Citizen Astronomy Final Flashcards
How far away is sun from center of milky way galaxy
28,000 Light years
Halo stars
very old stars (and bunches of stars called globular clusters) that form an almost spherical halo around the Galaxy
Which stars are almost as old as the universe itself
Halo Stars
Disk of the Galaxy
host to massive amounts of gas and dust, and the stars there are much younger
how are disk stars formed
large collections of gas called molecular clouds
Bulge
dense collection of older stars, believed to be the remnants of previous collisions of smaller galaxies that eventually formed the Milky Way.
older stars are ____ than younger stars, and that means that they appear _____ than young stars. Hot young stars in the disk appear _____
Cooler
redder
bluer
hot objects like stars will radiate all colors of light, but the amount of each color of light depends of the _____ of the gas.
temperature
How are stars formed
Gas collapses under it’s own self gravity. Heats up allowing nuclear fusion in the core. Gas and dust flattens into a disk.
Stars in the Halo are on average bluer than stars in the Disk.
False
Which has older stars, the Disk or the Halo of the Milky Way?
Halo
The stars Vega and Fomalhaut
are older than 5 million years old.
The Disk Hunters citizen science project makes use of images from the
Wide-Field Infrared Survey Explorer
The Milky Way is
a galaxy
interstellar medium
collection of gas, dust, plasma (remember the ionized gas in the Sun from Module 2), and magnetic fields
How bubbles form on infrared images
ultraviolet radiation (UV) from the hot, massive stars will ionize the interstellar medium in there vicinity, forming the holes or “bubbles” in the infrared images
the more massive the star, the _____ its lifespan (in runs out of fuel),
shorter
Massive stars have UV Light and
strong stellar wind, which push gas and dust into the interstellar medium.
How is a shock wave is formed
When these winds are faster than the speed of sound in the surrounding gas,
How do some stars get slingshotted into the interstellar medium
when stars are forming in clusters where close gravitational encounters are frequent
What happens when stars get slingshotted into the interstellar medium
the shockwave is bent into a bow shock
For every low-mass star that forms in the interstellar medium, is there are many more high-mass stars.
False
Two stars are born at the same time, one high-mass and one low-mass. Which one will live longer?
The low-mass star
A shock is formed in the interstellar medium when
the stellar winds of a massive star are moving faster than the local speed of sound
Interstellar dust grains are on average
about ten times smaller than a grain of sand
Bow shocks show up as ______ in the WISE images.
red features
The total number of galaxies in our observable universe ranges from
200 billion to 2 trillion
3 types of galaxies
spiral, elliptical, and irregular
Spiral galaxies
tend to have lots of gas, and thus are constantly making new stars. Milky Way
Elliptical galaxies
spherical or elongated spheroids that lack the gas and dust to make new star
Population of stars in elliptical galaxies
old, low-mass, and cool (often called “red and dead” because the cooler stars are redder in color than the hot massive stars that dominate a spiral galaxy’s disk)
Irregular galaxies
have no regular shape, and are likely the results of recent collisions between galaxies.
some have gas and are making new stars, while other have had their gas stripped away and are not.
Dark Matter
. The missing mass , NOT stars, gas, and dusT
particles that float about the Universe, clumping up and interacting gravitationally with itself and other matter, but it could pass right through your body without you ever feeling it
Many supernovae are the result of
the violent deaths of massive stars,
Which type of galaxy has more gas for making stars?
Spiral
Which type of galaxy appears more blue (has more hot stars)?
Spiral
Which type of galaxy has most likely undergone a recent collision with another galaxy?
Irregular
In what environment do mergers between galaxies have the largest effect?
In the outskirts of clusters or in small groups
There is more Dark Matter in the Universe than ordinary matter (like atoms).
True
that the expansion of the Universe is
Speeding up
Chandrasekhar limit
When the white dwarf reaches a critical mass of about 1.4 times the mass of the Sun,
What happens after the Chandrasekhar limit
it will collapse under its own gravity to create a neutron star. Release of energy is so bug is will outshine the rest of the galaxy it’s in
What is important for the discovery of the accelerated expansion of the Universe is that the total energy given off by these supernovae
should all be about the same, as they occur under the exact same condition
How are astronomers able to calculate an accurate distance to the galaxy
With the known energy of an object and the observed brightness, . These distances are the critical measurements for calculating the expansion of the Universe
Type Ia supernovae occur when
a white dwarf accretes enough gas to explode and turn into a neutron star.
The Chandrasekhar limit is
the mass at which a white dwarf collapses to a neutron star.
A black hole will form when
a high-mass star runs out of fuel and its core has a mass of 5 times that of the Sun or more
Elements heavier than iron are made
in supernovae
Pulsars are
neutron stars
the first to come up with a universal theory of gravity (1687)
Newton
Newton
any object will attract any other object with a force whose strength is proportional to the product of the masses of the objects, and inversely proportional to the square of the distance separating them.
Who presented the special theory of relativity and general theory of relavtivity
Einstein
special theory of relativity
that nothing could travel faster than the speed of light
general theory of relativity
objects with mass bend space and time, and that the gravity that other objects feel is simply those objects moving through warped space-time
one of the strange predictions of this theory of gravity
rapidly accelerating objects, like two massive stars orbiting very close together, should produce ripples in space-time that should propagate through the Universe.
gravitational waves
The ripples in space time from 2 massive stars orbiting close together
indirect evidence for gravitational waves was found by
measuring the rate at which two neutron stars lost energy as they orbited each other.
How many direct detections of gravitational waves have been found
3
Gravitational waves where first detected indirectly detected using
orbiting neutron stars
The first gravitational wave to be directly detected is believed to be caused by
two orbiting black holes
In Einstein’s theory, what is gravity?
The reaction of masses to space-time that has been warped by other masses.
The change in length of a 4 km long arm of the LIGO observatory by a gravitational wave is about
10,000 times smaller than the diameter of a proton
A major consequence of Einstein’s theory was that
massive objects should deflect light rays
black holes
objects whose gravity was so strong that light would not be able to escape.
most being the remnants of the collapse of very massive stars during a supernova
supermassive black holes
Larger black holes, found at center of most galaxies like milky way
How to see monster black holes
by the X-rays given off by the hot gas around them, or by the radio waves emitted when they launch gas out in jets from the center of the galaxy
The Milky Way has a supermassive black hole in its core.
True
is Light is the only particle (or wave) not affected by the curvature of space-time.
false
Which particle has more mass, an electron or a muon?
muon
What kind of light is the Veritas telescope (array) looking for?
Cherenkov light
Most of the points of light in a radio image of the sky come from
supermassive black holes
