The first data from the Radial Velocity Experiment (RAVE) have just been released, marking the first of what promise to be numerous contributions from this extraordinary project. The study of dark matter in particular will be immeasurably enhanced by this spectroscopic survey that measures the radial velocities and stellar atmosphere parameters (temperature, metallicity, surface gravity) of up to one million stars near the Sun.
The new data cover the first year of RAVE’s operations at the Anglo-Australian Observatory (New South Wales). Using the ‘six degree field’ multi-object spectrograph on the 1.2-m UK Schmidt telescope there, the team can get spectroscopic data on 150 stars at a time. Thanks to RAVE, we now have data on line-of-sight motions of 25,000 stars, along with a rich lode of information on their brightness and color.
And here’s an interesting note: one of the astronomers working on RAVE is George Michael Seabroke, whose great-great-grandfather, George Mitchell Seabroke, was a pioneer in measuring stellar velocities. Working at Temple Observatory (Rugby School, Warwickshire) in the 1880s, the elder Seabroke could study the spectrum of only a single star at a time. RAVE’s equipment looks at an area more than 100 times greater than the full Moon, with 100 optical fibres that each act like an eyepiece. What Seabroke senior would have made of RAVE can only be imagined.
Image: George Mitchell Seabroke (1848-1918), a pioneer in stellar velocity measurements. Credit: British Astronomical Association.
The multi-national RAVE has several years to run, and in its progress should tell us much about the evolution of our galaxy. Moreover, the accurate study of stellar motions will help to determine how much dark matter is holding the galaxy together. The fact that dark matter remains an enigma testifies to how much we still have to learn before we can speak with any confidence about the structure of our own stellar neighborhood.
Further news on dark matter comes in a BBC story discussing ongoing work at the Institute of Astronomy at Cambridge. By studying twelve dwarf galaxies near the Milky Way, the Cambridge team has made detailed, three-dimensional maps of the movement of their stars to extrapolate the effects of dark matter. 7000 separate measurements have shown that the galaxies contain 400 times more dark matter than normal (baryonic) matter. “The distribution of dark matter,” says professor Gerry Gilmore, “bears no relationship to anything you will have read in the literature up to now.”
Be sure to read the entire article, which discusses the most unusual of these observations: dark matter particles seem to be far warmer than would have been predicted, moving at about nine kilometers per second. An additional offshoot of these investigations is that the Milky Way is more massive than once thought, larger than Andromeda. How little we know: fully 25 percent of matter in the universe is now thought to be dark, with the stuff you and I and the stars are made of accounting for a mere 5 percent. And of the 70 percent of everything that seems to be ‘dark energy’ we know even less, a reminder of how many surprises the universe has in store.
Ah, the good old UK Schmidt. This brings back memories. As a summer student, I worked with FLAIR, 6dF’s predecessor (it only had about 40 fibres, instead of 150). In fact I wrote the book on it, or the data reduction manual anyway! Seems like a long time ago now … good to see they are still churning out good science.
Good science indeed, and fascinating to hear of your involvement with FLAIR.
Centauri Dreams readers with an interest in aviation history should be aware of Brett’s Airminded weblog:
http://airminded.org
A recent entry there on Japanese civil defense posters continues a longer discussion about the perception of airpower in the early 20th Century. How we perceive our technologies and how we extend them are very much a part of the continuing discussion over the future of spaceflight as well.
Being only a layman with an interest in the subject, I’m not even sure how to present an idea on dark matter that I’ve had for a very long time. But in a nutshell:
Dark matter is merely anti-matter. As anti-matter, it creates anti-gravity and other forms of anti-energy. It seems that an anti-matter universe exists in a commingled way with our material universe. There are anti-stars, anti-planets, anti-galaxies, even anti-light. The reason we cannot see the ‘dark matter’ is because gravity and anti-gravity will ‘push’ against each other as opposed to ‘pull’. Even anti-light approaching earth would be pushed away by the gravity of our galaxy, sun, earth and even individual atoms. Even if some form of anti-radiation were to reach our region of matter and actually come into full contact, it would be annihilated. The meeting of matter/energy and anti-matter/anti-energy would simply cancel each out of existence. This is largely avoided due to the repulsion of the two opposing forms of matter.
The idea of anti-matter and, therefore, anti-gravity, may be a possible explanation for the continued expansion of the universe.
Any comments on this line of thinking would be greatly appreciated.
Lance Knoechel
lknoechel@cinci.rr.com
Lance, it’s a pleasure to have you on the site. I always enjoy deeply speculative thinking. But here’s a problem I see in this idea of symmetry of yours: you’re assuming that antimatter creates anti-gravity. But while a particle and its anti-particle do have opposite charges, I know of no research that ties antimatter to anti-gravity. Maybe some others can jump in here with their thoughts — many of the readers of Centauri Dreams are far more qualified than I am to talk about the details of antimatter work, and I’ll be interested in their response.