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[SM] the 3 year eclipse



 
 
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Old February 22nd 16, 06:06 AM posted to sci.misc,sci.astro
RS Wood
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Default [SM] the 3 year eclipse

From the «good time for a nap» department:
Title: Eclipse that lasts more than 3 years smashes record
Author: David Salisbury-VU
Date: Thu, 18 Feb 2016 15:22:46 -0500
Link: http://www.futurity.org/eclipse-bina...tem-1108242-2/

[image 1]

Scientists have discovered a binary star system nearly 10,000 light years from
Earth where every 69 years the sun disappears in a near total eclipse that
lasts for three and half years.

The newly discovered system, known only by its astronomical catalog number TYC
2505-672-1, sets a new record for both the longest duration stellar eclipse and
the longest period between eclipses in a binary system.

“It’s the longest duration stellar eclipse and the longest orbit for an
eclipsing binary ever found … by far,” says Joey Rodriguez, a doctoral student
at Vanderbilt University and first author of the paper[2],*which has been
accepted for publication in the Astronomical Journal.

The previous record holder is Epsilon Aurigae, a giant star that is eclipsed by
its companion every 27 years for periods ranging from 640 to 730 days.
[These rings are 200 times bigger than Saturn’s][3]

“Epsilon Aurigae is much closer—about 2,200 light years from Earth—and
brighter, which has allowed astronomers to study it extensively,” Rodriguez
says. Epsilon Aurigae consists of a yellow giant star orbited by a normal star
slightly bigger than the sun embedded in a thick disk of dust and gas oriented
nearly edge on when viewed from Earth.

“One of the great challenges in astronomy is that some of the most important
phenomena occur on astronomical timescales, yet astronomers are generally
limited to much shorter human timescales,” says coauthor Keivan Stassun,
professor of physics and astronomy. “Here we have a rare opportunity to study a
phenomenon that plays out over many decades and provides a window into the
types of environments around stars that could represent planetary building
blocks at the very end of a star system’s life.”

Scientists say two astronomical resources made the discovery possible:
observations by the American Association of Variable Star Observers (AAVSO)
network and the Digital Access to a Sky Century @ Harvard (DASCH) program.

AAVSO is a non-profit organization of professional and amateur astronomers
dedicated to understanding variable stars. It provided a few hundred
observations of TYC 2505-672-1’s most recent eclipse.

Next eclipse will be in 2080

The DASCH survey is based on thousands of photographic plates taken by
astronomers at Harvard University between 1890 and 1989 as part of a regular
survey of the northern sky. In recent years Harvard has begun digitizing these
plates. In the process TYC 2505-672-1 caught the eye of Sumin Tang at the
Harvard-Smithsonian Center for Astrophysics.

Rodriguez attended a conference where Tang presented her results on TYC
2505-672-1 and the system piqued his interest. He’s a member of the survey team
for the low-cost Kilodegree Extremely Little Telescope (KELT) system that
consists of a pair of robotic telescopes designed to find exoplanets around
bright stars operated by astronomers around the world. KELT has an extremely
wide field of view (26 degrees by 26 degrees) and he thought it was likely that
the KELT database contained a number of recent images of the distant binary
system.

After the lecture Rodriguez and Tang began a collaboration. Searching the KELT
database, Rodriguez found about 9,000 images of the obscure system taken in the
last eight years that they could combine with the 1,432 images taken over the
last century at Harvard. Rodriquez also contacted the AAVSO network and
obtained several hundred more observations of the system’s most recent eclipse
to help fill in the picture.

The resulting analysis revealed a system similar to the one at Epsilon Aurigae,
with some important differences. It appears to consist of a pair of red giant
stars, one of which has been stripped down to a relatively small core and
surrounded by an extremely large disk of material that produces the extended
eclipse.

“About the only way to get these really long eclipse times is with an extended
disk of opaque material. Nothing else is big enough to block out a star for
months at a time,” Rodriguez says.
[Star pretending to be a supernova has a strange companion][4]

TYC-2505-672-1 is so distant that the amount of data the astronomers could
extract from the images was limited. However, they were able to estimate the
surface temperature of the companion star and found that it is about 2,000
degrees Celsius hotter than the surface of the sun. Combined with the
observation that it appears to be less than half the diameter of the sun has
led them to propose that it is a red giant that has had its outer layers
stripped away and that this stripped material may account for the obscuring
disk. However, they don’t know that for certain.

In order to produce the 69-year interval between eclipses, the astronomers
calculate that they must be orbiting at an extremely large distance, about 20
astronomical units, which is approximately the distance between the Sun and
Uranus.

“Right now even our most powerful telescopes can’t independently resolve the
two objects,” Rodriguez says. “Hopefully, technological advances will make that
possible by 2080 when the next eclipse occurs.”

Other researchers from Vanderbilt and from Penn State, Lehigh University, Ohio
State University, Las Cumbres Observatory Global Telescope Network;, and the
American Association of Variable Star Observers contributed to the work.

The National Science Foundation and provided funding.

Source: Vanderbilt University[5]

The post Eclipse that lasts more than 3 years smashes record[6] appeared first
on Futurity[7].

Links:
[1]: http://www.futurity.org/wp/wp-conten...ipse2_1170.jpg (image)
[2]: http://arxiv.org/abs/1601.00135 (link)
[3]: http://www.futurity.org/exoplanet-rings-saturn-845972/ (link)
[4]: http://www.futurity.org/star-superno...ion-1107322-2/ (link)
[5]: http://news.vanderbilt.edu/2016/02/l...ellar-eclipse/ (link)
[6]: http://www.futurity.org/eclipse-bina...tem-1108242-2/ (link)
[7]: http://www.futurity.org (link)


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