AST201H1 Study Guide - Midterm Guide: Thermal Energy, Westron, Photon

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skylocust785

13 Oct 2012

School

UTSG

Department

Astronomy & Astrophysics

Course

AST201H1

Professor

Marija Stankovic

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AST201H1 Full Course Notes

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If we looked at a galaxy that is 7 billion light years away, we"d see the universe at half its current age. If we looked at a galaxy that is 12 billion light years away we"d see the universe as it was when it was 2 billion years old. If we tried to look beyond 14 billion light years we"d be looking to a time more than 14 billion years ago - before the universe existed: our observable universe is 13. 7 billion light years. 150 million kilometers: earth"s orbital path defines a flat plane that we call the eliptic plane, when we look outside the local group we discover, 1. Virtually every galaxy outside the local group is moving away from us: 2. The more distant the galaxy the faster it appears to be racing away: this happens because the universe is expanding. Lecture 1 much energy: planets orbit a star.

Related Questions

The great astronomer Edwin Hubble discovered that all distant galaxies are receding from our Milky Way Galaxy with velocities proportional to their distances. It appears to an observer on the Earth that we are at the center of an expanding universe. Figure 3.64 illustrates this for five galaxies lying along a straight line, with the Milky Way Galaxy at the center. Using the data from the figure, calculate the velocities: (a) relative to galaxy 2 and (b) relative to galaxy 5. The results mean that observers on all galaxies will see themselves at the center of the expanding universe, and they would likely be aware of relative velocities, concluding that it is not possible to locate the center of expansion with the given information.

Figure 3.64 Five galaxies on a straight line, showing their distances and velocities relative to the Milky Way (MW) Galaxy. The distances are in millions of light-years (Mly), where a light-year is the distance light travels in one year. The velocities are nearly proportional to the distances. The sizes of the galaxies are greatly exaggerated; an average galaxy is about 0.1 MlY across.

ceruleangiraffe295

(a) relative to galaxy 2 and

(b) relative to galaxy 5.

The results mean that observers on all galaxies will see themselves at the center of the expanding universe, and they would likely be aware of relative velocities, concluding that it is not possible to locate the center of expansion with the given information.

pinkswan477

Here is the info about the question. what i just dontunderstand isin the dispersion equation, v-v_ave. I know to use theaverage velocities for v_ave obviously,but what value isto be used for v?

Assume that the galaxy cluster of question 2 has a radius of 1Mpc(=3 x 10²² m). What is its mass?
Hints: use the virial equation s² = GM/R = 4.5x10^-9 M/R, where M is expressed in M_sun, sisin km/sec, and R is in Mpc.
s is the velocity dispersion: s={[sum(v-v_ave)²]/(N-1)}1/2

Galaxy Name	Redshift (km/sec)
G001	1915
G002	953
G003	2741
G004	1095
G005	2178
G006	2630
G007	1245

fyi: here is question 2:
A galaxy cluster contains the galaxies listed in the tablebelow.What is the distance to this cluster?

Galaxy Name	Redshift (km/sec)
G001	1915
G002	953
G003	2741
G004	1095
G005	2178
G006	2630
G007	1245

i got 25 mpc for the distance.

AST201H1 Study Guide - Midterm Guide: Thermal Energy, Westron, Photon

AST201H1 Full Course Notes

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