What are stars made of?
Gases, primarily Hyrdrogen, then Helium
What provides the energy (and so light and heat) of a star?
Atomic energy/ nuclear reactions
How many Jupiters would fit across the sun?
~10
How many earths fit across Jupiter?
11
The sun is ____ times more massive than the earth
300,000 times
The surface temperature of the Sun is ___ times hotter than water's boiling point
16
The luminosity of the sun is
3.8 x 10^26 Watts (if you divide by 100, then you get 3.8 x 10^24 100 W lightbulbs)
What is the general result of the pathetically pitiful chain?
4H -> He + energy + other products
What did Einstein show to be equivalent to energy?
Mass
What part of the sun do we see?
Photosphere
If nuclear reactions in the core produce harmful gamma rays, why are Earthlings not destroyed?
The gamma rays are converted to visible light by the time they reach the photosphere
What is the main requirement for a habitable zone?
Liquid water
How much longer does the sun have to live?
~ 5.5 billion years
What fraction of the solar system's mass is in the Sun?
About 99%
How large is the Sun? (How many Earths would fit across? How many inside?)
109 Earths across, 1.3 million Earths inside
What actually produces the energy in the Sun?
Mass of reacting elements is larger than that of the products (some converted to energy in the core)
What is the closest stellar system to the Solar System and how far away is it?
Alpha Centauri, ~4.3 light years away
What happens to the parallax as a star gets farther away?
The parallax decreases as the distance increases
What is the distance in parsecs d= 1/p if p is in arcseconds?
100
B= L/ (4? R2)
B= brightness
L= luminosity
The brightest star is?
Sirius, the Dog Star
What factor is not in the Drake Equation?
Communication lag due to large distances between stars
What does the Drake Equation estimate?
The number of technological civilizations in the Milky Way
The first planets ever discovered outside our solar system were
In orbit around a millisecond pulsar, not a normal star
What is not part of the radial velocity method?
A planet passing in front of its host star
If the radius of star A is twice the radius of star B, but both have similar temperatures, how do their luminosities compare?
**L= 4?R^2
Star A is 4 times as luminous as star B
Consider star C, a measly 3000 K star, and star D, an impressive 9000 K star. Assuming they are about the same size, how do their luminosities compare?
Star D is 81 times as luminous as star C
Have objects like Jupiter been found? How?
Yes, hot Jupiters have been found from the radial velocity method
What methods does "wobbling stars" refer to?
Astrometry and radial velocity
What method does "stars that fade" refer to?
Transits
What kinds of stars are being looked at to find these hiding bandits?
Stars with large parallaxes
What is the brightest star in the constellation Bootes, the Herdsman?
Arcturus
What is true about Antares?
A: name means "Rival of Mars"
B: �700 times the size of the Sun
C: possibly egg-shaped
D: cooler than the Sun
E: all of the above*** ANSWER
Why does the Sun appear red at sunrise and sunset?
light passes through more atmosphere and red gets through whereas blue scatters
Which is not a type of gravitationally bound stellar binary?
Apparent binary
Which type of binary give information about the star sizes in addition to the combined masses?
Eclipsing binary
Which of the following has the largest luminosity?
most massive Main Sequence
Which is NOT true?
A star that appears brighter than another is always closer
What is the lowest rung on the astronomical distance ladder?
the Solar System
What is NOT used in determining a distance from spectroscopic parallax?
None of the above- they're all used!
What are the 5 main properties of stars?
Mass, Temperature, Size, Luminosity, Age on Main Sequence
Compared to low mass MS star, a high mass MS star has
high luminosity, shorter lifetime
Star 1 on he MS has T= 10,000K & star 2 on the MS has T= 3000K. How do their sizes compare?
Star 1 is 30 times bigger than star 2
Which star evolves off the MS first if all formed at once?
O-type star
What is NOT true about the interstellar gas?
It is primarily Helium
What happens to ISM atoms as they approach a star?
they are deflected around the star
A large patch of darkness surrounded by many stars is probably a:
Bok Globule
Why does a cloud speed up once it starts to collapse?
As particles clump together, their gravitational attraction grows
What is the Trapezium?
**Both A and C
A) Four massive stars at the heart of the Orion Nebula
B) Three massive stars on the outskirts of the Orion Nebula
What objects are sometimes called "failed stars"?
