Research presents most detailed ever catalogue of our galactic neighbourhood

An international team of astronomers, including experts from the University of Leicester, have today (Thursday) announced the most detailed ever catalogue of stars in a huge swathe of our Milky Way galaxy.

The measurements of stellar position and movement are included in the third data release from the European Space Agency’s Gaia space observatory, now publicly available.

Initial findings include the first optical measurement of the acceleration of the solar system. The data set, and early scientific discoveries, were presented at a special briefing by the Royal Astronomical Society.

Professor Martin Barstow is a professor of astrophysics and space science at the University of Leicester and director of strategic partnerships for Space Park Leicester, and formed part of the team who analysed data from the Gaia satellite.

He said:

“The Gaia Catalogue of Nearby Stars, one of the papers published using this data release, is the most complete survey of the solar neighbourhood yet, cataloguing more than 300,000 stars within 236 light years of the Sun.

“Measurements of the motion of these stars reveal that the solar system is at a ‘cosmic cross-roads’ of constantly-changing stellar patterns as these stars orbit in the disk of the Milky Way.”

Launched in 2013, the Gaia space observatory orbits the so-called Lagrange 2 (L2) point, approximately 1.5 million kilometres away from the Earth. At this point the gravitational forces between the Earth and Sun are balanced, meaning the spacecraft can operate in a stable position with long-term views of the sky unobstructed by either body.

Gaia continuously scans the sky, measuring any change in the positions of stars and other objects over time resulting from the Earth’s movement around the Sun.

Using the parallax method, scientists can then use any tiny shift in the apparent position of a star to calculate its distance from our solar system.

On Earth this is made more difficult by the blurring of the Earth’s atmosphere, but in space the measurements are only limited by the optics of the telescope.

This new data brings the total number of stars catalogued to just under 2 billion, with the accuracy of their positions significantly more accurate than in earlier data.

An area of particular focus for the Leicester researchers also used new data of the 300,000 stars within the closest 326 light years to the Sun to predict how the star background will change in the next 1.6 million years. They also confirm that the solar system is accelerating in its orbit around the Galaxy.

This acceleration is gentle, and is what would be expected from a system in a circular orbit. Over a year the Sun accelerates towards the centre of the Galaxy by 7 mm per second, compared with its speed along its orbit of about 200 kilometres a second.

Dr Floor van Leeuwen of the Institute of Astronomy at the University of Cambridge led the new work, and said:

“Gaia is measuring the distances of hundreds of millions of objects that are many thousands of light years away, at an accuracy equivalent to measuring the thickness of hair at a distance of more than 2000 kilometres.

“These data are one of the backbones of astrophysics, allowing us to forensically analyse our stellar neighbourhood, and tackle crucial questions about the origin and future of our galaxy.”

Gaia also tracks the changing positions of the stars over time across the line of sight (their so-called ‘proper motion’), and by splitting their light into spectra, measures how fast they are moving towards or away from the Sun and assesses their chemical composition.

Gaia findings also show the two largest companion galaxies to the Milky Way, the Small and Large Magellanic Clouds, allowing researchers to see their different stellar populations and their make-up. A dramatic visualisation shows these subsets, and the bridge of stars between the two systems.