The most detailed star catalogue ever released
“Although the catalogue is based solely on the first two years of observations, it is already unmatched in terms of scope and accuracy. It is the most detailed star catalogue in the history of astronomy”, says Lennart Lindegren, astronomer at Lund University and initiator of the entire Gaia project.
The Gaia satellite was launched into space in December 2013 by the European Space Agency. Since the beginning of 2014, Gaia has been situated at the second Lagrange point approximately 1.5 million km from Earth.
From this position, it has helped researchers to map the exact location and brightness of 1.7 billion stars in the Milky Way, as well as the colours and proper motion of a very large proportion of these stars.
The extensive research material that has now been released is officially known as the Gaia Data Release 2. The catalogue is a milestone of the Gaia project, as astronomers can now, for the first time on a large scale, compare theoretical models of the Milky Way with direct measurements of how its stars are distributed, that is, their three-dimensional positions and movement patterns.
The catalogue contains information about the physical properties of the stars, particularly their luminosity and temperature, which give an idea of when the stars were formed. All in all, it not only enables mapping the current structure of the Milky Way, but also provides better knowledge of its emergence and development, which is one of the main aims of the Gaia project.
The brand-new catalogue also contains the spectroscopic radial speeds of more than 7 million stars, which enables researchers to calculate the stars’ paths in the galaxy. It provides the estimated temperature of 160 million stars, and a record of almost half of the stars’ luminosity, i.e. the total amount of energy emitted in Watts. Another aspect mapped through Gaia is interstellar extinction, that is, the amount of dust in space between a given star and us. This has been measured for 88 million stars.
The observations made through Gaia are not limited to the stars in the Milky Way. There are also accurate positions for closer objects, namely 14 000 asteroids in our own solar system. Gaia has also managed to collect data from space outside the Milky Way by determining, with high precision, the position of half a million active galaxy cores, known as quasars.
Researchers at Lund University have worked on the Gaia project for over 20 years, and have played a prominent role since the first ideas were drafted in 1993. It was Lennart Lindegren who, 25 years ago, submitted the proposal to the European Space Agency to focus on a high-tech satellite project for measuring distance in space. In recent years, more than 400 astronomers in Europe have been involved.
Gaia’s measurements were initially planned to be conducted for five years, but the researchers now hope that the satellite will receive approval to continue its observations for another five years. The technical lifespan of the satellite is estimated to be a total of 10 years.
“Future Gaia catalogues will enable discoveries of thousands of so far unknown exoplanets around stars other than the Sun”, says Lund astronomer David Hobbs who has been Lindegren’sclosest colleague within the Gaia project since 2007.
The discovery of exoplanets is enabled by measuring the interference in the stars’ positions caused by the planets in question. Together with former Lund colleague, Piero Ranalli, Hobbs and Lindegren recently published a study on the value of allowing Gaia to continue for another five years.
According to the study, large exoplanets with orbits of up to 20 years may be discovered around most sun-like stars at a distance of up to 65 light years from Earth; this involves approximately 750 stars. These types of Jupiter-like giant planets are important for the stability of the exoplanet systems and for the possibility of life evolving in these systems, but they are difficult to detect using other methods.
“Our study therefore provides a strong argument for continuing the Gaia observations as long as it is technically possible”, concludes Lennart Lindegren.
Lena Björk Blixt