- 4076 - MILKY WAY GALAXY - learn about your home? How can we see our Galaxy while living inside it? All the stars we see is the Milky Way Galaxy, but, the milky path across the sky is what gives it its name. The Milky Way is what we see looking at our galaxy edge-wise.
----------- 4076 - MILKY WAY GALAXY - learn about your home?
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Ancients did not know these were stars.
It was in 1610 that humans first invented the telescope and could
resolve the milky path as consisting of billions of stars. We now know that our galaxy is a barred
spiral galaxy composed of 200,000,000,000 stars.
- The life of each of these stars is
determined by its mass. The very small
stars are Brown Dwarfs that are between 1.2 % and 7% of the mass of the
Sun. Their surface temperatures are 600
Kelvin compared to our Sun’s 5,600 Kelvin.
These Brown Dwarfs are not massive enough to fuse hydrogen. They produce their energy by fusing
deuterium, a special isotope of hydrogen.
- Stars the size of our Sun and up to 8 times
the mass of our Sun end their lives as “planetary nebula” leaving a core that
becomes a “White Dwarf” star. There are
3,000 planetary nebula that have been discovered in the Milky Way.
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- The planetary nebula itself will only live
for 10,000 years before the glowing gas dissipates into space. The Helix Nebula and the Ring Nebula
(M57) are 2 examples of planetary nebula
still alive. The White Dwarf that is
left behind slowly cools and exists forever as a big rock in space.
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- If a star is over 8 solar mass it ends its
hydrogen burning life as a supernova explosion.
Only 300 supernovae explosion remnants have been found in the Milky Way. The remnants of these explosions last about
50,000 years. So that works out to mean
there are about 1 or 2 supernovae explosions per century. The last one we say was in 1987.
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- Stars in Open Clusters like the Pleiades
(M45) and the Beehive Cluster (M44) are formed from hot, young stars formed out
of the gas clouds. There are 1,100 of
these Open Clusters in the Milky Way.
Estimates for the total number is up to 100,000.
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- Globular Clusters are millions of stars
that are much older and the clusters much bigger. The stars average 10 billion years old. The cluster can be 200 lightyears in
diameter. There are 200 of these
Globular Clusters found so far in the Milky Way.
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- The Bulge in the center of the Milky Way is
12,000 lightyears across, 10% the diameter of the galaxy. The center of the bulge is a Blackhole that
is 4,000,000 Solar Mass.
-
- Our Milky Way as several other dwarf
galaxies nearby. Some are even merging
with the bigger galaxy. Currently the
Milky Way is devouring the Sagittarius Dwarf Galaxy. The group of galaxies that are
gravitationally bound with the Milky Way are called the “ Local Group” of
galaxies. The Andromeda Galaxy is the
other big galaxy in our group.
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- Each galaxy is believed to be surrounded by
a halo of Dark Matter. the Dark Matter
halo that surrounds our galaxy is believed to be 600,000 lightyears
across. This Dark Matter contains 90% of
the mass of the total system.
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- A single nebulae like the “Rosetta Nebula”
or the “Eagle Nebula” (M16) have the capability to build 100,000 stars like our
Sun. The Orion Nebula (M42) is only
1,300 lightyears away and offers great viewing of star formation in
action. Great binocular viewing on a
clear night!
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- The number of planets in the Milky Way is
estimated to be 1,000,000,000,000, of which we have discovered 5,000, so far.
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- The Milky Way we can see is 120,000
lightyears across.
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- We are 26,000 lightyears from the center,
and 34,000 lightyears from the edge.
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- It takes us 225,000,000 years to complete
one orbit around the center.
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- The Sun is 4,500,000,000 years old while the oldest stars in the Milky Way are
13,200,000,000 years old. That means the
Milky Way first formed 1,500,000,000 years after the Big Bang.
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- The galaxies total mass is 1 trillion Solar
Mass, 10^12 Solar Mass. 90% of the mass
is Dark Matter. Resting inside the Dark
Matter is 200 billion stars. Our Sun is
one of them.
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July 4, 2023 MILKY WAY GALAXY
- learn about your home? 1114
4075
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Wednesday, July 5, 2023 ---------------------------------
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