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Cosmology and art |
New on the tutorial:
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 foreseeable 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, 5, 6, 7], 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.
Slides for recent talks:
The course notes (130 pages, 398 equations, 51 figures) for the upper division undergraduate Stellar Systems and Cosmology course, Astronomy 140, that I last taught in spring 2008 are available on the Web. And for a much more technical discussion of cosmology see my graduate course Astro 275 lecture notes (126 pages, 381 equations, 42 figures). This course was last taught in the spring of 2009. If this course Web site gets closed, you can use a backup copy of the A275 notes.
Jean-Loup Puget reported today that the Planck HFI was at 0.1 K and signals are being received from the bolometers. This is similar to the startup of WMAP, which took a slower route to L2 but did not need to be as cold. WMAP made its first data release 587 days after launch. Let's see if Planck can match WMAP: 21 Dec 2010 would be that goal.
The lowest commandable 3He rate is giving good cooling so the prospects are good for a two-year mission.
15 May 2009 - After 2090 days of crygenic operation in space, the Spitzer Space Telescope has used up its entire stock of liquid helium and is warming up. I first worked on Spitzer when it was the Shuttle Infrared Telescope Facility in 1976.
14 May 2009 - Herschel and Planck have launched! ESA has a page listing the latest press releases. Herschel is a 3.5 meter diameter far-infrared telescope. The BLAST balloon-borne large sub-millimeter telescope was a test of one of the Herschel intruments. I first heard about Herschel when it was called FIRST and was an 8 meter telescope, back in the early 1980's. At that time NASA was planning to build a a 20 meter far-infrared telescope call the Large Deployable Reflector. In 1980 this NASA project was called LADIRT. Planck is a new CMB anisotropy mission many times more sensitive than WMAP and also covers a larger range of frequencies with better angular resolution. It should do very good work on small angular CMB anisotropy and the Sunyaev-Zeldovich effect. And the first of many planned spacewalks during the STS-125 mission to repair the Hubble Space Telescope is going well today.
07 May 2009 - Riess et al. report a new value for the Hubble constant of Ho = 74.2 +/- 3.6 km/sec/Mpc based on Cepheid measurements in galaxies that have hosted Type Ia supernovae, including the nuclear ring maser galaxy NGC 4258 which has a very precise distance determined by geometric means.
28 Apr 2009 - NASA and the CfA issued press releases about a gamma-ray burst that went off on 23 April 2009, known as GRB 090423. The burst showed a fading infrared transient but no flux in the optical. In fact there was no flux shorter than 1.1 microns. If this edge is assigned to the Lyman α forest edge at 122 nm, then the redshift is z = 8. No paper has been submitted to the preprint server, but a collection of GCN Circulars is available. Update 8 Jun 2009: Tanvir et al. and Salvaterra et al. have been posted.
09 Apr 2009 - BLAST has published results in today's Nature: Devlin et al (Nature, 2009, 458, 737) showing that half of the CIRB at 250 to 500 micron wavelengths comes from redshifts less than 1.2, and half comes from redshifts greater than 1.2. The arXiv version includes the supplemental information. A more complete paper discussing these results is Marsden et al.
24 Feb 2009 - The Reid et al. paper describing the press announcment is finally on the preprint server. The value for the distance from the Sun to the Galactic Center is 8.4 +/- 0.6 kpc. The rotational speed at this distance from the Galactic Center is 254 +/- 16 km/sec. Allowing for the 5.3 km/sec peculiar velocity of the Sun in the direction of Galactic rotation, a predicted proper motion for the Galactic Center of 6.50 +/- 0.20 milli-arcseconds/year is found compared to the observed proper motion 6.379 +/- 0.024 milli-arcseconds/year. This rotation speed is very similar to the rotation speed of Andromeda at the same radius, implying that the Milky Way and Andromeda are very similar in mass. This represents an increased mass for the Milky Way.
