Astronomy

Astronomy

Asterisms are small groups of stars which make familiar shapes. Found within constellations.
Nebula - a gas cloud in which stars can be formed.
Nebulae are faint, fuzzy patches of light.
Stars can be used as pointers.
Greek letters are used to indicate the brightness of stars. Eg. Alpha = brightest, beta = 2nd brightest, gamma = 3rd brightest, etc.
All stars along the ecliptic are seasonal.
Declination and right ascension used for co-ordinates. Celestial equator has a declination of 0 degrees. North of the equator is positive, south is negative.
Right ascension is measured from the point on the celestial equator where the Sun passes from the Southern to the Northern Hemisphere.
Ecliptic - eastward path of the Sun
Zodiacal Band - 8 degrees either side of the ecliptic.
Circumpolar star -a star that never sets below the horizon from a location. A star is circumpolar is declination > 90 - latitude
Stars appear to rise in the East and set in the West.
Stars are said to culminate when they cross the meridian.
Culmination of a star is the best time to observe it because there is less atmosphere between the star and the observer, so it appears brighter. This is because there is less atmosphere to absorb the light.
Right Ascension < >
In history they thought the Solar System was geocentric. It is actually heliocentric.
The Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
In the Solar System there are 8 planets, satellites, the Sun, dwarf planets, comets, asteroids, Trans-Neptunian Objects, and centaurs .
Centaur - half comet, half asteroid in behaviour..
Pluto is now a dwarf planet, because planets must: be large enough to be spherical, be in orbit around the Sun, have cleared its orbit of other objects.
1 AU is distance between the Earth and Sun.
Longer man missions than to the Moon have lots of problems.
1. Need for supplies
2. Technological challenges
3. Psychological challenges
4. Physiological challenge - muscle fatigue, brittle bones, reduced red blood cell count.
5. Space Adaptation Syndrome
6. Communication problem.
Earth's orbital plane is the ecliptic - all planets are within a few degrees of this.
Planets only within the Zodiacal Band.
Inferior Planets are Mercury and Venus.
Superior Planets are Mars, and the Gas Giants.

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