Astro Exam Three

the physical structure of saturn's rings is

a sequence of many thousands of separate ringlets consisting of ice and ice coated rock

the oort cloud is

a spherical distribution of distant comets around the sun, extending out about 50,000 AU

in the hertzsprung-russell diagram, how does the position of a typical star change while it is at the main-sequnce phase of its evolution?

a star's position on the main sequence is determined only by its mass, not its age, so stars do not move along the main sequence during evolution

the total time the sun will spend as a main-sequence stat is

about 10 billion years

how far away is the nearest star beyond the sun?

about 4 ly away

the stars in an open cluster are useful for studying the early stages of stellar evolution because all the stars in a cluster have the same

age

what is parallax?

apparent shift in position of an object as the observer moves

what is the similarity between jupiter and the earth?

auroras are produced by magnetospheres on both jupiter and the earth

what is the second most abundant element in the universe (after hydrogen)?

helium

a cepheid variable is a

high-mass giant or supergiant star that pulsates regularly in size and brightness

how is the length of a star's lifetime related to the mass of the star?

higher-mass stars run through their lives faster and have shorter lifetimes

new stars are formed from

huge, cool dust and gas clouds

the major constituent in the interior of saturn is

hydrogen

what is the most abundant element in the universe?

hydrogen

where has water ice been found on mercury?

in permanently shadowed crater floors at the north and south poles

where in the solar system would you look for liquid hydrogen?

in the deep interiors of Jupiter and Saturn

venus appears to be very bright in our skies at certain times because

it is covered by very reflective clouds

mars experiences similar seasonal changes to those on the earth because

it spin axis is tilted at about the same angle to its orbit plane as it the earths axis

the major feature that distinguishes a sunspot from other regions on the sun is

its very powerful magnetic field

what is a spicule on the sun?

jet of rising gas in the chromosphere

evidence of lava flow, either recent or ancient, in not found on

jupiter

on what planet is the great red spot on?

jupiter

the orion nebula is a

large interstellar gas and dust cloud containing young stars

what is a prominence on the sun?

large loop of gas supported by magnetic fields

the word chromosphere refers to a

layer in the suns atmosphere

in a group of stars with a range of masses, stars with different mass

leave the main sequence of the hertzsprung-russell diagram at different times after their birth

what physical characteristics are the earth and mars most similar to each other?

length and solar day

what characteristic features are seen on the visible surface of jupiter?

light and dark bands parallel to the equator

what physical feature of the planet mercury causes the deflection of solar wind particles away from its surface?

magnetic field that, like the Earth's, produces a magnetosphere surrounding the planet

where on the hertz sprung-russell diagram so most local stars in our universe congregate?

main sequence, where stats are generating energy by fusion reactions

over what stages of stellar evolution does the radius of a star remain approximately constant?

main-sequence phase

what planet is the only one whose surface features can easily be seen through a telescope from the earth?

mars

the asteroid belt exists between the orbits of the planets

mars and jupiter

what physical properties of Venus are very similar in value to those of earth?

mass and radius and hence average density and surface gravity

how do massive stars normally end their lives?

massive stars explode

what is the solar wind?

material from the corona, accelerated out into space

comet tails are the result of

melting and evaporation of ices from the comet core

this planet has a large iron core, a heavily cratered surface, and no atmosphere

mercury

this planet most resembles the moon in visible surface features and atmosphere

mercury

what body does not exhibit some differential rotation?

moon

how many moon are now known to orbit jupiter?

more that 60

Jupiter has a magnetic field that is

much more powerful than that of the earth

what is the "face" on mars?

natural rock formation that looks like a face in the right light

the most likely places in which stars and planetary systems are forming the universe are

nebulae composed of gas and dust

venus has

no magnetic field

suppose that an astronomy news item announces the discovery of a brown dwarf. what is it that has been discovered?

object too large to be a planet but too small to be a star

the group of stars that is formed when a giant molecular cloud collapses is called an

open cluster

tomorrows weather report for venus would be

overcast and very hot

a visible light spectrum of the sun reveals many dark adsorption lines. These lines are caused by photon absorption, which takes place in the

photosphere

of the following objects in the solar system, what planet has the greatest orbital inclination (orbit at the greatest angel to that of earth)?

pluto

what planet or dwarf planet in our solar system has the moon with largest diameter compared with the diameter of the planet or dwarf planet?

