What are the two techniques for measuring the mass of a galaxy?
Describe two techniques for measuring the mass of a galaxy. Astronomers can calculate the masses of some spiral galaxies by determining their rotation speed by measuring the Doppler shift of various spectral lines versus distance from the galactic center.
What does a galaxy’s rotation curve tell us about its total mass?
The rotation curve tells you the amount of mass inside a given distance from the center. You find how the mass is distributed in the Galaxy by looking at how the amount of enclosed mass changes with the size of the orbits.
What provides evidence of dark matter?
Primary evidence for dark matter comes from calculations showing that many galaxies would fly apart, or that they would not have formed or would not move as they do, if they did not contain a large amount of unseen matter.
What does the rotation curve and Kepler’s third law reveal about the Galaxy?
Rotation following Kepler’s 3rd law is shown above as planet-like or differential rotation. Notice that the orbital speeds falls off as you go to greater radii within the Galaxy. This is called a Keplerian rotation curve. This means that the mass of the Galaxy increases with increasing distance from the center.
What can you infer about the mass at the center of the galaxy?
Using such ideas and mathematical relations between various cosmic components, astronomers were able to infer how large and how massive the object at the center of our galaxy is. The object is likely 4.1 million solar masses, and 6.2 light hours in diameter (roughly Uranus’ orbit around the Sun).
How do astronomers know dark matter exists if they can’t see it?
If scientists can’t see dark matter, how do they know it exists? Scientists calculate the mass of large objects in space by studying their motion. Astronomers examining spiral galaxies in the 1970s expected to see material in the center moving faster than on the outer edges.
What is the fastest particle?
tachyon
Are black holes dark matter?
Dark matter, the mysterious substance that exerts gravitational pull but emits no light, might really consist of vast concentrations of ancient black holes created at the very start of the universe, according to a new study.