Welcome to Ned Wright's Cosmology Tutorial

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Cosmology is the study of the origin, current state, and future of our Universe. This field has been revolutionized by many discoveries made during the past century. My cosmology tutorial is an attempt to summarize these discoveries. It will be "under construction" for the forseeable future as new discoveries are made. I will attempt to keep these pages up-to-date as a resource for the cosmology courses I teach at UCLA. The tutorial is completely non-commercial, but tax deductible donations to UCLA are always welcome.

Astronomy and cosmology are very much mathematical sciences, but I have attempted to avoid higher math in these pages. I do use high school algebra and geometry - courses required for admission to UCLA - but I have also included some animations [1, 2, 3, 4], some Java applets [1, 2], and many illustrations in the tutorials, the ABC's of Distances, and the answers to some of the Frequently Asked Questions.

In addition to the cosmology tutorial, there is also a relativity tutorial and extensive discussions on the age, density and size of the Universe. There is also a bibliography of books at a range of levels, and a Javascript calculator of the many distances involved in cosmology.

The course notes (0.7 Mb Postscript, 96 pages, 349 equations, 29 figures) for the upper division undergraduate Stellar Systems and Cosmology course, Astronomy 140, that I taught in spring 2000 are still available on the Web.

And for a much more technical discussion of cosmology with 335 equations and 29 Figures, see my graduate course Astro 275 lecture notes (0.7 Mb Postscript). Use Ghostview to view this file, or save it to disk and send it to a Postscript printer.

News of the Universe

Faster than light? - No!

20 Jul 2000 - Today's Nature has an article reporting on "superluminal" propagation, but it is just anomalous dispersion. The media are fooled again!

Cosmic Microwave Background Anisotropy

9 May 2000 - Hanany et al. announce reults of the August 98 flight of the MAXIMA experiment which are generally in agreement with the BOOMERanG results below, but without any tendency to favor a slightly closed Universe. My CMB angular power spectrum graphs have been updated to include MAXIMA.

27 Apr 2000 - Today's Nature has an article reporting the results from the 10 day long duration balloon flight of the BOOMERanG project. These measurements of very small CMB temperature fluctuations over 1% of the sky with a beam size 40 times smaller than COBE's 7o beam confirm earlier work by a group at Penn & Princeton and data from BOOMERanG's test flight, but provide 3 to 4 times more accuracy. Based on this data, de Bernadis et al. (2000, Nature, 404, 955) conclude that the Universe is flat.

The angular size of the characteristics spots on the sky, about 1o, shows that the Universe is flat, or that the total energy density is equal to the critical density. This confirms a prediction of the inflationary scenario. The amplitude of the characteristics spots, about 69 microK, indicates the ratio of ordinary matter (baryonic matter) to dark matter. Detailed studies of the harmonics or overtones of the fundamental oscillations that lead to these spots will provide much more information about the Universe. Stay tuned.

The New York Times, the Los Angeles Times, and the Washington Post all covered this story extensively.

The first of what will certainly be many interpretations of the BOOMERanG data by outside groups was posted to the LANL preprint server on the same day the Nature paper came out by White, Scott & Pierpaoli.

Sloan Digital Sky Survey finds z=5.82 Quasar

13 Apr 2000 - SDSS announced a quasar with a redshift of z = 5.82. Of course, the press release called it the "Most Distant Object Ever Observed" which discounts the z = 6.68 galaxy. However, the spectrum of the SDSS object taken by Fan, White, Davis, Becker et al. at the Keck Observatory is much better than the noisy spectrum of the extremely faint z=6.68 object. Notice the very strong and wide Lyman alpha line of hydrogen, redshifted from 122 nm to 829 nm wavelength. The blue side of the line has been absorbed in the Lyman alpha forest.

New Most Distant Quasar

18 Feb 2000 - Daniel Stern et al. announce the discovery of the most distant known quasar, with a redshift of z = 5.5. The previous record holder has a redshift of z = 5.0.

Cosmic Microwave Background Anisotropy

26 Nov 99 - The New York Times had a front page story about new CMB temperature fluctuation data released by the BOOMERanG project. Based on this data, which confirms earlier work by a group at Penn & Princeton, they conclude the Universe is flat.

Cosmic Near Infrared Backgound

27 Sep 99 - Gorjian, Wright(*) & Chary have found an extragalactic IR background of 22.4 +/- 6.0 nW/m2/sr at 2.2 microns and 11.0 +/- 3.3 nW/m2/sr at 3.5 microns. This result completes the primary goals of the COBE mission.
(*) - that's me.

And then on 27 Dec 99 Wright & Reese confirmed the cosmic IR background (CIRB) obtaining 23.1 +/- 5.9 nW/m2/sr at 2.2 microns and 12.4 +\- 3.2 nW/m2/sr at 3.5 microns.

Mystery Object! - NY Times publishes a SPECTRUM!!

21 Aug 99 - The "mystery object", PSS 1537+1227, found on the Digital Palomar Observatory Sky Survey (DPOSS) by Djorgovski et al. has been identified as a Broad Absorption Line quasar (BAL QSO) with a redshift of 1.2. The spectrum of the mystery object shown at right is very similar to the spectrum of the radio-loud BAL QSO 0840+3633 discussed by Becker et al. (1997), redshifted to z = 1.19.

But the most amazing part of this story is that the NY Times published a spectrum in the 17 Aug 99 print edition - a clear violation of the "5 W's but no Z" rule that I think must be taught in science journalism schools. The graph at right is a plot of the flux received from the mystery object in microJanskies vs. the wavelength of the light in nanometers.

Since spectroscopy is the tool most used by astronomers today, this article in the NY times was very significant. Spectra tell astronomers what elements are in distant stars and galaxies, how hot and dense these objects are, and how rapidly they are moving towards us or away from us.

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