Gabby+and+Kareem

What is a star? Kareem A **star** is a massive, luminous ball of [|plasma] that is held together by its own [|gravity].The nearest star to [|Earth] is the [|Sun], which is the source of most of the [|energy] on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun. For most of its life, a star shines due to [|thermonuclear fusion] in its [|core] releasing energy that traverses the star's interior and then [|radiates] into [|outer space].I found this at wikipedia.com.

What is a comet? Kareem

A **comet** is a [|Small Solar System Body] that orbits the [|Sun] and, when close enough to the Sun, exhibits a visible [|coma] (atmosphere) or a tail — both primarily from the effects of solar radiation upon the [|comet's nucleus]. Comet nuclei are themselves loose collections of ice, dust and small rocky particles, measuring a few kilometres or tens of kilometres across. Comets have a variety of different orbital periods, ranging from a few years, to hundreds of thousands of years, while some are believed to pass through the inner Solar System only once before being thrown out into interstellar space. Short-period comets are thought to originate in the [|Kuiper Belt], or associated [|scattered disc], I found this at [|wikipedia.com].

What is a nebula? Kareem A **nebula** is an [|interstellar cloud] of [|dust], [|hydrogen] gas and [|plasma]. Originally //nebula// was a general name for any extended [|astronomical] [|object], including [|galaxies] beyond the [|Milky Way], some examples of the older usage survive; for example, the [|Andromeda Galaxy] was referred to as the //[|Andromeda] Nebula// before galaxies were discovered by [|Edwin Hubble].Nebulae often form star-forming regions, such as in the [|Eagle Nebula]. This nebula is depicted in one of [|NASA]'s most famous images, the "[|Pillars of Creation]". In these regions the formations of gas, dust and other materials 'clump' together to form larger masses, which attract further matter, and eventually will become big enough to form stars. The remaining materials are then believed to form [|planets], and other [|planetary system] objects.I found this at [|wikipedia.com]

what is a supernova? Gabby One of the most energetic explosive events known is a supernova. These occur at the end of a star's lifetime, when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy. If the star is particularly massive, then its core will collapse and in so doing will release a huge amount of energy. This will cause a blast wave that ejects the star's envelope into interstellar space. The result of the collapse may be, in some cases, a rapidly rotating neutron star that can be observed many years later as a radio pulsar. On average, [|supernova] occur about once every 50 years in a galaxy the size of the Milk way. Several kinds of supernovae exist that may be triggered in one of two ways, either turning off or suddenly turning on the production of energy through nuclear fusion.

What is a [|black hole]?Gabby Despite its invisible interior, a black hole may reveal its presence through interaction with matter orbiting the event horizon. For example, a black hole may be perceived by tracking the movement of a group of stars that orbit its center. Alternatively, one may observe gas (from a nearby star, for instance) that has been drawn into the black hole.According to Einstein's theory of general relativity, a **black hole** is a region of space in which the gravitationsl fieldis so powerful that nothing, including electromagnet radition (e.g. visible light), can escape its pull after having fallen past its event horizon. The gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation that can be detected from earthbound and earth-orbiting telescopes. For example, a black hole may be perceived by tracking the movement of a group of stars that orbit its center.

what is th big bang thoey?Gabby The observed abundances of the light elements throughout the cosmos closely match the calculated predictions for the formation of these elements from nuclear processes in the rapidly expanding and cooling first minutes of the universe, as logically and quantitatively detailed according to Big Bang nuceosythesis.