07 Jan 2009 - The ARCADE experiment reported ( NYT, Science News, GSFC press release) the existence of an extragalactic radio background. But this signal has the same spectrum as the radio emission from the Milky Way, and could well be due to an error in determining the galactic contribution to the total signal. The papers are available here, here, here and here. The ARCADE data are beautiful but mainly cover higher frequencies where the extragalactic radio background is not detectable, so the "ERB" depends on a debatable assumption about the lower frequency data, which are all tied to the Haslam 408 Mhz map, published in 1981, but with a zero point set using Pauliny-Toth & Shakeshaft, published in 1962! Pauliny-Toth & Shakeshaft certainly did not see an ERB or even the CMB in their data.
05 Jan 2009 - Mark Reid reported at the AAS meeting on very precise distances to radio masers that have led to an increase in the estimated size and rotation velocity of the Milky Way (NYT, BBC). The distance scale scale and velocity both increase by 15 percent so the angular velocity stays about the same. This leads to a 50 percent increase in the estimated mass of the Milky Way.
24 Sep 2008 - Kashlinsky et al. (2008) have claimed a detection of a bulk flow in the motion of many distant X-ray emitting clusters of galaxies. Unfortunately this paper and the companion paper have several errors so their conclusions cannot be trusted. A technical discussion of these errors can be found here.
26 Aug 2008 -
NASA
released an all sky map
in gamma rays
from the satellite formerly known as GLAST, newly renamed as
the Fermi Gamma-ray Space Telescope or FGST.
Enrico Fermi discovered the Fermi-Dirac statistics followed by
particles known as fermions, such as electrons and protons,
emigrated to America to escape fascism, and built the first
nuclear reactor as part of the Manhattan Project.
FGST will have greatly improved angular resolution and sensitivity for
high energy gamma rays with E > 1 GeV at the short wavelength
end of the electromagnetic spectrum, and
should discover thousands of
gamma ray sources at cosmological distances.
20 Jun 2008 - Murphy, Flambaum, Muller & Henkel (2008) show that the ratio of the proton mass to the electron mass has varied by less than 1.8 parts per million (95% CL) since redshift z = 0.68466. They compared the radio inversion lines of ammonia to the pure rotation lines of HCN and HCO+. All of these lines are measured very precisely using radio astronomy techniques, and the redshifts are consistent. But the ammonia lines are much more sensitive to the proton:electron mass ratio so this quantity has not varied in the past 6 billion years. This report is an improvement over previous results using the same quasar absorption line cloud.
17 Jun 2008 - Bradac et al. (2008) have found another bullet cluster where two clusters of galaxies have collided, leaving the hot gas in between the clumps of galaxies, but the source of gravity has passed right through the collision, staying with the galaxies. Since the hot gas is most of the normal matter, this shows that the source of gravity is not the normal matter, but rather dark matter. This is a problem for alternative models that modify gravity to eliminate the need for dark matter.
22 May 2008 - Soderberg et al. report an observation of a soft X-ray flare from a spot that later turned out to be a Type Ibc supernova. The peak flux was about 7 x 10-10 erg/cm2/sec for about 400 seconds. At the 27 Mpc distance of the host galaxy NGC 2770 this is about 2 x 1046 ergs in X-rays produced when the shockwave breaks out of the massive star whose core has collapsed. The UV peaked a day later, and the optical 20 days later as the remains of the star expanded and cooled.
This was quite an interesting result when it appeared three months ago on arxiv.org, but it was embargoed by Nature until publication so I didn't post this news item until now.
13 May 2008 - Srianand et al. have announced a measurement of TCMB at a redshift of 2.418. Absorption lines from carbon monoxide (CO) molecules were seen in the spectrum of a distant quasar, and showed rotational excitation in the CO ground vibrational state. The temperature seen is 9.15 +/- 0.7 K, while the Big Bang model predicts 9.315 K. So this observation is consistent with the Big Bang, but contradicts the Steady State model.
28 Apr 2008 -
Kowalski et al. (2008)
of the Supernova Cosmology Project present a union catalog of supernovae.
The catalog contains 332 SNe that pass all cuts when the low
redshift SNe
are included. Click on the thumbnail at right for binned ΔDM
vs. redshift tables and plots.
