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In this image released Thursday, Feb.
3, 2005, by NASA/JPL, a mosaic of 35 individual infrared
exposures made on Feb. 4, 2004, at the W.M. Keck I
Observatory, Mauna Kea, Hawaii, shows what scientists say are
the sharpest views of Saturn's temperature emissions ever
taken from the
ground.
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Astronomers using a giant telescope atop a volcano
have discovered a hot spot at the tip of Saturn's south pole. The
infrared images captured by
the Keck I telescope at the W.M. Keck Observatory atop Mauna Kea on the
Big Island suggest a warm polar vortex
- a large-scale weather pattern likened to a jet stream on
Earth that occurs in the upper atmosphere. It's the first such hot vortex
ever discovered in the solar system.
The team of scientists say the images are the sharpest thermal views of
Saturn ever taken from the ground. Their work will be published in
Friday's editions of the journal Science.
This warm polar cap is believed to contain the highest temperatures on
Saturn; the scientists did not give a temperature estimate.
On Earth, the Arctic Polar Vortex is typically located over eastern
North America in Canada and plunges cold arctic air to the northern Plains
in the United States.
Polar vortices are found on Earth, Jupiter, Mars and Venus, and are
colder than their surroundings. The new images from the Keck Observatory
show the first evidence of a polar vortex at much warmer temperatures.
"Saturn's is the first hot polar vortex that we've seen because it's
been sitting in the sunlight for about 18 years," said Glenn S. Orton, a
scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Saturn, which takes many earth years to orbit the sun, just had its
summer solstice in 2002.
"If the increased southern temperatures are solely the result of
seasonality, then the temperature should increase gradually with
increasing latitude, but it doesn't," Orton said. "We see that the
temperature increases abruptly by several degrees near 70 degrees south
and again at 87 degrees south.
Scientists may learn more from the data coming from the infrared spectrometer on the Cassini
spacecraft currently orbiting Saturn, Orton said.
(Reuters) |
天文學家們使用巨型望遠鏡在一座火山頂上觀測太空，結果發現土星南極頂端有一個“熱點”。凱克I望遠鏡位于夏威夷大島基亞山頂的凱克天文臺上，它捕捉到的紅外線圖像顯示土星南極頂端有溫暖的極地渦流。渦流是一種波及范圍較廣的天氣形態，類似于地球高層大氣中的急流。這是迄今為止人類第一次在太陽系里發現如此高溫的渦流。
科學家小組表示，該圖像是從地球上觀察土星所能看到的最強烈的上升熱氣流。他們的研究結果將發表在周五出版的《科學》期刊上。
盡管科學家并未做出具體的氣溫評測，但他們相信這處“溫暖”極冠包含著土星上的最高氣溫。
在地球上，北極的極地渦流主要集中在北美洲東部的加拿大，將寒冷的北極空氣卷入美國北部平原。
人們在地球、木星、火星和金星上都發現了極地渦流，它們比周圍的氣候環境更冷。來自凱克天文臺的新圖像成為存在更溫暖的極地渦流的最早的證據。
“人類在土星上發現了第一個溫熱的極地渦流，因為18年來它一直處在陽光照射下。”科學家格倫·S·奧頓說，他是美國宇航局噴氣推進實驗室（位于加州帕薩迪納市）的科研人員。
土星繞太陽公轉一周要花很多年的時間。2002年，土星剛剛度過了它的夏至。
奧頓說：“如果不斷升高的南方氣溫僅僅是季節性變化的結果，那么氣溫應該隨著緯度的增加逐漸升高，但事實卻并非如此。我們發現溫度在南緯70度附近突然升高了幾度，同樣的情況再次發生在87度附近。”
奧頓說，科學家們也許能從“卡西尼”太空船上的紅外線分光計采集的數據中了解更多這方面的情況。“卡西尼”目前正圍繞土星旋轉。
（中國日報網站譯） |
Updated: 2005-02-07 15:13