A clash of titans would seem to be the perfect cause for a giant explosion, and for years scientists thought it was massive collisions between galaxies that triggered the black hole violence seen at the heart of many active galaxies.

A new study suggests, however, these galaxy mergers may not be at fault, and that less obvious sources are the culprit.

Our Milky Way galaxy and most others have
supermassive black holes at their hearts. Some of these monster black holes are relatively calm, but others known as “active galactic nuclei” or AGN can spew out more radiation than our entire galaxy does, and from a patch of space no larger than our solar system. Astronomers suspect this energy is released when matter heats up as it gets sucked into the black holes.

Until now, the main suspects for what made these supermassive black holes into active galactic nuclei were galactic mergers. The crashes were thought to be what drove matter into the black holes, ramping up their activity. [
Gallery: Black Holes of the Universe ]

But after looking at telltale signs of galactic mergers among 140 active galaxies, as well as more than 1,200 comparable inactive galaxies, over the last 8 billion years, a team of astronomers found no significant link between the galaxy crashes and black hole outbursts.

“The implication is that the universe is not evolving in such a violent way as previously thought, at least for the last 8 billion years,” research team leader Mauricio Cisternas, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany, told SPACE.com. The universe is thought to be about 13.7 billion years old.

Cisternas and other scientists analyzed galaxies from the COSMOS survey, which investigates an area of sky comprehensively mapped by Hubble and other telescopes at different wavelengths. In that area, which is roughly 10 times the area covered by the moon, they identified active galaxies by using X-ray observations from the European Space Agency’s XMM-Newton space telescope, and studied them in greater detail with optical images taken by the
Hubble Space Telescope.

A galactic police lineup

For each of the active galaxies the researchers inspected, they chose nine comparable nonactive galaxies of roughly the same cosmic age and thus stage of evolution. (One can estimate how old a galaxy is by figuring out its distance from us in light years; knowing how many years it took the galaxy’s light to get here can tell you its age.) They examined all these galaxies for evidence of mergers.

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“You can usually tell when galaxies have been involved in a merger,” said researcher Knud Jahnke, a astronomer at Max Planck. “Instead of the neat, geometric spiral or smooth elliptical shapes you usually see in Hubble images,
colliding galaxies typically look distorted and warped.”

At the researchers’ request, 10 galaxy experts from eight institutions independently evaluated whether each of the galaxies was distorted, without being told which ones contained an active galactic nucleus. (The researchers had removed the bright spot in the images of active galaxies that had such nuclei.)

None of the experts’ findings established a significant link between a galaxy’s activity and its involvement in a major merger. The researchers concluded that the cause of at least three-quarters and possibly all of active galactic nucleus activity over the last 8 billion years must have a different explanation.

“We do not rule out that mergers actually might cause AGN activity in some cases,” Jahnke told SPACE.com. “But they do not dominate the buildup of black hole mass over the last 8 billion years.”

When galaxies collide

Not every major galactic collision has to result in gas falling into the
black holes at the centers of galaxies, Cisternas said.

For example, he explained, gas can get stalled at some point as it gets drawn toward the cores, and is kept far away from the black hole. “Another possibility is that due to the violence of the merger event, a relevant fraction of the gas is simply stripped away,” he said.

So what might have caused the violence witnessed in active galaxies? Potential culprits include collisions of molecular clouds, instabilities within galaxies, or gravitational disruptions by other galaxies flying by. Any of them could have fed matter into the black holes to spike up activity.

The researchers plan on looking at mergers from even further in the past to see whether they are linked with active galaxies.

“At these times there were more frequent mergers, by a factor of 10 or so, and the amount of gas in galaxies was much higher,” Jahnke explained. “Hence physics could be different and other mechanisms could be at work.”

The scientists will detail their findings Jan. 10 in the Astrophysical Journal.

• 
  Gallery: Black Holes of the Universe
• 
  Hubble Photos: When Galaxies Collide
• 
  Video Show The Black Hole That Made You Possible

© 2011 Space.com. All rights reserved. More from Space.com.

CAPE CANAVERAL, Fla. — NASA on Tuesday began modifications to the shuttle Discovery’s fuel tank, hoping to thwart a potential debris hazard during a planned February launch to the International Space Station.

Managers decided to buttress at least 34 of the tank’s 108 metal support structures after cracks were discovered in five beams following a launch attempt on November 5.

