20 terms

Earth Sci 6 - Observational Astronomy

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conjunction
alignmnet of two celestial bodies such that they present the least angular separation (6 degrees or less when veiwed from Earth)
constellation
A group of stars that form a pattern in the sky
A region of the sky that contains a recognizable star pattern and that is used to describe the location of objects in space
A group of stars that form a pattern in the sky
ecliptic
apparent path of the Sun and planets across the sky
horizon
a point where the dome of the sky meets the Earth
elongation
the angular separation between two bodies
opposition
when a celestial body is opposite from the Sun in the sky
Universal Time (UTC)
solar time along the prime meridian passing through Greenwich England (zulu time).
local time
time based on the rotation of the earth as compared to the sun
DST = UTC - 4 hours
EST = UTC - 5 hours
declination
the angular distance to a point on a celestial object measured north or south from the equator
right ascension
a measure of how far east a celestial object is from the point at which the sun appears on the first day of spring
celestial equator
The projection of the earth's equator into space (on the celestial sphere); position of 0 degrees declination
astronomy
The study of the moon, stars and other objects in space
diffuse nebula
a nebula containing gas and dust, but containing no star at its center
double star
Two stars that appear close together in the sky. If the two stars revolve around each other, the system is called a binary.
galaxy
a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.
globular star cluster
a spherical collection of stars that orbits a galactic core as a satellite
light year
a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.5 × 10¹² km (nearly 6 trillion miles)
open star cluster
a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age
planetary nebula
a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives
variable star
a star whose brightness as seen from Earth fluctuates
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