Astronomy Ch. 5

moon (natural satellite)

bodies that orbit larger objects, which in turn orbit stars

metals

in astronomy, all elements except hydrogen and helium

solar system

the Sun and everything that orbits it, including planets, their moons, dwarf planets, and small solar system bodies

proto-sun

the Sun prior to the time when hydrogen fusion began in its core

Solar nebula

the cloud of gas and dust from which the Sun and the rest of the solar system formed

Jeans instability

the condition under which gravitational forces overcome thermal forces to cause part of an interstellar cloud to collapse and form stars and planets

Snow line

the distance from the Sun beyond which ices stayed frozen in the early solar system

albedo

the fraction of sunlight that a planet, asteroid, or satellite scatters directly back into space

accretion

the gradual accumulation of matter spiraling in toward a star or black hole

micro-lensing

the gravitational focusing of light from a distant star by a closer object to give a brighter image of the star

average density

the mass of an object divided by its volume

Planetesimal

Primordial asteroid-like object from which the planets accreted.

Asteroids, meteoroids, and comets are also classified as what (one) kind of object today?

Small Solar System Bodies

What is the Nice model's explanation for why there is no planet in the vicinity of the asteroid belt.

So the asteroids seen today in the outer edge of the asteroid belt originally came from much farther out in the solar system and so have retained their water ice and other signatures, while the asteroids in the inner portions were natives to the belt region.

Kuiper belt object (KBO)

Space debris orbiting the Sun beyond Neptune in the Kuiper belt. The debris includes small solar system bodies like Pluto, as well as myriad small rocky and ice objects, including many comet nuclei.

Which planets are terrestrial and which are giant?

Terrestrial planets: Mercury, Venus, Mars, and Earth Giant planets: Jupiter, Saturn, Uranus, and Neptune

Pluto is most similar in composition to which of the following objects?

Eris, a dwarf planet - Both Pluto and Eris are mixtures of ices and rock.

dwarf planet

A celestial body that is in orbit around the Sun and has sufficient mass for its self-gravity to pull the body into a nearly spherical shape, but does not have enough gravity to clear its orbital neighborhood of all the small debris orbiting there.

comet

A small body of ice and dust in orbit about the Sun. While passing near the Sun, a comet's vaporized ices give rise to a coma, tails, and a hydrogen envelope.

Nice model

A theory that describes the formation of the planets and other objects orbiting the Sun, with Jupiter and the other giant planets forming first, followed by the inner planets, asteroid belt, Kuiper belt, and Oort comet cloud.

Oort cloud

A thick spherical shell of the solar system beyond the Kuiper belt where most comets are believed to spend most of their lives.

Planet

An object orbiting a star that is held together by its own gravitational force in a nearly spherical shape, that is able to clear its neighborhood of debris, and is not the moon (or satellite) of a larger orbiting body.

What created most of the craters in the solar system?What else could create craters?

Asteroids, comets, meteors

Name one dwarf planet (other than Pluto) and state where it is located.

Eris, which is located in the Kuiper belt.

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.

Jeans instability is responsible for what event in the life of the solar system?

Forming stars and planets

trans-Neptunian objects (TNOs)

Objects orbiting the Sun beyond the orbit of Neptune

Which giant planet formed first?

Jupiter and then the giant planets formed in sequence.

According the the Nice theory, where did the Kuiper belt objects and Oort cloud objects come from?

Kuiper belt objects and Oort cloud objects are icy planetesimals that were flung outward by the encounters with the giant planets.

Name and briefly describe one small solar system body.

The Oort Cloud is a spherical shell of millions of icy bodies which surrounds the solar system at vast distances and is thought to be the birth place of long-period comets.

Orbital inclination

The tilt or angle of an object's orbital plane around the Sun compared to the ecliptic.

asteroid belt

a 1 1/2 astronomical unit wide region between the orbits of Mars and Jupiter in which most of the asteroids closer to the Sun than Neptune are found

crater

a circular depression on a celestial body caused by the impact of a meteoroid, asteroid, or comet or by a volcano

Proto-planetary disks (proplyd)

a disk of material encircling a protostar or a newborn star

Kuiper belt

a doughnut-shaped ring of space around the Sun beyond Neptune and centered on the ecliptic that contains many frozen comet nuclei and other debris, some of which are occasionally deflected toward the inner solar system

meteoroid

a small rock in interplanetary space

small solar system body (SSB)

all objects in the solar system that are not planets, dwarf planets, or moons

terrestrial planet

any of the planets Mercury, Venus, Earth, or Mars; a planet with a composition and density similar to that of Earth

dense core

any of the regions of interstellar gas clouds that are slightly denser than normal and destined to collapse to form one or a few stars

asteroid

any of the rocks larger than about ten meters in diameter (and not classified as a planet or moon) that orbits the Sun