AS101 Study Guide - Midterm Guide: Solar System, Great Circle, Right Ascension

52 views7 pages
Published on 17 Apr 2013
School
Department
Course
AS101 Midterm 2/12/2013 9:53:00 AM
Astronomical unit (AU): the average distance from the earth to the sun
Solar system: the sun and its asteroids, planets, comets and so on
Planet: a non luminous body in orbit around a star; large enough to be
spherical and to have cleared its orbital zone of other objects
Star: a globe of gas held together by its own gravity and supported by the
internal pressure of its hot gases, which generate energy by nuclear fusion
Light year (ly) unit of distance equal to the distance light travels in one year
Lecture 2
The nearest star system is Alpha Centauri 44 trillion km
Lecture 3
From largest to smallest:
o universe
o Walls
o Voids
o Filaments
o Superclusters
o Clusters
o Galaxy
o Solar system
o Star
o Planet
The local group: a group of 40 galaxies
Belongs to the Local Supercluster (aka Virgo Supercluster)
Jupiter is 10 times bigger in diameter than the earth
Size of the Milky way: about 80 000 ly
Distance to a nearby galaxy: 2 600 000 ly
The sun is a medium sized star
Constellations: groups of stars
o Aren’t necessarily close together
Asterism: any recognizable group or pattern of stars, more like a
landmark ie the big dipper
The celestial sphere: imagine the stars as being on the surface of
an imaginary sphere that surrounds the earth
Lecture 4
A star can be part of more than one asterism
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in
We measure angular size of an object and the angular distance
between two objects
The angular size looks smaller if the object is further away
Angular size= physical size X 360 degrees
2(pi)x distance
Zenith: directly overhead
Horizon: all points 90 deg. away from the zenith
Meridian: a line passing through the zenith and connecting the N
and S points on the horizon (the sun crosses the meridian around
noon)
Altitude: angular distance from the horizon (if negative, that means
something is below the horizon)
Azimuth: direction, expressed as an angle (usually from south)
Celestial Sphere: imaginary sphere surrounding the earth
containing the stars, planets, sun etc
Celestial Pole: a point on the celestial pole directly above one of the
earth’s poles
Celestial Equator: a circle around the celestial sphere directly above
earth’s equator
The Earth rotates from West to East, so for someone standing on
Earth’s surface, the celestial sphere appears to rotate from east to
west
Latitude and longitude are to earth, as declination and right
ascension are to the celestial sphere
o Declination: angular distance from the celestial equator,
positive if North, negative if South; from -90 to +90
Lines go around horizontally
o Right ascension: an angle measured eastward from the vernal
equinox. Usually measured in hours from 0-24
Lines go around vertically
o The full circle is 360 deg or 24 hours
o If you are at a latitude of 40 deg north:
Zenith= 40 degree declination
Celestial north pole= 90-40=50 degrees away from
zenith
40 degrees above the horizon, to the North
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Astronomical unit (au): the average distance from the earth to the sun. Solar system: the sun and its asteroids, planets, comets and so on. Planet: a non luminous body in orbit around a star; large enough to be spherical and to have cleared its orbital zone of other objects. Star: a globe of gas held together by its own gravity and supported by the internal pressure of its hot gases, which generate energy by nuclear fusion. Light year (ly) unit of distance equal to the distance light travels in one year. The nearest star system is alpha centauri 44 trillion km. From largest to smallest: universe, walls, voids, filaments, superclusters, clusters, galaxy, solar system, star, planet. The local group: a group of 40 galaxies. Belongs to the local supercluster (aka virgo supercluster) Jupiter is 10 times bigger in diameter than the earth. Size of the milky way: about 80 000 ly. Distance to a nearby galaxy: 2 600 000 ly.

Get OneClass Grade+

Unlimited access to all notes and study guides.

YearlyMost Popular
75% OFF
$9.98/m
Monthly
$39.98/m
Single doc
$39.98

or

You will be charged $119.76 upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.