The launch initially was scuttled by an unrelated hydrogen fuel leak, but inspectors also found a 21-inch-long (50-centimeter-long) crack in the fuel tank’s insulating foam, which likewise would have nixed liftoff, said shuttle program manager John Shannon.

The concern is that bits of cracked foam could break off and hit the shuttle during liftoff, such as what happened during the 2003 launch of the shuttle Columbia. The damage caused the shuttle to break apart as it flew through the atmosphere for landing 16 days later, killing seven astronauts aboard.

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      10-year-old girl discovers a supernova
      
      
      

   
   

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Additional inspections of Discovery’s tank revealed cracking in underlying support beams, known as stringers. Engineers have been unable to determine the root cause of the cracks, but they suspect it is due to the metal flexing from the extreme cold of the shuttle’s liquid oxygen and light hydrogen propellants.

To reinforce the stringers, technicans are installing additional pieces of metal over the tops of the 21-foot-long (6.4-meter-long) ribs, said NASA spokesman Allard Beutel.

The modifications are expected to take about a week.

Discovery’s launch remains targeted for Feb. 3. If the shuttle isn’t off the ground by Feb. 10, the flight will be delayed to the next launch opportunity, which begins Feb. 27. The mission is among the final shuttle flights before NASA retires its three-ship fleet this year.

Copyright 2011 Thomson Reuters. Click for restrictions.

The morning skies over Europe, the Mideast and elsewhere dimmed in an unnatural twilight early Tuesday when the moon blocked part of the sun in the first partial solar eclipse of the year.

In Rome, cloudy skies made the solar eclipse a touch eerie as the moon appeared to take a bite out of the sun during the three-hour eclipse. [
partial solar eclipse from Rome, where the sun was just under two-thirds — about 61 percent — obscured by the moon. In Sweden, where the eclipse was at its maximum, the moon blocked out about 80 percent of the sun’s disk.

Skywatcher Dennis Put of Maasvlakte in the Netherlands snapped stunning photos of the solar eclipse at sunrise, despite a disheartening weather forecast. “The expectations on viewing the eclipse the day before were not very high due to a great chance on complete cloud overcast, but it turned out well!” Put said in a description of the event. [
Photoblog: More images from the solar eclipse

Put’s photos show the solar eclipse already under way as the sun was rising, giving the dawn what he described as a “double sunrise” look. At one point, an airplane passed across the face of the sun, offering a double eclipse of sorts. [

Solar eclipses occur when the moon passes between the sun and the Earth and appears to line up with the sun when observed from the ground.

When the sun and moon line up perfectly, a
total solar eclipse occurs and completely covers the sun. Sometimes, however, the moon only covers a portion of the sun, creating a partial solar eclipse like the one seen on Tuesday.

“I was impressed to see many casual observers trying to look at the sun,” Masi said. “People were quite informed, I must say: Eclipses are among the things happening up there they like more.”

Tuesday’s partial solar eclipse occurred just after the peak of the Quadrantid meteor shower.

The eclipse was the first of four partial solar eclipses set for 2011.  The next partial solar eclipse will occur on June 1, according to NASA’s eclipse tracking website.

There will not be a total solar eclipse this year, as there was in 2010. Earth’s next brush with totality is due in November 2012, with the total phase of the solar eclipse visible from northern Australia and the South Pacific.

• 
  Photos: The Total Solar Eclipse of 2010
• 
  Video: Meteor Shower, Solar Eclipse of January 2011
• 
  Solar Eclipse and Meteor Shower to Launch 2011 Skywatching Season

You can follow SPACE.com Managing Editor Tariq Malik on Twitter
@tariqjmalik.

© 2011 Space.com. All rights reserved. More from Space.com.

More than 30 years after NASA’s Viking landers found no evidence for organic materials on Mars, scientists say a new experiment on Mars-like soil shows Viking did, in fact, hit pay dirt.

The new study was prompted by the August 2008 discovery of powerful oxygen-busting compounds known as perchlorates at the landing site of another Mars probe called Phoenix.

Scientists repeated a key Viking experiment using perchlorate-enhanced soil from Chile’s Atacama Desert, which is considered one of the driest and most Mars-like places on Earth, and found telltale fingerprints of combusted organics — the same chemicals Viking scientists dismissed as contaminants from Earth.

