'N Sync and a Whopper

With its demurely twinkling stars, glowing planets and a moon that waxes and wanes like clockwork, the night sky seems like an awfully sedate, G-rated show. But appearances can be deceptive. Beyond the reach of the naked eye, black holes slurp up surrounding matter, churning columns of dust and gas 6 trillion miles tall erupt in newborn stars, and galaxies cannibalize their smaller neighbors for a V-chip worthy performance. No wonder it takes more than a pretty supernova to catch astronomers' attention. Several new discoveries nevertheless manage the trick. There's nothing like the old "this blows all our theories out of the water!" ploy to command attention.

What's up?

Way, way up--light-years away--are two newly discovered and "clearly bizarre" planetary systems. Finding solar systems (planets orbiting stars) has become so old hat, what with astronomers having seen evidence of more than 50 since 1995, that to make a splash you need to find a really weird one. Or two. That's what a team led by planet-finders extraordinaire Geoffrey Marcy and Paul Butler did, they told last week's annual meeting of the American Astronomical Society, in San Diego, Calif. They spied one star, 123 light-years away in the constellation Serpens, circled by what seems to be the biggest planet ever found. Around another star, they found two planets whose orbits are in almost perfect harmony. (Of course, "found" is a term of art. They didn't actually see the planets. But from the wobble in the orbit of the mother star, they inferred the planets' presence.) "Both of these systems are quite unique," says Marcy, an astronomer at the University of California, Berkeley, "and a little frightening."

But the cosmos is full of scary stuff, like rogue asteroids that might have a date with Earth. What's so bad about that?

Well, astronomers tend to break out in a cold sweat when something doesn't fit their theories. The XXL planet is at least 17 times more massive than Jupiter (our own solar system's heavyweight). When the system formed a few million years ago, the great cosmic architect apparently said, Supersize that, please. "I call it a mystery object," says Butler, of the Carnegie Institution. "We never expected nature would make such gargantuan planets, and indeed maybe they aren't planets at all." As far as astronomers know, stars form when a cloud of dust and gas collapses under its own weight. Planets form when the leftovers around the new star agglomerate like puff-pastry dough. It's doubtful that a neoplanet could accrete enough stuff to get this big, this fast. The big bag of gas circling the star named HD168443 is in fact big enough to qualify as a brown dwarf, a "failed star" that never collected quite enough mass to sustain the nuclear fire that makes a star shine. "To find a planet 17 times the mass of Jupiter says there's got to be another way to make planets," says astronomer Alan Boss of Carnegie. "Nature has thrown a monkey wrench into what we thought we understood about planetary formation." Of course, if there are more ways under a sun to cook up planets, there may be a whole lot more of them up there.

And what about this harmony of the spheres?

Two little planets orbiting Gliese 876, a star only 15 light-years from Earth, have what are called resonant orbits: one takes 30 days to make the trip and the other takes twice that long. Through mutual gravitation, the planets maintain this synchrony. Although four moons of Jupiter--Io, Europa, Ganymede and Callisto--also have resonant orbits, these are the first full-fledged planets to earn that honor. Until they get official names, we propose 'N Sync.

And what else is scaring astronomers?

Only the largest structure ever observed in the universe.

Uh, how large?

About 500 million light-years across. If you hitched a ride on a light beam, it would take you that long to traverse it. Pack a lunch.

What and where is this beast?

It seems to be a cluster of galaxies--that is, a bunch of Milky Ways or Andromedas that hang together thanks to gravitational attraction. It's more than 6.5 billion light-years away, just south of the constellation Leo.

That's comforting.

Not really. Something that far away is also that long ago. In other words, since what we see is what light carries to use at 186,000 miles per second, astronomers are seeing this whopper as it was 6.5 billion years ago. The universe was only about one third its present age then. According to the standard theory of how the cosmos formed, affectionately known as the big bang, that's awfully fast for something this big to get organized: gravity would have had to sweep up huge structures over immense distances really, really quickly. "Gravity simply wouldn't have had time to pull a structure together, 500 million light-years across, given the age of the universe back then," says Gerard Williger of the National Optical Astronomy Observatories, who led the discovery team.

And yet, there it is.

Perhaps there was a little extra dollop of matter in that neighborhood of the young universe. "Maybe you throw on a little bit more mass, and then galaxies start popping off like flashbulbs," Williger speculates. Or maybe our pet model of genesis has some holes--and we don't mean of the black variety. Cosmologists act all jittery when someone finds something that seems to threaten the big-bang theory. But we suspect they secretly love the challenge of making it rise to the occasion.