Hubble Uncovers a Lot of New Globular Star Clusters

Hubble Uncovers a Lot of New Globular Star Clusters

At first glance, this image is dominated by the vibrant glow of the swirling spiral to the lower left of the frame. However, this galaxy is far from the most interesting spectacle here — behind it sits a galaxy cluster. Galaxies are not randomly distributed in space; they swarm together, gathered up by the unyielding hand of gravity, to form groups and clusters. The Milky Way is a member of the Local Group, which is part of the Virgo Cluster, which in turn is part of the 100 000-galaxy-strong Laniakea Supercluster. The galaxy cluster seen in this image is known as SDSS J0333+0651. Clusters such as this can help astronomers understand the distant — and therefore early — Universe. SDSS J0333+0651 was imaged as part of a study of star formation in far-flung galaxies. Star-forming regions are typically not very large, stretching out for a few hundred light-years at most, so it is difficult for telescopes to resolve them at a distance. Even using its most sensitive and highest-resolution cameras, Hubble cannot resolve very distant star-forming regions, so astronomers use a cosmic trick: they search instead for galaxy clusters, which have a gravitational influence so immense that they warp the spacetime around them. This distortion acts like a lens, magnifying the light of galaxies sitting far behind the cluster and producing elongated arcs like the one seen to the left of centre in this image.
Credit: NASA

Scientists may have moved a step closer towards finding the origin of galaxies.

Using NASA’s Hubble Space Telescope, astronomers have discovered a huge cluster of stars about 300 million light-years away. The number of these star clusters reach a total of a whopping 22,426.

Globular star clusters are more common than full-scale galaxies which makes it easier to study the effects of gravity on space. Published in ‘The Astrophysical Journal’, a survey will allow astronomers to create a map of these stars and the matter around them.

The unseen mass, which we know nothing of, is often referred to as Dark Matter. To visualize a star cluster, it looks like a globe shaped white entity which is made up of thousands of stars.

We don’t need to look much far to see such clusters as our own galaxy, the Milky Way, is home to about 150 such clusters, which appear as ‘blurry’ stars. They are at such a massive distance that they appear as tiny dots of light even to state-of-the-art telescopes like Hubble. These clusters are thought of to be ancient, as old as the creation of the galaxy itself.

For sake of understanding, the universe can be divided into several components. Some of these common components include Clusters, Galaxy Groups, Galaxies, and Super-clusters. So far, there is no definitive conclusion as to how these star clusters actually form. We only know that the clusters are present due to the gravitational pull of all these stars.

It is believed that they have low metallicity as they are really old. In the world of astronomy, metals are any components besides Hydrogen and Helium. Old stars have low metallicity because ‘metals’ are used up as nuclear fusion occurs inside the core of the star.

It is possible that the stars inside the discovered cluster may be so old that they were the part of the Big Bang itself. Some of these clusters appear to form ‘bridges’ between galaxies, the reason for which is unknown.

Even though Hubble can view the clusters, it is at a big disadvantage: the telescope has a tiny field of view. On the bright side, Hubble’s resolution and level of detail it captures is unmatched. Juan Madrid, an Astronomer at the Australian Telescope National Facility in Sydney, talked about that and said,

“One of the cool aspects of our research is that it showcases the amazing science that will be possible with NASA’s planned Wide-Field Infrared Survey Telescope (WFIRST) that will have a much larger field of view than Hubble. We will be able to image entire galaxy clusters at once.”

To map the stars, numerous images stored in the Space Telescope Science Institute were used together. The program also allowed students with little to no prior experience, learn and gain experience in the field of Astronomy. The team behind the discovery developed algorithms to scan the images and to filter out the unneeded background details such as other galaxies and stars.

This allows the astronomers to view the clusters without distractions from other entities. One may wonder: why are astronomers studying these ‘fuzzy’ stars? For starters, studying these clusters is essential for understanding how the galaxies were created and what processes took place. Karla Alamo-Martinez, who was a part of the researching team, referred to the importance of this discovery in the following words:

“In our study of Abell 1689, we show how the relationship between globular clusters and dark matter depends on the distance from the center of the galaxy grouping. In other words, if you know how many globular clusters are within a certain distance, we can give you an estimate of the amount of dark matter.”

John Blakeslee, the Team Lead of the study, strengthened her claims by saying:

“The globular clusters are fossils of the earliest star formation in Abell 1689, and our work shows they were very efficient in forming in the denser regions of dark matter near the center of the galaxy cluster. Our findings are consistent with studies of globular clusters in other galaxy clusters but extend our knowledge to regions of higher dark matter density.”

In the near future, the James Webb Space Telescope will take clearer images of the clusters. Many of these clusters are not clearly visible to Hubble because the brightness is not enough for Hubble to catch. James Webb Space Telescope is equipped with upgraded systems that will allow it to take not only better images but will also enable it to discover more globular star clusters.

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