Question

Multiple choice: Which one of the following has not been used to suggest that there is “dark matter” in the Universe?

(a) The orbital speeds of planets around the Sun.

(b) The orbital speeds of stars in our Milky Way Galaxy and in other spiral galaxies.

(c) The orbital speeds of galaxies in binary pairs.

(d) The orbital speeds of galaxies in clusters.

(e) The gravitational lensing of background galaxies by foreground clusters of galaxies.

Multiple choice: Which one of the following statements about galaxies is false?

(a) Our Milky Way Galaxy is a spiral galaxy, with arms in a flattened disk that surrounds a more spherical bulge.

(b) We can tell that relatively nearby galaxies are outside the Milky Way by measuring the distances to Cepheid variable stars in those galaxies.

(c) Elliptical galaxies are rich in emission nebulae that give them their characteristic red color.

(d) Peculiar galaxies often show signs of present or past gravitational interaction with other galaxies.

(e) Hubble’s law should not be used to estimate the distances of galaxies in our Local Group.

Multiple choice: Suppose Galaxy Lily and Galaxy Jacob have the same intrinsic luminosity. Galaxy Lily has redshift z = 0.02, while Galaxy Jacob has z = 0.06. Thus, Galaxy Jacob will appear to be about

(a) 9 times as bright as Galaxy Lily.

(b) 3 times as bright as Galaxy Lily.

(c) 1/3 as bright as Galaxy Lily.

(d) 1/9 as bright as Galaxy Lily.

(e) 1/12 as bright as Galaxy Lily.

Answer 1

a)The orbital speed of planet around the star doesn't illustrate anything about the dark matter, it follows the Kepler law.

Dark matter is heavily dense matter that is found inside the galaxy so it influence the speed of star around it, also the speed of galaxy.

b) elliptical galaxies are red because of presence of large number of red giant stars in it.

they are basically don't having the naebulas .

All other options are completely correct.

c) correct option is d. Brightness is inversely proportional to the luminosity distance square and thus it is inversely proportional to redshift square which implies that brightness of jacob is 1/9 of lily.

plz like , if have any other doubt ask me comment.