Create an account
Describe the three main layers of the solar atmosphere and how you would best observe them.!
1. Photosphere - the optical surface of the sun.
2. Chromosphere - layer of gas.
3. Corona - the glow around the sun.
You can observe all of these layers using appropriately safe filters during a solar eclipse.
Give some everyday aspects of heat transfer by convection and radiative transport.!
-Hot air rising, cooling, and falling (convection currents)
-An old-fashioned radiator (creates a convection cell in a room by emitting warm air at the top and drawing in cool air at the bottom).
-Heat from the sun warming your face
-Heat from a lightbulb
-Heat from a fire
-Heat from anything else which is warmer than its surroundings.
Why do thermonuclear reactions in the Sun take place in its core?!
In order for nuclear reactions to occur enormous pressures and temperatures must exist. This is only possible in the Sun's core (or in the core of other stars).
What is hydrogen fusion? This process is sometimes called "hydrogen burning." How is hydrogen burning fundamentally unlike the burning of a log in a fireplace?!
What is stellar parallax?!
the apparent motion of nearby stars among the background of more distant stars due to earths motion around the sun
How and why is the spectrum of a star related to its surface temperature?!
the hotter the surface of a star is, the more ionized the hydrogen on the surface becomes. Ionized hydrogen does not give off spectral lines like normal hydrogen does, so the fainter you see spectral lines from hydrogen, the hotter the surface of the star must be.
Draw an H-R diagram and sketch the regions occupied by main-sequence stars, giants, supergiants, and white dwarfs...!
What is a radial velocity curve? What kinds of stellar systems exhibit such curves?!
Radial velocity over time, used to detect unseen companions to stars, such as planets, brown dwarfs, etc...in variable stars it can be used to determine changes in the star's radius...it is just the doppler effect, the side of the object moving toward you will have a blue shift and the side moving away from you will have a red shift...the distance between the star and its companion will change the values of the doppler shifts indicating the size and distance they are from each other...
What is meant by the light curve of an eclipsing binary? What sorts of information can be determined from such a light curve?!
What are giant molecular clouds, and what role do they play in star formation?!
giant molecular clouds are a large interstellar cloud of cool gas and dust in a galaxy.
Stars form inside dense concentrations of interstellar gas and dust known as molecular clouds. These regions are extremely cold, just above absolute zero. The deep cold also causes the gas to clump. Star formation is often triggered by an external shock wave, for instance an exploding supernova. When the density reaches a certain point, the cloud collapses under their own weight.
Such clouds typically have masses around 10^4 solar masses. As the core is denser than the outer cloud, it collapses first. Quickly they fragment into clumps around half a light year in size and 10 to 50 solar masses in mass. These clumps then form into hundreds of protostars.
The whole process takes about 10 millions years.
Why do thermonuclear reactions not occur on the surface of a main-sequence star?!
1. Temperatures hot though they may be, are nowhere NEAR as hot as they must be for nuclear fusion to occur. Even a man-made thermonuclear device (hydrogen bomb) requires the heat and pressure-force generated by an atomic bomb for the more powerful fusion part of the bomb to work.
2. Pressure. Atomic nuclei tend to repel one another when they get too close. At a star's core there is sufficient pressure and density of material for the repulsive tendencies of nuclei to be overcome.
What is an evolutionary track, and how do such tracks help us interpret the H-R diagram?!
on the H-R diagram, the path followed by a point representing an evolving star
What will happen inside the Sun 5 billion years from now when it begins to evolve into a giant?
It will start to burn heavier elements like hydrogen and will grow much bigger. This will cause it to grow bigger and become much hotter. It will easily eat Earth and make Mars like Mercury because it will grow that big.
Explain how and why the turnoff point on the H-R diagram of a cluster is related to the clusters age.!
Why do astronomers believe that globular clusters are made of old stars?!
Spectroscopic study of globular clusters shows that they are much lower in heavy element abundance than stars such as the Sun that form in the disks of galaxies. Thus, globular clusters are believed to be very old and consisted from an earlier generation of stars (Population II), which have formed from the more primordial matter present in the young galaxy just after (or even before) its formation. The disk stars, by contrast, have evolved through many cycles of starbirth and supernovae, which enrich the heavy element concentration in star-forming clouds and may also trigger their collapse.
Why is knowing the temperature in a star's core so important in determining which nuclear reactions can occur there?
