Astronomy Final

Front 1

What causes solar eclipses?

Back 1

The moon and the earth’s axis must align with each other. The moon blocks
light of the sun from its shadow. E.g. the moon blocks the sun from our view. NOTE:
can only happen during a NEW moon

Front 2

What causes lunar eclipses?

Back 2

Earth blocks the sun’s illumination of the moon from the earth’s shadow. e.g. the moon passes behind the earth into its umbra. NOTE: can only happen during a FULL moon. Earth and moon are not on the same plane, so eclipses won’t happen every month

Front 3

Blackbody spectrum

Back 3

solids or hot dense gas produce continuous spectra

Front 4

Absorption

Back 4

blackbody radiation travels through cooler, low density (diffuse) gas, produce absorption lines (atoms/molecules absorb photons, moving electrons from inner to outer shells)

Front 5

Emission

Back 5

hot, diffuse gas produces emission lines (electrons move from outer to inner shells in atoms/molecules, emitting photons)

Front 6

HII regions

Back 6

Very hot, diffuse

Front 7

HI gas

Back 7

Cool

Front 8

Molecular Cloud

Back 8

Cold

Front 9

Extinction

Back 9

makes stars appear dimmer than they really are (by absorbing/ scattering light)

Front 10

Reddening

Back 10

scatters blue light preferentially, making the stars appear redder than they really are.

Front 11

Stars form by:

Back 11

he collapse of a cold clump of molecular gas, with the core collapsing faster than the outer regions (an “inside-out” process)

Front 12

Core Accretion Theory

Back 12

According to the core accretion theory, both gas giants and terrestrial mass planets formed in young protoplanetary disks. Terrestrial mass planets formed by disk material colliding & growing larger & larger (dust turning into pebbles, rocks, planetesimals, planetary embryos, then planets). Gas giant cores start forming the same way. Once gas giant cores reach a size of 10 Earth masses, they start rapidly accreting nearby gas (this gas forms the bulk of the planet).

Front 13

Disk Instability Theory

Back 13

According to the disk instability theory, gas giants form in young protoplanetary disks; terrestrial mass planets aren’t formed via this theory. Gas giants form by the rapid gravitational collapse of a part of the disk.

Front 14

Radial Velocity Technique

Back 14

Most successful explanatory discovery technique to date -- ~500 planets detected
How: gravitational star/exoplanet interactions cause star to move (“wobble”) about system's center of mass - closer/further
Measure: star's spectrum Redshifts/Blueshifts as star moves towards/away from our Earth vantage point (radial motion)

Front 15

Astrometric Detection Technique

Back 15

Exoplanets gravitationally interact with their host stars, inducing a ‘wobble’ in the star’s motion on the sky; Astrometry measures star's position & records "wobble" - left/right

Front 16

Transit Photometry Detection Technique

Back 16

An exoplanet which transits its parent star will block out a repeating, small amount of light emitted by the central star. - Eclipses some light
Measure: observe transit depth --> determine planet's radius; observe duration of transit & period --> determine planet mass accurately

Front 17

Direct Imaging

Back 17

Uses coronagraphy & obtains image of exoplanet's IR wavelengths
Requires: high contrast imaging, ability to image nearby host star, 2 more detections to confirm orbit, suppress speckles (noise feature of scattered light)

Front 18

Microlensing

Back 18

Light from distant source is bent around a lensing object; causes light from source to be magnified; if lensing object has a planet, the planet will induce a secondary magnification of distant source.

Front 19

(Primary) Transit Photometry

Back 19

Yields planetary masses & radii --> densities --> composition

Front 20

primary eclipse transmission spectroscopy or maybe (Secondary) Transit Photometry

Back 20

Key parameter derived --> Blackbody temperature of exoplanet (planet temperature = temperature of system when planet is detectable - temperature of system during secondary eclipse)

Front 21

IR Phase Mapping

Back 21

Diagnoses atmospheric winds (& atmospheric recirculation efficiency)

Front 22

Transmission Spectroscopy

Back 22

yields the spectrum of the exoplanet’s atmosphere

Front 23

examples of Earth’s biosignatures

Back 23

“Keeling Curve”, Red Edge

Front 24

criteria are required for habitability?

Back 24

Tides - some tidal force is good, but too much creates extreme
volcanic activity 2) Planet tilt - Earth's relatively stable tilt 2.5 deg/41,000
years, compared to Mars' 15-35 deg/~100,000 years 3) Presence of
(dominant) gas giants - acts a shield 4) Atmosphere - Greenhouse
effect from earth's atmosphere modifies Solar System HZ to be 0.55-1.1 AU 5)
Time dependence of HZ - Energy output of main-sequence stars gradually increases over time. Atmospheres can change over time

Front 25

Red Giant

Back 25

Use up Hydrogen in core, core shrinks, gets Hydrogen shell
burning.

Front 26

SN Type II

Back 26

Iron (Fe) core collapses into ball size of a few Km (of neutrons) in
fractions of a second. Energy of collapse powers a supernova type 2
explosion. SN explosion blows most of the star apart and supplies nearly all
of the Iron (Fe) in the universe

Front 27

Neutron Star/ Pulsar:

Back 27

Ball of very dense neutrons left over. 1-2 solar masses
condensed into around 10km diameter. “Jets” emits a rapid, periodic pulses
of radio waves

Front 28

black holes

Back 28

Black holes are distortions in the spacetime continuum. High mass Iron (Fe)
core collapses but does not have SN explosion due to their enormous mass. Neutron
star becomes greater than 2-3 solar masses and then the neutron star collapses producing a black hole. Black holes are NOT a physical hole in space

Front 29

What stage of a star’s post-main-sequence evolution will recycle material back into the interstellar medium?

