When two spiral galaxies collide, the stars generally do not run into each other, but the gas clouds do collide, triggering a burst of new star formation. (a) Estimate the probability that our Sun would collide with another star in the Andromeda Galaxy, if a collision between the Milky Way and Andromeda were happening at the present time. To simplify the problem, assume that each galaxy has 100 billion stars exactly like the Sun spread evenly over a circular disk with a radius of 100,000 light-years. (Hint: First calculate the total area of 100 billion circles with the radius of the Sun and then compare that total area to the area of the galactic disk.) (b) Estimate the probability that a gas cloud in our galaxy could collide with another gas cloud in the Andromeda Galaxy. To simplify the problem, assume that each galaxy contains 100,000 gas clouds of warm hydrogen gas, that each cloud has a radius of 300 light-years, and that these clouds are spread evenly over a circular disk with a radius of 100,000 light-years. [Hint: Use the same method as in part (a).]
Stellar evolution
We may see thousands of stars in the dark sky. Our universe consists of billions of stars. Stars may appear tiny to us but they are huge balls of gasses. Sun is a star of average size. Some stars are even a thousand times larger than the sun. The stars do not exist forever they have a certain lifetime. The life span of the sun is about 10 billion years. The star undergoes various changes during its lifetime, this process is called stellar evolution. The structure of the sun-like star is shown below.
Red Shift
It is an astronomical phenomenon. In this phenomenon, increase in wavelength with corresponding decrease in photon energy and frequency of radiation of light. It is the displacement of spectrum of any kind of astronomical object to the longer wavelengths (red) side.
When two spiral galaxies collide, the stars generally do not run into each other, but the gas clouds do collide, triggering a burst of new star formation. (a) Estimate the probability that our Sun would collide with another star in the Andromeda Galaxy, if a collision between the Milky Way and Andromeda were happening at the present time. To simplify the problem, assume that each galaxy has 100 billion stars exactly like the Sun spread evenly over a circular disk with a radius of 100,000 light-years. (Hint: First calculate the total area of 100 billion circles with the radius of the Sun and then compare that total area to the area of the galactic disk.) (b) Estimate the probability that a gas cloud in our galaxy could collide with another gas cloud in the Andromeda Galaxy. To simplify the problem, assume that each galaxy contains 100,000 gas clouds of warm hydrogen gas, that each cloud has a radius of 300 light-years, and that these clouds are spread evenly over a circular disk with a radius of 100,000 light-years. [Hint: Use the same method as in part (a).]
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