Fusion reactions occur when the strong force, the force that binds the neu- trons and protons, binds two nuclei in two initially separate atoms. The strong force acts at very short distances. However, the nuclei are positively charged and therefore repel at the average distances between the nuclei in the gas. Therefore, in order for binding to occur, the nuclei have to be pushed close together, overcoming the repulsion of the electric force. This requires that the nuclei have very high relative velocity.
What determines the temperature in the core of a star?
3. Gravitational fields
4.dist from sun
5.revolution speed/ planet speed/ approximation to star
What is a planetary nebula, and how does it form?
a planetary nebula is a luminous shell of gas ejected from an old, low-mass star.
Compare a white dwarf and a neutron star
Remnants of low-mass stars
Supported by Electron Degeneracy Pressure
Maximum Mass ~1.4 Msun (Chandrasekhar Mass)
Remnants of some post-supernova massive stars
Supported by Neutron Degeneracy Pressure
Pulsar = rapidly spinning magnetized neutron star
Why do astronomers believe that pulsars are rapidly rotating neutron stars?
A pulsar is a rapidly rotating neutron star. It produces flashing signals, either in the visible light spectrum, or the radio spectrum, or both. When radio pulsars were first discovered, the period of the signal was so precise, it was originally thought that they were radio signals from an alien source.
In what way is a black hole blacker than black ink or a black piece of paper?
A black hole is black not just in the sense that it emits no light, but also in that it reflects no light and scatters no light. Black ink and black paper shine a little bit under a lightbulb. If you were to shine a flashlight on a black hole, you wouldn't see any difference - it would absorb every single photon. Of course, if you got too close, it would absorb you, too, so we don't recommend this exercise.
f the Sun suddenly became a black hole, how would Earths orbit be affected?
There would be no effect on the earth's orbit. Even though the shrunken sun's gravitational attraction would become insurmountably large at the position of its event horizon, that gravitational attraction would be unchanged at the distance of the earth's orbit.
!Why are all of the observed stellar-remnant black hole candidates members of close binary systems?
Describe four methods for discovering exoplanets.
Extrasolar planets can be discovered by observing them indirectly by using microlensing, by observing the Doppler shift of the star due to the pull of the orbiting planet, by observing the periodic variation of the proper motion of a star, and by observing the periodic variation of the starlight due to the planet passing between that star and Earth, an event called a transit.
Why is the Earth's surface not riddled with craters as is that of the Moon?!
At one time, the Earth's surface was probably as peppered with craters as the Moon's. Earth's plate tectonics, along with wind and water erosion, have eliminated all but the most recent craters. Furthermore, most small pieces of debris falling earthward today vaporize in the Earth's relatively dense atmosphere before they strike the Earth and cause new cratering.
Describe the process of plate tectonics. Give specific examples of geographic features created by plate tectonics.
How do we know about the Earth's interior, given that the deepest wells and mines extend only a few kilometers into its crust?
We detect and study seismic waves created by powerful earthquakes and other activities in the Earth. Scientific models of the Earth's interior can be tested and modified by comparing their predictions of the speed and intensity of seismic waves with the actual time and location of the waves that reach the Earth's surface
Why is the center of the Earth not molten?
The inner core at the Earth's center is not molten because the pressure is high enough to solidify it in spite of the high temperature.
What kind of features can you see on the Moon with a small telescope?
Maria (areas of dark form lava flows), craters, center peaks in some craters, and terrae (light colored highland)
What is a tidal force? How do tidal forces produce tides in Earth's oceans?
A tidal force is the force that tends to distort the shape of a body due to the fact that the gravity of a nearby body weakens with distance so that it is felt more strongly on the near side than the far side. The combination of tidal force from the Moon and the motion of the Earth around its center of mass with the Moon, the barycenter, creates two-thirds of the ocean tides here. The tidal force of the Sun combined with the Earth's orbit around it creates the rest of the tide.
Why do most scientists support the collision- ejection theory for the Moon's formation?
Most scientists support the collision-ejection theory because this theory is the only one that successfully accounts for the Moon's composition and orbital motion.
Compare the surfaces of Mercury and our Moon. How are they similar? How are they different?
Both Mercury and the Moon have many impact craters.The Moon has many maria, whereas Mercury has smaller lava flood plains and scarps.
Astronomers often refer to Venus as Earth's twin. What physical properties to the two planets have in common? In what ways are the two planets dissimilar?
Venus and Earth are similar in mass, size, and composition.Venus is 28 percent closer to the Sun than the Earth.That relatively small difference prevented water from condensing on the surface ofVenus.They are vastly different in atmospheric composition, atmospheric pressure, surface temperature, and rates of rotation.
