Topic 3.2 - Observing The Night Sky Flashcards
What do astronomers do to locate objects in the night sky?
Use a system of grid lines similar to those of longitude and latitude on a conventional map
What are the astronomical equivalents?
Right ascension and declination
What is right ascension?
It’s like longitude. It locates where a star is along the celestial equator and is the angle between it and the celestial prime meridian. It is measured in hours and minutes.
What is declination?
If we imagine the Earth at the centre of a giant celestial sphere, declination is almost identical to Latitude. It is a projection of latitude onto the sphere. It is the angle of a point above the celestial equator. The Declination of a star never changes
What has fixed co-ordinates and what doesn’t and why?
Stars, nebulae and galaxies have fixed co-ordinates, however, the Sun, Moon and planets don’t because of their orbital motions
What’s the celestial prime meridian?
This is the point on the celestial equator on which the sun moves from the southern to the northern hemisphere. Spring Equinox (March 21st)
What’s the zodiacal band?
This is the part of the sky that contains the constellations of the zodiac and is the region in which the planets and Moon are located. It straddles the Ecliptic by 8 degrees on either side.
Which way to stars appear to rotate about Polaris?
Anti clockwise
How can we determine if a star will be circumpolar using the observer’s latitude and the stars declination?
Declination > 90 – latitude
What’s a circumpolar star?
This is a star that does not set. It is above the observer’s horizon all the time. Which stars are circumpolar depends on the observer’s horizon
Explain how a star will be circumpolar from a given latitude so long as the declination is > 90 -latitude.
My latitude is 52 degrees. 90-52 = 38 degrees Therefore any stare with a declination >38 degrees will be circumpolar. Any star with a declination of 52 degrees will be at my Zenith
Name 4 considerations when planning an observation.
- Phase of the moon
- Weather forecast
- Likelihood of meteor shower
- The visibility of a comet, planets or interesting Messier objects
What is ideal for observing stars?
Dark adapted vision 20-30mins of darkness allows retinas rods to become most sensitive Relaxed eye Consider eye-patch Averted vision Focus light onto more sensitive rods e.g. M31
Who was Charles messier?
Compiled a list of 110 “fuzzy” objects in the sky. Named “Ferret of Comets”
