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.