黯淡神秘的冥王星引起科学家关注（在线收听）

Dim and Mysterious, the Planet Pluto Has Scientists' Attention

黯淡神秘的冥王星引起科学家关注

Don't pace the floor waiting for the results of the visit to this far-off hunk of rock, which meanders around the sun for 248 years in a single orbit. If the New Horizons probe is launched, it will take 11 years to reach Pluto.

Bruce Betts: Sounds like there'd be no rush, but there actually is a rush, scientifically.

Bruce Betts, a scientist at the Planetary Society, a space-advocacy group based in California says that's because Pluto has made the turn at one pointy end of its almond-shaped orbit and is now heading away from the sun.

Bruce Betts: At some point -- and it's not exactly clear when -- Pluto's atmosphere is likely to freeze out on the surface. So, if you want to see the planet while it actually has an atmosphere -- and also see whatever surface there is below what would freeze out -- you need to get a next couple of decades.

Like rings drawn on a table, our sun's planets orbit on the same, mostly flat plane. But Pluto's orbit tilts a bit. It even intersects Neptune's orbit for 20 years, briefly making Neptune our farthest planet.

Russ Poch is a physics professor at Howard Community College in Maryland, who often writes about planets on the college's website.

Russ Poch: they're pretty much on opposite sides of the sun. So it's more likely you're going to have a comet hitting a planet before that.

Pluto was first spotted 75 years ago by a young American astronomer, Clyde Tombaugh, who named the distant dark planet for the Roman god of the underworld. Pluto remained mysterious until 1990, when the Hubble telescope was launched into orbit 600 kilometers above the Earth. Hubble provided clear photos and a spectral analysis of Pluto and its lone, curious moon, Charon -- curious because Charon is half as big as Pluto itself. Charon wasn't found until 1978, hiding among the so-called Kuiper Belt of objects, including Pluto, which traverse the edges of our solar system beyond Neptune.

The Planetary Society's Bruce Betts says the region is still yielding astonishing new information about our solar system.

Bruce Betts: There have been a couple of other discoveries. The most notable, in the past year or so, is a body called Sedna, which is still much smaller than Pluto but is a good-sized body. Sedna has a really strange orbit. It's very, very elliptical. It goes much, much farther out than Pluto.

Scientists are itching to get a close look at Pluto because, like the four inner planets -- Mercury, Venus, Earth, and Mars -- it's some form of rock, though ice-covered most of the time. It's not a giant gaseous sphere like the other four outer planets -- Jupiter, Saturn, Uranus, and Neptune. Pluto also has some unexplained bright markings that fascinate scientists.

So what? Who cares? What? Howard Community College's Russ Poch says even far-off Pluto may help us understand our world.

Russ Poch: It was found to have some gases that were very similar to what our early Earth's atmosphere had. People always want to hypothesize, 'Well, if this is there, could life exist?' We're based on carbon-based life, but are there other kinds of life that might be based on other types of materials? So it would be interesting to see if there were chemicals out there that primitive life could evolve from.

A more familiar Pluto -- Mickey Mouse's pet dog in Walt Disney cartoons -- made his first appearance in 1930, the same year Clyde Tombaugh named the new and distant planet. But the dog did not get its name until the following year. Whether or not Mr. Disney named the floppy-eared canine after the planet, he never said.

I am Ted Landphair.

注释：

hunk [hQNk] n. 大块

meander [mi5AndE] n. 漫步

almond-shaped 杏仁形状的

astronomer [E5strRnEmEr] n. 天文学家

Neptune [5neptju:n] n. 海王星

elliptical [i5liptikEl] adj. 椭圆的

itch [itF] vi. 渴望

gaseous [5^AsiEs] adj. 气体的，气态的

hypothesize [hai5pCWisaiz] v. 假设，假定，猜测

canine [5keinain] n. 犬齿动物