- 3923 - GALAXY CLUSTERS - and our Milky Way? The globular cluster of stars is located around 31,000 light-years from Earth in the inner region of the Milky Way. This is so deep into our galaxy that it is just 4,600 light-years from our galaxy's central supermassive black hole, Sagittarius A*.
-------- 3923 - GALAXY CLUSTERS - and our Milky Way?
- Globular
clusters like this one are home to tens of thousands to millions of stars, all
tightly bound by mutual gravitational attraction. These dense stellar
populations give globular clusters a roughly spherical shape.
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- The globular
cluster NGC 6355, located in the inner Milky Way, is densely packed with tens
of thousands to millions of stars.
Globular clusters are found in galaxies of all shapes and sizes and tend
to be the oldest structures in their home galaxies. They are packed with older
and redder stars than those found in open star clusters, which are smaller than
globular clusters.
-
- The central
red and blue stars of NGC 6355 can be distinguished clearly, demonstrating the tremendous observational
power of the Hubble telescope, which has revolutionized the study of globular
clusters.
-
- Hubble is
capable of capturing these amazing views because it is positioned around 330
miles above our planet's surface. This vantage point frees the telescope from
the distorting effects of Earth's atmosphere that make it almost impossible for
ground-based telescopes to distinguish the individual stars in globular
clusters.
-
- In 2006,
the telescope made the first direct observations of white dwarfs, faint stellar
remnants that form when stars with masses similar to the sun's run out of fuel
for nuclear fusion and undergo gravitational collapse, in globular star
clusters. These observations gave astronomers a better understanding of the
ages and origins of stars in globular clusters and the evolution of those
clusters.
-
- In 2021,
Hubble observations allowed astronomers to make the first measurement of black
holes in the core-collapsed globular cluster NGC 6397. They were expecting to
find an intermediate-mass black hole at the heart of this globular cluster, but
instead, they discovered a concentration of smaller black holes throughout NGC
6397, which is located around 7,800 light-years from Earth.
-
- Hubble also
has produced images of Messier 15, which, at about 12 billion years old, is the
most ancient known globular cluster.
-
- Astronomers
have discovered new evidence that Andromeda, the galaxy next door to our own,
grew by merging with another galaxy. The event triggered a mass migration of
stars into the galaxy.
-
- This event
suggests that the migration of stars to Andromeda and the galaxy's growth
history is very similar to that of the Milky Way. That means the findings have
implications for our understanding of both galaxies.
-
- The
evidence came from observations of the individual motions of almost 7,500 stars
in the inner halo of Andromeda. This showed these stars had begun their lives
as part of another galaxy that merged with Andromeda around 2 billion years
ago.
-
- Scientists
have long predicted that large galaxies like the Milky Way and Andromeda have
grown to their current sizes via collisions and mergers throughout their
history, but the patterns in the motions of stars that could confirm this have
been elusive.
-
- Although
the night sky may seem unchanging, the universe is a dynamic place. Galaxies
like M31 and our Milky Way are constructed from the building blocks of many
smaller galaxies over cosmic history.
-
- The majority
of the stars in the Milky Way's halo are also believed to have originated in
another galaxy finding a new galactic home during a massive merger event
thought to have occurred between 8 to 10 billion years ago.
-
- Looking at
relics of a previous merger and stellar migration event in Andromeda could help
astronomers hunt for similar artifacts in our own galaxy. The history of the Andromeda Galaxy is
similar to that of our own galaxy, the Milky Way. The inner halos of both
galaxies are dominated by a single immigration event.
-
- To trace
stellar migration in the galaxy, the team turned to DESI due to the fact that
it is the most powerful multi-object survey spectrograph in the world, capable
of measuring the spectra of more than 100,000 galaxies in a single night.
-
- The
astronomers will now continue to use the team-up between DESI and the Mayall
Telescope to investigate stars located closer to the edge of Andromeda. They
hope this will further reveal the galaxy's structure and the immigration
history of its stars.
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- It's
amazing that we can look out at the sky and read billions of years of another
galaxy's history as written in the motions of its stars — each star tells part
of the story. Who knows what new
discoveries await!
-
March 19, 2023 GALAXY CLUSTERS
- and our Milky Way 3923
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------ “Jim Detrick” -----------
--------------------- --- Sunday, March 19, 2023
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