Annie Aquino's Quiz

Chapter 15

Astronomy

Annie Aquino

5/3/13

What are the three major types of galaxies?

-Spiral

-halo, bulge, disk, spiral arms

-Elliptical

-

-irregular

How are galaxies grouped together?

-spiral galaxies are often found in groups of galaxies to a few dozen galaxies

-elliptical galaxies are much more common in huge clusters of galaxies

How do we measure the distance to galaxies?

-brightness alone does not provide enough information to measure distance

-1.determine the size of the solar system using radar

-2. determine distances out to a few hundred light years using parallax

3.divide luminosity by area to get brightness

Apparent brightness of a stars clusters main sequence tells us its distance

-knowing a star clusters distance we can determine the luminosity of each type of star

within it

-apparent brightness of a white dwarf supernova tells us the distance to its galaxy

What is Hubble's law?

-Hubble settled e debate by measuring the distance to the Andromeda galaxy using

cepheid variables using Cepheid variables as standard candles

-Hubble also knew that the spectral features of virtually all galaxies are redshiftefd,

they're all moving away from us

-distances of the farthest galaxies are measured from red shifts

How do distance measurements tell us the age of the universe?

-the expansion of the universe came into being at a single moment in time

-distances between faraway galaxies change while light travels

-astronomers think in terms of look back time rather than distance

-expansion stretches photon wave lengths causing a cosmological redshift directly

related to look back time

How do we observe the life histories of galaxies?

--images of deep universer

How did galaxies form?

-matter originally filled all of space almost uniformly

-gravity of denser regions pulled in surrounding matter

-denser regions contracted forming protogactic clouds

-supernova explosions from the first of the gas rom forming stars

-left over gas settled into a spinning disk

Why do galaxies differ?

- initial angular momentum of protogalactic cloud could determine the size of the

resulting disk

-elliptical galaxies could come from dense protogalactic clouds that were able to cool

and form stars before gas settled into a disk

-observations of some distant red elliptical galaxies support the idea that most of their

stars vey early in the history of the universe

-the collisions we observe nearby trigger bursts of star formation

-collisions may explain why galaxies may be found where galaxies are closer together

What are quasars?

-an unusually bright center of galaxy

-quasars powerfully radiate energy over a very wide range of wave lengths, indicating

that they contain matter with a wide range of temperatures

What is the power source from quasars and other active galactic

nuclei?

-quasars are probably powered by matter falling into super massive black holes

Do supermassive black holes really exist?

-observations of rapidly orbiting material at the centers of galaxies indicate that at least

some galaxies and perhaps all of them harbor supermassive black holes