Globular clusters are among the oldest objects in the Universe. The early Universe was filled with dwarf galaxies and its just possible that globular clusters are the remains of these ancient relics. Analysis of the stars in the clusters reveals ages in the region of 12-13 billion years old. A new paper just published shows that the globular clusters are home to two distinct types of stars; the primordial ones with normal chemical composition and those with unusual heavy amounts of heavier elements.
Continue reading “Globular Clusters Evolve in Interesting Ways Over Time”A Star Was Kicked Out of a Globular Cluster by an Intermediate-Mass Black Hole
Astronomers have solid evidence for the existence of stellar-mass black holes and supermassive black holes. However, evidence for Intermediate Black Holes (IMBHs) is more elusive. Their existence remains hypothetical.
However, study by study, evidence is accumulating for IMBHs. The latest comes from the globular cluster M15, where a fast-moving star suggests the presence of something massive. Could it be an elusive IMBH?
Continue reading “A Star Was Kicked Out of a Globular Cluster by an Intermediate-Mass Black Hole”Webb Sees Globular Clusters Forming in the Early Universe
Picture the Universe’s ancient beginnings. In the vast darkness, light was emitted from a particular galaxy only 460 million years after the Big Bang. On the way, the light was shifted into the infrared and magnified by a massive gravitational lens before finally reaching the James Webb Space Telescope.
The galaxy is called the Cosmic Gems arc, and it held some surprises for astronomers.
Continue reading “Webb Sees Globular Clusters Forming in the Early Universe”This Globular Cluster is Plunging Toward the Milky Way’s Centre
Globular clusters (GCs) are spherical groups of stars held together by mutual gravity. Large ones can have millions of stars, and the stars tend to be older and have lower metallicity. The Milky Way contains more than 200 globulars, possibly many more, and most of them are in the galaxy’s halo, the outer reaches of the galaxy.
But they’re not all in the halo, and astronomers are keen to find ones nearest the galactic centre. Now, researchers have found one GC that’s plunging toward the Milky Way’s Centre.
Continue reading “This Globular Cluster is Plunging Toward the Milky Way’s Centre”The Milky Way’s Stolen Globular Clusters
Modern astronomy holds that all major galaxies (with the Milky Way as no exception) are the accumulation of numerous small mergers. Thus, it should be expected that some of the globular clusters that are now part of our galaxy are likely inherited from other galaxies which have been cannibalized by the Milky Way, or even stolen from intact companion galaxies such as the Magellanic Clouds.
Associations between these clusters and the various progenitors began in the 1990’s, but recent research is beginning to paint a more comprehensive picture on exactly what percentage of our globular clusters were stolen, and precisely which ones.
Continue reading “The Milky Way’s Stolen Globular Clusters”The Hubble Imaged Some Globular Clusters in an Unusual Place: Near the Milky Way’s Centre
Our galaxy has about 200 Globular Clusters (GCs,) and most of them are in the galaxy’s halo. Astronomers think most GCs were taken from dwarf galaxies and merged with the Milky Way due to the galaxy’s powerful gravity. That explains why so many of them are on the outskirts of the galaxy. But they’re not all in the halo. Some are towards the Milky Way’s galactic bulge. What are globular clusters doing there?
Continue reading “The Hubble Imaged Some Globular Clusters in an Unusual Place: Near the Milky Way’s Centre”Where Are the Missing Black Holes? The Hubble May Have Helped Find One
Most black holes are stellar mass black holes. They’re created when a star several times more massive than our Sun reaches the end and collapses in on itself. There are also supermassive black holes (SMBH,) the behemoths at the center of galaxies that can boast billions of times more mass than the Sun.
But where are the intermediate-mass black holes?
Continue reading “Where Are the Missing Black Holes? The Hubble May Have Helped Find One”New Clues to the Formation of Globular Clusters: Their Ultramassive Stars
Globular clusters are odd beasts. They aren’t galaxies, but like galaxies, they are a gravitationally bound collection of stars. They can contain millions of stars densely packed together, and they are old. Really old. They likely formed when the universe was only about 400 million years old. But the details of their origins are still unclear.
Continue reading “New Clues to the Formation of Globular Clusters: Their Ultramassive Stars”Globular Star Clusters are Constantly Kicking Stars out of the Galaxy
All the stars we can see with the naked eye are part of the Milky Way. The gravitational power of the galaxy’s combined mass binds the stars to the galaxy. But sometimes stars are evicted from the galaxy.
These stars are called hypervelocity stars, and some of them are born from powerful gravitational interactions in globular clusters.
Continue reading “Globular Star Clusters are Constantly Kicking Stars out of the Galaxy”