Google Sky is a terrific idea, letting you roam at will through the heavens in a realm of high resolution imagery and information overlays that becomes a useful teaching tool as well as a dazzling personal excursion. The new feature mines imagery from the Space Telescope Science Institute, the Sloan Digital Sky Survey and many other sources. The latest version of Google Earth is needed to use it. To keep up with Google Sky developments, you should be reading Frank Taylor’s Google Earth Blog, which now includes a ‘Sky’ category in its archives. Frank’s original Sky announcement includes a video demonstrating how Google Sky works.
——-
How many stars are in the Milky Way? I notice that SETI optimists tend to higher numbers, usually citing 400 billion, while SETI pessimists lean toward 200 or even 100 million (the number I remember being taught back in the 1960s). This outstanding video is optimistic indeed, claiming a whopping 500 billion, but whatever the number, its look at the Hubble Deep Field captures the magic of staring into a patch of ’empty’ sky and seeing galaxy after galaxy receding into a darkness deep beyond comprehension. Nice work indeed by Tony Darnell of Deepastronomy.com.
——-
When you’ve predicted the temperature of the cosmic microwave background back in the 1940s and worked on the abundance of elements in the early universe, you doubtless hope for more recognition than Ralph Alpher received. The physicist, who died this past week at the age of 86, worked with George Gamow on a paper that would launch cosmology as its own branch of physics. Gamow invited Hans Bethe in as co-author to create authorship by “Alpher, Bethe, Gamow,” punning on the first letters of the Greek alphabet, though Bethe himself did little of the work. The New York Times profiles the cosmologist who, having left the field in the 1950s, remained in many ways the forgotten man of Big Bang science. Image credit: Union College.
——-
Be aware of an upcoming meeting of astronomers from around the world to discuss plans for research over a five to fifteen year time frame at the Arecibo Observatory. Hosted by Cornell University’s National Astronomy and Ionosphere Center (NAIC), the sessions will be held September 12-13 in Washington, D.C., at the Hall of the States Building, 444 North Capitol St., NW. Among numerous topics is the critical matter of Arecibo’s planetary radar, threatened by closure, and its role in finding and cataloging Earth-crossing objects that may one day endanger our planet.
Follow with RSS or E-Mail
Google Earth and now Google Sky are really the best manifestations of the dream of what the internet could be that we all had back in the roaring 90’s. I like videos of cats flushing toilets on YouTube as much as the next person, but Google Earth/Sky is really the vision fullfilled.
Hi Paul
I am rather puzzled by just how many stars there are in the Milky Way too. Different sources give different figures, but ask an astronomer and they usually say 100 billion, roughly. That figure comes from actually measuring the light put out by the Milky Way and doing the sums.
If you look at the mass of the Milky Way – for example by taking the orbital radius and velocity of the stars at the galactic periphery, then working backwards – you get hundreds of billions of solar masses. However a BIG fraction is dark-matter and dark gas etc. and we really don’t know how much there is of either. If you look at the Milky Way from M31 and measure its mass via its satellite galaxy orbits you get about 1.2 trillion solar masses.
The total luminosity gives a less theory laden measure. That works out at about 55 billion solar luminosities and a baryon mass of about 60 billion solar masses. Divide that by the average stellar mass and multiply by the fraction that is stars, and you only get about 100 billion stars. About 20 billion of those are roughly Sun-like. Assuming a Galactic disk age of 10 Gyr, a random spread of ages, and an oxygenic biosphere life-time of 1 billion years, thus there’s about 2 billion stars that could have planets with oxygen.
I’ll put my head out and say that 50% have planets (Marcy’s estimate) and 50% of those systems have a planet in the habitable zone (Kasting’s estimate.) Thus there’s 500 million planets as old as Earth and in the right place for life-as-we-know-it. Not a lot different from Stephen Dole’s estimate from 1964 of 640 million. But know we KNOW there are planets out there.
Adam, are you aware of any recent work on this question of how many stars are in the Milky Way? I’m curious to find some current sources to check just how variable the estimates tend to be, and on what basis.
Back in the olden days astronomers underestimated the # of red dwarfs, so I think that that acknowlegement is what has driven the ESTIMATES higher. Look at RECONS data on stars within 10 parsecs.
http://www.chara.gsu.edu/RECONS/census.posted.htm
I’m assuming that Ls and Ts count as ‘stars’.
Gs and Ks, long lived stars with HZs outside tidal lock (except for late K) are less than 20% of all stars. Ms and later are over 70%. Nobody cites white dwarfs >5% as potential sites for planets with O2.
Hi Paul & philw
Just visit my blog for a recent paper link. It pretty much agrees with other sources I’ve read that spell out the breakdown of mass and objects in the Galaxy. Hard to find a detailed breakdown because most popular sources are happy quoting something they’ve read.
I think the current gross over-estimates (a trillion stars I’ve heard) come from dividing the galaxy’s observed mass by the average stellar mass. But the virial mass of the whole galaxy, as inferred from satellite orbits, is not the same as the actual mass of stars we can see. In reality there’s about 10-20 times as much mass in dark mass as there is in “bright mass”. Detailed studies of the local mass in the disk indicate only a slight excess mass compared to stars, so the dark mass is a halo phenomenon.
