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What is the typical hydrogen content of stars that are forming right now in the vicinity of the sun?

70 %

What is the most common form of gas in the interstellar medium?

About 15% of the visible matter in the Galaxy is in the form of gas and dust, serving as the raw material for new stars. About 99% of this interstellar matter is in the form of gas—individual atoms or molecules. The most abundant elements in the interstellar gas are hydrogen and helium.

What kind of star is most likely to be found in the halo?

Old stars with few heavy elements are referred to as population II stars and are found in the halo and in globular clusters. Population I stars contain more heavy elements than globular cluster and halo stars, are typically younger and found in the disk, and are especially concentrated in the spiral arms.

How do we determine the Milky Way’s mass?

For spiral galaxies the rotation curve is used to measure their masses like is done to find the mass of the Milky Way. The rotation curve shows how orbital speeds in a galaxy depend on their distance from the galaxy’s center.

Where is the most mass in the Milky Way?

The new mass estimate puts our galaxy on the beefier side, compared to other galaxies in the universe. The lightest galaxies are around a billion solar masses, while the heaviest are 30 trillion, or 30,000 times more massive.

Where in the Milky Way would you most likely find a globular cluster?

Globular star clusters are known to be located mostly in the great spherical halo of the Milky Way. Spiral galaxies like our Milky Way contain stars, gas and dust, mostly organized into a flat disk containing the spiral arms, but with the addition of a more rounded bulge and halo, centered on the galaxy’s center.

How can you tell how old a globular cluster is?

By determining the mass of the main-sequence turnoff stars, we get the age of the cluster. The cluster age equals the main-sequence lifetime of the turnoff stars. This is one of the ways we have studied the age of the Universe and the formation history of the Galaxy.

How old is the oldest globular star cluster?

about 12.8 billion years

Why do astronomers believe that most globular clusters are made of old stars?

Why do astronomers believe that most globular clusters are made of old stars? they have high amounts of heavy elements that newer stars like the sun do not have. They are related to the instability strip because higher mass stars become cepheids when they pass across the instability strip.