ASTRO 7N UNIT 4
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