Early universe 'warmed up' later than previously believed

A new study from Tel Aviv University reveals that black holes, formed from the first stars in our universe, heated the gas throughout space later than previously thought. 

They also imprinted a clear signature in radio waves which astronomers can now search for. 

The work is a major new finding about the origins of the universe.

"One of the exciting frontiers in astronomy is the era of the formation of the first stars," explains Prof. Rennan Barkana of TAU's School of Physics and Astronomy, an author of the study.

Rennan Barkana

"Since the universe was filled with hydrogen atoms at that time, the most promising method for observing the epoch of the first stars is by measuring the emission of hydrogen using radio waves."

The study, just published in the journal Nature, was co-authored by Dr. Anastasia Fialkov of TAU and the École Normale Supérieure in Paris and Dr. Eli Visbal of Columbia and Harvard Universities.

Cosmic archaeology
Astronomers explore our distant past, billions of years back in time. Unlike Earth-bound archaeologists, however, who can only study remnants of the past, astronomers can see the past directly.

The light from distant objects takes a long time to reach the earth, and astronomers can see these objects as they were back when that light was emitted.

Anastasia Fialkov

This means that if astronomers look out far enough, they can see the first stars as they actually were in the early universe.

Thus, the new finding that cosmic heating occurred later than previously thought means that observers do not have to search as far, and it will be easier to see this cosmic milestone.

Cosmic heating may offer a way to directly investigate the earliest black holes, since it was likely driven by star systems called "black-hole binaries."

These are pairs of stars in which the larger star ended its life with a supernova explosion that left a black-hole remnant in its place.

Gas from the companion star is pulled in towards the black hole, gets ripped apart in the strong gravity, and emits high-energy X-ray radiation.

This radiation reaches large distances, and is believed to have re-heated the cosmic gas, after it had cooled down as a result of the original cosmic expansion.

The discovery in the new research is the delay of this heating.

More information: 'The observable signature of late heating of the Universe during cosmic reionization' dx.doi.org/10.1038/nature12999

The Thylacine enigma: A Marsupial Wolf or a Tasmanian Tiger?

A study of the bones of the now extinct thylacine, called both a marsupial wolf and a Tasmanian tiger, has determined that the solitary, ambush-style predator was more cat than dog but also clearly a marsupial.

“We provide quantitative support to the suspicions of earlier researchers that the thylacine was not a pursuit predator,” says Borja Figueirido, a postdoctoral researcher at Brown University and the paper’s lead author.

The research is reported in the journal Biology Letters.

“Although there is no doubt that the thylacine diet was similar to that of living wolves, we find no compelling evidence that they hunted similarly.”

For millions of years, Thylacinus cynocephalus roamed mainland Australia. Its numbers declined as humans settled throughout the continent, beginning some 40,000 years ago and as the dingo, a small, dog-like animal, was introduced, about 4,000 years ago.

Thylacines’ last remaining outpost was in dingo-free Tasmania, but a concerted eradication effort wiped out the species. The last known thylacine died at a zoo in 1936.

It’s unclear why the animal fared so poorly with the arrival of humans and dingoes, but speculation is that human activity disrupted the thylacine habitat and perhaps its food sources.

The role dingoes had on the thylacine demise is less clear. Speculationis that because dingoes were the placental spitting image of the marsupial thylacines, evolved in isolated settings, called evolutionary convergence. When dingoes arrived in Australia, they helped push the thylacines out.

But Figueirido and Christine Janis, professor of biology and a co-author on the paper, say there’s more to the story.

The researchers compared the thylacine’s skeleton with pumas, panthers, jackals, wolves, hyenas, and Tasmanian devils, that are the largest living carnivorous marsupials.

Previous research had discovered the elbow joint is a clue to predator habits, because it shows whether the animal is built for flexibility and dexterity in handling prey or for chase and speed in tracking down the next meal.

Figueirido and Janis found that the thylacine’s humerus, or upper arm bone, was oval and elongated at the end closest to the elbow, implying that the animal’s forearm bones, the radius and ulna, were separate.

That means the Tasmanian tiger would have been able to rotate its arm so that the palm faced upwards, like a cat. The distal humerus on dog-like animals, such as dingoes and wolves, is more squared-up and shorter.

This indicates the radius and ulna were closer together in these species, reflecting that these animals’ hands are more fixed in the palm-down position.

In terms of hunting, the increased arm and hand movement would have given the thylacine a greater capability of subduing its quarry after a surprise attack. Since dingoes and other dog-like creatures have less latitude in arm-hand movement, that helps explain why these animals hunt by pursuit and in packs, rather than in an ambush setting.

“It’s a very subtle thing,” says Janis. “You never would think that the shape of just one bone would mean so much.”

