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Science Notes/ Astronomy and paleontology

Visitors from other stars?

Some of the most famous comets, such as Halley and Hale-Bopp, may have originated in other solar systems -- much farther away than previously imagined, an international team of astronomers says.

Many comets originate in what is known as the Oort cloud, a vast, rough sphere of comets that encompasses our solar system and extends nearly halfway to the next nearest star, Proxima Centauri. Scientists have thought that this cloud was formed during the birth of the solar system, about 4 billion years ago. As the planets formed, icy, rocky material was thrust farther and farther outward in space, eventually creating the Oort cloud.

But a team led by Hal Levison, a planetary scientist at the Southwest Research Institute in Boulder, Colo., says the theory may be wrong. The astronomers suggest a different chain of events. The sun, they note, may have formed in a cluster of stars. That cluster could have been surrounded by a body of comets that had been pulled out of their orbits around the individual stars. Before the star cluster fully dispersed, the sun was able to capture a large cloud of these comets.

If the theory is true, it could mean samples of the chemistry of several solar systems exist relatively close to home and can provide information about distant stars' evolution and composition.

-- Los Angeles Times


Warm and cold blood

Some of those enormous marine reptiles prowling the Earth's prehistoric seas may have had a surprising edge in their search for prey, researchers say. They may have been warm-blooded.

In a study published online in the journal Science, French scientists explored whether three types of marine predators -- ichthyosaurs, plesiosaurs, and mosasaurs -- might have been able to maintain their body temperature internally much the way that mammals and birds do. Two of them appear able to have done so.

Ichthyosaurs sported a dolphin-like body with a fish-like tail; plesiosaurs had long necks and paddle-like limbs. Both were known as "cruisers," meaning they moved frequently and actively searched for prey. That's typical of warm-blooded animals.

Mosasaurs shared the long neck and paddle-like limbs of plesiosaurs but were known as "accelerators," meaning they lay in wait and grabbed prey as the opportunity arose. The ability to regulate body temperature would not have been as useful to them.

Analyzing temperature-dependent oxygen isotopes in fossilized teeth led scientists to conclude the "cruisers" appeared to maintain their body temperature, while the mosasaurs' internal heat appeared to vary slightly with the water temperature at the time.

-- Los Angeles Times

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