Astronomy /Space Science

Astronomy is the field of science that studies the stars,

planets, and other objects in space – how they formed, how

they interact with each other, and what will happen to them

in the future.

A

atmosphere – the gas that surrounds a celestial object, on

Earth it consists mostly of nitrogen and oxygen.

B

binoculars – an instrument with lenses in two short tubes

used to make far away objects appear closer - not as

powerful as a telescope, but with even simple binoculars we

can see craters on the Moon.

C

D

comet – a ball of ice, dust, and gas that travels through

space in a very elongated orbit around the Sun. When a comet

gets close to the Sun, it sprouts tails of gas and dust.

day – length of time it takes for one complete rotation (one spin)

of a planet; on Earth, 24 hours.

E

Earth – the planet that humans live on, the third from the

Sun.

F

full Moon – a phase in the Moon’s monthly cycle where it is

opposite the Sun in the sky and it appears from Earth as a

fully illuminated round object (Moon’s phases: new > waxing

crescent > first quarter > waxing gibbous > full > waning

gibbous > last quarter > waning crescent > new).

G

galaxy – a large group of billions to hundreds of billions of

stars held together by gravity. Within the universe, there are

hundreds of billions of galaxies. The Earth is located in the

Milky Way Galaxy.

H

Hubble Space Telescope – a telescope orbiting 375 miles above

the Earth that takes detailed pictures of objects in the

universe. Many telescopes on the ground are bigger, but unlike

Hubble, their view is blurred by the atmosphere.

I

Interstellar medium – the gas and dust between stars in our

galaxy. Where it is thickest, it blocks our view of more

distant stars.

J

Jupiter – in the same solar system as Earth, it is the fifth

and largest planet from the Sun. Its thick atmosphere includes

the Great Red Spot, a gigantic hurricane-like storm that’s

been raging for hundreds of years. The dark spot indicates

the shadow of one of its moons.

K

Kuiper belt – a disk of icy asteroids and comets that orbit the

Sun from just about Neptune’s orbit to beyond Pluto.

L

Lunar Rover – a dune buggy - like vehicle that helped carry

astronauts around the Moon as they explored for rocks to

bring back to Earth.

M

Moon – a natural satellite that orbits around a planet. Earth

has 1, and Saturn has at least 62.

N

nova – a star that pulls gas from a companion star and then

explodes, suddenly brightening by hundreds of thousands of

times and then fading away within a few weeks.

O

observatory – a collection of buildings equipped with

telescopes, both large and small, used to study the objects in

the universe.

P

planet – any large spherical object that revolves around a

star but doesn’t shine by its own light (instead reflecting the

light of its star). Smaller spherical objects that revolve

around stars are called dwarf planets.

Q

Quadrantids – a meteoroid is a solid body that travels in

space, it becomes a meteor, also called a “shooting star,”

when it enters the earth’s atmosphere and burns up, a meteor

shower occurs when several dozen or hundreds strike at the

same time. The Quadrantids meteor shower strikes the Earth

annually around January 3rd.

R

rotation – the spinning of an object about its axis or center

point. For a planet in our solar system, because of rotation, at

any given time half the planet faces the Sun (the day side)

and the other part faces away from the Sun (the night side).

Minute by minute, part of the Earth comes into the light and

part goes into the dark.

S

star – a huge ball (typically millions of miles across) of hot gas

that generates its own light through nuclear fusion in its

center. Stars take millions of years to form and can burn for

billions of years. Our Milky Way Galaxy contains several

hundred million stars.

T

telescope – an instrument that uses mirrors or lenses in a tube

to collect and focus light from distant objects, such as

planets and galaxies, making them appear closer and larger.

U

Uranus – a planet in our solar system, seventh from the Sun,

and the first to be discovered with a telescope, in 1781 by

William Herschel.

V

Voyager – a NASA mission that launched two identical

spacecraft to the outer planets in 1977, providing close-up

views of Jupiter, Saturn, Uranus, and Neptune and many of

their moons. Voyagers 1 and 2, both still transmitting signals,

are now headed out of the solar system.

W

world – a planet, such as Earth, that does or could support

life. It must have water, a breathable atmosphere, the right

temperature, and so on. Astronomers are searching for other

worlds like ours.

X

X-ray astronomy – the field that studies some of the most

energetic radiation in the universe, such as the glow of hot

gas in the space between galaxies, which is invisible to

ordinary (visible-light) telescopes.

Y

year – the time it takes for a planet to orbit its star. The

Earth takes 365¼ days to circle the Sun, so for us, 1 year is

365¼ days.

Z

zenith – the point in the sky directly overhead (in other

words, straight up).