Units 32-33 Flashcards
Galaxy
A large collection of stars, dust, and gas that is found in a wide variety of sizes ranging from a few million solar masses for a small galaxy to large galaxies with more than a trillion solar masses of material.
Radar ranging
A technique for measuring distance where pulses of microwaves (radar) traveling at the speed of light are sent to a nearby object and the reflected pulse is timed in order to determine the distance.
Laser Ranging
A technique for measuring distance similar to radar ranging, but instead of reflecting microwaves, laser light is reflected off a nearby surface and the time for the reflected pulse is observed.
True or False: Radar ranging is limited to our solar system
True
Why is radar ranging too weak for measuring distances to stars?
Because it’s an echo of microwaves. The echo is too weak on the return to be detected at much farther distances
What method is used to find the distance to stars?
Triangulation
Triangulation
A distance measuring technique that involves observing the angle to a distant object from at least two different locations with a known separation. Then you determine the unknown by comparing the observed angles.
Basic trigonometry.
True or False: According to the triangulation method’s calculations, a larger shift in angle means the object is closer
True
Light year
The distance light travels in a year. About ten trillion kilometers
Distance ladder
A method used in astronomy where greater and greater distances are determined using many different measuring techniques that overlap to establish a sequence of increasing distances.
What is the brightness distance technique?
Estimate the diameter of a star and look at its labels to determine how far away it is. Based on the brightness we can observe.
True or False: Brightness distance technique used for far away objects within 100 galaxies of earth
True
Doppler shift
The change in the frequency of a wave when the source and the observer are moving relative to each other.
Terrestrial planets
The rocky planets Mercury, Venus, Earth, and Mars
Jovian planets
Giant gas planets Jupiter, Saturn, Uranus, and Neptune
What does color tell us?
What the planets’ chemical composition is
What did the IAU (international astronomical union) determine were the qualifications of being a “planet”?
- Orbits the sun
- Has sufficient mass for its self-gravity to overcome rigid body forces in order to assume a nearly round shape
- Has cleared the neighborhood around its orbital path (pluto hasn’t done that yet)
True or False: Reflecting light through the gases of jovian planets helps us understand their chemical composition
True
Nebular hypothesis
The idea that the sun, the planets, and other objects in the solar system all formed from a single gigantic cloud of gas and dust. This hypothesis explains the major features and structure of the solar system.
True or False: The Jovian planets likely have metallic cores (liquid or solid)
true
What does “dust” mean in astronomical terms?
The metals and everything that is solid in the cold of space
Why is the center of the solar system so hot?
Because of all the kinetic energy from objects being pulled to the densest part of the solar system (gravitational potential energy causes kinetic)
Why is the solar system on a plane?
Because of the law of conservation of angular momentum. The cloud flattened out into a disk of rotating gas and dust being pulled inward.
When the solar system is pulled inward, does it move faster or slower?
Faster (angular momentum)
What is “accretion”?
Gas molecules bouncing off each other while dust sticks together forming larger and larger collections.
What is a protoplanet?
When the dust molecules accumulated so much that their diameter was more than a few kilometers. Then gravity becomes more important than random collisions
Why are the Jovian planets larger than the terrestrial planets?
Because there was more ice material in the solar system than metals
Lunar highland
The old, heavily cratered terrain on the moon that is thought to contain material from the original lunar surface.
Maria
The large, generally crater-free lava plains commonly found on the side of our moon that faces Earth (singular: mare).
What speed does radar ranging travel at?
Speed of light
Do stars that are farther away or closer have small angles when using the triangulation method?
Farther away
On what step of the distance ladder is parallax?
It’s with triangulation
What does a red shift mean?
It applies to absorption lines. It means the object is moving farther away from the earth
How do we know the masses of planets outside of earth?
- We know the gravitational acceleration, we do THIS by #2.
- An orbiting object is falling. By measuring the orbit of ANY orbiting object, we know the gravitational acceleration.