Why is Venus hotter than Mercury?
Venus is hotter because of the runaway greenhouse effect. The atmosphere on Venus is so thick and heavy that it traps the solar energy that penetrates its cloud
Whatisthegreenhouseeffect? Whatroledoes it play in the atmospheres of Venus and Earth?
The greenhouse effect keeps Venus' atmosphere at about 860 degrees F even on the nighttime side of the planet and near the poles (this is 750 degrees higher than the average temperature the planet would have if it had no atmosphere). On Earth the greenhouse effect raises the temperature about 74 degrees from what it would otherwise be.
What evidence have astronomers accumulated that liquid water once existed in large quantities on Mar's surface? What evidence is there that water exists, still under its surface?
What causes the belts and zones in Jupiter's atmosphere?
Belts and zones in Jupiter's atmosphere are thought to be due to thermal interactions of the gas in its atmosphere. Convection currents are thought to cause the belts. Similar to weather patterns here on Earth due to variations in pressure and temperature, these same variations cause belts and zones in Jupiter's atmosphere.
Describe the structure of Saturn's rings. What are they made of?
The rings are highly concentrated in Saturn's equatorial plane but very broad in the radial direction. Saturn's rings are composed of thousands of ringlets of rocky or icy objects each less than ten meters in diameter.
Why do features in Saturn's atmosphere appear to be more "washed out" than comparable features in Jupiter's atmosphere?
Saturn's features are hazy because its atmosphere is thicker. Jupiter's mass is greater than Saturn's. Therefore, its gravity is higher and a higher surface gravity compresses the atmosphere to 75 km in thickness. On Saturn, the low mass means less surface gravity and the atmosphere is thicker at 300 km from top to bottom. The result is that Saturn's atmosphere has more haze and its features (turbulence, cyclones, etc.) are blurred and hard to see. This also causes its colors are muted into a general yellowish hue.
Describe the seasons on Uranus. Why are the Uranian seasons different from those on any other planet?
I think it's because both Uranus and Neptune have an atmosphere that contains methane whereas Jupiter and Saturn are two-thirds hydrogen.The methane gas stuff absorbs all the red light coming from the sun but reflects the blue light back into space. ?????
Compare the ring systems of Saturn and Uranus. Why were Uranus's rings unnoticed until the 1970s?
The rings of Saturn are largely composed of various types of ice and are very reflective.
The rings of Uranus on the other hand are very thin and comprised of dark material.
The rings of Uranus were not discovered until 1977, and it was by accident. Astronomers were watching a star pass behind Uranus and were hoping to gain some incites to the planets atmosphere. They were quite surprised to see the star-lite blink out several times before the star passed behind the planet, and them blink out again several time after the star passed the planet
Explain why Triton will never collide with Neptune, even though Triton is spiraling towards that planet.
Triton will never collide with Neptune because Triton will be torn apart when it reaches Neptune's Roche limit.
What role did Charon play in enabling astronomers to determine Pluto's mass?
Applying Kepler's third law to the motion of Charon around Pluto enabled astronomers to determine Pluto's mass.
Why are asteroids, meteoroids, and comets of special interest to astronomers who want to understand the early history of the solar system?
Asteroids, meteorites, and comets are of special interest to astronomers who want to understand the early history of the solar system because these bodies have undergone fewer changes over billions of years compared with planets and satellites. This unchanged matter still contains information about the early solar.
Describe the objects in the asteroid belt, including their sizes, orbits, and separation.
Most comets have a gas or ion tail and a dust tail. The ion tail is composed of ionized atoms that are vaporized ices blown off the comet and are swept into a tail by interaction with the magnetic field of the sun. This tail always points directly away from the Sun.
The dust tail is made of dust, ice vapor and other debris that blows of the comet as the dust particles are liberated from the nucleus as the ices vaporize. The dust particles are left behind in the comet's orbit, and blown slightly away from the Sun by the pressure of the light from the Sun.
in what directions do comet tails point, and why?
The gas tail points away from the Sun, the dust tail lies along the path of the comet due to interactions with the Solar Wind.
What and where is the Kuiper belt, and how is it related to debris left over from the formation of the solar system?
What is the celestial sphere, and why is this ancient concept still useful today?
Ancient concept still in use to relate positions and apparent motions in the sky.
What is the celestial equator, and how is it related to Earth's equator? How are the north and south celestial poles related to Earth's axis of rotation?
