Universe Today

April 2, 2008December 24, 2015 by Nancy Atkinson

STEREO Spacecraft Captures Footage of a Solar Tsunami

A solar tsunami blasted its way through the sunâ€™s lower atmosphere on May, 19 2007, and the action was captured by the twin STEREO spacecraft. Solar tsunamis are launched by huge explosions near the Sun’s atmosphere, called coronal mass ejections (CMEs). Although solar tsunamis share much in common with tsunamis on Earth, the solar version can travel at over a million kilometers per hour. Last yearâ€™s tsunami blasted and rolled for about 35 minutes, reaching peak speeds around 20 minutes after the initial flare. The observations were made by a team from Trinity College, Dublin.

“The energy released in these explosions is phenomenal; about two billion times the annual world energy consumption in just a fraction of a second. In half an hour, we saw the tsunami cover almost the full disc of the Sun, nearly a million kilometers away from the epicenter,” said David Long, a member of the team that made the observations.

STEREO’s Extreme Ultraviolet Imager (EUVI) instruments monitor the Sun at four wavelengths which correspond to temperatures ranging between 60,000 and 2 million degrees Celsius. At the lowest of these temperatures, scientists can see structures in the chromosphere, a thin layer of the solar atmosphere that lies just above the Sun’s visible surface. At temperatures between 1 and 2 million degrees Celsius, scientist can monitor features at varying levels in the solar corona.

The SOHO spacecraft, which was launched in 1995, also monitors the Sun at these wavelengths but only took images four times per day, giving scientists rare snapshots of these tsunamis. STEREO’s EUVI instruments take an image every few minutes to create a series, making it possible for scientists to track how the wave spreads over time.

Click here for a Quicktime animation of the event.

This is the first time that a tsunami has been observed at all four wavelengths, which enabled the team to see how the wave moved through the different layers of the solar atmosphere.

“To our surprise, the tsunami seems to move with similar speed and acceleration through all the layers. As the chromosphere is much denser than the corona, we’d expect the pulse there to drag. It’s a real puzzle,” said Dr. Peter Gallagher, another member of the team.

To complicate matters, the interval between images is not the same for all four cameras. At the time of the tsunami, the cameras monitoring radiation at 1 million degrees Celsius were set to take an image every 2.5 minutes. They recorded much higher speeds and accelerations for the wave than the other cameras, which were on 10 or 20 minute cycles. By taking a sample of one image in four, the data from these cameras matched the lower values observed in the other layers.

“We’ve thought for some time that the tsunamis might be caused by magnetic shockwaves but, in previous snapshots, the waves appeared to be travelling too slowly. However, we’ve seen from this set of observations that if the time interval between images is too long, it’s easy to underestimate the speed that the waves are moving. With a few more rapid-sequence observations of solar tsunamis, we should finally be able to identify the cause of these waves,” said Gallagher.

The discovery will be presented by David Long at the RAS National Astronomy Meeting in Belfast on Wednesday April 2, 2008.

For more information and animations, see Trinity College’s pageabout the solar tsunami.

Original News Source: RAS press release

April 1, 2008December 24, 2015 by Ian O'Neill

So, What Does an Anti-Satellite Weapon Actually Look Like?

In February, the Universe Today followed the sad tale about a dead US satellite called US-193, lifelessly floating around in orbit, possibly threatening the world by dumping hazardous fuel onto a city somewhere. This was the perfect time for the US Navy to launch their Standard Missile-3 (SM-3) into space, smashing US-193 to tiny bits. It worked and it worked well.

Although we’ve seen loads of pictures of the rocket being launched, and the pinpoint accuracy it accomplished by detonating in low Earth orbit, but what technology goes into the actual warhead that takes out the satellite? Well, in an article just published, images of an older generation “Kinetic Energy” anti-satellite weapon are on display. And to be honest, it doesn’t look that scary…

There’s more than one way to kill a satellite. You can make it self destruct by firing its thrusters, sending it in a deadly descent through the atmosphere. But say if you don’t have communication with the craft? You could capture it in orbit using a robotic or manned spaceship. But this would be prohibitively expensive and dangerous. You could simply shoot it down… now this idea (although far from beingÂ “simple”) is the most popular and effective method to get rid of a satellite from orbit.

The anti-satellite (ASAT) idea has been around since the Cold War, as far back as the 1960’s, but very little information is available. In fact, according to Dwayne Day’s article in The Space Review on the 31st March, since the Cold War nobody has been bothered to write much about American ASAT technology development, policy, and doctrine. It is unclear if this is down to the military being (understandably) secretive, or whether people simply lost interest in the “Star Wars” program proposed by U.S. President Ronald Reagan in 1983.

But there are some clues as to the US anti-satellite capabilities back in the 1990’s, namely a cool-looking mock-up of one of Lockheed’s proposals for a kinetic energy anti-satellite warhead (or KE-ASAT, pictured left), the author discovered at the Aerospace Legacy Foundation’s offices located at the former North American Aviation Downey factory. The owner, a Dr. Jim Busby showed off a low fidelity mock-up of a Lockheed KE-ASAT, which he acquired in the early 1990s, when a previous owner discarded it.

