astronomy final
the universe is approximately how old
14 billion years
temperature of the universe is about
3k
Energy from a Black Hole
- Gravitational potential energy of matter falling into a black hole turns into kinetic energy - Friction in the accretion disk turns kinetic energy into thermal energy (heat) - Heat produces thermal radiation (photons) - This process can convert 10-40% of E=mc^2 into radiation. Compare to fusion
Characteristics of Active Galaxies
- Luminosity can be enormous (>10^12Lsun) - Luminosity can rapidly vary (comes from a space smaller than solar system) - They emit energy over a wide range of wavelengths (contain matter with wide temperature range) - Some drive jets of plasma at near light speed - Galaxies around quasars sometimes appear disturbed by collisions
Black Holes in Galaxies
- Many nearby galaxies-perhaps all of them-have supermassive black holes at their centers - These black holes seem to be dormant active galactic nuclei - All galaxies may have passed through a quasar-like stage earlier in time
galaxy groups are for how many and what type of galaxies
-about 50 -spiral galaxies
properties of a star related to their masses
-bigger stars are more luminous
comets
-composed of ice and dust -travel from outer to inner solar system locations while others remain in the outer solar system -approaches the sun and starts to melt, gas comes off when it melts -comets can break apart, change their orbit, or run into planets
asteroids
-composed of metal and rock -cannot have an atmosphere bc they're too small
telescope advantages
-don't have to look through the earth's atmosphere -can see objects clearly -
sun's fusion process
-extreme temp and pressure makes hydrogen atoms fuse together to make helium -A nuclear process whereby several small nuclei are combined to make a larger one whose mass is slightly smaller than the sum of the small ones. The difference in mass is converted to energy by Einstein's famous equivalence E=mc2. This is the source of the Sun's energy and, ultimately, of (almost) all energy on Earth.
greenhouse gases and effects
-greenhosue gases include: carbon doixide, methane, and nitrous oxide. -suns rays are absorbed by earth and some are reflected back out into space. Some get out but others are trapped by greenhouse gases. Greenhouse gases trap sun radiation and warm the earth. -too much pollution causes extreme amounts of these greenhouse gases which traps heat on earth and a thicker atmosphere of greenhouse gases forms -this increasing its surface temperature
star mass determination
-if it is in a binary orbit we can determine it mass by doppler shifts -w Kepler's 3rd law we measure its mass
what happens when two galaxies collide?
-if its a small and big a]galaxy, the big one will engulf small one and the new galaxy will have a bigger center -two large galaxies will combine together and morf into a new galaxy
properties of light
-light passes through a prism and a rainbow colored band of light called a continuous spectrum comes through the other side -things get dimmer as they get farther away
parts of the electromagnetic spectrum
-longest to shortest: radio, microwave, infrared, violet (visible light), ultra violet, x-ray, gamma rays -longer wavelength means means low energy and low frequency -Shorter wavelength means high energy and high frequency
what does dark matter do
-makes stars keep a constant speed -dominates galaxy clusters -gives off x-rays -with out this, our universe would not have structure
galaxy clusters are for how many and what type of galaxy
-more than 50 -elliptical galaxies
Jupiter's atmosphere
-mostly made of hydrogen and a little helium -methane, ammonium, and water vapor are a small portion of atmosphere
what is dark matter
-particles that dont give off light -extremely hot gas held together by gravity
past and future of the sun
-sun will continue to produce energy and light as a main sequence star but will later become a red supergiant -supergiant means it will decrease in temperature and increase in luminosity -star will eventually die and fall apart
celestial tilt
-the celestial equator is tilted by 23.5 degrees to the ecliptic -effects the seasons
Hubble's law
-the farther away a galaxy is the faster it is moving away -tells us how long the expansion of galaxies has been going on -Ho(slope of graph)= velocity/distance
Kepler's 2nd law
-the speed of planets change while traveling around the sun, when its closer it goes faster, farther away, it moves slower -angular momentum
galileo galilei thought...
-used a telescope to look at sky -observed phases of Venus -discovered moon's mountains and valleys -father of psychics (did experiments when people said things)
Fifteen years ago, a quasar was observed that was found to be located 8 billion light years away. If our universe is approximately 14 billion years old, when did the quasar emit the light that we observe?
8 billion years ago
Accretion Disk
A cloud of inward-falling objects, matter, gas, light, etc, all doomed to fall inward to the black hole. Only has this is black hole has a quasar.
