To get there, astronomers studied NGC 1333-IRAS2A, a binary star located in the Perseus Molecular Cloud. It is a cluster of gas and dust with an estimated mass of 10,000 solar masses. It is located 600 light years from Earth in the constellation Perseus.
Observations of this binary star were possible by exploiting the Atacama Large Millimeter/Submillimeter Antenna Array (ALMA). It is a state-of-the-art telescope located high in Chile in the Atacama Desert. These antennas are intended for the study of millimetric and sub-millimetric radiation whose wavelength is of the order of a millimeter, between infrared and radio waves.
This binary star is very young on the astronomical time scale since it formed about 10,000 years ago. The two stars of the binary system are separated from each other by a distance of 200 astronomical units (AU). To realize this distance, 1 AU represents the distance between the Earth and the Sun, approximately 152 million kilometers.
This binary star system is surrounded by an accretion disk made up of gas and dust. By supplementing the information received from ALMA with computer simulations, the researchers were able to study how gas and dust move toward the disk in this binary star system.
A discontinuous movement of gas and dust
NGC 1333-IRAC2A is too young to harbor planets, but comets pass through this binary star system.
Astronomers have realized that gases and dust follow a discontinuous movement. During short periods of 10 to 100 years and which are repeated every 1000 years, gases and dusts have a much faster and more agitated movement. At the same time, the brightness of the binary star becomes 10 to 100 times stronger.
The researchers explain this phenomenon by the existence of the two stars. As they orbit around their common center of gravity, they circle each other at times. Thus their common gravity causes large amounts of dust and gas to fall towards the two stars. This fall in matter leads to an increase in the temperature of the stars characterized by a stronger brilliance.
The NGC1333-IRAC2A binary system is still too young for planets to orbit the binary star. And therefore to detect the presence of a form of life there. Scientists then study comets that could contribute to the appearance of life. With their high ice content, comets passing through this binary system could contain organic molecules.
When the two-star planetary system is filled with planets, comets could slam into their surface seeding the planet with organic molecules.
The researchers believe that the binary star's cyclical phenomenon of temperature increase will lead to an increase in temperature on the surface of the planet. This phenomenon may modify the very structure of the elements that enter into the composition of the molecules.
A set of powerful tools to search for the presence of life
Thanks to ALMA, researchers can discover quite complex organic molecules. For example, those containing 9 to 12 atoms, such as carbon. This set, consisting of 66 antennas with a diameter of between 7 and 12 meters and spaced from 150 meters to 16 km. It works on the principle of interferometry.
In its search for life in space, ALMA will, in some time, be joined by the James Webb space telescope, put into orbit at the end of 2021. Around 2027, James Webb and ALMA will be supplemented by the European Large Telescope (ELT ) and the powerful Square Kilometer Array (SKA).
The European Large Telescope will be built by the European Southern Observatory at an altitude of 3000 meters in Chile. With its 39 meter mirror, it will be the largest optical telescope in the world. It will enable major advances in the observation of galaxies and the atmospheric conditions of exoplanets.
The Square Kilometer Array (SKA) is a radio telescope project consisting of interferometric arrays deployed over a large area in South Africa and Australia. The SKA is intended to provide answers to the big questions of scientists. On the birth of the Universe and on the origin of life forms. When in service, this instrument will be able to directly observe large organic molecules.
By combining the data obtained by these different means of observation, the researchers hope to obtain an impressive number of exciting results. In order to better understand the origins of life and its possible presence elsewhere than on Earth.
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