The European space mission will shed light on hidden asteroids, the expansion of the universe and exoplanets.
The Gaia Space Telescope, launched in late 2013 by the European Space Agency (ESA), will hand over its first map of the Milky Way on September 14. The catalog will show the location of 2,057,050 stars and other objects in 3D, and describe how this location has changed over the past 20 years. Over time, the map will contain one billion objects, becoming 1,000 times more extensive and at least 10 times more accurate than anything that has been compiled before.
The release of the map will be accompanied by the publication of 19 scientific papers by the astronomers of "Gaia", already familiar with the telescope data. Independent teams are just getting ready to take a look at them. Astronomer Lennart Lindegren of Sweden's Lund Observatory, who has been the driving force behind Project Gaia since it was announced in 1993, expects scientists to write approximately 100 papers within weeks of the catalog's draft release.
Some organizations are preparing events called "Gay Hack" and "Gay Sprint", in which researchers will work collectively to understand how to best use the manna that suddenly fell on them. "Gaia will revolutionize our knowledge of the stars and the galaxy," says New York University astronomer David Hogg, who is leading part of the work. So what discoveries could Gaia make?
Archeology of the Milky Way
A three-dimensional image of the Milky Way in motion will show how the stars move under the influence of its combined gravity. This will expand knowledge about the structure of the Galaxy, including about those parts of it that cannot be seen directly from the Earth, say, "bridges" - two stripes that extend directly from the galactic center and attach it to the spiral arms.
Researchers will be able to identify "anomalous" clusters of stars that move together at high speed. They are believed to be remnants of mergers with smaller galaxies, says astronomer Michael Perryman, who teaches at University College Dublin and was previously a senior research fellow at ESA on the Gaia program. This detailed map, combined with available information on factors such as color, temperature and chemical composition of stars, will allow researchers to recreate the archeology of the Galaxy, describing how it got to its current state over the past 13 billion years. “During its work, Gaia will significantly influence our understanding of the structure of the Milky Way and its evolution,” says Monica Valluri, an astronomer from the University of Michigan.
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Where is the dark matter of the Milky Way?
Detailed information about the trajectory of stars within the Galaxy will show the distribution of not only visible, but also dark matter, which makes up the bulk of the mass of most galaxies. And this, in turn, will help to understand what dark matter is.
Gaia can also test some exotic theories. Standard dark matter theory predicts that the galaxy's gravitational field is spherically symmetric near the galactic center, but then stretches out like a soccer ball, Valluri says. However, an alternative theory called MOND (Modified Newtonian Dynamics) suggests that this field is more like a pancake in shape. By analyzing the speed of the stars, which depends on the gravitational field, "Gaia" will be able to check which of the theories is correct.
Telescope data may even support the theory that dark matter killed the dinosaurs. If dark matter is concentrated in a relatively thin dark disk near the galactic plane, says this bold theory, then it could cause an asteroid crash that causes mass extinctions when the solar system periodically crosses this disk.
Disputed distances to stars
Accurate measurement of the distances from certain stars to the Sun will allow astrophysicists to refine their models of the evolutionary development of stars. The fact is that current theories rely mainly on distance estimates to understand how a star's brightness changes over time.
First of all, scientists will want to explore the open cluster of stars in the constellation Taurus of the Pleiades. According to observations, including with the Hubble Space Telescope, this cluster is located about 135 parsecs from us (this is 440 light years). But the results, based on data from the European high-precision parallax collection satellite HIPPARCOS, which were collected before the launch of Gaea, suggest that the Pleiades are only 120 parsecs away from us.
Some argue that this discrepancy casts doubt on the accuracy of HIPPARCOS. The Gaia telescope uses a similar but improved method, and so astronomers will keep a close eye on the observations. “I believe Gaia will surely refute the HIPPARCOS results,” said David Soderblom, who works at the Baltimore Space Research Institute and is the author of the Hubble research.
Thousands of new words
Astronomers have discovered thousands of planets orbiting other stars, in most cases registering tiny dips in the brightness of stars as a planet passes in front of them. Gaia will discover planets in a different way: by measuring the slight fluctuations in the position of the stars, which are caused by the force of gravity of the planets.
“You can bet that this mission will open up thousands of new worlds,” says astronomer at Yale University Gregory Laughlin (Gregory Laughlin).
The Gaia search method is best suited for discovering large planets in relatively large orbits, said Alessandro Sozzetti, a researcher at the Turin Astrophysical Laboratory in Italy, working for the Gaia Project. Unlike the first method, Gaia will directly measure the mass of the planets. If everything works out, it will be an amazing return to the technique with many false starts.
But discovering planets in this way will take several years of observation, with a preliminary review expected no earlier than 2018, Sozetti says.
How fast is the universe expanding
While Gaia will primarily explore the Milky Way, it will have an impact on the exploration of the entire observable universe.
The method of direct measurement of distances "Gaia" works only in relation to objects in our Galaxy and its immediate environment. To determine the distance to distant galaxies, astronomers usually wait for Type Ia stellar supernova explosions. The brightness of such a supernova indicates how far away the corresponding galaxy is. Such pointers, or "standard candles", are the main tool for determining the rate of expansion of the universe. The measurements have led astronomers to hypothesize that a mysterious "dark energy" is accelerating this expansion.
But in order to use supernovae as pointers, astronomers must compare them to other types of standard candles in our galaxy. "Gaia" in the near future will measure distances up to thousands of such stars with high accuracy. Over time, such measurements will allow cosmologists to refine their maps of the Universe, and possibly also resolve some contradictions in assessing the rate of its expansion.
H evidimaya asteroid threat
By continuously scanning the sky, Gaia will also detect things much closer to Earth. Ultimately, it could discover an estimated 350,000 asteroids within the solar system and detect hundreds of new asteroids, says Paolo Tanga, an astronomer from the Gaia program at the Nice Observatory in France. Among them will be near-earth objects, whose orbit will take them to a distance of about 200 million kilometers from the Earth.
Having detected such near-Earth objects, "Gaia" will alert laboratories, which can then use ground-based telescopes to determine how dangerous they are. Occupying an advantageous position in outer space, "Gaia" will scan almost the entire sky and detect objects that at certain times are very close to the Sun, which makes them impossible to observe from Earth, says Anthony Brown, an astronomer at the Leiden Observatory in the Netherlands. Brown, who leads the data processing team with Gay. “We will be able to observe them in areas that are usually inaccessible from Earth at the same time,” he says.
By monitoring the way certain asteroids orbit the Sun for several years, Gaia will be able to perform sophisticated tests of gravity from Einstein's theory of general relativity.