astronomy 102 study guide 1

If a star's distance is 10 pc, what is its parallax?

0.1 arcsec

Two main-sequence stars have the same temperature. If star A is four times brighter than star B, then how much further away is star B

2 times further

We observe neutral hydrogen gas using

21-cm emission

how many arc seconds are there in 1 degree

3,600

star A and star B appear equally bright, but star A is twice as far away from us as star B. how much more luminous is star A than star B?

4 times brighter

If a star's measured parallax is 0.2 arcsec, what is its distance?

5 pc

to measure the most accurate parallax possible from earth surface, we would make two measurements of a stars position on the sky separated by

6 months, far side of orbit

The star named Capella has an apparent magnitude of 0, while the star named Polaris has an apparent magnitude of 2. this means the Capella appears _______________ in our sky than Polaris

6.25

What type of spectrum do most stars produce

Absorption spectrum on a black body curve

Star A is a red star. Star B is a blue star. Which is hotter?

B ,Blue

what is the difference between apparent brightness and luminosity

Brightness: is how much light we see Luminosity: is how much light is emitted

What happens when a molecular cloud fragments

Different fragments form stars

What spectral class is the Sun?

G2

When looking at the space between stars, what might you see?

Gas

The interstellar medium is divided into three different kinds of gas clouds. these are:

Hot: 1 million k /Warm: 8,000 k/ Cold 100k

Stars are mostly made of

Hydrogen

Herbig-Haro objects are almost always found

In pairs on a young prostar

As a protostar is evolving, it temperature

Increases

molecular cloud cores are placed where you might find

Molecular hydrogen, prostars, and hirbigaro and carbon monoxide

List the spectral classes of stars in order from hottest to coolest

OBAFGKM

Molecular clouds, which have temperatures of around 10k, are best observed at _______________ wavelengths

Radio

Star E is the same temperature as star F, but star E is four times as luminous as star F. How do the radii of the stars compare?

Radius of Star E is twice that of F

Magnetic fields inside a molecular cloud act to

Slow down gravitational collapse

You observe two stars in a visual binary system using a blue filter that is centered at a wavelength of 550 nm and a red filter that is centered at a wavelength of 650 nm. Star A has a temperature of 10,000k while star B has a temperature of 4000k, and you know that both stars are the same size. Which star will be brighter in each filter?

Star A is brighter in both filters

Which stars show the largest amount of absorption from molecules such as TiO and CN?

Stars with least mass

Radio waves with 21cm wavelengths are important because they

Stud neutral hydrogen and interstellar medium

Use the figure shown below to complete the following statement: A low-mass protostar remains roughly constant in ________ and decreases in ________ until it makes a turn towards the main sequence, as it follows its evolutionary track.

Temperature, luminosity

Interstellar extinction refers to

The absorption of light by dust grains, resulting in "redder" light

dose it feel hotter to stand in 100 degree air or sit in 100 degree bath.

The bath, more dense

When radiation from an object passes through the interstellar medium, what happens to our view of that object

becomes red and dimmer

if you could watch stars forming out of a gas cloud, which star would form first

c. High mass stars

Parallax is used to measure a stars

distance

a parsec is a measure of

distance

A surprising fact about a 1 M sun protostar is that, even though nuclear reactions have not yet started in their cores, they are__________ than the sun

e. More luminous

What type of binary systems contain stars that pass in front of one another during their orbit?

eclipsing binary

Brown dwarfs are considered failed stars because

hydrogen fusion never begins in their cores

As a protostar evolves towards becoming a main sequence star, its core temperature will

increase

what relationship exists between a stars distance and its parallax

inverse relationship

The red emission (bright region at the top) in the figure shown below is due to

ionized hydrogen

in the interstellar medium, molecules survive in regions with

lots of dust

The absolute magnitude of a star is a measure of

luminosity

One phenomenon that can slow star formation in a molecular cloud is

magnetic fields

If one star appears brighter than another in the night sky, then the brighter star

not enough info

Star A is a red star. Star B is a blue star. You are able to determine that both stars are the same in size. Which star is brighter in your sky

not enough info

What critical event transforms a protostar into a normal main-sequence star?

nuclear fusion

Where have astronomers observed the existence of planets?

orbiting other stars, our stars, binary systems, roaming

Dust reddens starlight because it

preferentially affects light at visible and shorter wavelengths.

The spectral class of stars is related to its

temperature

A protostars evolutionary rack in the H-R diagram traces

temperature, luminosity, and radius change over time