AST Part Flashcards

Black hole
Terms Definitions
blue supergiant
Average earth-moon distance
absolute 0 in Kelvin
*Ch.21 Q#11: Summarize the supermassive black hole model for the energy output of quasars and other active galactic nuclei. What evidence suggests that such black holes really exist?
EPICYCLE explanation of retrograde motion of the planets (solar system is like a gear up on a gear)
radio lobe
Roundish extended region of radio-emitting gas, lying well beyond the center of a radio galaxy.
caused the seperation btw astronomy and astrology
the prominent line of points (representing main-sequence stars) running from the upper left to the lower right on an H-R diagram
Gamma-Ray Bursts(GRBs)
Central Engine
1. Jet expands at speeds close to the speed of light
2. Jet interacts with the surrounding medium
3. Surrounding medium is heated, emission in x-ray, optical and radio at regular phase.
4. Last hours to days (long lived emission)
Radiation from GRBs is beamed in different directions
Average redshift is z=2.5
Which of the following was recently 'demoted' (or reclassified) to being call 'dwarf planet?'
Large, relatively empty region of the universe around which superclusters and "walls" of galaxies are organized. One of their maps is shown in Figure 16.21 on page 447. It indicates that galaxies and galaxy clusters are arranged in a network of filaments (walls) surrounding large, empty regions of space known as voids. Some voids measure 100 Mpc across. There is a resemblence to beads on a string.
A positron is:
the anti-particle to an electron
The atmosphere of Titan is composed mainly of
When all external forces are balanced out.
All the planets' orbits are evenly spaced
A relatively small and rocky object that orbits a star; asteroids are officially considered part of a category known as "small solar system bodies.
the time of earth's orbit or revolution around the sun, 365.25 days
How big is a cloud, usually?
1 parsec
An object that generates light by converting hydrogen into helium is
a star
variable star
A star whose luminosity changes with time. The discovery of variable stars enabled astronomers to determine distances to remote objects. Variable stars vary in brightness over a period of time. Without going into the details of how this is done, I will briefly discuss the fundamentals. There are two types of variable stars that have played central roles in determining the dimensions of the Milky Way Galaxy and distances to other galaxies. They are known as RR Lyrae variables and Cepheid variables. These stars can be identified by the shape of their light curves. For these two types of variable stars, the luminosity is related to the period between maximum brightness. If the luminosity is determined and the apparent magnitude is measured, the distance can be calculated. This method was developed by Henrietta Leavitt in 1908.
Forces inward
due to gravity, without the forces acting outwards the star would collapse.
planet that is cold enough to freeze most compounds we think as gases
Molecular Clouds
A cold, dense interstellar cloud which contains a high fraction of molecules. It is widely believed that the relatively high density of dust particles in these clouds plays an important role in the formation and preservation of the molecules
occurs when a light source is moving quickly toward and observer
Of the planets, ________ is the least dense, and could float on water
Outer Planets
planets that are composed of LIGHTER elements, due to their distance from the sun
The eruption of molten rock, or lava, from a planet's interior onto its surface.
HR diagram
A graph relating to the temperature and brightness of stars.
irregular galaxy
Galaxies that look neither spiral nor elliptical.
5. White dwarf:
Core supported by electron degeneracy pressure. 
Cools. Luminosity only based on temperature. Cools
 down and becomes fainter.
cosmic density parameter
Ratio of the universe's actual density to the critical value corresponding to zero curvature. Cosmologists define the cosmic density parameter as the ratio of the actual density of the universe to the critical density.
The sequence of fusion reactions that converts hydrogen to helium in the cores of massive stars is:
the C-N-O cycle
The surface of Europa is most like the Earth's ________ pole
electromagnetic spectrum
a range of light waves extending in wavelength from radio waves to gamma rays
Which three worlds have almost identical densities
Mercury. Venus, and Earth
neutron star
a star that has collapsed under its own gravity
What is the dominant gas in Venus' atmosphere?
Carbon dioxide.
Olbers' Paradox
A paradox pointing out that if the universe were infinite in both age and size (with stars found throughout the universe), then the sky would not be dark at night.
Elliptical galaxies.
1. Round galaxies where 2. stars orbit in random directions.3. Old red star4. Relatively gas free- no new star formation.5. E0s are very round, E7s are somewhat flat.
galactic bulge
The galactic bulge is at the center of the galactic disk and is somewhat thicker than the galactic disk.
The largest difference between Mars' northern and southern hemispheres is that
the northern hemisphere appears younger with ancient seabeds preserved
1.2 seconds
how long it takes for the moon's light to reach us
Convection of Stars
energy is carried from core to surface by convection
core -> radiation -> convection -> photosphere
The amount of time between a low tide and the next low tide is about:
12 hours.
inverse-square law (of light)
The law stating that an object's apparent brightness depends on its actual luminosity and the inverse square of its distance from the observer:
Measuring Masses with Visual Binaries
Revision of Kepler's 3rd law (M1+M2)P2= a3P in years A in AU
Kepler's First Law
Each planet moves around the sun in an orbit that is an ellipse with the sun at one focus of the ellipse.
Which of the following statements about brown dwarfs is not true?
(a)Brown dwarfs eventually collapse to become white dwarfs.
(b)Brown dwarfs form like ordinary stars but are too small to sustain nuclear fusion in their cores.
(c)Brown dwarfs are suppo
(a)Brown dwarfs eventually collapse to become white dwarfs.
The terms "brown dwarf" and "white dwarf" may sound like they should be related, but they are not. Brown dwarfs will never collapse into white dwarfs.
Property of Star - Diameter
found with angle and distance. can also be found with eclipsing binaries
10. What is the maximum mass of a white dwarf star that can be supported by electrondegeneracy pressure (also known as the Chandrashekhar mass)?
(a) 1.4 M☉
Binary Stars:
1. Give us MASS! (no other way to get this).2. Over 60% of stars are in binaries.3. Eclipsing binaries also give us size (their radii) and distance.
Why does Saturn radiate even more excess heat than Jupiter?
helium rain falling inward generates heat as it descends
Which of these does not depend on a close binary system to occur?
a type II supernova
What is the Roche Limit?
A distance from a planet inside of which gravitational tidal forces tend to disrupt satellites.
note 2 Distance of Sun from galactic center
8 kpc or 26,000 light years
Seismic waves can most usefully map
the interior mantle and core of the Earth and other worlds
Which is characteristic of globular star clusters?
old age and hundreds of thousands of stars lying about 300ly wide
If we have a new moon today, when will we have the next full moon?
In about 2 weeks.
Hubble's Tuning fork diagram
_____________________ Elliptical ( Spiral_____________________( ( Barred Spiral
Ch.19 Q#29: Where are most of the Milky Way's globular clusters found? (a) in the disk (b) in the bulge (c) in the halo *explain your answer*
Most of the globular clusters are found in the halo cause they contain old stars
A method for identifying a black hole is to
look for their effects on nearby companions
Dark matter only interacts through?
Gravity Does NOT: Give off light Form stars Kill stars Do anything else that could allow us to spot it
What is true of Jupiter's magnetosphere?
It has a tail that extends at least to Saturn's orbit
Why did Einstein believe the sun could have another form of energy? How would this happen (equation)?
If the sun could turn mass into energy, then it would do so by E = MC^2
What are the two bumps in the diagram? What two planets?
Ice line and methane ice belt; Jupiter and Neptune.
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