Astronomy exam 2

Characteristic of outer planets

their orbits are seperated by relatively large distances

They are primarily made of hydrogen and helium.

They all have rings

They all have large quantities of gas.

Main constituents of the jovian planets

hydrogen and helium

What is the great red spot on jupiter

a long-lived high pressure storm

true statements about the jovian planets

Some of the moons are big enough that we'd call them planets (or minor planets) if they orbited the Sun.

Many of the moons are made largely of ices 

One of the moons has a thick atmosphere

Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?

countless icy particles, ranging in size from dust grains to large boulders

Leftover rocky planetesimals that formed in the inner part of the disk of the newly forming solar system, inside the frost line are ________

asteroids

Pieces of asteroids that have fallen to Earth are called    

meteorites

Comets are ________________

Leftover icy planetesimals from the outer part of the solar system that did not form into planets

The Rosetta space mission flew to and studied ____________

a comet

Meteor showers are associated with debris from  

comets

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

gamma rays, X-rays, ultraviolet, visible light, infrared, radio

One of the absorption lines of hydrogen has a rest wavelength of 656 nanometers (nm), (at rest means with respect to the observer, like in a lab). You observe several stars and measure the wavelength of this same hydrogen absorption line in each star. Based on the measured wavelength of this line, which star is moving towards the Earth the fastest?

630 nm

If a star is moving away from you at a constant speed, how do the wavelengths of the absorption lines change as the star gets farther and farther away?

The wavelengths would be longer than observed if the star was at rest and would remain the same regardless of the distance.

When an electron in an atom goes from a higher energy state to a lower energy state, the atom

emits a photon of a specific frequency

If you heat a low-density gas so that collisions are continually bumping electrons to higher energy levels,when the electrons fall back to lower energy levels the gas produces

an emission line spectrum

What is the method that NASA’s Kepler telescope mission uses to detect extrasolar planets?

transit method

How does a “Hot Jupiter” differ from Jupiter?

its much closer to its star

We use the terms “face-on” and “edge-on” to describe how a star-planet orbit is oriented from our viewpoint.  Which detection method could detect a planet in an orbit that is face-on to Earth?

Astrometric method

Which detection method, or methods, allows us to estimate the mass of a planet by measuring the gravitational tug of a planet on its star?

the astrometric AND Doppler methods

Which one of the following properties of a planet can be determined using the transit method?

its size (diameter)

Consider a planet detected by the Doppler method, in which the periodic variations in the Doppler shift of light from a star is caused by a planet orbiting it. What Doppler shift is observed from the star, when the planet is moving the fastest toward us?

maximum redshift

What is the astrometric technique for discovering extrasolar planets?

It is the observation of changes in the position of the star due to the gravitational effects of an orbiting planet

Two planets are detected by the Transit method. Planet A has a diameter 5 times larger than Planet B.  What is the biggest difference that would be observed in the light curve of Planet A, compared to B?

The dip in brightness in A would be deeper

How many planets  around other stars have been found and confirmed to date?

thousands

Which of the following techniques did the Kepler mission use to find extrasolar planets?

transits

Which of the following parts of the Sun has the highest temperature?

core

Why does the sun shine

because of nuclear fission

How do the nuclear reactions in the Sun’s core produce energy?

The mass of the product of the reaction is less than the mass of the hydrogen atoms that enter the reaction

What is the temperature of the surface of the Sun that we see?

6000 K

What is responsible for Solar Activity phenomena, such as sunspots, solar flares and CMEs?

magnetic force

At the center of the Sun, fusion converts hydrogen into:

Helium and energy

Which of these layers of the Sun is coolest?

photosphere

Which of these groups of particles has the greatest mass?

four individual protons

Why do sunspots appear darker than their surroundings

they are cooler than their surroundings

What do we need to measure in order to determine a star’s luminosity?

apparent brightness and distance

The star Betelgeuse in the Orion constellation is red colored and the star Rigel is blueish. This indicates Betelgeuse is ______________  than Rigel.

cooler

What technique do astronomer's use to measure the distances to relatively nearby stars?

parallax

Where are the largest (biggest diameter) stars located on the H-R diagram?

upper right

How far away is a star that  exhibits a parallax angle of  p=0.01 arcesconds?

100 parsec

How do astronomers measure masses of stars?

motions of stars orbits in binary pairs

What slows down the contraction of a star-forming cloud when it makes a protostar?

trapping of thermal energy inside the star

Which of these stars has the hottest core?

a white main-sequence star

What would you most likely find if you returned to the solar system in 10 billion years?

a white dwarf

What happens to the core of a high-mass star after it runs out of hydrogen?

it shrinks and heats up

Which of these stars does not have hydrogen fusion occurring in its core?

a red giant

What is the most fundamental property of a star in determining its evolution?

mass

Where is a star located on the Hertzsprung-Russell diagram if it is burning hydrogen into helium in its core?

along the main sequence

Which of the following is a main-sequence star

the sun

Direct Planet Detection

Light directly from the planets themselves is detected (very rare because the star often way outshines the planet)

indirect Planet Detection

measurements of properties of the stars which reveal the effects of orbiting planets

Why are Uranus and Neptune blue?