Personally I think MOND is a better bet, but there’s lots of candidates for dark matter, many of which can’t be ruled out as yet. My favourite is Shadow Matter, which puts a whole other Universe next to ours. But it could be just about anything.
Personally I think MOND is a better bet,
Didn’t the recent observations of galaxy clusters in which the center of mass (as determined by gravitational lensing) and the center of the visible matter distribution were not in the same place pretty much destroy MOND? MOND can’t be ruled out completely, since in full generality it’s too ill-specified to actually falsify, but theories that have gravity acting off at a cockeyed angle from the source seem to me to be too much to swallow.
Hi Paul
Actually MOND explains all sorts of configurations and MONDers like Stacy McGaugh are pretty inventive so I’m adopting a “wait-and-see” policy anytime weird “dark mass” configurations are reported.
Sky in Google Earth: The Next Frontier in Astronomical Data Discovery and Visualization
Authors: Ryan Scranton, Andrew Connolly, Simon Krughoff, Jeremy Brewer, Alberto Conti, Carol Christian, Craig Sosin, Greg Coombe, Paul Heckbert
(Submitted on 5 Sep 2007)
Abstract: Astronomy began as a visual science, first through careful observations of the sky using either an eyepiece or the naked eye, then on to the preservation of those images with photographic media and finally the digital encoding of that information via CCDs. This last step has enabled astronomy to move into a fully automated era — where data is recorded, analyzed and interpreted often without any direct visual inspection. Sky in Google Earth completes that circle by providing an intuitive visual interface to some of the largest astronomical imaging surveys covering the full sky. By streaming imagery, catalogs, time domain data, and ancillary information directly to a user, Sky can provide the general public as well as professional and amateur astronomers alike with a wealth of information for use in education and research. We provide here a brief introduction to Sky in Google Earth, focusing on its extensible environment, how it may be integrated into the research process and how it can bring astronomical research to a broader community. With an open interface available on Linux, Mac OS X and Windows, applications developed within Sky are accessible not just within the Google framework but through any visual browser that supports the Keyhole Markup Language. We present Sky as the embodiment of a virtual telescope.
Comments: 10 pages, 3 figures, to be submitted to PASP
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0709.0752v1 [astro-ph]
http://arxiv.org/abs/0709.0752
Many consider Ralph A. Alpher, Ph.D., D.Sc. as the Father of Astrophysics. He was certainly a central figure during the time when Cosmology became a more “respectable” field for Physicists to commit significant career work to. The “alpha, beta, gamma” (Alpher, Bethe, Gamow” paper is often mistakenly attributed to three authors–it was the first publication of the results of my father’s Doctoral Dissertaion at George Washington University in 1948, and it would not be unusual to have the Dissertatin Advisor’s name added (George Gamow), but the addition of Hans Bethe (originally submitted as “in absentia” although this was left off of the April 1, 1948 publication in the leading journal “Nature.” Later, Bethe did not object to the addition of his name to the groundbreaking work, however. It is interesting that no one yet had any comments on my Dad’s passing, yet he is ranked with the likes of Einstein, Galileo, Copernicus in terms of his intellectual achievements in providing the foundation for the ultimate acceptance of the Big Bang model of the early Universe over the competing Steady State Theory, of which the most significant proponent was Sir Fred Hoyle. Four Nobel prizes have been given for Big Bang observations (Penzias, Wilson in 1978, Mather and Smoot in 2006. Dr. Alpher’s final recognition was the National Medal of Science (2005), awarded on July 27, 2007 by President Bush at the White House.
Dr. Alpher, you’ll find my comments on your father on the occasion of his death here, along with his picture:
https://centauri-dreams.org/?p=1425
As you’ll see, I join you in your estimation of him, an excellent cosmologist indeed whose work has not received the recognition it should.
Hi Paul & Dr. Alpher
I’m saddened that I never knew about his achievements until his death. I knew his name, of course, but didn’t learn of his pivotal role until I read Prof. Edward Wright’s eulogy to his work at Wright’s Cosmology website…
http://www.astro.ucla.edu/~wright/cosmolog.htm
…where Wright notes that Fred Hoyle ignored Alpher’s work, much to Hoyle’s scientific detriment. Dr.Alpher your father seems to have been one of the true backbones of cosmology, more interested in where Nature was guiding him in the search for Truth than attracting attention to himself.
I’d have to agree that my Dad was not much for braying about his accomplishments. They are legion, and anyone who is 27 today who racked up anything like is personal and professional CV/Resume would receive much more attention today, given the relative ease of disseminating information and hawking one’s own contributions in any area of science, literature, and the arts.
