Constellations are a group of stars that form an object. There are 88 official constellations recognised by the International Astronomical Union. Each constellation has its own abbreviation. The constellations in the Northern Hemisphere look more like the object they're supposed to represent.
Zodiac constellations move along the ecliptic.
The Bayer Designation system orders stars in a constellation according to brightness. The brightest star is known as the alpha star, α.
The constellations Orion, Ursa Major, Crux and Ursa Minor can tell you the four cardinal directions.
Asterisms are a group of stars that form a recognisable pattern. They aren't officially recognised by the IAU, and can be found in a constellation, or a constellation can be found in it.
Deep sky objects can be any one of the following:
Star clusters;
Nebulae; or
Galaxies.
Messier Objects can be found in the Catalogue des Nébuleuses et des Amas. It currently has 110 objects catalogued in it. They have the prefix 'M' in their Messier number, and usually have an associated NGC number. The NGC is the New General Catalogue of Nebulae and Stars and consists of more than 7800 entries. It is an updated version of the Messier catalogue.
Open star clusters usually form from the same molecular cloud and usually have similar ages. They don't have a fixed shape and there are a few thousand stars in each of them. There are at least 1100 of them in the Milky Way.
Globular star clusters, on the other hand, are larger than open star clusters and form a spheric shape. They have a higher number of stars, causing more gravitational force, keeping the stars together.
Reflection nebulae are only visible as they reflect light from nearby stars. They cannot produce their own light.
Planetary nebulae are emission nebulas formed when a red giant sheds its outer layers. It is usually small as it comes from only one source. The Helix Nebula is one example of this.
I learnt that you can tell directions using the night sky, and that it would be useful if you are stranded without a compass. It is also interesting to see that there are many interesting features of the night sky. You need patience to see some of them, as you need to use a camera with a very long exposure time to do so.
Zodiac constellations move along the ecliptic.
The Bayer Designation system orders stars in a constellation according to brightness. The brightest star is known as the alpha star, α.
The constellations Orion, Ursa Major, Crux and Ursa Minor can tell you the four cardinal directions.
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| By IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg) - IAU, CC BY 3.0, Wikimedia Commons |
Deep sky objects can be any one of the following:
Star clusters;
Nebulae; or
Galaxies.
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| By NASA, The Hubble Heritage Team, STScI, AURA - Great Images in NASA Description, Public Domain, Wikimedia Commons |
Messier Objects can be found in the Catalogue des Nébuleuses et des Amas. It currently has 110 objects catalogued in it. They have the prefix 'M' in their Messier number, and usually have an associated NGC number. The NGC is the New General Catalogue of Nebulae and Stars and consists of more than 7800 entries. It is an updated version of the Messier catalogue.
Open star clusters usually form from the same molecular cloud and usually have similar ages. They don't have a fixed shape and there are a few thousand stars in each of them. There are at least 1100 of them in the Milky Way.
Globular star clusters, on the other hand, are larger than open star clusters and form a spheric shape. They have a higher number of stars, causing more gravitational force, keeping the stars together.
Reflection nebulae are only visible as they reflect light from nearby stars. They cannot produce their own light.
Emission nebulae make their own light by ionising gases. They are the main places where stars form. The Omega Nebula is both an emission and a reflection nebula.
Dark nebulae are visible by blocking light from another source, usually an emission nebula. An example of this is the Horsehead Nebula.
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| By Ken Crawford, CC BY-SA 3.0, Wikimedia Commons |
I learnt that you can tell directions using the night sky, and that it would be useful if you are stranded without a compass. It is also interesting to see that there are many interesting features of the night sky. You need patience to see some of them, as you need to use a camera with a very long exposure time to do so.
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