An ocean of galaxies awaits

Sometime around 400 million years after the birth of our universe, the first stars began to form. The universe's so-called dark ages came to an end and a new light-filled era began. More and more galaxies began to take shape and served as factories for churning out new stars, a process that reached a peak about 4 billion years after the Big Bang.

Luckily for astronomers, this bygone era can be observed. Distant light takes time to reach us, and our telescopes can pick up light emitted by galaxies and stars billions of years ago (our universe is 13.8 billion years old). But the details of this chapter in our universe's history are murky since most of the stars being formed are faint and hidden by dust.

A new Caltech project, called COMAP (CO Mapping Array Project), will offer us a new glimpse into this epoch of galaxy assembly, helping to answer questions about what really caused the universe's rapid increase in the production of stars.

"Most instruments might see the tip of an iceberg when looking at galaxies from this period," says Kieran Cleary, the project's principal investigator and the associate director of Caltech's Owens Valley Radio Observatory (OVRO). "But COMAP will see what lies underneath, hidden from view."

The current phase of the project uses a 10.4-meter "Leighton" radio dish at OVRO to study the most common kinds of star-forming galaxies spread across space and time, including those that are too difficult to view in other ways because they are too faint or hidden by dust. The radio observations trace the raw material from which stars are made: cold hydrogen gas. This gas is not easy to pinpoint directly, so instead COMAP measures bright radio signals from carbon monoxide (CO) gas, which is always present along with the hydrogen. COMAP's radio camera is the most powerful ever built to detect these radio signals.

The first science results from the project have just been published in seven papers in The Astrophysical Journal. Based on observations taken one year into a planned five-year survey, COMAP set upper limits on how much cold gas must be present in galaxies at the epoch being studied, including the ones that are normally too faint and dusty to see. While the project has not yet made a direct detection of the CO signal, these early results demonstrate that it is on track to do so by the end of the initial five-year survey and ultimately will paint the most comprehensive picture yet of the universe's history of star formation.

"Looking to the future of the project, we aim to use this technique to successively look further and further back in time," Cleary says. "Starting 4 billion years after the Big Bang, we will keep pushing back in time until we reach the epoch of the first stars and galaxies, a couple of billion years earlier."

Anthony Readhead, the co-principal investigator and the Robinson Professor of Astronomy, Emeritus, says that COMAP will see the not only the first epoch of stars and galaxies, but also their epic decline. "We will observe star formation rising and falling like an ocean tide," he says.

COMAP works by capturing blurry radio images of clusters of galaxies over cosmic time rather than sharp images of individual galaxies. This blurriness enables the astronomers to efficiently catch all the radio light coming from a larger pool of galaxies, even the faintest and dustiest ones that have never been seen.

"In this way, we can find the average properties of typical, faint galaxies without needing to know very precisely where any individual galaxy is located," explains Cleary. "This is like finding the temperature of a large volume of water using a thermometer rather than analyzing the motions of the individual water molecules."

Read more at Science Daily

A history of the Crusades, as told by crusaders' DNA

This image shows the bones of the Crusaders found in a burial pit in Sidon, Lebanon.

History can tell us a lot about the Crusades, the series of religious wars fought between 1095 and 1291, in which Christian invaders tried to claim the Near East. But the DNA of nine 13th century Crusaders buried in a pit in Lebanon shows that there's more to learn about who the Crusaders were and their interactions with the populations they encountered. The work appears April 18 in The American Journal of Human Genetics.

The remains suggest that the soldiers making up the Crusader armies were genetically diverse and intermixed with the local population in the Near East, although they didn't have a lasting effect on the genetics of Lebanese people living today. They also highlight the important role ancient DNA can play in helping us understand historical events that are less well documented.

"We know that Richard the Lionheart went to fight in the Crusades, but we don't know much about the ordinary soldiers who lived and died there, and these ancient samples give us insights into that," says senior author Chris Tyler-Smith, a genetics researcher at the Wellcome Sanger Institute.

"Our findings give us an unprecedented view of the ancestry of the people who fought in the Crusader army. And it wasn't just Europeans," says first author Marc Haber, also of the Wellcome Sanger Institute. "We see this exceptional genetic diversity in the Near East during medieval times, with Europeans, Near Easterners, and mixed individuals fighting in the Crusades and living and dying side by side."

Archaeological evidence suggested that 25 individuals whose remains were found in a burial pit near a Crusader castle near Sidon, Lebanon, were warriors who died in battle in the 1200s. Based on that, Tyler-Smith, Haber, and their colleagues conducted genetic analyses of the remains and were able to sequence the DNA of nine Crusaders, revealing that three were Europeans, four were Near Easterners, and two individuals had mixed genetic ancestry.

Throughout history, other massive human migrations -- like the movement of the Mongols through Asia under Genghis Khan and the arrival of colonial Iberians in South America -- have fundamentally reshaped the genetic makeup of those regions. But the authors theorize that the Crusaders' influence was likely shorter-lived because the Crusaders' genetic traces are insignificant in people living in Lebanon today. "They made big efforts to expel them, and succeeded after a couple of hundred years," says Tyler-Smith.