I just noticed that you wrote “Bethe did little of the work.” This is not quite correct. Hans Bethe was widely recognized by the time my father wrote his dissertation, and some of his work is cited in the dissertation. However, he had no hand in any of Ralph A. Alpher’s work or publications. They never knew one another. George Gamow added Bethe’s name to the initial publication of my father’s work (a dissertation adviser’s prerogative, perhaps), in the tradition of Gamow’s unique sense of humor. This publication, appearing in the April Fool’s Day 1948 issue of Nature, has acquired the burden of being known as the “alpha, bethe, gamma” paper, after Alpher, Bethe, and Gamow.
And a famous paper it is. Thank you for the clarification, Dr. Alpher. Gamow is someone I’ve always wished I had known.
For those who are interested, I have written three papers (two are already published now) for the journal Radiations (an American Institute of Physics joural about my Dad and his career. There is much documentation in these papers not seen elsewhere.
Before receiving his doctorate, for almost 10 years he was involved in work at the National Bureau of Standards and the Carnegie Institution (at one time he was Scott Forbush’s secretary), and in 1940 joined a secret organzation that was pursuing rapid development of new Naval Ordnance, degaussing/demagnetizing seagoing vessels in order to render them invulnerable from German and Japanese magnetic mines and magnetic detonators. He also led a team late in the War for about a year that developed a reliable torpedo detonator (Germany’s problems with this are more well-known thanks to Buchheim and Das Boot.)
Before leaving the Johns Hopkins Applied Physics Laboratory (the U.S. Government gave over administration of the secret organization to Hopkins during the War) he also spent a significant amount of time with van Allen in the “High Altitude Research Group). in 1955, he moved to G.E. Research and Development, working primarily in a small group on atmospheric re-entry problems (which had a defense contract with wider applications). From 1986 to 2004 he was on the faculty at Union College as Distinguished Professor of Physics and Astronomy.
Many if not most published obituaries contain significant errors. He never “left” the field of Cosmology, althouh until joining the Union faculty it was never his full-time day job. He continued to write, lecture, and publish as well as staying current in the field. With no disrespect to Gamow or Herman, his frequent collaborators, he was awarded the National Medal of Science for his own work on nucleosynthesis and the first theoretical–not just the idea, but the numbers–prediction of the Cosmic Microwave Background Radiation (CMBR). Soviet Physicist Igor Novikov was part of a group that made a similar calculation and prediction in 1964 before Robert Wilson and Arno Penzias accidentally observed the Radiation at about 2.73 degrees Kelvin (cold enough to be out of the visible range) sometime in 1964. Wilson and Penzias published their results in 1965 with a following article by two Princeton Physicists. Ironically, the CMBR had probably been observed correctly with a radiotelescope with publication in the Soviet Union in 1957. This is discussed intensively in my third paper in Radiations.
Gamow tried several subsequent calculations after my Dad, as did he and Bob Herman. Oddly, Gamow did not provide reference to my father’s work (his doctoral student), and was quite far off (he didn’t “show his work” and was not particularly known as a mathemetician–my Dad was).
Thanks to some journalistic license, after a Discover 99 article people had the impression he’d left Cosmology, and was sour about the following work. Anyone who knows him knows this is quite misleading. Regarding obits, I’d recommed the Washington Post as that writer actually consulted me before writing it. The articles in Radiations are somewhat limited by space, and I hope to expand on those publications in the future. Aside from my Dad’s own book, the 2001 “Genesis of the Big Bang” with Bob Herman as coauthor (he passed away in 1997), these papers are the only ones I know of that use his own papers and collection of reprints, books, etc. as primary source material.
Also, in a previous comment I mentioned four Nobels given on the CMBR. If you broaden this a bit (5 Nobels) to include “early” Big Bang Cosmology, it would be five–you’d have to include Willy Fowler’s Nobel for showing how the heaver elements are formed in stars. As with most dissertation directors, Gamow’s name was on my Dad’s first and most important paper on nucleosynthesis of Helium and Hydrogen, demonstrating how the neutron-capture method leads to the observed distributions of these elements.
The award year for the National Medal of Science is 2005, although it was awarded in 2007 shortly before he passed away. Sadly, as similar awards seem not to be give posthumously, the opportunity for other such recognition would seem to have passed.
As we all know, Pope Pius the 12th basically endorsed the Big Bang or inflationary Universe (an earlier theorist and theologian, LeMaitre, spend much time at the Vatican, so this field does not face the same dilemma the Evolutionists have.
I have published scholarly works on this subject. The so-called alpha, beta, gamma paper was derived from R. Alpher’s dissertaion, which he had not yet defended. The joke was on him–Gamow’s name was it as the usual formality in academia (dissertation chair). Bethe got a free trip to D.C. to visit
Gamow by serving on the Dissertation Defense Committee. Somewhere between the first postage stamp and the final paper, “in absentia” was removed from Bethe’s name. This Gamowian practical joke cost R. Alpher, because when he published the larger paper of nucleosynthesis later in 1948, it garnered less notice. Thus, R. Alpher is not credited for his origination of the way 99% of the universe was formed out of helium and hydrogen. He is also not credited for the origin of the idea that a “fossil past” should be observable today. It is, and 4 Nobel Prizes have been awarded so for, for observing it.