:: OSEL.CZ :: - Phantom drama: Something tore apart the nearest Hyada star cluster

–

Hyads and their stellar currents. Credit: ESA / Gaia / DPAC, CC BY-SA 3.0 IGO; acknowledgment: S. Jordan / T. Sagrista.

–

The European space observatory Gaia observes a large number of stars in detail. And as it turns out, it has become an immensely rich source of remarkable discoveries that emerge one after another. Now there was evidence in the observatory’s data that something had ruptured the nearest star cluster, or Hyada. Something extremely powerful and material, but at the same time completely invisible.

Tereza Jeřábková. Credit: ESA.

–

Tereza Jeřábková from the ESA European Space Research and Technology Center (ESTEC) and her colleagues found out. They used Gaia Observatory data from the Early third Data Release (EDR3) file, along with older observatory data. If they are not mistaken and we are really witnessing the destruction of the popular open star cluster Hyada, then we have probably traced the action of a large and material structure from dark matter, in this case referred to as subhalo dark matter. If such formations exist, they could be remnants of the Milky Way that now move through the Galaxy like unseen gravitational ghosts. And apparently they can do damage.

Researchers chose Hyades for their research because of their proximity. They are only about 153 light-years away. The cluster is visible to the naked eye on Taurus’s head, in the constellation of the same name. Hyades form several hundred stars, which occur mainly in a spherical region over 60 light-years in size. But that’s not all.

Hyades in an amateur film. Credit: Tdvance ~ commonswiki / Wikimedia Commons.

–

Star clusters such as Hyades lose stars in a “natural” way. When such a cluster forms, the stars act on each other by gravity and push into each other. Some get out of the star cluster and gradually move away. Another thing is that the gravity of the home galaxy, the Milky Way, “pulls” the stars out of the cluster. This creates two distinct streams of stars, ie “tidal tails”. Such currents are more well known in galaxy collisions, but it works very similarly in star clusters.

Tracking stellar currents from the Hyads was very difficult. It would not be possible without accurate measurements of distances and movements of more than one billion years in the Milky Way. Fortunately, we have such data, because that is exactly what is described in the work of the Gaia Observatory. Jeřábková a spol. they then simulated the behavior of the stars in the Hyades, during the history of this cluster, which is about 625 million years long.

Simulations and observations have shown that the trailing tidal tail has lost some of the stars. This suggests that the Hyades encountered much more brutal gravity than being dragged between the stars or the distant gravity of the Milky Way. According to the simulations, something about 10 million Suns has apparently encountered this “back” stellar current. It must have been a collision similar to the collision of galaxies that had consequences.

The problem is that nothing like this can be seen near Hyad. You won’t miss an object with a mass of 10 million suns, unless it’s something like a black hole or a structure made of dark matter. And researchers are also leaning towards the second option. Be that as it may, there is something in our relatively close cosmic neighborhood that the solar system would certainly not want to encounter. The consequences would probably be devastating. Hyades are 153 light-years away. The question is whether it is far enough.

Video: Locating the Hyades tidal tails