Archive for 2012-07-08

Unsolved Mystery - Observations with CSIRO's Australia Telescope Compact Array have confirmed that astronomers have found the first known "middleweight" black hole.

Outbursts of super-hot gas observed with a CSIRO radio telescope have clinched the identity of the first known "middleweight" black hole, Science Express reports.

Called HLX-1 ("hyper-luminous X-ray source 1"), the black hole lies in a galaxy called ESO 243-49, about 300 million light-years away.

Before it was found, astronomers had good evidence for only supermassive black holes -- ones a million to a billion times the mass of the Sun -- and "stellar mass" ones, three to thirty times the mass of the Sun.

"This is the first object that we're really sure is an intermediate-mass black hole," said Dr Sean Farrell, an ARC Postdoctoral Fellow at the University of Sydney and a member of the research team, which included astronomers from France, Australia, the UK and the USA.

Since 2010 the researchers have been studying the black hole with CSIRO's Compact Array radio telescope near Narrabri, NSW.

CSIRO's Dr Ron Ekers, who studies supermassive black holes in the centres of galaxies, said "We don't know for sure how supermassive black holes form, but they might come from medium-size ones merging. So finding evidence of these intermediate-mass black holes is exciting."

HLX-1 was discovered by chance in 2009, because it stood out as a very bright X-ray source.

As gas from a star or gas cloud is being sucked into a black hole, it is heated to extreme temperatures and shines in X-rays.

"A number of other bright X-ray sources have been put forward as possibly being middleweight black holes. But all of those sources could be explained as resulting from lower mass black holes," Dr Farrell said. "Only this one can't. It is ten times brighter than any of those other candidates. We are sure this is an intermediate-mass black hole -- the very first."

Since 2010 the researchers have been studying the black hole with CSIRO's Compact Array radio telescope near Narrabri, NSW.

"From studying other black holes we know that sucking in the gas creates X-rays, but there's then a sort of reflux, with the region around the black hole shooting out jets of high-energy particles that hit gas around the black hole and generate radio waves," said Dr Farrell.

"So what we tend to see is the X-ray emission and then, a day or two or even a few days later, the source flaring up in radio waves."

By looking at the source's X-ray output, the researchers predicted two occasions when it should also be brightening in radio waves -- and they were right both times.

Dr Farrell speculates that a companion star traverses a very eccentric orbit around the black hole. When the companion comes close, the black hole strips gas from its partner, and it is this that gives rise to the X-ray flaring.

The brightness of the X-ray and radio flares have allowed the team to put an upper limit on the mass of the black hole of 90,000 times the mass of the Sun. However, Dr Farrell says that this is a conservative estimate, and for a variety of reasons a lower figure of around 20,000 solar masses is more likely.

Why have we found only this one confirmed intermediate-mass black hole? "There maybe lots of others out there that are not currently feeding, and so are not detectable, or are feeding at a very low rate, so they don't stand out as intermediate-mass black holes," Dr Ekers said.

HLX-1 may have been the central black hole of a low-mass "dwarf" galaxy, Dr Farrell speculates; a dwarf galaxy that was swallowed by the larger galaxy ESO 243-49, just as our own Milky Way Galaxy has swallowed dwarf galaxies. There is evidence of star-formation about HLX-1, which would be consistent with a "plunging dwarf." The research team is now looking for other signs of disturbance around the site of the black hole, such as gas streams, which would also support this idea.

Source : http://www.sciencedaily.com/releases/2012/07/120709102720.htm

Unsolved mystery - Scientists from the Wits Institute for Human Evolution based at the University of the Witwatersrand in Johannesburg have just announced the discovery of a large rock containing significant parts of a skeleton of an early human ancestor. The skeleton is believed to be the remains of 'Karabo', the type skeleton of Australopithecus sediba, discovered at the Malapa Site in the Cradle of Humankind in 2009.

Professor Lee Berger, a Reader in Palaeoanthropology and the Public Understanding of Science at the Wits Institute for Human Evolution, will make the announcement at the Shanghai Science and Technology Museum in Shanghai, China on 13 July 2012.

"We have discovered parts of a jaw and critical aspects of the body including what appear to be a complete femur (thigh bone), ribs, vertebrae and other important limb elements, some never before seen in such completeness in the human fossil record," says Berger. "This discovery will almost certainly make Karabo the most complete early human ancestor skeleton ever discovered. We are obviously quite excited as it appears that we now have some of the most critical and complete remains of the skeleton, albeit encased in solid rock. It's a big day for us as a team and for our field as a whole."

Professor Lee Berger, a Reader in Palaeoanthropology and the Public Understanding of Science at the Wits Institute for Human Evolution, will make the announcement at the Shanghai Science and Technology Museum in Shanghai, China on 13 July 2012.

"We have discovered parts of a jaw and critical aspects of the body including what appear to be a complete femur (thigh bone), ribs, vertebrae and other important limb elements, some never before seen in such completeness in the human fossil record," says Berger. "This discovery will almost certainly make Karabo the most complete early human ancestor skeleton ever discovered. We are obviously quite excited as it appears that we now have some of the most critical and complete remains of the skeleton, albeit encased in solid rock. It's a big day for us as a team and for our field as a whole."

Source : http://www.sciencedaily.com/releases/2012/07/120712162744.htm

Unsolved mystery - A vast city built by the ancient Maya and discovered nearly a century ago is finally starting to yield its secrets.

