GAIA will unveil the secrets of the coldest stars of the Milky Way

Among the hundreds of billions of stars that populate the Milky Way it is very difficult to distinguish one from the other. In particular, there is a group of stars called ultra-cold dwarfs, with temperatures below 2,500 K, which include the coldest stars and brown dwarfs. This group of stars has a great astrophysical interest, since they are the most long-lived objects of our galaxy and, therefore, can provide information about their primitive chemical composition, and that is why it is one of the objectives of the GAIA mission that the Space Agency European will put into orbit predictably next November.

Although observationally they are very similar, there is a clear boundary between brown dwarfs and cold stars: in the former the necessary temperature has not been reached for nuclear reactions typical of cold stars to occur (in this case, they are indistinguishable from other stars). You could say that brown dwarfs are failed stars and the cause is the lack of mass.

"We have calculated how many ultra-cold dwarfs GAIA will detect and will be tens of thousands but, most important, is that we have validated the method with which we will estimate its physical parameters such as temperature and severity, "explains Luis Sarro, researcher at the Department of Artificial Intelligence of the UNED and senior author of the study published in the journal Astronomy & amp; Astrophysics.

But, in addition, "the efficient exploitation of GAIA will require adequate planning with ground-based telescopes to carry out complementary observations at observatories such as Calar Alto or Roque de los Muchachos" explains David Barrado, co -author of the work and researcher of the CAB and director of the observatory of Calar Alto.

The National University of Distance Education, the Center of Astrobiology (CSIC-INTA), the University participate in the research of Cádiz, the Calar Alto Observatory and the Institute of Cosmos Sciences (ICCUB-IEEC).

The most elusive ultra-cold

Knowing the parameters that GAIA is capable of measuring and its design characteristics, researchers have used data mining techniques to perform the estimations. "We have developed computer programs that learn, from examples, to estimate the physical properties of objects," says Sarro.

With this method, the final sensitivity of the data is considerably improved. will allow us to know the temperature of the ultra-cold dwarfs with a margin of error "surprisingly small for the characteristics of the instrument", says the astrophysicist. This improvement in sensitivity also allows the number of ultra-cold dwarfs that can be detected to increase to tens of thousands.

Within this group, only a few tens can be detected and characterized of the most elusive, those whose temperature is below 1,500 K and their brightness is extremely weak at the wavelengths observed by GAIA.

More on GAIA

GAIA is an ambitious mission of the ESA that aims to collect about a billion stars of the Milky Way, determining its magnitude, position, distance and displacement with extraordinary precision. To do this, he will observe each of the stars more than 70 times throughout the five years that his mission will last.

In addition, GAIA is expected to detect hundreds of thousands of new celestial objects, from exoplanets to brown dwarfs, even other galaxies or quasars. Also, in our Solar System, it will catalog hundreds of thousands of asteroids and comets. "GAIA will become the Rosetta Stone of the Milky Way", compares Sarro, because its results will serve to understand the physical processes that underlie the great variety of objects that populate the galaxy.

GAIA launch is planned for the end of 2013, aboard a Soyuz-Fregat from the European Spaceport, in French Guiana. GAIA will remain in a Lissajous orbit around the Lagrange point L2. This point, which is in opposition to the Sun a million and a half kilometers from Earth, is one of the five points of gravitational equilibrium in a system of two bodies (in this case the Sun and the Earth), therefore, it moves synchronously with the Earth around the Sun. It has the advantage that it is quite stable. In addition, being in opposition to the Sun, it is eclipsed by the Earth, so the thermal shielding required is less. At this point you can find the Herschel Space Observatory and it is the chosen point for the future James Webb Space Telescope.


Fuente: UCC-CAB


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