This ancient DNA can tell us things about history that modern DNA can't. In fact, when the researchers sequenced the DNA of people living in Lebanon 2,000 years ago during the Roman period, they found that today's Lebanese population is actually more genetically similar to the Roman Lebanese.

"If you look at the genetics of people who lived during the Roman period and the genetics of people who are living there today, you would think that there was just this continuity. You would think that nothing happened between the Roman period and today, and you would miss that for a certain period of time the population of Lebanon included Europeans and people with mixed ancestry," says Haber.

These findings indicate that there may be other major events in human history that don't show up in the DNA of people living today. And if those events aren't as well-documented as the Crusades, we simply might not know about them. "Our findings suggest that it's worthwhile looking at ancient DNA even from periods when it seems like not that much was going on genetically. Our history may be full of these transient pulses of genetic mixing that disappear without a trace," says Tyler-Smith.

That the researchers were able to sequence and interpret the nine Crusaders' DNA at all was also surprising. DNA degrades faster in warm climates, and the remains studied here were burned and crudely buried. "There has been a lot of long-term interest in the genetics of this region, because it has this very strategic position, a lot of history, and a lot of migrations. But previous research has focused mainly on present-day populations, partly because recovering ancient DNA from warm climates is so difficult. Our success shows that studying samples in a similar condition is now possible because of advances in DNA extraction and sequencing technology," says Haber.

Next, the researchers plan to investigate what was happening genetically in the Near East during the transition from the Bronze Age to the Iron Age.

Read more at Science Daily

Lost Dark Age Kingdom Uncovered in Scotland

Archaeologists may have finally found the lost kingdom of Rheged, the most elusive of all the sixth century kingdoms of Dark Age Britain.

The mysterious kingdom was pre-eminent in northern Britain in the sixth century, but faded into obscurity after it was deliberately destroyed in the beginning of the following century.

Historians had speculated that the kingdom was headquartered in Cumbria, a county in north west England, but no evidence of it was ever found. Then digs carried in 2012 at Trusty's Hill, which overlooks the Fleet valley in Galloway in south-west Scotland, revealed clues of the presence of a royal stronghold.

"Our excavation revealed all the hallmarks of an early medieval royal site," Ronan Toolis at GUARD Archaeology in Glasgow, told Seeker.

The discovery is detailed in a new book, "The Lost Dark Age Kingdom of Rheged," which is being released Saturday.

Toolis and co-author Christopher Bowles found that in the decades around 600 A.D. the summit of the hill was fortified with a timber-laced stone rampart. They also recovered remains of supplementary defenses and enclosures along the lower-lying slopes, revealing that Trusty's Hill was fortified.

"This is a type of fort that has been recognized in Scotland as a form of high status secular settlement of the early medieval period," Toolis said. "The evidence makes a compelling case for Galloway being the core of the kingdom of Rheged."

Anglo-saxon style bronze jewellery. Originally gilded and silvered and made of leaded brass, it was probably brought to the site as loot.

Little is known about Rheged. Fragments of early medieval historical records and medieval poetry indicate the kingdom was particularly powerful under the warrior king Urien, whose prowess was celebrated by his court-bard Taliesin.

Toolis and Bowles discovered that anyone approaching the summit of the hill passed through a symbolic entrance way defined by Pictish carvings on one side and a large rock-cut basin on the other. The Picts were a tribal group of people who lived in what is today eastern and northern Scotland during the Late Iron Age and Early Medieval periods.

"It was a rite of passage where early medieval kings were perhaps anointed and ceremonies performed," Toolis said.

He noted the entrance way bears a close resemblance to one found some 180 miles north at Dunadd hillfort, the royal center for the kings of Dalriada in what is now Argyll and Bute. There, an entrance way with Pictish carving and a rock-cut basin was also found.

The king's hall may have stood at the highest part of Trusty's Hill on the west side. On the slightly lower area on the eastern side, the archaeologists found a workshop that produced metalwork of gold, silver, bronze and iron.

The team also unearthed e-ware, a type of pottery imported from continental Europe, which indicates the royal household was part of a trade network that linked western Britain with Ireland and continental Europe.

Other activities at Rheged included the spinning of wool, preparation of leather and feasting.

A laser scan image of the carved Pictish symbols.

"The household's wealth relied on their control of farming, animal husbandry and the management of local natural resources — minerals and timber — from an estate probably spanning the wider landscape of the Fleet valley and estuary," Christopher Bowles, Scottish borders council archaeologist, said.

"Control was maintained by bonding the people of this land and the districts beyond to the royal household, by gifts, promises of protection and the bounties of raiding and warfare," he added.

Analysis of the Pictish stone carvings revealed the symbols cannot be deciphered.

"The literal meaning of the symbols at Trusty's Hill will probably never be known. There is no Pictish Rosetta Stone," Toolis said.

Read more at Discovery News