P - Q
- R
Select
the letter that (probably) leads off the word in question. Please
suggest new words or corrections.
P
-
perihelion:
The
point nearest the sun in the orbit of a planet or other celestial
body.
-
Phobos:
One of two small moons orbiting Mars discovered in 1877
by American astronomer Asaph Hall.
-
photosphere:
The visible outer layer of a star, especially of the Sun.
-
planet:
A large, round object, larger than an asteroid, that is formed
inside an accretion disk. Unlike a star, a planet does not produce
its own energy via nuclear reactions. There are nine planets
in our solar system. Ex. Earth.
-
planetary
nebula:
An expanding gas cloud that was created as the result of gas
being expelled from a sunlike star in the later stages of its
life. Ex. M57 - The Ring Nebula.
-
Pluto:
The ninth and final known planet from the Sun. Pluto is the
smallest planet in diameter. It is rocky and orbited by one
moon named Charon.
-
Prime
Meridian: The
longitude on Earth from which the 24 hour UTC clock is centered.
It runs through Greenwich, England, among other places. Also
see "Universal Coordinated Time".
-
pulsar:
A very fast-spinning and highly dense object that emits light,
radio and/or X-rays in very tight beams, similar to a lighthouse.
A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z
Q
A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-S-T-U-V-W-X-Y-Z
R
-
red giant:
A large, red sunlike star in its latter stages of life.
-
redshift:
An measurement of the increase in the wavelength of light often
due to the Doppler effect. It is used as a means of more accurately
predicting the distances to cosmic objects. Objects with higher
observed redshifts are farther away than those with lower redshifts.
-
right
ascension:
The coordinate system in the sky that corresponds to longitude
on Earth. It is measured eastward from the vernal equinox. Also
see "vernal equinox".
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