The speed of light is 186,282 miles per second. or 671 million miles per hour. From the Moon to the Earth 1.3 seconds. From the Sun to the Earth 8.3 minutes. From the Andromeda galaxy to the Earth 2.5 million years. Link to Speed of light
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A light year is a unit of distance. It is the distance that light travels in a vacuum in one year. The distance from Earth to Proxima Centauri, the next nearest star to us after our Sun is 4.24 light years. A light year also = 5,865,696,000,000 miles.
A supernova is an exploding star. Supernovae are very bright and generate bursts of radiation that can briefly outshine a whole Galaxy before declining in brightness over a few weeks or months. In this time the supernova can emit as much energy as our Sun might over it's entire lifetime. Link to Supernova
A black hole is a point in space.The death of some stars at least 15 x the mass of our Sun can cause the birth of a black hole, after the supernova stage, there cores keeps getting smaller and denser and smaller and denser until the gravity at the core is so great that nothing can escape from it, not even light itself. Link to Black Holes
Apogee and Perigee refer to the distance of the Earth to the Moon or an artificial satellite. Apogee is the farthest point from Earth and Perigee is the closest point. The apogee and perigee of the Moon has a big effect on the tides on Earth.

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The closet point to the Sun in a planet's orbit is called Perihelion. The furthest point is called Aphelion. When the Earth is at perihelion it is about 91 million miles from the Sun, when it is at aphelion it is about 95 million miles from the Sun.
Globular clusters are spherical or near spherical cluster of stars that can consist of 10,000 to over a million, there is about 120 in our galaxy. They consist of old stars formed early on in our galaxy history. They can also be found in other galaxies. Image M13 Globular cluster
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Open clusters are physically related groups of stars held together by mutual gravitational attraction. There are more than 1,200 open clusters in our galaxy. Open clusters were formed at the same time from similar material. The pleiades is an example of a open cluster. Image M45 The Pleiades.
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Neutron stars are very small and "superdense" stars mostly composed of neutrons. They are thought to have formed when massive stars go supernova and explode. A neutron star has the mass of 2-3 Suns, compressed into a globe only 12 miles in diameter. Link to Neutron Stars
Galaxies are a congregation of millions or sometimes billions of stars. All these stars are held together by gravity and some other force. Galaxies come in many shapes and sizes, the basic types of galaxies are - Spiral,Barred,Elliptical and Irregular. Our own galaxy the Milky Way is a Barred Spiral galaxy which looks quite flat with a central bulge with spiral arms that resembles a Catherine wheel. Image M101 Spiral Galaxy
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The lunar terminator is the division between the illuminated and dark part on the the Moon. It is also the Moons day and night division line.The Image shows the terminator on the Moon the left hand side being night time and the illuminated part being day time.
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A very bright meteor that can be bright enough to be seen in the daylight, they also can occasionally hit the Earth, they are then called Meteorites. Some fireballs are satellites and other space junk that are burning up in the Earth's atmosphere.
Diurnal motion is the daily motion of the heavens from east to west in which celestial objects seem to rise and set. The motion is caused by the Earth's rotation from the west to the east, this apparent motion coincides with the Earth's axis of rotation. Images of Star trails are an example of diurnal motion.
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Dark nebula or Nebulae consists mainly of dense clouds of molecular hydrogen with dust and other gases which partially or can sometimes completely absorb light from behind it. The horsehead nebula is a fine example of a dark nebula.
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Comet's are Icy bodies that orbit the Sun, they consists mostly of ice mixed with dust. They are often referred to as a dirty snowball. As a comet approaches the Sun its nucleus heats up,releasing gas and dust which will form a coma around the nucleus. Gas and dust stream away from the coma to form one or more tails, these tails can be millions of miles long. A comets tail will always point away from the Sun.
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Sunspot's only look dark on the sun's surface because they are cooler than the surrounding area. If you could see them on their own they would be brighter than an electric arc . Sunspot's are formed by magnetic storms on the sun.They often come in groups and can last from a few hours to months at a time. Some sunspots can be up to 50,000 miles in diameter.
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The name Planetary nebula has nothing to do with planets, the name arose over 100 years ago when early astronomers thought what they were looking at was a planet. Planetary nebula are formed when a red giant type star shreds its outer layers in to space. Some of my images of Planetary nebula from left to right M57 Ring nebula - NGC 2392 Eskimo nebula & NGC 7293 Helix nebula. Link to more information on Planetary nebula
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Earthshine mostly occurs just before or after a new moon. At this time our Earth's surface is nearly fully illuminated from our Sun when viewed from the moon. Sunlight reflects off the Earth's surface onto the moon's surface.
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A supermoon is the apparent size of the Lunar disk as seen from Earth. The term supermoon originated from modern Astrology, there is nothing super about it what so ever, except the size of its disk. The technical name for this event is Perigee - Syzygy of the Earth - Moon - Sun system. This phenomena occurs four to six times a year.
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