Astronomy Exam

The central region of our galaxy is not as flat as its main disk of stars

- it has a bulge of old stars and its shape is like a bar

The nuclear/central bulge of our galaxy

1. Is difficult to see with visible light because of cosmic dust 2. There is evidence it is not exactly spherical but elongated 3. Thicker than the disk of the Galaxy 4. Consists of older stars

Dark Matter in the Galaxy

1. Measurements suggest that there may have been as much as ten or twenty times more dark matter in the Galaxy than the matter we have been able to observe 2. We can pretty much rule out the idea that the dark matter is made mainly of vast clouds or regions of hydrogen gas 3. Most of it cannot at present be observed with our telescopes( We only know its existence from the gravity it exerts)

Observational Evidence that makes us believe there is a black hole at the very center of the Milky Way Galaxy is:

1. The fact that Sagittarius A is a stationary radio source, while objects around it appear to be in motion 2. The observation that matter in the central region continues to be falling in toward the center 3. The motion of stars close to the center of indicates that there is a mass of 4.6 million solar masses inside their orbits 4. The existence of a strong radio source at the center whose size appears to be no larger than Jupiter's orbit(highly condensed)

There is a black hole with ______ at the center of our galaxy. Its event horizon is about __________.

4 millions times the mass of our sun, 17 times the size of the Sun

In the 1970s the first indirect detection of gravitational waves involved a binary system

A pulsar that was in the same star system with a neutron star.

Nothing escapes a

Black Hole

The main body of our galaxy is surrounded by an invisible halo called

Dark Matter

The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe is

Event Horizon

A cloud of gas or star that is _____ from the center of the will generally take _____ to orbit

Further, more time

the time it takes the sun to revolve once around the center of the Milky Way Galaxy

Galactic Year

The objects that astronomer Harlow Shapley uses as "signposts" to figure out the extent of the milky way galaxy and the location of its center

Globular Clusters

Astronomer who first worked out the mathematical description of a black hole event horizon

Karl Schwarzschild

Objects orbiting around the center of the Milky Way Galaxy obey

Kepler's Third Law

The key property to predict whether a star will ultimately become a black hole is

Mass

The sun and our planetary system is located at the so called

Orion Spur

Radio or Infared Radiation

Reveal most things in the galaxy( as it penetrates the dust and clouds in the galaxy)

The very strong source of radio waves at the center of our galaxy is called

Sagittarius A

A central point, deep inside a black hole(and hidden from our view) is the compressed center where all of the "stuff" of the star goes

Singularity

We know that our milky way is a

Spiral Galaxy

Dark matter could possibly be a new kind of

Subatomic Particle

A black hole in the center of our galaxy has acquired so much mass because:

The center of our Galaxy is a much more crowded region than where the Sun is found -- we still see material falling toward the center and material has fallen in for billions of years

Astronomers observe stars and other objects that orbit the center of the Milky Way Galaxy farther out than our Sun, but, they moved around faster than we do. EXPLAIN

There must be a great deal of invisible dark matter outside the orbit of the Sun whose gravitational pull explains the faster motions we see

The work of Harley Shapley and others about the location of the Sun in the Milky Way Galaxy

We are in a disk galaxy, about 3/5 of the way from the center

To find the distance of the Galaxy contained within the orbit of the Sun

We measure the distance to the center of the Galaxy and the Period of the sun's orbit and then use Kepler's Third Law

According to the general theory of relativity, the presence of mass causes a

curvature or warping of spacetime

The shape of the milky way resembles a

dvd or cd

Black holes eat

everything

The main reason that gravitational waves are very much harder to detect than electromagnetic waves is that ___________ , and therefore require precise equipment to detect.

gravitational waves are much weaker than electromagnetic waves

The first direct detection in 2015 of gravitational waves arriving by the LIGO experiment was gravitational waves arriving from the

merger of two black holes

Once a black hole forms the _____ of its event horizon is _______ only by _________ inside the event horizon

size, determined, the mass

All masses curve

spacetime and light has to follow that curvature

The Herschels thought that

the Sun and Earth were roughy at the center of the great grouping of stars we call the Milky Way. The reason was that the dust that extends throughout the disk of the Galaxy only allowed Herschel to see the small part of the milky way that surrounds us

Our Milky Way has ______ and a few fainter ones

two main spiral arms

The most massive stars(_______) become Black holes

type O or B or A