pluto

what is the observed feature that suggest that mercury's iron core is molten?

presence of a global magnetic field

what is a filament of the sun?

prominence seen in silhouette against the photosphere

the asteroid belt is believed by most astronomers to be composed of

rocky debris left over from the formation of the solar system

what planet has wide, bright rings that are easily visible from the earth?

saturn

a shooting star is a

small particle of interplanetary dust burning up and glowing as it enters earths atmosphere

Jupiter's great red spot is probably a

storm

what is helioseismology?

study of vibrations in the suns interior

what is not considered to be a feature of the quiet sun?

sunspot

when venus is at its brightest as seen from the earth (near greatest elongation) it is

the brightest celestial object in the sky other than the sun and the moon

the kirkwood gaps are caused by

the gravitational pull of jupiter, which nudges asteroids into the new orbits

How do the stars in a star cluster change with time?

the highest-mass stars evolve the most quickly

there is no evidence of plate tectonics on mercury. the most likely explanation is that

the planet cooled too rapidly and the mantel became too rigid

the next stage in a star's life after the main-sequence phases is

the red giant phase

a main-sequence star can be no smaller that 0.08 solar mass. the reason is that

the temperature in a contracting protostar of less that 0.08 solar mass does not become high enough for nuclear reactions to start

what is the energy source for the sun?

thermonuclear fusion in the core

asteroids that orbit the sun in the stable Lagrange points in jupiter's orbit are known as

trojans

what is the major constituent of the atmosphere of mars?

CO2 (carbon dioxide)

the four giant moons of jupiter were discovered by

Galileo,in seventeenth-century italy

the space between stars is known to contain

gas, bot atomic and molecular, and dust

what is plasma?

gaslike mixture of ions and electrons

all starts on the main sequence

generate energy by hydrogen fusion in their centers

the temperature at what thermonuclear reactions begin to convert helium into carbon (helium burning) is

100 million k

how many large, spherical moons are in orbit around jupiter?

4

what is the biggest planet in the solar system?

Jupiter

This planet has a solid, cratered surface, which is alternately very hot and very cold, and it has no atmosphere

Mercury

meteoroid is the term used to describe a solid particle that

a drifting around in space

the kuiper belt is

a flat or donut-shaped distribution of distant comets around the sun, extending out about 500 AU

an asteroid is

a planestesimal moving in an orbit around the sun

why should you never look directly at the sun?

blindness

how is the mass of jupiter determined?

by observing jupiters interaction with its satellites and using keepers third law

The orbits of periodic comets

can extend far out beyond the orbit of pluto and can be oriented in any direction in the solar system

the gas that is the major constituent of the atmospheres of venus and mars and a minor constituent of the earths atmosphere is

carbon dioxide

there are several mechanisms that can trigger star formation in a cold, dark nebula. In each mechanism, the key to star formation is

compressing the gas and dust so that gravitation will overcome the gas pressure

the granulation observed on the photosphere of the sun appears to be the result of

convection currents

sunspots are

cooler, darker regions on the suns surface

what are the most energetic eruptive events to occur on the sun?

coronal mass ejections

sunspots are caused by

differential rotation and its effects on weak magnetic fields just under the solar surface

which of the following properties of a nearby star is determined by a measurement of stellar parallax?

distance from earth

the clouds in the atmosphere of venus consist primary of

droplets of sulfuric acid

the cause of the "meter showers" seen at regal times each year on earth is most probably

earth moving through the remnant dust and rock fragments of an old comet that are orbiting the sun in the comets old orbit

the solar wind is almost entirely ionized gas

escaping through coronal holes

the rotation of the sun is

fastest at the equator, slower at mid-latitudes, and slowest near the poles

What is the name of a sudden, highly energetic, eruptive surge on the surface of the sun?

flare

the one terrestrial planet that rotates in the "wrong" way (opposite to the rotation of the most other planets and to the planets revolutionary direction is

venus

what planet is the hottest one in the solar system, measured at the surface?

venus

venus has a higher surface temperature that mercury. What is the explantation?

venus has a dense atmosphere of carbon dioxide

the photosphere of the sun is

visible "surface" of the sun

compared with that of the earth mercury's magnetic field is

weak but clearly present

the extremely high gas temperatures in the solar corona mean that this region is best observed at wavelengths of

x rays