3.2

A Cepheid variable in a nearby galaxy looks 106 (=1 000 000) times fainter thanan identical Cepheid within our Milky Way 1000 parsecs distant. How far away is the nearby galaxy? Hint: According to the inverse-square law, something will appear N times dimmer when it is square root of N (square root of N) times further away. 1 pc 1 kpc 1 Mpc 1 Gpc (=1000 Mpc)

1 Mpc

How long does it take light from the center of the Milky Way, 8 kpc away, to reach the solar system? Hints: Convert 8 kpc into pc (kiloparsecs into parsecs) using 1 kpc = 1000 pc. Convert that distance in parsecs to a distance in light-years using 1 pc = 3.26 ly. Since light takes one year of time to travel each light-year of distance, the answer should now be obvious. 2454 years 8000 years 24,540 years 26,080 years

26,080 years

A galaxy has a recession velocity of 19,250 kilometers per second, what is its distance in magaparsecs? Hint: Use Hubble's Law and H = 70 km/sec per Mpc. 275 Mpc 1161 Mpc 1741 Mpc 1,347,500 Mpc

275 Mpc

In the very distant future, given our best model of the accelerating universe, what will the universe look like? all the galaxies will start showing blue-shifts the universe will look pretty much the same as it does today the entire universe will become one huge black hole all the stars will die and the galaxies will be dark galaxies will shine even more brightly than today from all the dark energy i

??

In v = Hd, what is H called? Harlow's Folly Heisenberg Constant Hubble Constant Humason Ratio .

Hubble Constant

Why might a galaxy such as M31 (Andromeda) have a blueshift instead of a redshift? All nearby galaxies are blue in color. It is "behind" us, expanding in the opposite direction. It is undergoing a starburst, so it has many young, high-mass blue stars. Its orbital or local motion is bigger than the effect of the universe's expansion.

Its orbital or local motion is bigger than the effect of the universe's expansion

In our modern view of the expansion of the universe, we understand that it is space that is stretching; individual galaxies don't speed away from each other as if they were rockets. In that case, why do galaxies show a red-shift? as galaxies age, they get redder and redder as space stretches, the waves of radiation in space also stretch and their wavelength increases as space stretches, the presence of dark matter slows down the light between galaxies as time goes on, waves in space encounter more and more dust, and get redder

as space stretches, the waves of radiation in space also stretch and their wavelength increases

Most of the mass of a galaxy is contained in the form of black holes. cold interstellar gas. dark matter. O and B stars.

dark matter.

The reciprocal of the Hubble constant (1/H) is a rough measure of the: the period of a typical Cepheid variable the distance to the last galaxies that formed the age of the universe the luminosity of a type I supernova explosion

the age of the universe

One way astronomers deduce that the Milky Way has a disklike shape is that they see about the same number of stars in all directions in the sky. dark clouds of spinning gas and dust that must be flat. stars forming a circle around the north celestial pole. the great majority of stars in a band that encircles us.

the great majority of stars in a band that encircles us.