ΔDM is the difference in the
distance modulus between the data or model and an empty Universe
model. A higher distance modulus means the supernovae are fainter
than expected in an empty Universe.
24 Apr 2008 - Blondin et al. (2008) studied distant supernovae using spectra to judge the age of the object during each observation. They found an aging rate that varied with redshift z like
1/(1+z)(0.97 +/- 0.10),compatible with the expected 1/(1+z) for expanding Universes, but 9.7 standard deviations away from the constant aging rate expected in the tired light model.
17 Apr 2008 - The DAMA/LIBRA experiment announced a confirmation of their previously found annual modulation signal in the count rate of a deep underground CsI detector. They see a modulation of +/-0.027 counts/kg/keV/day in the 2.5 to 3.5 keV band, but since the amplitude of modulation is supposed to be at most 7% of the dark matter signal this implies a dark matter generated event rate of 0.38 cts/kg/keV/day or more. The total rate in the experiment is 1.24 cts/kg/keV/day in this 2.5-3.5 keV band, so the dark matter rate is at least 31% of the total. With such a large fraction of the total rate coming from dark matter events in this 3 keV bump one would expect to see a corresponding bump in the total rate spectrum and it is actually present. But the CDMS experiment in the Soudan mine saw no counts in 397.8 kg-days of exposure, so the high DAMA/LIBRA rate seems unlikely - but not impossible given the differences in the detector materials and methods. However, it is peculiar that the annual modulation technique is being used when the ratio of dark matter to background counts is this large.
19 Mar 2008 - The NASA satellite Swift has detected the most luminous explosion yet seen. Gamma Ray Burst GRB080219B got slightly brighter than optical magnitude 6, the limit of naked-eye visibility, and has a redshift greater than or probably equal to 0.937, the higher of two absorption line redshifts. The absolute magnitude is then -38! The press is catching up to this story: the New York Times, the Associated Press, and the Agence France Presse all have articles on this. Here is the NASA press release.
5 Mar 2008 - WMAP
released its five year dataset today,
with 7 papers and new maps and power spectra posted to
LAMBDA.
Highlights of the new results include:
The
NASA press release finally came out late on March 7. Coverage at
Science Daily, the
New Scientist, and the
New York Times, quoting me.
15 Feb 2008 - Roelofs, Bassa, Voss & Nelemans (2008) comment on the claimed detection by Voss & Nelemans (2008, Nature, 451, 802) of an X-ray binary progenitor at the position of the Type Ia supernova SN 2007on. They find that the X-ray source is probably still present, although significantly fainter. Furthermore, with better astrometry the X-ray position is slightly offset from the position of the supernova, by 1.18+/-0.27 arc-seconds. Since a Type Ia supernova completely disrupts the white dwarf that explodes, a surviving X-ray source is very unlikely. So the putative progenitor was quite possibly a chance coincidence with a variable X-ray source.
12 Feb 2008 - The HST and the Spitzer Space Telescope have issued a press release claiming the detection of a galaxy at redshift z=7.6. However, NO lines have been observed. Based on previous z=10 galaxies, we should require two lines before believing any story like this. The NASA budget must be tight.
11 Feb 2008 - Kervella et al. report a distance to the Cepheid variable RS Puppis of 1992 +/- 28 parsecs. This distance was obtained geometrically using a light echo technique. Cepheids are used to calibrate the Hubble constant that determines the age and size of the Universe. ESO has issued a press release. The paper will be published in Astronomy & Astrophysics.
18 Jan 2008 - Narlikar, Burbidge and Vishwakarma (2007, J. Astr. & Ap., 28, 67) claim to fit the CMB anisotropy data with the QSSC model. Not surprisingly, this claim is false.
17 Jan 2008 - the Crafoord Prize
in
Astronomy and Mathematics was split between Rashid Sunyaev
and two string theorists. Sunyaev is famous for the
Sunyaev-Zeldovich effect and other studies of
the Cosmic Microwave Background.
Born and raised in the Soviet Union, Sunyaev is now
director
of the Max Planck Institute for Astrophysics in Garching near Munich.
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© 1996-2009 Edward L. Wright. Last modified 24 July 2009