Back 29

a) planetary nebula
b) supernova
c) Luminous Blue Variable
d) all of the above

Front 30

When a star exhausts its source of fusion in its core and starts to collapse as it evolves off of the main sequence:

Back 30

the gravitational force in the star’s core is greater than the outward gas pressure

Front 31

Describe the 4 main techniques used in astronomy to measure distances & how each one works.

Back 31

1) Photometric Parallax: used for objects close to Earth. Looks at an object from
different viewpoints in Earth’s orbit around the sun and uses Geometry to detect the
distance.
2) Spectroscopic Parallax: 1) Measure a star’s apparent magnitude and spectral type,
2) place it on HR diagram to determine the star’s absolute magnitude, 3) use apparent
and absolute magnitude to calculate distance. Useful for about 1000 light years.
3) Pulsating Giant Stars: Post main sequence stars pulsate, physically expanding and
contracting in diameter which creates changes in brightness.
4) Type 1a Supernova: SuperNova explosions all reach nearly the same luminosity at
maximum which indicates they may be good standard candles

Front 32

What is the leading theory to explain how the Moon was formed?

Back 32

Large object collided with the Earth enriching Earth’s Iron (Fe) content. Part
of Earth broke off to form the Moon

Front 33

Describe the internal composition of Jovian planets

Back 33

The core is rock/metal. Outside of that is ice, and then hydrogen

Front 34

origin of the rings around Jupiter

Back 34

Asteroids crash into Jupiter’s moons and the collision creates a dust
cloud which is gravitationally captured by Jupiter’s large gravitational pull

Front 35

origin of the rings around Saturn

Back 35

composed of tiny ‘moonlets’ which range in size from small grains to
a few meters. They are NOT solid structures. Origin: tidal breakup of small
moon or leftover from planetary formation

Front 36

6 layers of the Sun and what are their basic properties

Back 36

1) Core - region in which fusion occurs
2) Radiative Zone - Energy from core is transported by radiation
3) Convective Zone - Energy is transported via convection (warm regions rise,
cool regions sink)
4) Photosphere - visible surface of the sun
5) Chromosphere - Region above the photosphere. Temperatures rise from 10,000 K to 200,000 K
6) Corona- Outermost layer of the sun. Very diffuse layer; only seen with coronagraph.

Front 37

What is granulation

Back 37

Evidence of convection. Material rises (hot) and falls (cooler) in pockets of gas in the photosphere

Front 38

What are the 3 different types of activity that occur on the Sun?

Back 38

1) Flares - energies and masses released in chronosphere and looped back into the sun.
2) Coronal Mass Ejections - big chunk of the corona gets blown off like a bubble
3) Sunspots - photosphere part of the sun where convection is temporarily

Front 39

Open cluster

Back 39

smaller, contains high mass (blue, shorter lifetime) and low mass
(red, longer lifetime) stars.

Front 40

closed cluster

Back 40

older, contains only low mass (red, longer lifetime) stars

Front 41

How are clusters used to measure ages in astronomy?

Back 41

find bluest star

main sequence turnoff

Front 42

4 main types of galaxies?

Back 42

1) Elliptical - Rounder, very little gas or dust, void of massive blue stars
2) Lenticular - bridge between elliptical and spiral galaxies. No spiral arms, little
gas, some dust, comprised of mainly older stars.
3) Spiral - spiral arms, a lot of gas and dust, active star formation (spiral arms),
contains hot, massive stars.
4) Irregular - irregular in shape, can contain gas, dust, massive, and lower
massive stars.

Front 43

What are the basic regions found in spiral galaxies?

Back 43

1)Thin disk - spiral arms.
2) Thick disk - contains many older stars.
3) Bulge - central concentration of a galaxy.
4) Halo - much older spherical distribution of stars and clusters.

Front 44

What are Active Galactic Nuclei (AGN)?

Back 44

guides accumulation of material to the center of black hole. Also exhibit
bipolar jets. Galaxies that have active blackholes that are actively eating matter in the center

Front 45

What is the Hubble law

Back 45

the more distant the galaxy, the faster it is receding from us (red shifted).

Front 46

What are 3 dark matter candidates?

Back 46

1) MACHO - Massive Compact Halo Object. Massive and small? located in the Halo and does not give off a lot of light
2) WIMPs - Weakly Interacting Massive Particles. Particles that have mass.
3) Modified Gravity - It does not exist and our understanding of gravity on a larger scale is incorrect

Front 47

What is causing the universe’s expansion to accelerate?

Back 47

Dark Energy.

Front 48

WHats the comp of the universe?

Back 48

Around 5% stuff that is seen

95% Dark Matter/ Dark Energy

30% dark matter

65% dark energy

Front 49

What evidence supports the big bang?

Back 49

1) Cosmic Microwave Background (CMB) - combination of free electrons with bare protons to produce atoms
2) observed composition of the universe, lots of He