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The Giant Spider Web at Lake Tawakoni

There is a giant spider web at Lake Tawakoni State Park in Texas. The web was found in August by Texas Parks & Wildlife employee Freddie Gowin while mowing the trails at Lake Tawakoni State Park. The web sparked interest from experts and bloggers when Donna Garde, Lake Tawakoni State Park Superintendent, posted her photo of the web -- click here to see a larger version of the web photo. Wired says that thousands of spiders from 12 different species have built the web that reaches 200 yards. Normally, the spiders are competitors and enemies, and work individually on their own orb-shaped webs. But entomologists say that bountiful insect hatches caused by heavy rainfall have provided so much food that the spiders instinctively repressed their traditional enmities in favor of cooperation. It's a population-level evolutionary behavior that's never before been witnessed (and thank goodness for that; spiders are scary enough on their own!) The web, first reported earlier in the summer, took more than a month to build; it's been blown down three times by wind and rain, and re-spun each time. Visitors describe the web as something out of science fiction. Said a park volunteer, "Hollywood couldn't have done as good a job in their best day as nature has done with this." In the movie Arachnophobia a new species of spiders was discovered in South America that operates more like organized army ants and killer bees than solitary spiders. Fortunately, these Lake Tawakoni spiders are neither poisonous or very scary. This website provides a great timeline of the social spider web. This webpage contains a list of the spiders collected from the Lake Tawakoni web. And some more informaton about social spiders and links to more webs can be found here. More coverage of the spider web in articles and blog posts can be found here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here, here and here. Here's a video clip of the web. Direct video link Permalink | Recent Headlines | News Feeds Read more…

Heaviest Stellar Black Hole Discovered In Nearby Galaxy

18.10.2007 13:44 Science - Source: ScienceDaily Headlines

Science Daily — Astronomers have located an exceptionally massive black hole in orbit around a huge companion star. This result has intriguing implications for the evolution and ultimate fate of massive stars.

The main component of this graphic is an artist's representation of M33 X-7, a binary system in the nearby galaxy M33. In this system, a star about 70 times more massive than the Sun (large blue object) is revolving around a black hole. This black hole is almost 16 times the Sun's mass, a record for black holes created from the collapse of a giant star. Other black holes at the centers of galaxies are much more massive, but this object is the record-setter for a so-called "stellar mass" black hole. (Credit: NASA/CXC/M.Weiss; X-ray: NASA/CXC/CfA/P.Plucinsky et al.; Optical: NASA/STScI/SDSU/J.Orosz et al.)

The black hole is part of a binary system in M33, a nearby galaxy about 3 million light years from Earth. By combining data from NASA's Chandra X-ray Observatory and the Gemini telescope on Mauna Kea, Hawaii, the mass of the black hole, known as M33 X-7, was determined to be 15.7 times that of the Sun. This makes M33 X-7 the most massive stellar black hole known. A stellar black hole is formed from the collapse of the core of a massive star at the end of its life.

"This discovery raises all sorts of questions about how such a big black hole could have been formed," said Jerome Orosz of San Diego State University, lead author of the paper appearing in the October 18th issue of the journal Nature.

M33 X-7 orbits a companion star that eclipses the black hole every three and a half days. The companion star also has an unusually large mass, 70 times that of the Sun. This makes it the most massive companion star in a binary system containing a black hole.

"This is a huge star that is partnered with a huge black hole," said coauthor Jeffrey McClintock of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "Eventually, the companion will also go supernova and then we'll have a pair of black holes."

The properties of the M33 X-7 binary system - a massive black hole in a close orbit around a massive companion star - are difficult to explain using conventional models for the evolution of massive stars. The parent star for the black hole must have had a mass greater than the existing companion in order to have formed a black hole before the companion star.

Such a massive star would have had a radius larger than the present separation between the stars, so the stars must have been brought closer while sharing a common outer atmosphere. This process typically results in a large amount of mass being lost from the system, so much that the parent star should not have been able to form a 15.7 solar-mass black hole.

The black hole's progenitor must have shed gas at a rate about 10 times less than predicted by models before it exploded. If even more massive stars also lose very little material, it could explain the incredibly luminous supernova seen recently as SN 2006gy. The progenitor for SN 2006gy is thought to have been about 150 times the mass of the Sun when it exploded.

"Massive stars can be much less extravagant than people think by hanging onto a lot more of their mass toward the end of their lives," said Orosz. "This can have a big effect on the black holes that these stellar time-bombs make."

Coauthor Wolfgang Pietsch was also the lead author of an article in the Astrophysical Journal that used Chandra observations to report that M33 X-7 is the first black hole in a binary system observed to undergo eclipses. The eclipsing nature enables unusually accurate estimates for the mass of the black hole and its companion.

"Because it's eclipsing and because it has such extreme properties, this black hole is an incredible test-bed for studying astrophysics," said Pietsch.

The length of the eclipse seen by Chandra gives information about the size of the companion. The scale of the companion's motion, as inferred from the Gemini observations, gives information about the mass of the black hole and its companion. Other observed properties of the binary were used to constrain the mass estimates.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Gemini is an international partnership managed by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation.

Note: This story has been adapted from material provided by Chandra X-ray Center.