“Contrary to 30 years of perceived wisdom, Viking did detect organic materials on Mars,” planetary scientist Christopher McKay, with NASA’s Ames Research Center in California, told Discovery News. “It’s like a 30-year-old cold case suddenly solved with new facts.”

“If the Viking team had said ‘Well, maybe there’s perchlorate in the soil,’ everybody would have said they’re crazy — why would there be perchlorates in the soil? It was only by having it pushed on us by Phoenix where we had no alternative but to conclude that there was perchlorate in the soil … Once you realize it’s there, then everything makes sense,” McKay added.

The Viking team’s verdict that Mars lacked organics was the linchpin argument against another Viking experiment that looked for signs of microbial life. In the experiment, a bit of nutrient-laced water was added to a sample of Martian soil.

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The air above the soil was then monitored for signs that the nutrients had been metabolized. The instrument detected tracer gases the first time the experiment was done, but subsequent runs did not. The results were considered inconclusive and remain contested.

New evidence for organics on Mars does not mean Viking found life, cautions McKay.

“Finding organics is not evidence of life or evidence of past life. It’s just evidence for organics,” he said.

But if NASA had realized there were organics on Mars, there might not have been a 20-year hiatus in sending landers for follow-up studies, said Rafael Navarro-González, with the Institute of Nuclear Science at the National Autonomous University in Mexico.

“We might have had continuing missions,” Navarro-González told Discovery News.

NASA plans to launch a follow-up mission to look for organics on Mars in November.

The research appears in last month’s Journal of Geophysical Research.

© 2011 Discovery Channel

More than 30 years after NASA’s Viking landers found no evidence for organic materials on Mars, scientists say a new experiment on Mars-like soil shows Viking did, in fact, hit pay dirt.

The new study was prompted by the August 2008 discovery of powerful oxygen-busting compounds known as perchlorates at the landing site of another Mars probe called Phoenix.

Scientists repeated a key Viking experiment using perchlorate-enhanced soil from Chile’s Atacama Desert, which is considered one of the driest and most Marslike places on Earth, and found telltale fingerprints of combusted organics — the same chemicals Viking scientists dismissed as contaminants from Earth.

“Contrary to 30 years of perceived wisdom, Viking did detect organic materials on Mars,” planetary scientist Christopher McKay, with NASA’s Ames Research Center in California, told Discovery News. “It’s like a 30-year-old cold case suddenly solved with new facts.”

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“If the Viking team had said ‘Well, maybe there’s perchlorate in the soil,’ everybody would have said they’re crazy — why would there be perchlorates in the soil? It was only by having it pushed on us by Phoenix where we had no alternative but to conclude that there was perchlorate in the soil. … Once you realize it’s there, then everything makes sense,” McKay added.

The Viking team’s verdict that Mars lacked organics was the linchpin argument against another Viking experiment that looked for signs of microbial life. In the experiment, a bit of nutrient-laced water was added to a sample of Martian soil.

The air above the soil was then monitored for signs that the nutrients had been metabolized. The instrument detected tracer gases the first time the experiment was done, but subsequent runs did not. The results were considered inconclusive and remain contested.

New evidence for organics on Mars does not mean Viking found life, cautions McKay.

“Finding organics is not evidence of life or evidence of past life. It’s just evidence for organics,” he said.

But if NASA had realized there were organics on Mars, there might not have been a 20-year hiatus in sending landers for follow-up studies, said Rafael Navarro-González, with the Institute of Nuclear Science at the National Autonomous University in Mexico.

“We might have had continuing missions,” Navarro-González told Discovery News.

NASA plans to launch a follow-up mission to look for organics on Mars in November.

The research appears in last month’s Journal of Geophysical Research.

© 2011 Discovery Channel

GENEVA — Wintry skies darkened over Switzerland on Tuesday morning, but Romanians were treated to a pinkish ethereal light and Swedes to a beautiful sunrise, as a partial solar eclipse that began over the Mideast extended across much of Europe.

In Switzerland, the pall of clouds and light snow seemed like dusk with lights twinkling in cities — time in reverse just as people streamed off trains and buses to arrive at work. The solar occurrence was at its height over Geneva, Bern and other Swiss cities in the midmorning, then the grayness at the lower altitudes began to brighten a bit.

As much as two-thirds of the sun slipped from view behind the moon, something that hasn’t occurred in Switzerland since August 1999. A more minor eclipse happened in August 2008.

Some Genevois asked via Twitter how they could see the eclipse as it snowed.