Excavating for the first time in the sprawling complex of Xultún in Guatemala's Petén region, a team of archaeologists lead by Boston University Assistant Professor of Archaeology William Saturno has uncovered a structure that contains what appears to be a work space for the town's scribe, its walls adorned with unique paintings -- one depicting a lineup of men in black uniforms -- and hundreds of scrawled numbers. Many are calculations relating to the Maya calendar.

One wall of the structure, thought to be a house, is covered with tiny, millimeter-thick, red and black glyphs unlike any seen before at other Maya sites. Some appear to represent the various calendrical cycles charted by the Maya -- the 260-day ceremonial calendar, the 365-day solar calendar, the 584-day cycle of the planet Venus and the 780-day cycle of Mars, reports Saturno, who led the exploration and excavation.

"For the first time we get to see what may be actual records kept by a scribe, whose job was to be official record keeper of a Maya community," Saturno said. "It's like an episode of TV's 'Big Bang Theory,' a geek math problem and they're painting it on the wall. They seem to be using it like a blackboard."

The discovery is reported in the June issue of National Geographic magazine and in the May 11 issue of the journal Science.

The project scientists say that despite popular belief, there is no sign that the Maya calendar -- or the world -- was to end in the year 2012, just one of its calendar cycles. "It's like the odometer of a car, with the Maya calendar rolling over from the 120,000s to 130,000," said Anthony Aveni,, professor of astronomy and anthropology at Colgate University, a coauthor of the Science paper. "The car gets a step closer to the junkyard as the numbers turn over; the Maya just start over."

The mural represents the first Maya art to be found on the walls of a house. "There are tiny glyphs all over the wall, bars and dots representing columns of numbers. It's the kind of thing that only appears in one place -- the Dresden Codex, which the Maya wrote many centuries later. We've never seen anything like it," said David Stuart, Schele Professor of Mesoamerican Art and Writing at the University of Texas-Austin, who deciphered the glyphs.

The vegetation-covered structure was first spotted in 2010 by Saturno's student Max Chamberlain, who was following looters' trenches to explore the site of Xultún, hidden in the remote rain forest of the Petén. Then, supported by a series of grants from the National Geographic Society, Saturno and his team launched an organized exploration and excavation of the house, working urgently to beat the region's rainy seasons, which threatened to erase what time had so far preserved.

Xultún, a 12-square-mile site where tens of thousands once lived, was first discovered about 100 years ago by Guatemalan workers and roughly mapped in the 1920s by Sylvanus Morley, who named the site "Xultún" -- "end stone." Scientists from Harvard University mapped more of the site in the 1970s. The house discovered by Saturno's team was numbered 54 of 56 structures counted and mapped at that time. Thousands at Xultún remain uncounted.

The team's excavations reveal that monumental construction at Xultún began in the first centuries B.C. The site thrived until the end of the Classic Maya period; the site's last carved monument dates to around 890 A.D. Xultún stood only about five miles from San Bartolo, where in 2001 Saturno found rare, extensive murals painted on the walls of a ritual structure by the ancient Maya.

"It's weird that the Xultún finds exist at all," Saturno said. "Such writings and artwork on walls don't preserve well in the Maya lowlands, especially in a house buried only a meter below the surface."

The Writing on the Walls

The house contains three intact walls, each telling its own story to researchers -- and posing its own mysteries:

The north wall lies straight ahead as one enters the room. An off-center niche in the wall features a painting of a seated king, wearing blue feathers. A long rod made of bone mounted on the wall allowed a curtain to be pulled across the king's portrait, hiding it and revealing a well-preserved painting of a man whose image is wrapped around the wall; he is depicted in vibrant orange and holds a pen. Maya glyphs near his face call him "Younger Brother Obsidian," a curious title seldom seen in Maya text. Based on other Maya sites, Saturno theorizes he could be the son or younger brother of the king and possibly the artist-scribe who lived in the house. "The portrait of the king implies a relationship between whoever lived in this space and the royal family," Saturno said.

Four long numbers on the wall representing one-third of a million to 2.5 million days likely bring together all of the astronomical cycles -- such as those of Mars, Venus and the lunar eclipses -- the Maya thought important, dates that stretch some 7,000 years into the future. This is the first place Maya archaeologists have found that seems to tabulate all of these cycles in this way. Another number scratched into the plaster surface likely records the date -- 813 A.D., a time when the Maya world had begun to collapse.

The west wall: Three male figures loom on this wall, all of them seated and painted in black, wearing only white loincloths, medallions around their necks and identical single-feathered, miter-style head dresses. "We haven't seen uniform head dresses like that anywhere before," Saturno said. "It's clearly a costume of some kind." One of the figures is particularly burly, "like a sumo wrestler," and he is labeled "Older Brother Obsidian." Another is labeled as a youth.

The east wall: Although badly eroded, another black-painted human figure and remnants of others can be seen. But the wall is dominated by numerical figures, including columns of numbers representing counting and calendrical calculations. Some of the numbers track the phases of the moon; others try to reconcile lunar periods with the solar calendar. "Skywatching like this was a tool for predicting eclipses," Saturno said. One well-preserved section contains numerical notes painted in red that appear to be corrections to more formal calculations appearing alongside them.

"The most exciting point is that we now see that the Maya were making such computations hundreds of years -- and in places other than books -- before they recorded them in the Codices," Aveni said.

The scientists say the symbols reflect a certain world view. "The ancient Maya predicted the world would continue, that 7,000 years from now, things would be exactly like this," Saturno said. "We keep looking for endings. The Maya were looking for a guarantee that nothing would change. It's an entirely different mindset."

Source : http://www.sciencedaily.com/releases/2012/05/120510141905.htm