- 2057
- Our closest galaxy, not the
Andromeda Galaxy. - The Andromeda Galaxy is our
closest large spiral galaxy. The closest
small galaxies are a formation that is actually within the Milky Way itself. These are dwarf galaxies that we’ve only known
about the last ten years. The closet
known galaxy in the Milky Way is the Canis Major Dwarf Galaxy.
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---------------------------------- 2054 -- Our Closest Galaxy
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- Scientists
have known for some time that the Milky Way Galaxy is not alone in the
Universe. In addition to our galaxy being part of the Local Group of galaxies. The Local Group is a collection of 54 galaxies
and dwarf galaxies. Our galaxy is also part of the larger
formation known as the Virgo Supercluster of galaxies.
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- The Andromeda
Galaxy is our closest large spiral galaxy. The closest small galaxies are a formation that
is actually within the Milky Way itself. These are dwarf galaxies that we’ve only known
about the last ten years.
-
- The closet known small galaxy in the Milky Way
is the Canis Major Dwarf Galaxy. This stellar formation is about 42,000 light
years from the galactic center, and 25,000 light years from us. This puts it
closer to us than the center of our own galaxy, which is 30,000 light years
away from the Solar System.
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- The Canis Major Dwarf Galaxy Dwarf Galaxy is
believed to contain one billion stars in all. A high-percentage
of which are in the Red Giant Branch phase of their lifetimes. It has a roughly
elliptical shape and is thought to contain as many stars as the Sagittarius
Dwarf Elliptical Galaxy, the previous contender for closest galaxy to our
location in the Milky Way.
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- In addition to the dwarf galaxy itself, a long
filament of stars is visible trailing behind it. This complex, ring like structure
wraps around the galaxy three times. It was in the course of investigating this
ring of stars that the Dwarf Galaxy was first discovered. The current theory is
that this galaxy is being accreted ,or swallowed up, by the Milky Way Galaxy.
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- Other globular clusters that orbit the center
of our Milky Way as a satellite, NGC 1851, NGC 1904, NGC 2298 and NGC 2808, are thought to have been part of this Dwarf
Galaxy before its accretion. It also has associated open clusters, which are
thought to have formed as a result of the dwarf galaxy’s gravity perturbing
material in the galactic disk and stimulating star formation.
-
- Prior to its discovery, astronomers believed
that the Sagittarius Dwarf Galaxy was the closest galactic formation to our
own. At 70,000 light years from Earth, this galaxy was determined in 1994 to be
closer to us than the Large Magellanic Cloud, the irregular dwarf galaxy that
is located 180,000 light years from Earth, and which previously held the title
of the closest galaxy to the Milky Way.
-
- All of that changed in 2003 when The Canis
Major Dwarf Galaxy was discovered.
The discovery came from a survey of 70% of the sky that
detecting about 5,700 celestial sources of infrared radiation. Infrared
astronomy takes advantage of advances in astronomy that see more of the
Universe because infrared light is not blocked by gas and dust to the same
extent as visible light.
-
- Using infrared telescopes the astronomers were
able to detect a very significant over-density, giant stars in a part of the sky occupied by
the Canis Major constellation. The cool,
“Red Dwarfs” are not very luminous compared to other classes of stars, and
cannot even be seen with the naked eye. However, they shine very brightly in
the infrared and appeared in great numbers.
-
- The discovery of this galaxy and the analysis of
the stars associated with it has provided some support for the current theory
that galaxies may grow in size by swallowing their smaller neighbors. The Milky
Way became the size it is now by eating up other galaxies.
-
- The Sagittarius Dwarf Elliptical Galaxy held the position of closest galaxy to our own
prior to 2003 at 75,000 light years away. This dwarf galaxy, which consists of
four globular clusters that measure some 10,000 light-years in diameter, was
discovered in 1994. Prior to that, the Large Magellanic Cloud was thought to be
our closest neighbor.
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- The Andromeda Galaxy (M31) is the closest
spiral galaxy but it is 2,540,000 light
years away. Andromeda is currently approaching our galaxy at a speed of about 68
miles per second (244,800 miles per hour). In roughly 4 billion years, the Andromeda
Galaxy is expected to merge with our own, forming a single, "super-galaxy".
-
- Astronomers also believe that the Canis Major
Dwarf Galaxy is in the process of being pulled apart by the gravitational field
of the more massive Milky Way Galaxy. The main body of the galaxy is already
extremely degraded, a process which will continue as it travels around and
through our Galaxy.
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- In time, the
accretion process will likely culminate with the Dwarf Galaxy merging entirely
with the Milky Way depositing its 1 billion stars to the 200 t0 400 billion
that are already part of our galaxy. Let
me know how it goes.
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Some reviews are at:
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------------------------- Tuesday, April 10, 2018
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