The Article :
'Alien
Earth' is among eight new far-off planets
By Jonathan Webb Science reporter, BBC News, Seattle Artist's
impression: Kepler has identified many exoplanets but few are within their
star's "Goldilocks zone" One of eight new planets spied in distant
solar systems has usurped the title of "most Earth-like alien world",
astronomers have said. All eight were picked out by Nasa's Kepler space
telescope, taking its tally of such "exoplanets" past 1,000. But only
three sit safely within the "habitable zone" of their host star - and
one in particular is rocky, like Earth, as well as only slightly warmer.
The find was revealed at a
meeting of the American Astronomical Society. Red sky. The three potentially habitable planets join Kepler's "hall of fame", which now boasts eight fascinating
planetary prospects. And researchers say the most Earth-like of the new
arrivals, known as Kepler 438b, is probably even more similar to our home than
Kepler 186f - which previously looked to be our most likely twin.
At 12% larger than Earth, the new claimant is bigger than
186f but it is closer to our temperature, probably receiving just 40% more heat
from its sun than we do from our. So if we could stand on
the surface of 438b it may well be warmer than here, according to Dr Doug
Caldwell from the SETI (Search for Extra-Terrestrial Intelligence) Institute in California.
"And
it's around a cooler [red dwarf] star... so your sky would look redder than
ours does to us," Dr Caldwell said. With the three new arrivals, Kepler's
'hall of fame' expands to eight small, habitable-zone exoplanets That
first-person encounter, however, is unlikely - both because the planet is 475
light-years away and because we still have essentially no idea what it's made
of.
Images from the Kepler telescope, which trails behind the Earth and peers far into the distance as we
orbit our own sun, are used to identify far-off planets by observing
"transits". This refers to the dimming of a star's light when a
planet passes in front of it.
- Launched in 2009, the Kepler space telescope sought to find Earth-like
worlds orbiting distant stars in the Constellation Lyra
- It used the so-called transit
technique - looking for the periodic dips
in light as exoplanets pass in front of their host stars
- Last year, a single release of
Kepler results added 715 exoplanets to the tally
- How does the Kepler telescope work?
- How rare is our blue planet?
A large team of researchers then uses additional data from
Earth-bound telescopes to further explore these unfamiliar solar systems. They
try to calculate how big the planets are, and how closely they orbit their host
stars. Not everything that causes such a dimming eventually turns out to be a
planet, however. At the same time as the eight confirmed new exoplanets were
announced by a 26-strong team spanning Nasa and multiple US institutions, the
Kepler mission's own scientists released another tranche of more than 500
"candidate" planets.
The size of the habitable, or "Goldilocks" zone,
where a planet is far enough from its sun to hold water but not so distant that
it freezes, depends on how confident scientists want to be with their
guess-work. According to Dr Cardwell, just three of the eight new exoplanets
can be confidently placed in that zone - and only two of those are probably
rocky like the Earth. More detailed description is very difficult.
An artist's view of Kepler 186f, which experts say has now
been pipped as "most Earth-like" known exoplanet "From the Kepler measurements and the
other measurements we made, we don't know if these planets have oceans with
fish and continents with trees," Dr Caldwell told BBC News. "All we
know is their size and the energy they're receiving from their star. "So
we can say: Well, they're of a size that they're likely to be rocky, and the
energy they're getting is comparable to what the Earth is getting. "As we
fill in these gaps in our solar system that we don't have, we learn more about what it means to be Earth-like, in some
sense."
Speaking at a related event at the conference, Prof Debra
Fischer from Yale University said she remembered a time before the first exoplanet was discovered, more than two decades
ago. "I remember astronomers before that point being very worried,"
she said. "We really had to step back and say: Maybe the Star Trek picture
is wrong. That filled me with despair." Prof Fischer said that sensitive
telescopes like Kepler had ushered in an era of "amazing and impressive
work". "We're talking about a planet - and we can only see its star
with a powerful telescope. "And we can draw graphs and sketch its
composition and have serious scientific discussions. This is incredible."
From the article do
this assignment
1.
Find out some prepositions that direct
about time, place or which have other meaning!
Answer:
a. At
= direct the place, it follows the statement a meeting of the American
astronomical
Society
b. In
= directs the place, it follows the word
California (name of city)
c. On
= directs the place, it tells about the surface
of planet
d. Behind = directs the place, it the Earth and peers far into the
distance as we orbit
our own sun
e. Looking
for = it means searching, and it directs the time
because telling the periodic
dips
f. Move
around = It
means doing something, it directs the place for the habitable zone.
g.
About =
directs the place, it tells about earth like
h.
Before =
directs the place, it tells about the first exoplanet was discovered.
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