Wandering Stars Have Been Adrift Between Galaxies for Billions of Years

Hubble Space Telescope images of two massive clusters of galaxies named MOO J1014+0038 (left panel) and SPT-CL J2106-5844 (right panel).. Credits: NASA/ESA/STScI/James Jee (Yonsei University)/Joseph DePasquale (STScI)

In the giant galaxy clusters in the Universe, which can consist of hundreds or thousands of galaxies, there are countless “rogue” stars wandering between them. These stars are not gravitationally bound to any individual galaxy but to the halo of galaxy clusters themselves and are only discernible by the diffuse light they emit – “Ghost Light” or “Intracluster light” (ICL). For astronomers, the explanation for how these stars became so scattered throughout their galaxy clusters has always been an unresolved question.

There are several theories, including the possibility that the stars were pulled from their galaxies, ejected in the course of galactic mergers, or were part of their cluster since its early formation billions of years ago. Using NASA’s Hubble Space Telescope, a team from Yonsei University, Seoul, and the University of California, Davis, conducted an infrared survey of distant galaxy clusters. Their observations suggest that these wandering stars have been adrift for billions of years and were not stripped from their respective galaxies.

Continue reading “Wandering Stars Have Been Adrift Between Galaxies for Billions of Years”

Astronomers Detect the Faint Glow of Stars in Between Galaxies

Light 'between' the groups of galaxies – the "intra-group light" – however dim, is radiated from stars stripped from their home galaxy. Image Credit: MARTÍNEZ-LOMBILLA ET AL./UNSW SYDNEY

Not all stars are members of galaxies. Some stars exist in the space between galaxies, though they didn’t form there. They’re called intra-group stars, and astronomers study them by observing their light, called intra-group light (IGL.)

They’re challenging to observe because their light is extremely faint and overpowered by the light of nearby galaxies.

Continue reading “Astronomers Detect the Faint Glow of Stars in Between Galaxies”