NASA Says
Data Reveals an Earth-Like Planet, Kepler 452b
JULY 23, 2015
Inching ahead on their quest for what they
call Earth 2.0, astronomers from NASA’s Kepler planet-hunting spacecraft announced on
Thursday that they had found what might be one of the closest analogues to our own
world yet.
It is a planet a little more than one and a
half times as big in radius as Earth. Known as Kepler 452b, it circles a sunlike star in an orbit that takes 385
days, just slightly longer than our own year, putting it firmly in the
“Goldilocks” habitable zone where the temperatures are lukewarm and suitable for
liquid water on the surface — if it has a surface.
The new planet’s size puts it
right on the edge between being rocky like Earth and being a fluffy gas ball
like Neptune, according to studies of other such exoplanets. In an email, Jon Jenkins of NASA’s Ames
Research Center, home of the Kepler project, and lead author of a paper being
published in The Astronomical Journal, said the likelihood of the planet’s
being rocky was 50 percent to 62 percent, depending on uncertainties in the
size of its home star. That would mean its mass is about five times that of
Earth.
Such a planet would
probably have a thick, cloudy atmosphere and active volcanoes, Dr. Jenkins
said, and twice the gravity of Earth. Describing the planet during a news
conference, Dr. Jenkins lapsed into lines from John Keats’s poem “On First
Looking Into Chapman’s Homer”: “Then felt I like some watcher of the skies /
When a new planet swims into his ken.”
The star that lights this planet’s sky is about 1.5 billion
years older than our sun and 20 percent more luminous, which has
implications for the prospects of life, Dr. Jenkins said.
“We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to
understand and reflect upon Earth’s evolving environment,” he said. “It’s
awe-inspiring to consider that this planet has spent six billion years in the
habitable zone of its star, longer than Earth. That’s substantial opportunity
for life to arise, should all the necessary ingredients and conditions for life
exist on this planet.”
Asked if any radio telescopes had pointed at the planet to try
to detect extraterrestrial radio broadcasts, Dr. Jenkins said, “I hope so.”
To determine whether Kepler 452b deserves a place on the honor
roll of possible home worlds, however, astronomers have to measure its mass
directly, which requires being close enough to observe the wobbling of its star as
it is tugged around by the planet’s gravity. For now, that is impossible, as
Kepler 452b is 1,400 light-years away.
The planet is the first to
be confirmed in a new list of candidates unveiled by Kepler astronomers on
Thursday. It brings the number of possible planets discovered by Kepler to
4,696, many of them small like Earth. “We are the bread crumbs of the
universe,” said Jeff Coughlin, of the SETI Institute in Mountain View, Calif.,
who compiled the catalog.
The spacecraft, launched in 2009, spent four years staring at a
patch of the Milky Way on the border between the constellations Cygnus and
Lyra, looking for the dips in starlight caused by the passage of planets. Its
pointing system failed in 2013, but astronomers are still analyzing the data
Kepler collected. Every time they sift through it, new planets pop out.
In the meantime, Kepler has switched to a different mode of
observing in a mission called K2.
The NASA news conference coincided with a major anniversary:
It was only 20 years ago this fall that Michel Mayor and Didier Queloz, of the
University of Geneva, discovered a planet circling the star 51 Pegasi, about 50
light-years from here. It was the first planet known to belong to a sunlike
star outside our solar system, and its discovery ignited
an astronomical revolution.
Dr.
Queloz, now at the University of Cambridge in England, said at the news
conference, “This is a great time we live in.”
“If
we keep working so well and so enthusiastically,” he went on, it is not too
optimistic to think that in the future, “the issue of life on another planet
will be solved.”
Astronomers
say they now know from Kepler that about 10 percent of the 200 billion stars in
the Milky Way have potentially habitable Earth-size planets, Kepler 452b
probably among them. This means that of the 600 stars within 30 light-years of
Earth, there are roughly 60 E.T.-class abodes, planets that could be inspected by a
future generation of telescopes.
Structure of the lead:
WHO- astronomers from NASA’s Kepler planet-hunting spacecraft
WHEN- Thursday
WHAT- Kepler 452b
WHY- temperatures are lukewarm and suitable for liquid water on the surface
WHERE- Milky Way
HOW- planets that could be inspected by a future generation of telescopes
Keywords:
1. quest 尋找
2. analogue 類似物
3. orbit 軌道
4. lukewarm 微熱的
5. ken 視野範圍
6. luminous 發光的；明亮的
7. extraterrestrial 宇宙的
8. wobbling 擺動
9. unveil 揭開
10. ignited 點燃；激起
11. inspect 檢查
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回覆刪除I found the news is worthy to be read. Because I have little interest in news related to the universe or outer space, the contents are fascinating for me, which can trigger my interest to know more about our world. NASA’s Kepler planet-hunting spacecraft announced on Thursday that they had found what might be one of the closest analogues to our own world yet. After I noticed this, I felt so excited. I believe that people will live better with the progress.
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