6 Questions
What is the estimated age of the Milky Way Galaxy?
13.6 billion years old
Which component of the Milky Way Galaxy is estimated to make up around 90% of its mass?
Dark matter
How far away are the most distant stars and gas clouds in the Milky Way system whose distances have been reliably determined?
100,000 light-years
Which part of the Milky Way Galaxy is responsible for its rich and complex structure?
Central bulge
What is the approximate diameter of the Milky Way Galaxy?
$100,000$ light-years
Which part of the Milky Way Galaxy did Shapley's model accurately predict the size of?
Disk
Study Notes
The Milky Way Galaxy, our home galaxy, is a barred spiral galaxy with a rich and complex structure. It is estimated to be about 13.6 billion years old and has a diameter of approximately 100,000 light-years. The Milky Way is composed of various components, including a nucleus, a central bulge, a disk (both thin and thick), spiral arms, a spherical halo, and a massive halo of dark matter.
Structure
The Milky Way's structure can be viewed as consisting of six separate parts: a nucleus, a central bulge, a disk (both thin and thick), spiral arms, a spherical component, and a massive halo. The disk of the Milky Way system is just about as large as Shapley's model predicted, with neutral hydrogen somewhat more widely dispersed and dark matter perhaps filling an even larger volume than expected. The most distant stars and gas clouds of the system that have had their distance reliably determined lie roughly 100,000 light-years away.
Composition
The Milky Way Galaxy contains hundreds of billions of stars and large amounts of interstellar gas and dust. The precise constituents, shape, and true size and mass of the Milky Way are still not fully known, but it is estimated that dark matter makes up to 90% of the galaxy's mass.
Size
The size of the Milky Way is vast. It has a diameter of about 100,000 light-years and the Sun is located about 25,000 light-years from the center. The solar system, where our planet Earth resides, orbits the center of the Milky Way, taking approximately 250 million years to complete one orbit.
Galactic Center
At the very center of the Milky Way lies a massive black hole called Sagittarius A*, which has a mass of about 4 million times that of the sun. The existence of this black hole has been confirmed by radio observations and other data.
Spiral Arms
The Milky Way has four main spiral arms: Perseus, Scutum-Centaurus, Sagittarius, and the Local Arm. These arms are home to a high concentration of stars, dust, and gas, which trigger more intense star formation. The spiral arms are like traffic jams, with gas and stars crowding together and moving more slowly in the arms, leading to more star formation.
Explore the rich and complex structure of the Milky Way Galaxy, including its nucleus, central bulge, disk, spiral arms, spherical halo, and massive dark matter halo. Learn about the vast size of the galaxy, containing billions of stars and interstellar gas, and the presence of a massive black hole at its center.
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