Download Name: Period:______ Date:______ Astronomy Vocabulary List

Name:__________________________________ Period:_________ Date:_________
Astronomy Vocabulary List
1.
solar eclipse- The blocking of sunlight to Earth that occurs when the moon is
directly between the sun and Earth.
2.
lunar eclipse- The blocking of sunlight that occurs when the Earth is directly
between the sun and the moon.
3.
umbra- The darkest part of the shadow during an eclipse.
4.
penumbra- The lighter part of the shadow during an eclipse.
5.
spring tide- The tide with the greatest difference between high and low tide
that occurs when the sun and moon are in a straight line. Occurs during new and full
moon phases.
6.
neap tide- A tide with the lease distance between the low and high tides when
the sun and moon pull at right angles to each other.
7.
gravity-The force that pulls objects toward each other.
8. Retrograde motion- The apparent backward movement of a planet in the sky.
9. Apogee – The farthest point in the moon’s orbit around Earth.
10. Perigee – The closes point in the moon’s orbit around Earth.
11.
Spiral Galaxy- A galaxy with a bulge in the middle and arms that spiral
outward in a pinwheel pattern.
12.
Elliptical galaxy- A galaxy shaped like a round flattened ball or oval.
13.
Irregular galaxy- a cluster of stars with no specific shape or form.
14.
Constellation- a cluster of stars that make a pattern.
15.
Hubble’s Law- The observation that the farther away the galaxy is, the faster it
is moving away.
16.
Nebula- A large cloud of dust and gas in space.
17.
Supernova- a massive explosion of a dying star.
18.
Nuclear fusion- The combing of two atomic nuclei to produce a single larger
nucleus and much more energy. (ex: hydrogen in the core of the sun join together to
create helium and massive amounts of energy.)
19.
Hertzsprung-Russell Diagram- a graph that demonstrates the positive
relationship between temperature and color/brightness. As temperature increases,
brightness increases.
20.
Giant Star- an enormous red star that is ten times larger than our sun but
much cooler with temperature of only 3000°.
21.
Protostar- a baby star that is just beginning to form in a nebula.
22.
Neutron Star- a extremely high-mass, dense blue star with a size smaller than
our moon and a temperature of 35,000°C.
23.
Blackhole- an object with gravity that is so enormous the nothing can exist, not
even light can escape.
24.
White Dwarf- a white star with size about the size of Earth and a temperature
around 10,000 to 15,000°C.
25.
Medium Star- a yellow star in the middle of its life (our Sun is a medium star)
26. Pulsar – a star perceived from Earth as different colors due to its rotation, which
shows different surfaces of the star as it rotates.
27. Variable Star – a star that pulsates in brightness due to its outer layers expanding
and contracting.
28.
Big Bang theory- The initial explosion that resulted in the formation and
expansion of the universe. This explosion release hydrogen and helium which make-up
99% of our know universe.
29.
Absolute Brightness- the brightness of a star if it were at a standard distance
from the Earth.
30.
Apparent Brightness- the brightness of a star “as seen” from Earth.
31.
Asteroids- very large (size of a country or continent) chunks of rock that are
large enough to feel the gravitational pull of the Sun but not large enough to be a planet.
(usually found in the Asteroid Belt between Mars and Jupiter)
32.
Comet- a loose collection of ice, dust, with a small rock core and a tail of debris
that orbits the Sun.
33.
Meteor- A streak of light in the sky produced by a meteoroid burning up in the
Earth’s atmosphere. (referred to as a “shooting star”)
34.
Meteoroid- a meteoroid that withstands the burning through the Earth’s
atmosphere and lands on the Earth’s surface.
35.
Red shift- A shift of light towards the red end of the electromagnetic spectrum
of light to show that an object is moving AWAY from Earth. (blueshift would show the
object is moving towards Earth).
36. Galaxy-A huge group of stars, star systems, star clusters, dust and gas bound
together by gravity.
37. Synchronous Rotation – The state in which a planet or moon’s rotation and
revolution are equal.
38. Solstice – A point in the year when the north or south pole is pointed directly at the
sun at noon.
39. Equinox – Point in the year when Earth’s axis is perpendicular to the suns rays at
noon. (neither pole points to the sun)
40. Regolith – Layer of loose, ground up rock on the surface of the moon.
41. Rilles – Valley-like structures on the moon’s surface formed by old collapsed lava
tubes.
42. Ejecta – Material blasted out from the moon’s surface after a collision that falls back
to its surface.
43. Rays – Long trails of ejecta (see #40), that radiate outward from the center of a
crater.
44. Highland – Mountainous areas on the moon that surround crater impact areas.
45. Maria – Dark, smooth plains on the moon’s surface formed by old dried up lava
lakes.
46. Albedo – Percentage of incoming light that is reflected off the surface of a moon or
planet.
47. Dark Matter – An unknown substance, thought to be made of some new subatomic particle, which is believed to make up the majority of the mass in every galaxy.
48. Dark Energy – A hypothetical force/energy that is causing the known universe to
expand at an accelerating rate.
49. Background Radiation – The leftover debris, dust, and radiation (energy) from the
initial big bang explosion that is found in every area of our universe.
50. Eccentricity – ratio of the distance between the foci to the length of the major axis;
defines the shape of a planet’s orbit (more elliptical or circular).
51. Dwarf Planet – A body in that is large enough to pull itself into a spherical shape
and orbit around the sun, but not large enough to clear its “neighborhood” of all other
large objects.
52. Open Universe Theory – The theory that our universe will continue expanding for
eternity.
53. Closed Universe Theory – The theory that our universe will eventually stop
expanding and begin contracting inward for another big bang.
54. Flat Universe Theory – The theory that our universe will eventually stop expanding
but will not contract. It will “freeze” in place.
55.Nebular Theory – Theory that our solar system formed from a rotating and
contracting nebula.