ASTRO 7N UNIT 4

अब Quizwiz के साथ अपने होमवर्क और परीक्षाओं को एस करें!

What determines how long it takes an image to reach us?

The speed of light

Spirals - barred or not- are classified as

"a" "b" or "c" type

Blueshift

Coming closer to the observer

Where is dark energy in space?

Everywhere, but only a small amount per unit volume

Characteristics of Open Star Clusters

- have hundreds, up to thousands of stars -Stars formed around the same time, from the same initial gas & dust cloud -stars bound by gravity for a few million years -tend to have lots of but stars visible, because of relatively young ages -blue ones vastly outshine the redder ones

Milky Way Galaxy Characteristics

-Contain about 400 billion stars -Vast majority are red, M-type stars, but the blue stars are more luminous, so they outshine the red ones -empty space between is vast, galaxy is mostly empty space between stars

Spiral Galaxy Characteristics

-Have more gas, dust, and new star formation -Very noticeable disks (bluer color from younger stars) -Not the largest galaxies

Gravitons

-Have not.been discovered yet -thought to be the bosons that carry that force of gravity, and act on mass

Characteristics of Globular Star Clusters

-Hundred of thousands, to millions of stars -Tend to be yellow in color, with a number of red giants -many have ages around 10 billion years - overall considered old clusters

Elliptical Galaxy Characteristics

-Older stars, yellower colors not very noticeable disks -The largest galaxies (while also many small as well)

Types of fundamental particles

12 quarks/anti-quarks 12 leptons/anti-leptons 6 bosons

A neutron contains

2 down quarks and 1 up quark

A proton contains

2 up quarks and 1 down quark

What is the universe made of?

4.6% atoms, 24% dark matter, and 71.4% dark energy

Estimated number of galaxies in observable universe

50-100 billion galaxies - each with 1-100 billion stars per galaxy (as many as 10^22 stars in our universe)

Number of leptons

6 leptons and 6 anti-leptons

Hubbles constant

A number that expresses the current rate of expansion of the universe.

The mass of the galactic center

About 4 million solar masses

The local group contains

About 40 dwarf galaxies along with the larger Andromeda and Milky Way

How many stars do dwarf galaxies contain?

Around 1 billion

Fundamental particles cannot

Be broken up into smaller units

Gluons

Bosons that carry the "strong" force, that holds atomic nuclei together

Starburst Galaxies

Caused by collisions, fast rate of star formation

Andromeda and Milky Way will

Collide in 5 billion years and form a single galaxy

What causes the acceleration of the universe?

Dark energy (anti-gravity)

Molecular Cloud Characteristics

Dark, dusty and cool, about 10 degrees Kelvin

Different colors from

Different chemicals, also blue haze from electron glow

Three components

Disk, bulge, halo

Elliptical galaxy shape ranges from

E0 (circular) to E7 (elongated)

When were irregular. galaxies much more common?

In the earlier universe, because galaxies were in the process of being assembled

Redshift is larger when

Galaxies are further away

A merger of two spiral galaxies may

Give rise to an elliptical galaxy or an irregular galaxy

The four forces

Gravity, Electromagnetism, and Strong & Weak nuclear forces

Irregular Galaxies

Have more irregular structure and cannot be classified as spiral or elliptical

What was used to estimate number of galaxies?

Hubble Deep Field (tiny patch of the sky imaged for 10 full days)

Relationship of redshift and galaxies

Hubble's Law

Why are bosons exchanged between particles?

In order to make the forces work

What can you measure from knowing the luminosity of a standard candle?

Its apparent brightness and calculate its distance from the inverse-square law

Satellite dwarf galaxies of the Milky Way

Large Magellanic Cloud and Small Magellanic cloud

Leptons

Lighter fundamental particles and include electrons and neutrinos

Looking into the distance means

Looking back in time

Relationship between the parent brightness and redshifts for type Ia supernovae can be used to

Measure the geometry of space

Andromeda galaxy is similar to the

Milky Way, about 2.5 million light years away and has dwarf satellite galaxies

Where do stars form?

Molecular clouds (contain several million times the sun's mass worth of gas and dust)

Dark matter emits

No radiation of any form- no visible light, no heat, no X-rays, etc.

