Astronomy Prelim 3
Terms in this set (30)
5 methods of finding exoplanets
3) Direct Imaging
4) Gravitational Lensing
5) Atmospheric fingerprint
What properties of exoplanets can we measure
1) Orbital period (distance, and shape)
2) Planet mass (size and density)
3) Atmospheric properties
Why is it so hard to find planets around other stars?
1) Stars are much brighter than light reflected by planets
2) planets are close to the star relative to their distance to Earth
How can we find planets using the transit method? Is it easier to find larger or smaller planets?
Detecting very small changes in the light of stars. As the planet passes in front of its star, the light will briefly appear slightly dimmer. It is easier to find larger planets because they block more light
How do we find planets using the Radial Velocity Method? Is it easier to find planets that are more massive or less massive?
(Doppler Method) Looks at red/blue shifts of a star as the mass of a planet orbiting it tugs it away/toward us. It's easier to find more massive planets because they cause the star to shift more
What can you learn about a planet if it transits its star? (e.g. radius, distance from the star, mass, orbital period)
radius of planet, composition of atmosphere
What can you learn about a planet if you detect it by Radial Velocity (e.g. radius, distance from the star, mass, orbital period)
mass (lower limit) and shape of planet's orbit
How can you determine how far away a planet is from its star if you only know the period with which it orbits its star?
The orbital period increases as the orbital distance increases (a planet with an orbital period of 1yr orbits the planet at a distance of 1 AU)
What is the Habitable Zone?
The distance from a star where liquid water could be on surface
How are the limits of the Habitable Zone defined?
What is the light-fingerprint of life? Which chemicals do you need to find in a planet's atmosphere together to have no other explanation than life?
water (H20), methane (CH4), ozone (O3), CO2 and N20
Explain the Drake Equation
frames the question of what you need to know to find out how many civilizations could be sending radio signals right now
What are the best places to search for life in our own Solar System?
Europa, Enceladus, Titan
How long ago did fossil records indicate life started on Earth?
3.8 billion yrs
How do we observe the life history of galaxies?
Why do galaxies differ--explain the two possibilities why we see two kinds of galaxies (spiral and elliptical)
collisions between galaxies create two types
What are standard candles
objects with a known luminosity and can be used to measure the distance of objects
Explain how you can measure the distance to 1) a close star 2) star clusters in the milky way and 3) to a different galaxy
Why can you use Cepheids as standard candles?
They are variable stars, you can measure the period of variation to find luminosity (measures up to 10^7 light years away)
Why can you use Supernoval A as a standard candle?
Why can you use the Tully-Fischer Relation as a standard candle?
What did Hubble discover when we measured the distance of galaxies
The universe is expanding
What is Hubble's Law? Write it down and explain what the individual parts mean
Velocity= (Hubble Constant)(distance)
How does Hubble's law tell us the age of the universe?
How can you calculate the ago of the universe from Hubble's law?
Would the age of the universe be larger or smaller is the Hubble's constant was only half its value? Explain
Why does the observable universe have a horizon
How does expansion affect wavelength of emitted light?
the wavelength of emitted light gets stretched as the universe expands
Explain the 8 eras of the Big Bang
Explain what the early universe was like (hotter, colder, dense or not etc.)
Very hot and very dense (soup)
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