True or False: Astronauts “float” because they are falling
True
Which formed first on the moon, the lunar highland or Maria?
lunar highland
Why do clouds or anything spinning in 3D space eventually flatten into disks?
Because the upwards and downwards forces cancel out when the atoms/molecules/things crash into each other.
Why do all the planets spin in the same direction?
Because they were all formed from the same nebular cloud which spun in the same direction.
True or False: Gases have a hard time sticking together
True
What are the three fundamental interactions that determine how stars behave?
- Gravity
- EG
- Strong nuclear
Interstellar medium
Gas and dust found in the space between stars
Molecular cloud
A cold cloud of dust and gas dense enough to form stars. Sometimes billions of times denser than the typical interstellar medium
What two forces determine the current state of the star in its life cycle?
The balance between the EG and gravity
Protostar
An object that will become a star in the early stages of formation before it begins to produce energy from fusion.
A planet before there is technically a fully functioning “star”
True or False: The most massive stars are created more quickly than smaller stars
True
Brown dwarf
A low mass that is too small to sustain fusion reactions in its core
Main sequence
This describes stars in the longest lasting stage of their life, where hydrogen fusion is happening in the core
Photosphere
The visible surface of our sun or stars. The region where visible energy is radiated into space.
When does a protostar become a star?
When fusion becomes the energy source, instead of gravitational potential energy
What is the “adult” phase of a star formation?
Main sequence
What color are the coldest stars?
Red
What color are the hottest stars?
Blue
True or False: The hottest stars are most likely to be the most massive
True
True or False: Hottest stars (with high fusion rates) have the youngest lives
True
Red giants
A large, bright, cool star that has exhausted most of the hydrogen fuel in its core
Planetary Nebula
A glowing shell of gas that has been blown off a red giant star.
White dwarf
A small star that no longer sustains nuclear fusion and has shrunk to become a dense object about the size of earth
True or False: White dwarfs are very dense
True
True or False: Our sun can turn into a red giant and then into a white dwarf
True
Black dwarf
The remains of a sun-sized star that have evolved to a white dwarf and subsequently cooled to where it no longer emits light.
A dead star
Supernova
A rare celestial phenomenon involving the explosion of most of the material in a star, resulting in an extremely bright, short lived burst of energy.
Neutron star
The remnant of a supernova explosion that is composed almost totally of neutrons. It is so dense that the entire mass of our Sun could be contained in a sphere only a few tens of kilometers in diameter.
Pulsar
A variable radio source that is thought to be a rapidly rotating neutron star.
True or False: It is believed that all elements heavier than iron are produced in supernova explosions
True
Black hole
Any object where gravity is so strong that not even light can escape from its surface
Luminosity
The rate at which energy is radiated from an object
Apparent brightness
How bright a star appears to an observer on Earth. It is a measure of the absolute luminosity as affected by distance from the object.
Absolute luminosity
The actual amount of energy radiated from an object
H-R Diagram
A plot of stellar absolute luminosity verses color. Stars fusing hydrogen to helium in their cores lie along the main sequence in these diagrams
Cepheid Variable
A pulsating star used to find distances. It has a well known relation between its pulsation period and absolute luminosity
Apparent brightness
How bright a star appears to an observer on Earth. It is a measure of the absolute luminosity of the star as affected by the distance from the star to Earth.
Hydrogen burning
Hydrogen fusing to helium.
Main sequence
(1) Position on the H-R diagram where the majority of the stars fall; (2) stage of a star in which hydrogen fusion is occurring in the core of the star.
Pulsar
A radio source that is thought to be a rapidly spinning neutron star.
Type 1A Supernova
A type of supernova whose maximum brightness is always the same. It is, therefore, useful in determining distances.
Supernova remnant
A glowing shell of gas that was ejected from a supernova as well as the interstellar material that is swept up by this expanding shell of gas.
