Astronomy Terms- 2

Thermal Radiation

almost all objects emit light

• hotter objects emit more light at all frequencies per unit area

• hotter objects emit photons with a higher average energy

redshift

movement away from us shift light —> longer wavelengths

blueshift

movement towards us shifts light —> shorter wavelengths

light-collecting area

telescopes with a larger collecting area can gather a greater amount of light in a shorter time

angular resolution

Telescopes that are larger are capable of taking images with greater detail

refracting

focuses light with lenses

reflecting

focuses light with mirrors

solar nebula

name given to a cloud of gas from which our own solar system formed

atmosphere

layer of gas surrounding a world

asteroid

a relatively “small” rocky object that orbits a star

comet

a relatively “small” icy object that orbits a star

Kuiper Belt

group of small, icy bodies orbiting the sun in the plane (disk) of the solar system beyond Neptune, source of some comets

Oort Cloud

A vast spherical region of space that contains billions of comets

Meteroid

small, rocky/metallic body travelling through space; going to hit us

Meteor

flash of light in the sky caused by a particle entering the atmosphere at high speed (shooting star)

Meteorite

chunk of rock from space, after it has reached the Earth’s surface; reaches ground

Nucleus

a dirty snowball less than 20 km across; darker than charcoal

coma

huge, dust atmosphere surrounding the nucleus 100,00 km wide

tail

stretched out portion of coma, tons of millions of km long

plasma tail

water evaporating from comet; directed outwards from Sun

dust tail

dust evaporating from comet away from sun (try to follow elliptical orbit)

core

energy generated by nuclear fusion

radiation zone

energy transported upward by photons

convection zone

energy transported upward by rising hot gas

photosphere

visible surface of the sun

chromosphere

middle layer of solar atmosphere

corona

outermost layer of solar atmosphere

solar wind

a flow of charged particles from the surface of the sun

parallax

change in position caused by a change in the position of the observer

apparent magnitude

how bright the stars appear to us in the sky

absolute magnitude

how bright the star would be at a distance of to 10 parsecs from us

luminosity

star’s intrinsic brightness