Matter falling into supermassive black holes in the centers of galaxies is thought to be the source of:
1. Jets that shoot far into space 2. Active galactic nuclei 3. Strong radio emissions 4. Quasars ALL OF THE ABOVE
What can you conclude from the fact that quasars usually have very large redshifts?
1. They are generally very distant 2. They were more common early in time 3. Galaxy collisions might turn them on 4. Nearby galaxies might hold dead quasars ALL OF THE ABOVE
What is the luminosity of the most powerful quasars?
1000 times the luminosity of the Milky Way Galaxy
black holes
A region of space where the pull of gravity is so great that nothing-not even light- can escape. A possible outcome of the evolution of a very massive star
Do supermassive black holes really exist?
Astronomers believe that supermassive black holes lie at the center of virtually all large galaxies, even our own Milky Way. Astronomers can detect them by watching for their effects on nearby stars and gas. - Orbits of stars at center of Milky Way stars indicate a black hole with mass of 4 million Msun - Orbital speed and distance of gas orbiting center of M87 indicate a black hole with mass of 3 billion Msun
What powers active galactic nuclei?
Matter faling into a supermassive black hole
interstellar dust
Microscopic dust grains that populate space between the stars, having their origins in the ejected matter of long-dead stars.
Where in the universe are most quasars found?
More than halfway to the boundary of the observable universe
Which of the following is NOT true of supermassive black holes in the centers of galaxies?
The most massive detected so far is about 50 million solar masses
Imagine that you simultaneously receive the satellite transmission of 2 pictures of 2 people living on planets orbiting 2 different stars. Each image shows the people at their 21st birthday parties. Consider interpretations that could be made from your observations. Which do you think is the most plausible interpretation?
The person that is farther from you is actually the older of the two people
Galaxies and Black Holes
The mass of a galaxy's central black hole is closely related to the mass of its bulge - Galaxies with large bulges have large black holes and vice versa The development of a central black hole must somehow be related to galaxy evolution
Why should we not be surprised that galaxy collisions were rather common in the past?
The universe was much denser in the past, so its galaxies were much closer together, making collisions much more frequent
what are quasars
V. bright sources of light at v. large distances. Don't emit much blackbody. Must be old.
Describe how astronomers determine the composition of a star.
When a light passes through a prism, the light is broken up into different colors. Each color corresponds to a specific wavelength in the electromagnetic spectrum. Each element produces a unique pattern of spectral lines, which includes dark lines where light is missing at specific wavelengths. By comparing the spectral line patterns of known elements to those produced by stars, scientists can deduce the chemical composition of stars.
When we look at a very distant galaxy, billions of light years away, we see it...
When it was younger than now When the whole universe was younger than today
The black hole at the center of our own galaxy may once have powered an active galactic nucleus
Yes, active nuclei in other galaxies appeared to be powered by accretion into similar sized black holes
what is in the center of the milky way
a supermassive black hole
dark energy is responsible for
accelerating the universe's expansion
when the universe is measured by the percent energy in each component, what is the order from greatest to least
dark energy, dark matter, normal matter
the shape of our universe is determined by the
density of the universe
what happened when two supermassive black holes meet
first orbit each other then merge together
as the univers expands, light from earlier times will
gain longer wavelengths
moon/planet cratering with age
impacts from comets and meteors make craters
where are quasars located
in galaxies
what is the shape of the universe and why
it is flat because the universe is at critical density
voids represent
large volumes of space that lack galaxies
gravitational lenses can produce
multiple magnified images of distant galaxies
type 2 Supernova
star core turns to iron and its gravity makes it condense. It then explodes.
type 1A supernova
star in a binary system and one of the stars is a white dwarf. the white dwarf is the one that explodes.
quasars are more common at large redshifts. This can be interpreted as
they were more common in the past
supernova observations reveal what
universe expansion is accelerating
when do we think black holes in galaxies formed
when the galaxy formed
The Central Engine of an Active Galaxy
- A supermassive black hole, surrounded by an accretion disk - The strong magnetic field lines around the black hole channel particles into jets perpendicular to the magnetic axis - The black hole may be billions of solar masses
jets
Long narrow beams in which energy shoots out of a quasar.
What is the power source for quasars and other active galactic nuclei?
Quasars are believed to be powered by accretion of material into supermassive black holes in the nuclei of distant galaxies, making these luminous versions of the general class of objects known as active galaxies.