Astronomers observe the faint light of orphan stars

(ORDO NEWS) — The new method made it possible to see the radiation of stars that left their home galaxy. Their light is ten times weaker than the darkest night sky, but retains traces of past interactions between neighboring galaxies.

The vast majority of stars are part of galaxies that form gravitationally bound groups . However, individual stars can be ejected outside the parent galaxies, ending up in the empty space between them.

“The brightest regions of this radiation glow about 50 times fainter than the darkest night sky on Earth,” explained astrophysicist Cristina Martinez-Lombilla (Cristina Martínez-Lombilla). “It is very difficult to see even with the largest ground and space telescopes.”

Together with colleagues from the Australian University of New South Wales, she developed a new data processing method that allows you to get rid of the “extra” radiation and distinguish between the light of stars located between the galaxies of the group.

The effectiveness of this approach was demonstrated using the example of the 400138 group, for which it was possible to estimate the age and composition of stars ejected from parent galaxies.

Astronomers observe the faint light of orphan stars 2
Galaxy group 400138 is about 2.5 billion light-years away

“Intra-group” (intra-group) stars 400138 turned out to be younger than the stars located in the nearest galaxies, and contain less metals, elements heavier than hydrogen and helium. These properties bring them closer to the stars located in the elongated tail of one of the group’s more distant galaxies.

Apparently, these stars were thrown out of their places under the influence of the gravity of the galaxy passing nearby and turned out to be free-flying, following the group that attracts them.

“The amount and origin of intragroup radiation serves as a kind of fossil record that preserves the events that a group of galaxies experienced in the distant past, and gives us a holistic view of its history,” Martinez-Lombilla added.

In the future, scientists plan to apply their method to observe other groups of galaxies and the light of their “orphan stars”.

By collecting enough data, it will be possible for the first time to obtain statistics on the general properties of these stars, as well as the events experienced by groups of galaxies during their evolution.


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