Some cats, like cheetahs, use speed to catch their quarry, while some canid species, like foxes, rely more on the guile of the ambush. Janis says the thylacine’s hunting tactics appear to be a unique mix. “I don’t think there’s anything like it around today. It’s sort of like a cat-like fox.”

What that means for the dingo’s role in the thylacine’s disappearance from continental Australia is not clear, but it does show the animals, while similar in many respects, likely hunted differently, Janis says.

“Dingoes were more like the final straw (to the Tasmanian tigers’ demise in continental Australia), because they weren’t in the same niche. It’s not just that a dingo was a placental version of a thylacine.”

The research was funded in part by the Bushnell Foundation.

More news from Brown University: http://news.brown.edu

Aliens and Interstellar Archaeology on the Kardashev Galactic Scale

Kardashev Type III and Its Traces
What would happen if a true galaxy-spanning civilisation went to work on astro-engineering?

We call this a Kardashev Type III civilisation, one that could exploit the power resources of an entire galaxy, and the assumption made has always been that such a culture would be very high profile, if not, blindingly obvious. It's projects would be so vast that our astronomers would be able to detect them by noting anomalies, outside of natural occurences.

Imagine, for example, a galactic culture that encloses each individual star in a Dyson sphere.

Image: M81, a spiral galaxy in Ursa Major. A ‘wavefront’ Dyson sphere culture might spread across such a galaxy, causing stars to drop out of visible light spectrum entirely, and then one by one, to be detected in the infrared. Credit and copyright: Giovanni Benintende.

A Dyson sphere or ‘shell’ would absorb all of the visible light from a star, re-radiating stellar energy at infrared wavelengths. A Dyson ‘ring’ would use planetary materials that would mask only part of the star’s light.

Scientists have used a list of very interesting infrared sources from the Infrared Astronomy Satellite (IRAS) in their searches, but have come up with no strong Dyson sphere candidates. Nonetheless, Dyson spheres remain interesting, if only because they vastly increase the habitable area around a star.

What would a Type III civilisation do with technologies that could create Dyson spheres not only in one place but across the galaxy?

Whatever the answer, you would think it would be clearly noticeable. Freeman Dyson himself has said that “…a type III (Kardashev civilisation) in our own galaxy would change the appearance of the sky so drastically that it could hardly have escaped our attention.”

James Annis, who has studied anomalous galaxies in a quest for signs of a Type III civilisation, reports: “It is quite clear that the Galaxy itself has not transformed into a type III civilisation based on starlight, nor have M31 or M33, our two large neighbours.” Nonetheless, we wonder whether we should take these statements as conclusive or definitive:

…what would happen for a civilisation that was on its way to becoming a type III civilisation, i.e. a type II.5 civilisation that is developing?

If it was busily turning stars into Dyson spheres the civilisation could create a “Fermi bubble” or void in the visible light from a patch of the galaxy with a corresponding upturn in the emission of infrared light.

This bubble would grow following the lines of a suggestion attributed to Fermi… that patient space travellers moving at 1/1000 to 1/100 of the speed of light could span a galaxy in one to ten million years.

To read more on Interstellar Archaeology ......

The Burial Box of James - Jesus's Brother: A Case Against Fraud and Deception

The world of biblical archaeology was stirred in 2002 by the unveiling of a limestone burial box with the Aramaic inscription Yaakov bar Yosef akhui di Yeshua - "James, son of Joseph, brother of Jesus".

Allegedly dating to an era contemporaneous with Christ, the names were a tantalising collation of potentially great significance: James was indeed the name of a New Testament personage known as the brother of Jesus, both ostensibly the sons of Joseph the carpenter, husband of Mary.

If its dates were genuine, the burial box or 'ossuary', could well be circumstantial evidence for the existence of Jesus of Nazareth, a tenet supported only by gospels and scripture written, at the earliest, a generation after his crucifixion and, of course, by the faith of hundreds of millions through 2,000 years.

Experts, however, declared the 'ossuary', a modern-day forgery. It was seized by Israeli police and its owner, Tel Aviv collector Oded Golan, was arrested and charged with counterfeiting the 'ossuary' and dozens of other items. Golan and co-defendant Robert Deutsch were put on trial in the Jerusalem District Court in 2005.

Deutsch is accused of forging other valuables, though not the ossuary. Both men deny all charges. (Read a review of a book on fraudulent biblical relics and the ossuary of James.)

Their trial is still continuing. Many of the world's top archaeological experts have testified as both prosecution and defense witnesses in proceedings that already run to more than 9,000 pages. While the original charges against the 'ossuary' appear to have been popularly accepted as conventional wisdom, they seem to be headed for trouble in the courtroom where the fine reading of law comes into play.

Judge Aharon Farkash, who has a degree in archaeology, has wondered aloud in court how he can determine the authenticity of the items if the professors cannot agree among themselves. (Read a story from TIME's archive on the ossuary of James.)