On the horizon

Discovery of a distant Jupiter

What's a nice planet like you doing in a place like this?

That's what Cal Tech astronomer Maciej Konacki wanted to know after discovering a planet some 149 light-years away. The planet, with a mass roughly equal to Jupiter's, is orbiting a star that is about as large as our sun.

But by all rights, this "hot Jupiter" has no business being there. The reason: Its parent star is part of a triple-star system so tightly packed that the suns' interactions would have prevented the planet from forming. It's as if our solar system consisted of Jupiter orbiting at an average distance of 4.3 million miles from the sun (Earth is 93 million miles away), with two smaller sun-like stars in orbit some 1.1 billion miles away - a bit farther out than Saturn.

Current theories hold that hot Jupiters form far from their suns, then migrate inward, Dr. Konacki notes. But the extra suns in this odd solar system would have severely limited the size of the disk of dust and gas from which planets might form. Konacki describes this astronomical oddity - and the observational breakthrough it took to spot it - in Thursday's issue of the journal Nature.

Shortly after humans reached Australia 50,000 years ago, more than 85 percent of the continent's large creatures - weighing more than 100 pounds - became extinct.

But don't blame humans for overhunting these animals. Instead, most of the "megafauna" vanished as humans altered the landscape - and regional climate - with fire, researchers suggest. As a result, the outback went from an ecosystem of trees, shrubs, and tall grasses to the desert vegetation found today. The pickiest herbivores vanished, as did the predators who fed on them. The less finicky eaters survived.

A team of American and Australian researchers drew those conclusions after studying 1,500 fossilized eggshell fragments from emu and the extinct Genyornis, a bird roughly the size of an ostrich. The fragments date back as far as 140,000 years. The team also examined wombat teeth spanning much of the same time period. For the wombats and emus, which still inhabit the continent, the team found changes in shell and tooth chemistry consistent with a changed diet. The change dates to roughly 45,000 years ago.

"This study shows that the environmental footprints of humans can have very large and unexpected consequences," notes University of Colorado geochronologist Gifford Miller, a member of the research team. The study appears in the current issue of the journal Science.

Paleontologists in the United States and China have found unusually well- preserved fossils dating back 550 million years. The specimens, some of the oldest known organisms, are tubelike and probably lay on the bottom of primeval oceans, researchers say.

The organisms suggest how dramatically life on Earth changed from the specimens' era - the so-called Ediacaran Period - and the "Cambrian Explosion" that got under way some 10 million years later. The latter period is when creatures with structures similar to many of today's animals first appeared.

The ancient life-forms "provide the key to understand the prelude to the Cambrian Explosion" some 520 million to 540 million years ago, says Shuhai Xiao, a geoscientist and member of the research team. The organisms are only remotely related to today's creatures, the researchers say. Indeed, the team is not sure how these fossils, found in south China, relate to other organisms of that era. Their results appear in the current issue of the Proceedings of the National Academy of Sciences.

Polar bears, eagles, and other top-of-the-food-chain animals have often served as icons for saving threatened or endangered species. Some ecologists have argued that this focus often overlooks the need to preserve the ecosystems in which these animals live.

Now, three European ecologists argue that focusing on top predators alone may not be such a bad idea after all. They found that the sites some species of predatory birds occupy have much greater biodiversity than sites selected at random or sites whose dominant creatures sit further down the food chain. The results, they hold, show a tight link - in some biological systems - between the presence of "apex" predators and the system's overall biodiversity. The team's work appears in Thursday's issue of the journal Nature.