How often do we expect a supernova in the Milky Way?

Once every couple hundred years

Fundamental particles

Quarks, leptons, and bosons

Spiral galaxies without bar

S

Spiral galaxies with a central bar

SB

Dark matter must be

Some kind of unknown particle which has not been discovered yet

Our universe is expanding through

Space being added everywhere in between the galaxies

Observations of the type Ia supernova shows

The universe isn't just expanding, but that the expansion is accelerating

When galaxies collide, do planets collide?

There is a very low chance of this because of the space between them

Galaxy collisions leave behind

Tidal debris is left behind because of the gravitational pull of one colliding galaxy on another

Hydrogen lines are observed in

Type II supernovae, but not type Ia because they come from white dwarfs, made primarily of carbon

Stand Candles for dark energy

Type Ia supernovae (because they have well known luminosities which do not depend on the time in the universes history)

"Flavors" or types of quarks

Up, down, charm, strange, top, and bottom

For each type of quark, there is also

a corresponding anti quark (just add anti to beginning of name)

Planetary Nebulae

a low mass star runs out of core nuclear fuel, blows off outer layers, stars can pulsate and eject gas in layers, bipolar jets often lead to symmetry in the resulting nebula, lasts tens of thousands of years, can be a few light years in size, the core of the former star, a white dwarf, is left behind at the center of the nebula, this will be part of the end state of the sun, in about 5 billion years

Radius of the black hole is

about 100 astronomical units

Supermassive black hole has grown

by accreting mass from other objects over time

W+ W- and Z bosons

carry the 'weak' force (responsible for radioactive decay)

Nova

caused by a binary star, wherein one star of the two evolves faster than the other

If clouds mass is > Jeans mass

gravity dominates over internal gas pressure and it will collapse

1 light year is

how far light travels in one year

What does the "Jeans mass" tell us?

if a cloud will collapse to form stars

Sections of the cloud collapse into clumps,

in which individual stars form in with pro-planetary disks

If clouds mass is < jeans mass

internal pressure dominates and it will not collapse

Disk

is 100,000 light years in diameter, spiral pattern, young, blue stars dominate, stars form in 'density waves' in molecular clouds strewn about the disk's spiral arms, open clusters ten to be found in the disk

Halo

is larger, spherical region around whole galaxy, old stars, few heavy elements (globular star clusters live in the halo)

Conventional matter

is made of atoms, but atoms are not fundamental particles (everything we see on earth)

"a" type spiral galaxy

large bulge

"C" type spiral galaxy

loose, lumpy arms

Galaxy collisions form

new star clusters from gas in collisions, leading to young, massive blue stars

Supernova are more lunies than

novae, but only happen once the star is basically destroyed, novae can be a repeating process

We know dark matter exists through

observed large rotation velocities in galaxy disks, motions of galaxies in clusters, and by the way that light is bent by galaxies and galaxy clusters (its gravitational mass on ordinary matter)

Type II Supernovae

occur when massive stars die - the kinds that lead to neutron stars or black holes

Type Ia Supernovae

occur when very large amounts of material are suddenly added to a white dwarf from a binary companion; the resulting burst destroys the white dwarf

If the geometry is "closed"

parallel light rays converge

If the geometry is "open"

parallel light rays diverge

If the geometry is "flat"

parallel light rays will continue along parallel paths

Almost everything that we observe in nature is made up of

quarks and electrons, everything is is either not very stable and/or do not interact much with other matter

How to determine age of star clusters

seeing what spectral class of star has most recently "turned off" of the main sequence, in the cluster's H-R diagram , or many stars formed in clusters that later dispersed, leaving stars more isolated

Bulge

spherical region in center of disk, stars are older than in disk, so yellow colors

in a proton or a neutron,

the 3 quarks must have different "colors"

Photons

the bosons that carry the electromagnetic force, and act on electric charge

Redshift

the shifting of the lines in the spectrum of an object to longer wavelengths, due to its motion away from the observer

The galactic center is

toward the constellation of Sagittarius, called "sag A*"

Standard Candles

used to estimate the distances to galaxies


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