astronomy(finally got it right this time)?

Question

1a. for each of the four seasons, state one constellation that you can see best during that season.

1b. why can you see some of the constellations only during certain seasons?

2. do you think people in australia can see Polaris? explain your answer( short form)

3. if you could travel at the speed of light, how long would it take you to travel to the following stars.
a) sirius
b)arcturus
c)betelgeuse
d)deneb?

4a. what info about stars can astronomers obtain using a spectroscope?

4b. use examples to explain how the spectral type of a star gives info about a star

Answer 1

Spring Hydra
Summer Scorpius
Autumn Fornax
Winter Cancer
http://homepage.mac.com/kvmagruder/bcp/aster/constellations/index.html

Because if they are on the plane of the ecliptic, or near it, they are not visible when they are behind the Sun. Ones near the pole are visible more often. You can always see Ursa Minor if you are farther north than about 10N.

No. Polaris will always be below the horizon if you are south of about 2S.

Time at c = distance in l.y.
Sirius = 8.6 years
Arcturus = 34 years
Betelgeuse = ~1400 years
Deneb = ~3200 years

1. The composition of the star.
2. The composition of absorbtion nebulae that lie between the star and Earth.
3. The relative motion of the star.
4. The distance to the star, if it is in another galaxy.
5. The rotational speed of the star.

The first two based on the lines in the spectrum. The last three are based on changes in the spectrum due to redshifting.

Answer 2

1a. ;) I'll leave that for you. Orion is popular in winter, Cygnus the swan in the fall. Casseiopia is visible all year round, as is the little dipper and pan of the big dipper (depending upon how far north you are).

1b. There are twelve constellations along the zodiac (the arc of sky through which the sun passes). You cannot see the constellation behind the sun. As it takes the earth a year to orbit the sun (definition of a year), whatever constellation(s) are in the day time sky remain invisible--except during total solar eclipses.

2. People in Australia cannot see Polaris--it is well below the horizon from them (always below their feet).

3. At the speed of light any star is only a second away. No time passes for you.

For an earth bound observer monitoring your progress, your trip time would appear to be twice the distance in light years to each star. You can find those distances in a number of on line star tables.

Sirius is quite close--only 2.6 parsecs (8.5 lightyears)
Arcturus is 11 parsecs.
The great red giant Betelgeuse is 130 parsecs.
Deneb is nearly 1000 parsecs.

Antares (not mars) is 185 parsecs. I mention this star because Antares dwarfs Betelgeuse. Antares is to Betelgeuse what Betelgeuse is to our sun. Divide Sol's volume by that of the earth, and you get roughly the same ratio again.

Answer 3

4a. Spectroscopes allow you to divide the light from any given star, into the colors of the humans visual spectrum. In doing this, you can tell what a star is made of, as each element on the periodic table gives off a unique set of EMISSION lines on the spectromoter.

That may answer 4 a and b for you. I am currently in astronomy.