Some stars are not in the same group as the others. There are some stars in the space between the universes. Astronomers study them by observing the light they emit.

They are difficult to observe because their light is very weak and not as bright as nearby galaxies.

These stars are referred to as orphans by the astronomer. They were set loose into the universe. It's most likely that the cause is the interaction between the two galaxies.

A team of astronomer presented their findings in a paper. The title is "Galaxy and Mass Assembly (GAMA): extended intragroup light in a group at Z is 0.2 from deep Hyper Suprime-CAM images." The work was published in the monthly Notices of the Royal Astronomical Society.

According to Dr. Martnez-Lombilla, the bright parts of the light are 50 times fainter than the dark part of the sky. Even the largest telescopes on Earth can't detect it.

The National Astronomy Observatory of Japan (NAOJ) was the main developer of the Hyper Suprime cam. The camera is attached to the telescope. The summit of Hawaii's Maunakea is home to the 8.2-meter optical-infrared telescope.

The Hyper Suprime-Cam at the Subaru Telescope in Maunakea, Hawai?i. Image Credit: NAOJ

TheHSC is large. It is taller than a person. There is a 1.5 field of view. It has been in operation for three years and is currently on its third data release.

The analysis of extended faint structures within groups of galaxies can be done with the help of the new paper. The team looked at images from the survey. GAMA is a survey that looks at the evolution of the universe. The team combined data from GAMA and theHSC in their study.

The work is focused on a group of galaxies. The light is similar to looking back in time 2.5 billion years. The group is at red shift. The universe was 20% closer to each other than it was when it was first illuminated. The light is going to reach us.

400138 is a loose group of galaxies with three of them making up its dense core.

The core of the group is dense. Galaxies in these associations interact with one another in ways that cause stars from their original galaxies to be lost. Astronomers can't see individual stars They are too small to be seen by any observatory. If you have the right technique, they give off enough light to see it.

The light from the stars and the light from the galaxies can be removed. The light within the group is called the IGL or the light within thecluster is called the ICL.

Dr. Martnez-Lombilla said that they have developed a procedure that allows them to analyze the faintest structures in the Universe. The standard steps for the study of faint structures in astronomy are 2D modelling and the removal of all light except for the intra-group light.

This image from the study is a composite colour image of the 400138 group of galaxies. The numbers in white are individual galaxies, and the BCG is a bright cluster group. F1 and F2 are foreground galaxies, and S1, S2, and S3 are foreground stars. Image Credit: Martínez-Lombilla et al. 2022.
This image from the study is a composite colour image of the 400138 group of galaxies. The numbers in white are individual galaxies, and the BCG is a bright cluster group. F1 and F2 are foreground galaxies, and S1, S2, and S3 are foreground stars. Image Credit: Martínez-Lombilla et al. 2022.

The most important outcome is that every step of the study should be accounted for and eliminated. If you don't, your measurement will be wrong.

In astronomy, it's a common theme to remove unneeded light. Unlike other techniques, this one is modular and can be used in a variety of ways.

Dr. Martnez-Lombilla said that their technique is different because it is fully Python-based, so it is easy to apply to different sets of data from different telescopes.

This series of images shows a zoomed-in region of the study. Each panel represents a stage in the team’s image treatment procedure. 1 shows the region with the sky and stars subtracted. 2 shows the model of the three core galaxies and the IGL. 3 shows the core galaxies only. 4 shows the diffuse IGL only. Image Credit: Martínez-Lombilla et al. 2022.

Astronomers are interested in IGL because of its resemblance to a fossil record. Researchers can piece together the history of the universe by studying the amount of IGL. The pilot study shows that the Hyper Suprime- cam can be used to study the evolution of the universe.

The inter-group stars had different properties than the rest of the stars. Both of them are younger and less metal rich.

There are stray stars between the galaxies. We looked at the age and abundance of elements that composed them, and then we compared those features with the stars still belonging to galaxy groups, according to Dr. Martnez-Lombilla. The light from the group is younger and less metal-rich than the rest of the universe.

These results are in line with some of what we know about galaxy interactions. “These results are consistent with tidal stripping of the outer parts of Milky Way-like galaxies as the main driver of the IGL build-up,” the authors explain in their paper. “This is supported by the detection of substructure in the IGL towards the galaxy member 1660615, suggesting a recent interaction (<1>

The orphan stars have different properties than the other stars. The stars in the tail of a distant galaxy are similar to the ones in the picture. They are still bound to the group even though they were stripped of their origin.

According to Dr. Martnez-Lombilla, the individual stars were stripped from their home galaxies and now they are free to float. It's caused by the passage of massive satellite galaxies that pull stars in their wake.

This Hubble Space Telescope images show what tidal stripping looks like. The larger galaxy on the left is NGC 2207 and the less massive one on the right is IC 2163. NGC 2207's stronger tidal forces are stripping stars from IC 2163. The stripped stars are ejected into long streamers towards the right side of the image. The streamers are a hundred thousand light-years long. Image Credit: NASA and The Hubble Heritage Team (STScI).
This Hubble Space Telescope images show what tidal stripping looks like. The larger galaxy on the left is NGC 2207, and the less massive one on the right is IC 2163. NGC 2207’s stronger tidal forces are stripping stars from IC 2163. The stripped stars were ejected into long streamers towards the right side of the image. The streamers are a hundred thousand light-years long. (These galaxies are not part of the study but illustrate what tidal stripping looks like.) Image Credit: NASA and The Hubble Heritage Team (STScI).

Astronomers have never observed IGL from this group. The team can begin to piece together the history of the galaxies with the observations.

A fossil record of all the interactions a group of galaxies has undergone is provided by unveiling the quantity and origin of the light.

These events happened many years ago. We are observing the stars as they were 2.5 billion years ago. How long does it take for their light to reach us?

The formation and evolution of the universe is an important topic. The Universe started as a liquid and evolved into what we see today. The Large-Scale Structure of the Universe shows how matter is organized into more extensive patterns. Billions of light years are in some of the structures.

Image of the Universe’s large-scale structure, showing filaments and voids within the cosmic structure. Credit: Millennium Simulation Project.

The large-scale structure is made up of individual galaxies and stars. Stars rule our lives and our future. Understanding the context of our own galaxy, Solar System, and even our own civilization is one of the things that the effort to understand is about. There are forces that govern the evolution of the distant galaxies.

The pilot study was a success and the team would like to expand it.

We want to extend these results to a large sample of groups of galaxies. Dr. Martnez-Lombilla said that they could look at statistics and find out the typical properties of the formation and evolution of the group light.

The Vera Rubin Observatory will perform a large-scale survey called the Legacy Survey of Space and Time. Billions of objects will be imaged over a ten year period. One million of them are expected to be galaxy groups. A large number would be the basis for a large sample.

If the team can bring their method of studying light to bear on the LSST, it will add value to the effort.

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