By Edward L. Wright, Phd, UCLA
Read or Download Astronomy 275 Lecture Notes, Spring 2009 PDF
Similar astronomy books
This pretty calendar captures the main dramatic celestial occasions of the yr. lovely photos and art comprise photographs of a complete eclipse of the moon, a couple of galaxies colliding, and the Hubble house Telescope snapshot of Saturn. every month additionally comprises info on viewing a variety of celestial occasions.
With approximately 200,000 entries, StarBriefs Plus represents the main finished and adequately demonstrated number of abbreviations, acronyms, contractions and logos inside astronomy, comparable house sciences and different comparable fields. As such, this valuable reference resource (and its better half quantity, StarGuides Plus) may be at the reference shelf of each library, association or person with any curiosity in those parts.
Examines the actual features and prerequisites of Mars, describing its place relating to the solar and different planets and surveying humanity's makes an attempt to penetrate its mysteries.
- Revolutionaries of the Cosmos: The Astro-Physicists
- Nebulae and How to Observe Them (Astronomers' Observing Guides)
- The mathematics of physics and chemistry
- The Adaptive Optics Revolution: A History
- Hawkings Kosmos einfach erklärt: Vom Urknall zu den Schwarzen Löchern
Additional resources for Astronomy 275 Lecture Notes, Spring 2009
8788 Ω◦ h2 × 10−29 gm/cc. 000000000000000000000000000000000000000000000000000000000002 (99) which is really stretching the bounds of coincidence. This is known as the flatness-oldness problem in cosmology. 1 at a time 10−43 seconds after the Big Bang, it would recollapse in 10−42 seconds. Thus in order to have a Universe as old as ours with Ω◦ close to 1 requires Ω very very close to 1 at early times. 1. The Flatness-Oldness Figure The calculations involved in the flatness-oldness figure are as follows: Ωm /a + Ωv a2 + Ωr /a2 + Ωk a˙ = H◦ = (100 km s−1 Mpc−1 ) ωm /a + ωv a2 + ωr /a2 + ωk (100) with ωm = Ωm h2 etc.
We can express the redshift in terms of the flux by defining ζ = S1 /S where S1 = L/(4π(c/H◦ )2 ) is the flux the source would have in a Euclidean Universe with distance d = c/H◦ . Think of √ ζ (“zeta”) as a Euclidean distance in redshift units. Solving ζ = z(1 + z/2) gives z = −1 + 1 + 2ζ so for Ω = 0 the N(S) law is n◦ (L/4π)3/2 1 n◦ (L/4π)3/2 dN = = dS 2S 5/2 (1 + 2ζ)2 2S 5/2 1 1+2 S1 /S For an Ω = 2 matter dominated Universe we get cz dL = H◦ c d(dL ) = dz H◦ cdt c 1 √ = dz H◦ (1 + z)2 1 + 2z n◦ (L/4π)3/2 1 dN √ = 5/2 3 dS 2S (1 + z) 1 + 2z 2 (163) (164) For large z we have S ∝ z −2 in this model, so the source counts flatten to dN/dS ∝ S −3/4 .
160) dN n◦ (L/4π)3/2 1 + O(z 2 ) = dS 2S 5/2 (1 + z)4 (161) The q◦ dependence cancels out in the first two terms so We see that the correction term decreases the source counts below the Euclidean expectation. This flattening of dN/dS avoids the divergence implied by Olber’s paradox. 4. 50 We can easily work out the exact form of the relativistic correction for a few simple cases. For the empty Universe we get cz (1 + z/2) dL = H◦ c d(dL ) = (1 + z) dz H◦ cdt c 1 = dz H◦ (1 + z)2 n◦ (L/4π)3/2 1 dN = (162) dS 2S 5/2 (1 + z)4 For large z we have dL ∝ z 2 in this case so S ∝ z −4 .