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بسیار جالب !! حتما بخونید
#1
First Planets Found Around Sun-Like Stars in a Cluster



WASHINGTON
-- NASA-funded astronomers have, for the first time, spotted planets
orbiting sun-like stars in a crowded cluster of stars. The findings
offer the best evidence yet planets can sprout up in dense stellar
environments. Although the newfound planets are not habitable, their
skies would be starrier than what we see from Earth.

The
starry-skied planets are two so-called hot Jupiters, which are massive,
gaseous orbs that are boiling hot because they orbit tightly around
their parent stars. Each hot Jupiter circles a different sun-like star
in the Beehive Cluster, also called the Praesepe, a collection of
roughly 1,000 stars that appear to be swarming around a common center.


The Beehive is an open cluster, or a grouping of stars born at about
the same time and out of the same giant cloud of material. As such, the
stars share a similar chemical composition. Unlike the majority of
stars, which spread out shortly after birth, these young stars remain
loosely bound together by mutual gravitational attraction.


"We are detecting more and more planets that can thrive in diverse and
extreme environments like these nearby clusters," said Mario R. Perez,
the NASA astrophysics program scientist in the Origins of Solar Systems
Program. "Our galaxy contains more than 1,000 of these open clusters,
which potentially can present the physical conditions for harboring many
more of these giant planets."

The two new Beehive planets
are called Pr0201b and Pr0211b. The star's name followed by a "b" is the
standard naming convention for planets.

"These are the first
'b's' in the Beehive," said Sam Quinn, a graduate student in astronomy
at Georgia State University in Atlanta and the lead author of the paper
describing the results, which was published in the Astrophysical Journal
Letters.

Quinn and his team, in collaboration with David
Latham at the Harvard-Smithsonian Center for Astrophysics, discovered
the planets by using the 1.5-meter Tillinghast telescope at the
Smithsonian Astrophysical Observatory's Fred Lawrence Whipple
Observatory in Arizona to measure the slight gravitational wobble the
orbiting planets induce upon their host stars. Previous searches of
clusters had turned up two planets around massive stars but none had
been found around stars like our sun until now.

"This has
been a big puzzle for planet hunters," Quinn said. "We know that most
stars form in clustered environments like the Orion nebula, so unless
this dense environment inhibits planet formation, at least some sun-like
stars in open clusters should have planets. Now, we finally know they
are indeed there."

The results also are of interest to
theorists who are trying to understand how hot Jupiters wind up so close
to their stars. Most theories contend these blistering worlds start out
much cooler and farther from their stars before migrating inward.


"The relatively young age of the Beehive cluster makes these planets
among the youngest known," said Russel White, the principal investigator
on the NASA Origins of Solar Systems grant that funded this study. "And
that's important because it sets a constraint on how quickly giant
planets migrate inward. And knowing how quickly they migrate is the
first step to figuring out how they migrate."

The research
team suspects planets were turned up in the Beehive cluster because it
is rich in metals. Stars in the Beehive have more heavy elements such as
iron than the sun has.

According to White, "Searches for
planets around nearby stars suggest that these metals act like a 'planet
fertilizer,' leading to an abundant crop of gas-giant planets. Our
results suggest this may be true in clusters as well."

NASA's
Jet Propulsion Laboratory, Pasadena, Calif., manages NASA's Exoplanet
Exploration Program office. More information about exoplanets and NASA's
planet-finding program is available at:

در مورد اظهار نظر آقایون در تاپیک دلخوری باید بگم:
آقایون: کم گوی و گزیده گوی چون در// تا ز اندک تو جهان شود پر!!!
هرچند ک کلام گوهر بار از زبان شما جاری نشده، نمیشود و نخواهد شد!!!
پاسخ
#2
ممنون
بلخره اومدم :|
دلتون واسم تنگ شده بود
عخییییی d:
پاسخ
#3
خواهش میکنم
در مورد اظهار نظر آقایون در تاپیک دلخوری باید بگم:
آقایون: کم گوی و گزیده گوی چون در// تا ز اندک تو جهان شود پر!!!
هرچند ک کلام گوهر بار از زبان شما جاری نشده، نمیشود و نخواهد شد!!!
پاسخ
#4
(15-09-2012، 09:14 AM)مهدی علینقیان نوشته است:  ممنون
شرط میبندم نخونده اینو نوشتی ک یعنی بگی مام آره...سواد اینگیلیسیمون خوبه!


دهـانتان را به اندازه ای باز کنید که دیــــــــگران حرف در دهانتان نگذارند....!




پاسخ
 سپاس شده توسط amir astronomer
#5
دقیق زدی تو هدف
بلخره اومدم :|
دلتون واسم تنگ شده بود
عخییییی d:
پاسخ
 سپاس شده توسط malihe


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