Brown Dwarfs
A star spends most of its life
As a Main Sequence Star
Why does the Main Sequence part of a star's life end?
The Hydrogen in the core is exhausted
What kind of "spark" is the molecular cloud awaiting?
**B, C, or D are possible
B) Cooling until the cloud cannot support itself
C) A wind from a nearby massive star
D) A pressure wave from a nearby supernova
Molecular clouds have "what it takes" which is:
**All of the Above
A) lots of Hydrogen
B) some Helium
C) more than 100 times the mass of the Sun
What does not happen as the molecular cloud collapses?
It forms one huge star
What reactions would start a molecular cloud's core?
Hydrogen fusing into Helium
About how many globulars are there in the Milky Way Galaxy and how old are they?
~150, ~12 billion years old
Stars collide about every ___ in globulars, which is ___ in the solar neighborhood
100,000 years, much more often than
When a star is burning Helium in its core and has puffed out its outer layers it is
a red giant
What step in the Sun's life immediately preceeds the white dwarf phase?
Planetary Nebula phase
How are globular and open clusters similar?
**** All of the above
A) cluster members are about the same distance from Earth
B) Cluster members formed about the same time
C) cluster member colors and Main Sequence turnoffs indicate the cluster age
D) they are both made of stars held together by mutu
What eventually happens to open clusters?
They disperse to form field stars
A 10 solar mass star
will eventually develop an Iron core
In a high mass star, why does nuclear burning stop at Iron?
Iron is very stable so nuclear reactions involving Iron do not produce energy
About how many stars does a globular cluster have?
tens to hundreds of thousands
Why are stars in globular clusters about the same age but at different stages in their lives?
**A combination of all of the above
A) all the stars formed about the same time
B) the stars evolve at different rates because of their differing masses
C) high mass stars die before low mass stars
What are the young cousins of globular clusters?
Open clusters
What kind of aid is needed to see globular clusters?
a telescope
A planetary nebula:
is the ejected envelope of a low to intermediate mass star
What is at the center of a planetary nebula?
**Both A and C
A) the core of the dying star
C) something that will eventually become a white dwarf
Why are novae much more common than supernova?
A white dwarf's mass slowly increases with each nova but the whole white dwarf is completely obliterated during a supernova
A supernova can occur when:
Material from a companion star falls onto a white dwarf
What is the observational difference between Types I and II supernovae
I's are Hydrogen poor while II's are Hydrogen rich
Elements heavier than iron (like Gold) are formed:
**Both B and C
B) during Type II supernova explosions
C) during the deaths of massive stars
What is a pulsar?
**Both A and C
A) a rotating neutron star acting like a lighthouse
C) a result of Type II supernova
How fast do the fastest pulsars spin?
About 600 times per second (fastest speed on a blender)
True or False: Nothing can travel faster than the speed of light
TRUE
What does NOT happen when an object approaches a black hole?
it quickly gets sucked in even from a large distance
How do small stars die?
become white dwarfs, about the size of the Earth
How do medium stars die?
supernova then neutron star
Why can nothing (including light) escape a black hole?
The required escape velocity exceeds the speed of light
Why are things torn apart when they near a black hole?
The part of the object closer to the black hole feels a greater force
Where are the globular clusters found?
In the halo, spherically distributed around the Milky Way center
Why is the distribution of the globulars significant?
Spherical symmetry indicates the position of the Milky Way center
What kinds of objects are found in the Milky Way disk?
**All of the above
A) blue stars
B) some red stars
C) open clusters
D) Gas and dust
What is not true about the Milky Way bulge?
Old stars are very close to the center
What is at the very enter of the Milky Way and what is the best evidence for it?
A super massive black hole- detections of stellar orbits over 8 years
Why does the Milky Way appear as a bright band from Earth?
Because we are inside it and looking through the disk
What are the differing ages and shapes of the 3 main components?
old bar-like bulge, young pancake disk, old spherical halo
How do globular clusters tell the Sun's spot in the Milky Way?
They are spherically distributed around the center of the Milky Way
What is at the center of the Milky Way?
**All of the above
A) a super massive (>1 million solar masses) black hole
B) A cluster of young, hot stars zooming around
C) The center of the bulge/ bar
D) The loud radio source known as Sag A*