The celestial equator is the great circle on the celestial sphere that is midway between the celestial poles. The plane of the celestial equator is the same as the plane of the Earth's equator. The north and south celestial poles are at the intersection of the celestial sphere with the extension of the Earth's axis of rotation.
Why does the tilt of Earths axis relative to its orbit cause the seasons as Earth revolves around the Sun?
The tilt of the earth is what creates seasons. The 23.5 degree tilt of the earth means that its axis is never straight up and down. It's position in relation to revolutions around the sun determines the seasons. So when it's summer, in the northern hemisphere for example, that means that Earth's axis is pointing toward the sun. And when it's winter, it's pointing away from the sun. Earth's revolution around the sun determines its point in space. Because the earth is constantly moving, the view of the night sky changes. That's why constellations appear to be moving across the sky throughout the year.
Why does the Moon exhibit phases?
As the moon orbits the earth, it moves from west to east. Its position relative to the sun also changes and as a result, we see different lunar phases. The sun lights half of the moon at all times. The moon's phase that we see depends on how much its sunlit hemisphere is facing earth.
How did Copernicus explain the retrograde motions of the planets?
Aristotle believed in the geocentric model of the Universe. In this model, retrograde motion was explained by epicycles.
Copernicus was a supporter of the heliocentric model of the Universe. In this model, retrograde motion resulted naturally from the fact that all the planets, including Earth, rotated around the Sun. It was essentially just a curious side-effect.
What are Kepler's three laws? Why are they important?
First law states that the planets orbit around the Sun.
Second law says that a line joining a planet and the Sun sweeps equal areas in equal times.
Third law states that the square of a planet's sidereal period around the Sun is directly proportional to the cube of the length of its orbit's semimajor axis.
The three laws are important because they summarize how planets orbit the Sun and how moons orbit planets.
How did Newton's approach to understanding planetary motion differ from that of his predecessors?
Whereas his predecessors, like Kepler, approached planetary motion from astronomical observations, Newton approached it from a theoretical, mathematical description of gravity. His equations described the orbits of the planets, as well as the motion of other objects but he derived them from first principles using gravitational theory. Comparing the predictions of Newton's equations with Kepler's laws deduced from observed motion served to test the validity of the equations.
What are the three major functions of a telescope?
The three major functions are brighten, resolve, and magnify
Why must astronomers use satellites and Earth-orbiting observatories to study the heavens at X-ray !wavelengths?
The atmosphere is not transparent to X-rays (and nor to gamma rays). Therefore, these radiations must be studied from orbits outside the Earth's atmosphere.
What is a blackbody? What does it mean to say that a star appears almost like a black body?
A blackbody is a hypothetical object whose radiated spectrum depends only on its temperature. A star is described as almost like a blackbody when the continuous part of that star's spectrum follows the shape of a blackbody spectrum. Stars are not black because they are hot and emit large amounts of electromagnetic radiation. They would be black only if they gave off no electromagnetic radiation.
What is Wien's Law? How could you use it to !determine the temperature of a star's surface?
Wien's law is the mathematical relationship between the dominant wavelength and the temperature of a blackbody. It says that the hotter an object is, the shorter the wavelength of the peak of its blackbody curve. This peak is the wavelength that the body emits most intensely. Since all blackbodies with the same temperature have the same black body curves, finding the wavelength at the peak of the continuous spectrum enables you to directly calculate the object's surface temperature.
Explain how the spectrum of hydrogen is related to the !structure of the hydrogen atom.
Electrons have only certain allowed orbits around their nuclei. The allowed orbits, which are associated with unique energy levels, are different in all different types of atoms. The wavelengths of any atom's spectral lines are determined by the differences in the energies of the orbits between which its electrons transfer. The higher the energy difference, the shorter the wavelength of the photon that is emitted or absorbed. When electrons descend in orbit, they emit photons, creating emission spectra. When they go to higher orbits they absorb photons, creating absorption spectra. Since all elements have allowed orbits with different energy levels, the emission and absorption spectra of each element, such as hydrogen, has a unique set of wavelengths.
Please allow access to your computer’s microphone to use Voice Recording.
Having trouble? Click here for help.
We can’t access your microphone!
Click the icon above to update your browser permissions and try again
Reload the page to try again!Reload
Press Cmd-0 to reset your zoom
Press Ctrl-0 to reset your zoom
It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.
Please upgrade Flash or install Chrome
to use Voice Recording.
For more help, see our troubleshooting page.
Your microphone is muted
For help fixing this issue, see this FAQ.
Star this term
You can study starred terms together