Researchers took a look at the long-anticipated third Gaia Space Telescope data release. They uncovered several exciting phenomena, including evidence for a significant event that took place relatively recently in our home galaxy.

Moreover, it shows the contraction and separation of the Magellanic clouds, the acceleration of our sun in its movement through the Milky Way and for the first time, astronomers are able to study the outer side of the galaxy accurately from Earth.

Furthermore, additional data is now available for 330,000 stars located within 325 light-years of Earth!

Star trails. — This image shows the movement speed of 40,000 stars in our Milky Way Galaxy over a compounded timespan of 400,000 years. - Credit: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO.

Our sun’s movement and acceleration throughout the Milky Way

In one of the new publications based on the recent Gaia data, scientists measured the acceleration of our Solar System with respect to the rest of the Universe. Using the detected motions of very distant galaxies, the velocity of the Solar System has been observed to change by 0.23 nanometers every second.

Because of this minute acceleration, the trajectory of the Solar System is deflected by the diameter of an atom every second; in the course of a year, this adds up to approximately 115 kilometers. The acceleration measured by Gaia is in agreement with the theoretical predictions. It provides the first assessment of the curvature of the Solar System's orbit around the galaxy in the history of optical astronomy.

According to NOVA, on the one hand, researchers are happy with these results because it means current theories are correct. But on the other hand, it also means that there are no unusual physical phenomena at play near our solar system as some scientists theorized, making things slightly less exciting as examples of theorized explanations ran pretty wild involving phenomena such as a collection of small black holes or a nearby area with unknown dark matter.

The image below shows the acceleration of our sun through the Milky Way. It has enabled astronomers to observe how our solar system moves slightly faster and faster through the Milky Way over time. The hundreds of objects depicted here are quasars, they are located many billions of light-years away and so we cannot see them moving. Still, they seem to move, as indicated by the arrows. That is because we ourselves move through the Milky Way. The apparent movements of the quasars allow us to measure the acceleration of the sun in its orbit through the galaxy.

Acceleration of our Solar System as it moves through the galaxy - Image Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO

Our Milky Way from the inside out

The latest Gaia dataset makes it easier to study the outer side of the galaxy more accurately from Earth. The great thing about looking towards the very edge of our galaxy – the so-called galactic anticentre – is that the movement of the stars directly indicates how they move through space. Eduardo Balbinot (Kapteyn Institute, University of Groningen) adds that the new data allows scientists to confirm that the disk of the Milky Way was much smaller about 10 billion years ago than it is now. According to Balbinot, researchers already suspected this to be the case, but now they can actually prove it.

Computer models predicted that the disc of the Milky Way would grow larger with time as new stars are born. The new data allow us to see the relics of the 10 billion-year-old ancient disc and so determine its smaller extent contrasted to the Milky Way's current disc size.

The data from these outer regions also strengthened the evidence for another major event in the more recent past of the galaxy as it shows that in the outer areas of the disc, there is a component of slow-moving stars above the plane of our galaxy that are heading downwards towards the plane, and a component of fast-moving stars below the plane that are moving upwards. This unusual pattern had not been predicted before and might be the result of the near-collision between the Milky Way and the Sagittarius dwarf galaxy that took place in our galaxy's more recent past.

The Sagittarius dwarf galaxy only contains a few million stars and is in the process of being absorbed by the Milky Way right now. Its last close pass with our galaxy was not a straight hit, but it would have been sufficient enough for its gravity to disturb some stars in our galaxy.

Magellanic Clouds

Amina Helm (University of Groningen) was involved with research into the 'dancing' Magellanic Clouds (two small neighboring galaxies of our Milky Way), stated in a NOVA press release that we can now accurately define the velocities and positions of stars in the Small and Large Magellanic Clouds. This allows scientists to infer that they first moved towards each other and then moved away from one another.

About Gaia

The European space satellite Gaia measured the speed and position of 1.8 billion stars in our Milky Way and our neighboring galaxies. These measurements can be used to make a 3D map of the galaxy. Additionally, the data also provides information about the composition, formation, and evolution of our galaxy and our closest neighbors. Gaia launched in 2013; however, the first significant piece of data was only released in 2016. The second collection followed in 2018; following that release, the first part of the third batch was released on the third of December 2020. The publication of the complete third data archive is planned for 2022.

Anthony Brown (Leiden University), head of the European Gaia Data Processing and Analysis Consortium (DPAC, the consortium that prepares the data for the database), stated that initially, the idea was to release all information from data release 3 at once in 2022, but they have decided to make the first installment of data available earlier, as it would be a shame to keep the astronomers waiting for this treasure trove of information while parts of it are processed earlier.

We can’t wait to see what the 2022 release of the complete dataset will bring and will keep you posted. In the meantime, if you are curious about this early release, be sure to check out the papers listed below.

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