It’s a strange-looking device, resembling a mini-spaceship capsule (although, from the images and description, it is unclear how big it is) that would have sat on top of a rocket booster to send it from the ground and into space to hit its satellite target. This type of anti-satellite does not explode on impact; it relies on huge velocities and a high mass to generate enough kinetic energy to destroy the target on impact.

Some variations on this theme may have included a Kevlar “fly swatter” that would expand on impact, making it easier to hit the satellite and destroy it.

It is obvious from the images that the mass of the warhead is packed in the red cone at the front of the weapon; the infrared heat-seeker targeting system would also be housed there. There is also a main thruster (that would fire to life once the rocket boosters had carried it into space), and attitude controls at the rear to guide the high velocity projectile to its target. A similar method was used by the February 20th US spy satellite intercept, so the proposed technology this KE-ASAT is built on is not far from the current method employed by the US Navy.

Alas, the KE-ASAT never made it to the production line as Lockheed’s bid for use in an anti-satellite program was beaten by the Rockwell company in July 1990, the US Army opted for a far different-looking design, not dissimilar to the ASAT used today. Personally I think the Lockheed concept looked better, but would have been very scary, causing a huge mess…

Source: The Space Review

April 1, 2008December 24, 2015 by Astronomy Cast

Podcast: Space Junk

We’re polluting every corner of our own planet, so it only makes sense that we’ll take our trashy habits out into space with us. This week we look at the myriad of ways we’re messing up space, from the trash orbiting the planet to the radiation we’re leaking out into space.

Click here to download the episode

Space Junk – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

April 1, 2008December 24, 2015 by Fraser Cain

Astronomers Find the Smallest Black Hole

Black holes seem to have no upper limit; some weigh in at hundreds of millions of times the mass of the Sun. But how small can they be? Astronomers have discovered what they think is the least massive black hole ever seen, with a mere 3.8 times the mass of the Sun, and a diameter of only 25 km (15 miles) across.

The announcement was made by Nikolai Shaposhnikov of NASAâ€™s Goddard Space Flight Center and his colleagues at the American Astronomical Society High-Energy Astrophysics Division currently being held in Los Angeles, California.

The “tiny” black hole, known as XTE J1650-500, was discovered back in 2001 in a binary system with a normal star. Astronomers had known about the binary system for several years, but they were finally able to make accurate measurements using NASA’s Rossi X-ray Timing Explorer (RXTE) to pin down the mass.

Although black holes themselves are invisible, they’re often surrounded by a disk of hot gas and dust – material chokes up, like water going down the drain. As the hot gas builds up, it releases torrents of X-rays at regular intervals.

Astronomers have long suspected that the frequency of these X-ray blasts depend on the mass of the stars. As the mass of the black hole increases, the size of the accretion disk expands outward too; there are less frequent X-ray emissions.

By cross referencing this method with other, established techniques for weighing black holes, the team is very confident that they’ve got the trick to measuring black hole mass.

When they applied their technique to XTE J1650-500, they turned up a mass of 3.8 Suns, give or take half a solar mass. This is dramatically smaller than the previous record holder at 6.3 Suns.

What’s the smallest possible black hole? Astronomers think it’s somewhere between 1.7 and 2.7 solar masses. Smaller than that and you get a neutron star. Finding black holes that approach this lower limit will help physicists better understand how matter behaves when its crushed down in this extreme environment.

Original Source: NASA News Release

April 1, 2008April 6, 2008 by Fraser Cain

Virgin/Google’s Mission to Mars: Virgle

Set your April jokes on fool, dear reader because it’s April 1st. That means there’ll be a non-stop barrage of April Fools Jokes coming at you from all directions. We had to join in the fun, but we’re not the only ones. Check out this “offering” from Virgin Galactic and Google. They’re going to be setting up a colony on Mars and they’re looking for volunteers. You’ve got to know it’s serious because Google founders Sergey Brin and Larry Page make the offer personally. I like how they mentioned the one-way trip idea. Is someone reading Universe Today?

And Branson’s version is here:

April 1, 2008December 24, 2015 by Fraser Cain

National Astronomical Meeting 2008 Coverage

You’re going to see a flurry of astronomy news this week. That’s because it’s time for the UK’s National Astronomical Meeting, or NAM 2008. We couldn’t get to this one, but our friends across the ocean have it covered. Chris Lintott and Orbiting Frog team are going to be live blogging the conference.

Click here to read the NAM 2008 live coverage.

April 1, 2008December 24, 2015 by Nancy Atkinson

Early Universe Had Burst of Star Formation

Just as humans develop and grow the fastest when we are young, it also appears our universe grew and developed stars at an incredibly fast rate when it was young, too. New measurements from some of the most distant galaxies helps support evidence that the strongest burst of star formation in the history of the universe occurred about two billion years after the Big Bang. An international team of astronomers from the UK, France, Germany and the USA have found evidence for a dramatic surge in star birth in a newly discovered population of massive galaxies. The astronomers have been studying five specific galaxies that are forming stars at an incredible rate. The galaxies also have large reservoirs of gas to power star formation for hundreds of millions of years. These galaxies are so distant that the light we detect from them has been travelling for more than 10 billion years, meaning we see them as they were about a three billion years after the Big Bang.

