The Hyades star collection is gradually coming together with a backdrop of stars in the Milky Way. The browser is located 153 light-years away and is visible to the unsupported eye as the brightest V-shaped members of stars are in the Taurus constellation, the Bull. This image shows members of the Hyades as identified in the Gaia data. These stars are highlighted in pink, and the shapes of the various constellae are in green. Stars from the Hyades can be seen stretching out from the main group to form two ‘tails’. These tails are called tidal tails through which stars leave the universe. The image was created using Gaia Sky. Credit: ESA / Gaia / DPAC, CC BY-SA 3.0 IGO; confession: S. Jordan / T. Sagrista.
Data from ESA ‘s Gaia star mapping satellite have revealed interesting evidence that the gravitational impact of a large but unseen structure in our galaxy is disturbing the star group closest to the Sun.
If true, this could provide evidence for a suspected population of ‘dark subject sub-halos’. These invisible clouds of grains are thought to be memories from the creation of the Sweet Way, and are now scattered throughout the constellation, forming an invisible substructure that will give a noticeable gravitational effect to anything that moves too close to it.
The discovery was made by Tereza Jerabkova, ESA Researcher, and colleagues from ESA and the Southern European Observatory while studying the way in which nearby star clusters coalesce into general background of stars in our galaxy. This finding was based on Gaia’s third early data message (EDR3) and data from the second message.
The true extent of Hyades’ tidal tails was revealed for the first time with data from ESA’s Gaia mission. The Gaia data has allowed the old members of the star clock (shown in pink) to be traced across the entire sky. These stars are highlighted in pink, and the shapes of the various constellae are in green. The image was created using Gaia Sky. Credit: ESA / Gaia / DPAC, CC BY-SA 3.0 IGO; confession: S. Jordan / T. Sagrista
The team chose the Hyades as their target because it is the closest star cluster to the Sun. Located just over 153 light-years away, it is easily visible to observers in the northern and southern hemispheres as a prominent ‘V’ shape of bright stars marking the bull’s head. in the constellation Taurus. Beyond the bright and easily visible stars, telescopes reveal a hundred or so weaker ones that are in a spherical space, about 60 light-years across.
A star browser naturally misses stars because as these stars move within the universe they pull apart with each other. This permanent thatch changes the speed of the stars, moving some to the edges of the cluster. From there, the stars can be swept away by the galaxy’s drag, forming two long tails.
One tail follows the gathering of the stars, and the other pulls out in front of it. They are called tidal tails, and have been extensively studied in striking galaxies but have never been seen from a nearby open star group, until recently.
The key to finding tidal tails is to see which stars in the sky are moving in the same way as the group of stars. Gaia makes this easy because it definitely measures the speed and movement of over a billion stars in our galaxy. “These are the two most important measures we need to find tidal tails from star records in the Milky Way,” says Tereza.
Previous attempts by other teams have had little success as the researchers had only observed stars that closely matched the movement of the stars. This excluded members that disappeared earlier than 600-700 million years of history and are therefore now traveling in different orbits.
To understand the range of orbits found, Tereza built a computer model that would resemble the various collisions that escaping stars in the cluster could feel through hundreds of millions of their years in space. It was only after running this code, and then comparing the symbols to the actual data that the true level of Hyades tidal tails was revealed. Tereza and his colleagues found thousands of former members in Gaia data. These stars now stretch for thousands of light years across the constellation in two tidal tails.
But the real surprise was that the tide of the tide seemed to be missing stars. This shows that something far more brutal is happening than the star collection is gently ‘spreading’.
Running the symbols again, Tereza showed that the data could have been reproduced if that tail had been hit by a cloud of matter containing about 10 million solar masses. “Maybe there was a close interaction with this horrible lump, and the Hyades just broke up,” she says.
But what could that clump be? No gas cloud or nearby star browser is seen. If a visible structure is not found even in future targeted investigations, Tereza suggests that something could be a sub-halo of dark matter. These are lumps of naturally occurring dark material that are thought to help shape the constellation when it is formed. This new work demonstrates how Gaia is helping astronauts map out this invisible dark subject frame of the galaxy.
“With Gaia, the way we see the Sweet Trail has changed completely. And with these findings, we will be able to map the Milky Way infrastructure much better than ever before, ”said Tereza. And after proving the approach with the Hyades, Tereza and colleagues are now expanding the work by looking for tidal tails from other star farther fuels. .
Details: “The 800 pc tidal tails of Hyades star group: A possible discovery of the epicyclic horrors of a candidate from an open star group” by Tereza Jerabkova, Henri MJ Boffin, Giacomo Beccari, Guido de Marchi , Jos HJ de Bruijne and Timo Prusti, 24 March 2021, Astronomy and Astronomy.
DOI: 10.1051 / 0004-6361 / 202039949