• They have a higher fraction of methane gas than jupiter and saturn

• Methane absorbs red colors of sunlight

• Only blue light is reflected back into space by the clouds

Moons of Jovian planets

• dozens; some large ones with interesting geology

Rings of Jovian planets

• razor thin rings made of ice, snow, dust

Small moons

→ less than 300 km across

→ they are not spherical

→ probably captured asteroids

Medium-Large moons

→ formed like planets out of the “mini-solar nebulae” surrounding the Jovian planets

Io

Jupiter moon

→ friction generates heat

→ interior of Io is molten

→ Volcanoes erupt frequently

→ sulfur in the lava accounts for yellow color

Europa

Jupiter Moon

→ metallic core, rocky mantle, and a crust made of H2O ice

→ evidence of a subsurface ocean of liquid salt water beneath icy crust

→ where liquid water exists, there could be life

Ganymede

Jupiter Moon

→ largest moon in the solar system

→ part of surface heavily cratered (old), other grooved/few craters (young, like europa)

→ possibly subsurface ocean?

Callisto

Jupiter Moon

→ furthest of the 4 galilean moons

→ weak tidal forces

→ geologically dead/heavily cratered

Titan

Saturn Moon

→ Saturn's largest moon

→ thick atmosphere, mostly nitrogen

→ water frozen, but liquid ethane (clouds, rain, oceans)

→ atmosphere blocks view of surface, but huygens probe landed on surface revealing: interesting geology, land forms

Why are the Jovian planets so different from the terrestrial planets?

• They formed beyond the frost line to form large, icy planetesimals which were massive enough to

• Capture H/He far from the sun to form gaseous planets.

• Each jovian planet formed its own “miniature” solar nebula

• Moons formed out of these disks

What causes the distinctive bands of color at different latitudes on Jupiter?

• Three gasses condense in Jupiter's atmosphere

→ ammonia

→ ammonium hydrosulfide

→ water

• They freeze at different temps, so their clouds form at different altitudes

• They reflect different colors of light giving their different hues

High pressure storms

The great red spot on jupiter and the great dark spot on neptune

Meteors

a flash of light in the sky caused by a particle entering the atmosphere, regardless of its origins

Where are asteroids mostly built

in the asteroid belt between mars and jupiter

Trojan Asteroids

two clusters of asteroids in Jupiters orbit

Basic evidence for hypothesis that an asteroid impact led to mass extinction on Earth

• iridium layer (iridium is a rare element on earth but often found in meteorites, no Dinosaur fossils are found above the iridium layer)

• Enormous Crater (Chicxulub Crater in Yucatan)

• Consequences of Impact (send large amounts of debris into atmosphere blocking sunlight and leading to a change in climate)

Oort Cloud

• comets on random orbits extending to about 50,000 AU

Kuiper Belt

• Comets on orderly orbits at 30-100 AU in disk of solar system (pluto is found here)

Dwarf Planets

like pluto; objects that are smaller than planets, orbit the sun, and are large enough to be round

Pluto

• located in the inner region of the Kuiper belt

• much smaller than the major planets, and indeed nothing like the gas giant Jovian worlds

• icy composition, more like a comet

• highly elliptical and inclined orbit

• New large icy bodies discovered outside of Pluto’s orbit

• Pluto has more in common with comets than with the eight major planets.

Wavelength

length of one wave pattern

Frequency

• the number of times a point on the wave pattern goes through a full cycle per second

speed of light

3.00 × 10^8

wave speed

length x frequency

Photons

discrete chunks of light

higher frequency

higher energy

Visible light

narrow sliver of the full spectrum

Photon energy

E=h x f (h= planks constant)

Continuous Spectrum

spans all visible wavelengths without interruption

Emission Line Spectrum

emits lights only at specific wavelengths producing a spectrum with bright emission lines

Absorption Line Spectrum

cooler gas in outer atmosphere of stars absorbs the same wavelengths of light gas emits

Blueshift

a light source moving toward you has wavelengths shifted to shorter values

Redshift

a light source moving away from you has wavelengths shifted to longer values

Astrometric Method

motion of star in the sky is observed

Doppler Method

doppler shift of starlight is measured and properties of planets are inferred

Transit Method

small dips in the “light curves” of stars as the planets eclipse their star. Planet orbital periods, planet sizes can be learned from this method