A Heavenly Host
POWER HAS ITS PRIVILEGES, AND Robert Williams knew exactly how he wanted to use his. As director of the Space Telescope Science Institute, which runs the Hubble Space Telescope, Williams was entitled to "director's discretionary time" on the orbiting scope. Although his own specialty is exploding stars, Williams had a hunch that science was more likely to get a big bang out of a very different target: the farthest edge of the universe. So for 10 days in December, Williams had Hubble's handlers point the telescope's camera at a single slice of the sky. The tip of the wedge lay near the handle of the Big Dipper; the crust brushed the very edge of space and time. Yet this enormous slice covers a part of the sky equivalent to a grain of sand viewed at arm's length. And ff Williams didn't exactly see eternity in that grain, he came close. In 342 shots, the telescope spied at least 1,500 galaxies, Williams announced at a meeting of the American Astronomical Society in San Antonio, Texas, last week. Extrapolating from the number, he calculated that the universe is stuffed with 50 billion galaxies, not the 10 billion that astronomers previously thought.
The Jackson Pollock-ish photographs from Hubble show splotches and spirals, dwarfs and giants, footballs and drips. Some galaxies are dose by, others are unimaginably distant in space and therefore in time: even traveling at 186,000 miles per second, the light arriving at Hubble must have begun its journey from these deepest galaxies cons ago, bearing information about what the galaxy was like when the light began its journey. "We are clearly seeing some of the galaxies as they were more than 10 billion years ago," says Williams. "We might somehow be seeing our own origins in all of this." By "our," he means not merely the Milky Way galaxy, in whose exurbs our solar system spins, but the entire cosmos. Some galaxies in the wedge appear to have formed when the universe was a mere 1 billion years old (its age today is estimated at between 8 billion and 15 billion years). Astronomers won't know for sure until another telescope actually measures distances to the new worlds. (The powerful Keck Telescope in Hawaii started doing so last weekend.) "This beautiful picture is seeing galaxies in the process of forming," says cosmologist Craig Hogan of the University of Washington. "Some large fraction of the images in it are the first galaxies."
No astronomer can look at the photo, though, without the embarrassing thought that what it doesn't show swamps what it does. Based on how galaxies rotate, astronomers infer that there is something like 10 times more matter in them than can be seen. They call it dark matter. Theorists have suggested that the' missing matter is either in stars too dead to shine or in exotic particles nothing at all like atoms. The particles are called WIMPs (weakly interacting massive particles). The big stuff is called, we're sorry to say, MACHOs (massive compact halo objects). An 18-member team announced at the AAS meeting that MACHOs account for half the dark matter.
Their evidence is indirect. Using the 50-inch Great Melbourne Telescope in Australia, the team observed 9 million stars in the Large Magellanic Cloud, the Milky Way's nearest galactic neighbor. Over two years, seven stars became brighter; the reason, according to the theory floated by Bohdan Paczynski of Princeton University 10 years ago, is that a MACHO in the Milky Way's halo acted like a lens, splitting the starlight in two so that when it recombined it appeared brighter than usual. The length of time the stars remained extra bright, says MACHO-team member Kem Cook of Lawrence Livermore National Laboratory, implies a lens the size of a white dwarf, a burned-out star. And since the Milky Way is nothing special as galaxies go, it's likely that half the missing matter in the halos of other galaxies are white dwarfs, too.
But the case of the missing matter remains far from closed. "It's possible that what they saw is related to dark matter," says Paczynski, "but also possible that it's not. Seven events is not enough to tell." Many cosmologists remain convinced that most of the invisible matter in the cosmos consist of exotic particles. Without these particles, the universe could not have evolved from the sea of radiation and solitary bits of matter left over from the Big Bang into the highly structured heavenly vault of today: the particles act like drops of water in crumbly bits of pie-crust mix, making the matter-the crumbs-aggregate into galaxies. If this reasoning is right, "then most of the matter in the universe is not the same stuff that we are," explains physicist Michael Turner at the Fermi National Accelerator Laboratory.
That continues in the fine tradition of Copernicus. Not only are we not at the center of the universe, we aren't even made of the same material. But nothing would more profoundly shake man's sense of unique destiny than the news that we are not alone. No, the AAS didn't cap off its meeting with e-mail from little green men, but it may have gotten a return address. Astronomers announced that they had detected two new planets outside our solar system. Light from two stars--one in the Big Dipper and one in Virgo--wobbles, said Geoffrey Marcy and Paul Butler of San Francisco State; the wobbles must have been caused by the gravity of planets. The same astronomers had confirmed another new planet last year (NEWSWEEK, Oct. 80, 1995), but the latest two are different in an intriguing way: they're at the right temperature to sustain liquid water and complex molecules, the stuff of life.
The supposed planets are so dim that not even the Hubble can spy them, let alone glimpse anyone waving for the cameras. But at 35 light-years away, the planets would receive electromagnetic radiation 35 years after it leaves Earth. That radiation includes TV signals, which constantly leak into space. So 1962 episodes of "The Beverly Hillbillies" will be reaching the two planets any moment now. If anyone's up there, it's no wonder they don't bother to radio back.