Star Test

How do we know the distance to a star?

Astronomers use parallax to measure the distance to a star. Parallax is the apparent displacement of an object because of a change in the observers point of view.

After the hydrogen is fused into Helium, then the Helium is fused into heavier elements such as...(think about the Professor Dave video).

Carbon and Oxygen

nuclear fusion

Helium is created as stars fuse together lighter atoms of Hydrogen to form a heavier atom of Helium

H-R diagram

Hertzsprung-Russell diagram, a graph that shows the relationship between a star's surface temperature and absolute magnitude

What type of stars eventually explode during a supernova and scatter their heavy elements throughout the Univserse?

High mass stars

What type of stars will potentially one day form a black hole?

High mass stars

What term in astronomy describes the balance between the force of gas/radiation pressure and the force of gravity?

Hydrostatic equilibrium

event horizon

Imaginary spherical surface surrounding a black hole, with radius equal to the Schwarzschild radius, within which no event can be seen, heard, or known about by an outside observer

Are there limits to black hole growth?

In theory, no; however, black holes in the Universe do not have infinite food supply. At one point, they must consume all of the matter they can possibly consume. Material further away from the black hole will be affected by the gravitational field of it.

Luminosity vs. Brightness

Luminosity is an intrinsic property of a star; it is the amount of energy or light an object emits at a given time, while the brightness is something we observe (how we perceive how bright a star to be) and depends on the distance.

Which of the following are the most common type of stars?

Main sequence

All stars are created in a Stellar Nebula, but what factor controls what path a star will take in the next stages of its life? In other words, what is the single most important characteristic in determining the course of a star's evolution?

Mass

What term do we use to describe the name of that cloud of dust and gas in which a star is formed?

Nebula

Can X-ray telescopes see a black hole?

No light of any kind, including X-rays, can escape from inside the event horizon of a black hole. It is actually X-rays from matter close to the event horizon of black holes that Chandre observes. As matter approaches a black hole, it gets heated to millions of degrees, ultimately flowing in X-rays.

Is all matter in the disk around a black hole doomed to fall into the black hole?

No, as gas will escape in the form of a hot wind, blown away from the disk at high speeds. High-energy jets that X-ray and radio observations show exploding away from the vicinity of some black holes.

What statement is true, in terms of stellar evolution?

Sooner of later, gravity wins

What does the term luminosity mean when referring to stars?

The brightness of the star

Spectroscopic parallax

The method of measuring the distance to a star by comparing its absolute magnitude with its apparent magnitude

What determines the color of a star?

The surface temperature of a star determines the color of light it emits.

Radial velocity

The velocity of a star toward or away from the earth

How are black holes created?

They are created whenever enough matter is squeezed into a small space.

True or False: Black holes prevent the formation of stars close to them, but help create stars further out in the galaxy.

True

True or False? Nothing escapes a black hole, not even light.

True

True or false? The H-R diagram graphs absolute magnitude versus spectral type.

True

Red supergiant

cooler than the Sun

Describe what occurs to the temperature as the force of gravity begins to contract the cloud of dust and gas

increases

A type

not described above

What is the next stage in life after the Main Sequence stage for a small mass or average star such as our Sun?

red giant

What is at the center of almost every galaxy in the entire universe?

A black hole

accretion disk

A disk of gas and dust that can accumulate around a center of gravitational attraction, such as a normal star, a white dwarf, neutron star, or black hole. As the gas spirals in due to friction, it becomes hot and emits radiation.

True or false? The largest stars on the H-R diagram are also the stars with the greatest mass.

False

parallax angle

Half the maximum angle that a star appears to be displaced because of the earth's motion around the sun

Describe the process of hydrogen fusion that happens in the cores of stars.

Hydrogen fusion occurs when temperatures increase, causing two hydrogen atoms to collide and form a new atom called deuterium. Deuterium interacts with more hydrogen atoms in the 'proton-proton chain', causing four hydrogen nuclei to become one helium nucleus.

If you look at a distant galaxy and notice that it contains a lot of bright blue stars in its spiral arms and dim red stars in between the arms, where would you say that the most star formation is happening? Why?

In this case, we would say that most of the star formation is occurring in the galaxy's spiral arms. This is because bright blue stars have a short lifespan and are very young in comparison to other stars, so more blue stars means that star formation is occurring more actively compared to dim red stars.

The heaviest element that can be fused within a star is

Iron

The spectral classification of stars in correct order of increasing temperature (as read from left to right) is

MKGFABO

All stars are created in a Stellar Nebula, but what factor controls whether the star will take path A or path B in the next stages of its life?

Mass

What star characteristic controls whether the star will one day form a giant star or a Supergiant star?

Mass (size)

Can matter ever come back out of a black hole?

No. No matter how far the matter moves, it will not be able to escape once falling past the event horizon, because the gravitational field inside a black hole is so strong to the point space is curved on itself. Anything falling into a black hole can only travel in one direction toward the singularity at the center.

In the process of the formation of a star, what process eventually begins establishing an equilibrium and generating a yellow or red main sequence star?

Nuclear Fusion

What happens to objects when they get too close to a black hole?

Objects can orbit a black hole without any serious consequences as long as the size of their orbit is greater than the diameter of the event horizon of a black hole. If any object gets too close, the orbit will become unstable and the object will fall into the black hole.

How does proper motion affect the constellations?

Proper motion is smaller for distant stars and larger for constant stars. This apparent motion, or angular change in position, will change the viewer's idea of the location of stars in relation to one another, ultimately shifting the shape of various constellations.