Federal health officials warned people, especially children, to wear special eye protection rather than use homemade gear to see the eclipse. The Swiss government itself tweeted: “An astronomical show, but watch the eyes!”

For some the weather lent that protection. “It was covered,” Delio Macchi of the Neuchatel observatory said of the effect in Swiss skies.

Clear skies over southern Romania offered a chance to glimpse a pale pink, otherworldly glow that spread over Bucharest, the capital. People climbed atop snow-coated high-rise buildings to get a better view, or donned sunglasses and huddled outside subway stations in Revolution Square. Some watched it televised live; Romanians won’t see their next eclipse until March 2015.

“This morning I saw a strange light,” said Andrei Carlescu, a 21-year-old architecture student who was fascinated by the way the light dipped. “At first I didn’t know what was happening. There were children about 9 or 10 who were wearing special glasses and looking at it.”

The eclipse was first seen Tuesday over Jerusalem, where the sun appeared to have taken a large bit out of its upper right section.

A solar eclipse happens when the moon lines up between the sun and the Earth, casting a lunar shadow on the Earth’s surface and obscuring the solar disk. During a partial solar eclipse, only part of the sun is blotted out.

Western Europe woke up to a sunrise eclipse. Astronomers expected the greatest eclipse over Sweden, where about 85 percent of the sun will be blocked.

“It’s thanks to the position of the moon and so the shadow (of it) is very small,” said Niclas Henricson, head of the Tycho Brahe observatory in southern Sweden.

Ten people had gathered at Henricson’s observatory ready to check it out with their mobile telescopes should the cloudy weather disperse. He said Swedes only have such an opportunity about once every four to five years; their next full solar eclipse will be in 2126.

Rather than miss out, Christian Ander, a 31-year-old IT entrepreneur, went to a park to watch it, though he said that because it occurred so early in the morning, it wasn’t as noticeable as it might have been if it had happened later in the day.

“It was beautiful,” he said. “It was kind of like a sunrise.”

Polish viewers were treated to live television coverage of the eclipse from the southern city of Krakow, where the shadow of the moon could be seen gradually blacking out the sun.

The golden croissant-like shape was visible in the dark sky in the morning. However, most of Poland was covered by clouds that blotted out the spectacular sight.

A sunset eclipse will be visible from central Russia, Kazakhstan, Mongolia and northwest China.

___

AP writers Monika Scislowska in Warsaw, Louise Nordstrom and Malin Rising in Stockholm and Alison Mutler in Bucharest contributed to this report.

Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

A 10-year-old girl from Canada has discovered a supernova, making her the youngest person ever to find a stellar explosion.

The Royal Astronomical Society of Canada announced the discovery by Kathryn Aurora Gray of Fredericton, New Brunswick, (wonderful middle name!) who was assisted by astronomers Paul Gray and David Lane.

Supernova 2010lt is a magnitude-17 supernova in galaxy UGC 3378, in the constellation of Camelopardalis, as reported on IAU Electronic Telegram 2618. The galaxy was imaged on New Year’s Eve 2010, and the supernova was discovered on Jan. 2, 2011, by Kathryn and her father Paul.

The observations were made from Abbey Ridge Observatory, and this is the third supernova seen from this observatory. It was Lane’s fourth supernova discovery, Paul Gray’s seventh, and Kathryn Gray’s first.

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The discovery was soon verified by Illinois-based amateur astronomer Brian Tieman and Arizona-based Canadian amateur astronomer Jack Newton.

Since a supernova can outshine millions of ordinary stars, it can be easy to spot with a modest telescope — even in a distant galaxy such as UGC 3378, which is about 240 million light-years away. The trick is to check previous images of the same location to see if there are any changes. That’s what Kathryn was doing for the images of the galaxy taken by her father.

Supernovas are stellar explosions that signal the violent deaths of stars several times more massive than our sun, and can be used to estimate the size and age of our universe.

Supernovas are rare events. The Chandra X-Ray Observatory found evidence of a supernova explosion that occurred about 140 years ago in our galaxy (although no one saw the explosion take place), making it the most recent in the Milky Way. Previously, the last known supernova in our galaxy occurred around 1680, an estimate based on the expansion of its remnant, Cassiopeia A.

Source:
Royal Astronomical Society of Canada. Universe Today report:
“10-year-old girl discovers a supernova.”

Copyright © 2011 Universe Today. Republished with permission.