Browse Reference Articles
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Lunar space elevator
A lunar space elevator (also called a moonstalk) is a proposed cable running from the surface of the Moon into space. It is similar in concept to the better known Earth space elevator idea (a cable ... > more -
Hubble Deep Field
The Hubble Deep Field (HDF) is an image of a small region of the sky, based on the results of a series of observations by the Hubble Space Telescope. The field is so small that only a few foreground ... > more -
Orion Nebula
The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a glowing emission nebula with a greenish hue and is situated below Orion's Belt. It is one of the brightest nebulae visible to the ... > more -
Cepheid variable
A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of variability and absolute luminosity. Since the ... > more -
Black hole
A black hole is a concentration of mass great enough that the force of gravity prevents anything from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). The ... > more -
Spacecraft propulsion
Spacecraft propulsion is used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. There are many different methods. Each method has drawbacks and ... > more -
Magellanic Clouds
The two Magellanic Clouds are irregular dwarf galaxies orbiting our Milky Way galaxy, and thus are members of our Local Group of galaxies.The Large Magellanic Cloud (LMC) and its neighbour and ... > more -
Local Group
The Local Group (also called M31 group or the Andromeda group) is the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 30 galaxies, with its gravitational center ... > more -
Phase (matter)
A phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i.e. density, crystal structure, index of refraction, and so ... > more
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