What type of star forms after most of the Hydrogen is converted into Helium. In other words, what is the next stage of a star after the main sequence?

Red Giant

One day our Sun will begin its journey off the Main Sequence by expanding outward to become FIRST a ___________ and then to become a ___________

Red Giant; White Dwarf

what is considered one of the most important Black Holes to study

Sagittarius A*, it is found at the center of our Milky Way galaxy

How are stars classified?

Stars are classified using the Hertzsprung Russell diagram.

Proper motion

The angular velocity of a star as measured from the sun

stellar parallax

The displacement of a star as seen from an observer on Earth

Parsec

The distance from the Sun to an object that has a parallax angle of 1 arcsecond

What can happen to a galaxy if it just keeps creating more and more stars?

The galaxy can run out of gasses.

Main sequence

The part of the H-R diagram containing the majority of stars

Tangential velocity

The speed of a star across our line of sight

Which of the following is true about ultra massive black holes?

They are rare and 10 billion times larger than the size of our Sun.

What is the role of the magnetic vortex that forms these jets?

They limit the number of stars that form

Scientists are very interested in finding planets around stars that may be able to support intelligent life. Should they be looking around high-mass stars or low-mass stars? Why? (hint: most scientists believe that it takes billions of years for intelligent life to evolve.)

They should be looking around low-mass stars. This is because low-mass stars usually live longer than high-mass stars, which allows for the "billions of years" time period that scientists believe it takes for intelligent life to evolve. Furthermore, low-mass stars are much more stable in comparison to high-mass stars.

True or false? Early astronomers used the lack of observable parallax to argue that the Earth did not move, but Copernicus argued that the lack of parallax indicated the great distances to the stars.

True

True or false? The absolute magnitude of a star is an indication of its luminosity.

True

True or false? The largest stellar parallaxes are less than one arcsecond.

True

If you look at a distant galaxy and notice that it contains many dim red stars but almost no blue stars, would you assume that this galaxy has a lot of extra gas, or very little extra gas? Why?

You would assume that this galaxy has very little extra gas. This is because extra gas produces new stars, which appear blue. So if there are no blue stars, it is safe to assume that there's not enough extra gas to make new stars.

A star spends most of its life...

as a main sequence star

Brightness

associated with apparent magnitude

Apparent magnitude

associated with brightness

Absolute magnitude

associated with luminosity

M type

coolest

Why do larger stars life a shorter life?

higher temperatures force them to burn out faster

Stars can be classified according to the density of their atmospheres; e.g., they are grouped into _________ classes.

luminosity

What are the most important two "intrinsic" properties used to classify stars? (intrinsic means not related to quantity or not related to mass).* 5/5

luminosity and temperature

The small, hot stars at the lower left of the H-R diagram are called _______ stars.

white dwarf

What is considered the remnant of a huge dead star?

Black hole

The death of a massive stars end up as a brilliant explosion known as a

supernova

G-type star

the Sun

Apparent Magnitude vs. Absolute Magnitude

-Apparent: A star's brightness as it appears from Earth. -Absolute: Actual brightness of a star.

Describe the lifespan of a high mass star compared to the lifespan of a low mass or average star such as our Sun.

More massive stars have shorter lives

O type

hottest

The HR diagram is a plot of ___________.

luminosity vs temperature

In the modern H-R diagram, 90% of the stars are on the

main sequence

The mass-luminosity relationship only applies to _______________ stars on the H-R diagram.

main sequence

The brightest star in the night sky (when it can be seen) is

sirius

White dwarf

smaller than the Sun

The bright, reddish stars located at the top upper right of the H-R diagram are called

supergiants

Hertzsprung-Russell Diagram

A plot of absolute magnitude (or luminosity) versus temperature (or spectral type) for stars

singularity

A point in the universe where the density of matter and the gravitational field are infinite, as in the center of a black hole

relativistic jet

A powerful jet of radiation and particles traveling close to the speed of light

Define a "primer"

A primer accumulates around a center of gravitational attraction; it is much like a disk of dust, gas, and other particles. EX: stars, white dwarf, neutron star, black hole

True or false? The lowest mass main sequence stars are at the lower right corner of the H-R diagram.

True

True or false? The mass-luminosity relation holds only for main sequence stars.

True

Which colors of stars are the brightest?

Typically, blue stars are the brightest and red stars and the dimmest

What is the last stage in life for a low mass or average sized star like our Sun?

White Dwarf

What is the final life stage for our Sun?

White dwarf

Can ultra massive black holes kill their host galaxy?

Yes

Do black holes grow when matter falls into them?

Yes, the size and mass of the black hole increases by the amount of mass of the matter that was captured. The radius event horizon increases.

How do you find black holes with Chandra if you can't see them?

You can find black holes with Chandra by searching for the X-radiation from a disk of hot gas swirling toward a black hole. The friction between particles in the disk heats them to millions of degrees, producing X-rays.

Do scientists know how super massive black holes are created?

No

What two things do black holes emit (send out)?

Radiation and Cosmic winds

B-type star

hotter than the Sun

How are black holes created?

A massive star dies and collapses in on itself and forms a supernova.

What event marks the birth of a star?

Fusion of hydrogen atoms into helium atoms

What term is given to a cloud of dust and gas that eventually forms a star?

Nebula

True or False, our Sun is considered to be a low mass or average star.

True

True or false? The nearest night star is also the brightest.

False

Luminosity

associated with absolute magnitude

The spectral type of our Sun is

G2

O-type stars look

blue

G type

closest to the Sun in color and size