The recent discovery of a new type of extremely luminous galaxy during this early epoch of the universe – one that is very faint in visible light, but much brighter at longer, radio wavelengths – is the key to the new results. Using a new and much more sensitive camera that detects radiation emitted at sub-millimeter wavelengths (longer than the wavelengths of visible light that we see with but somewhat shorter than radio waves), astronomers first found this type of galaxy in 1997. In 2004 a group of astronomers proposed that these distant “submillimetre-galaxies” might only represent half of the picture of rapid star formation in the early Universe. They suggested that a population of similar galaxies with slightly hotter temperatures could exist but have gone largely unnoticed.

The team of scientists searched for the missing galaxies using observatories around the world: the MERLIN array in the UK, the Very Large Array (VLA) in the US (both radio observatories), the Keck optical telescope on Hawaii and the Plateau de Bure submillimetre observatory in France. The instruments found and pinpointed the galaxies, measured their distances and then confirmed their star-forming nature through the detection of the vastly extended gas and dust.

Click here for more images and a movie of the Sub-millimeter Star Forming Galaxies.

The new galaxies have extremely high rates of star formation, far higher than anything seen in the present-day universe. They probably developed after the first stars and galaxies had already formed in what would have been a perfectly smooth Universe. Studying these new objects gives astronomers an insight into the earliest epochs of star formation after the Big Bang.

This information was presented by Dr. Scott Chapman from the Institute of Astronomy in Cambridge at the Royal Astronomy Society’s National Astronomy Meeting on April 1, 2008. Chapman’s work is supported by a parallel study made by PhD student Caitlin Casey.

Original News Source: Royal Astronomy Society Press Release

April 1, 2008December 24, 2015 by Nancy Atkinson

Supernova Alert: Supernova Factories Discovered

Two â€œsupernova factories,â€ rare clusters of Red Supergiant (RSG) stars, have recently been discovered. Together they contain 40 RSGs, which is nearly 20% of all the known RSGs in the Milky Way, and all 40 are on the brink of going supernova. â€œRSGs represent the final brief stage in a massive starâ€™s lifecycle before it goes supernova,â€ said Dr. Ben Davies of the Rochester (New York) Institute of Technology. â€œThey are very rare objects, so to find this many in the same place is remarkable.â€

The two clusters are located next to each other on the edge of the central galactic bar, a long bar of stars within the central bulge of our Milky Way Galaxy. This galactic bar is believed to be made up of about 30 million stars, most of them older, red stars, and stretches 27,000 light-years from end to end. The bar is plowing through the disc of the Milky Way, and astronomers believe the interaction between the bar and the disc triggered the star formation event, creating the uncommon clusters.

The clusters are about 20,000 light years from Earth and about 800 light years from each other. Cluster 1 contains 14 RSGs and is 12 million years old; Cluster 2 contains 26 RSGs and is 17 million years old. Massive stars are rarely observed because they burn their fuel up very quickly. RSGs are doubly rare because they are only a brief period of that short life cycle.

Dr. Davies said, â€œThe next supernova could go off in one of these clusters at any time. We estimate that itâ€™s about 5000 years between explosions for these clusters and we can see the remnants of a supernova that went off around 5000 years ago. That means that the next one could be any time between today and 7008 AD.â€

The team identified the clusters initially using the mid-infrared Galactic Plane survey (GLIMPSE), a huge database of images taken by the Spitzer Space Telescope. They found two distinct groupings of bright stars very close to one another in the constellation of Scutum. Using the Keck Telescope in Mauna Kea, Hawaii, they were then able to pin-point the exact distance from Earth of each star in each group. These observations showed that, in each group, large numbers of stars were at exactly the same distance from Earth, and therefore were members of the same cluster.

â€œThe discovery of these clusters gives us a great opportunity to answer some long-standing questions in astrophysics,â€ said Davies, â€œsuch as exact mechanisms of how massive stars evolve toward supernovae, and how the Galactic Bar can trigger huge starburst events in the Milky Way.â€
Davies presented his findings at the Royal Astronomy Societyâ€™s National Astronomy Meeting in Belfast on April 1, 2008.

Original News Source: Royal Astronomy Society Press Release

April 1, 2008December 24, 2015 by Tammy Plotner

Solar Corona Revealed by Medical X-Ray Techniques

For several decades solar scientists have been hard at work trying to unravel the mysteries of the solar corona. Thanks to a medical x-ray technique known as tomography, scientists are able resolve solar activity in greater detail. By using a new way of processing images, active regions now take on dimensions never foreseen by computer models.

Today Dr. Huw Morgan presented his results to the Royal Astronomical Society National Meeting in Belfast. Using an adapted medical X-ray technique, scientists have produced the first detailed map of the structure of the Sun’s outermost layer, the corona. The application known as tomography uses a series of images taken from many different angles to reconstruct a 3-dimensional map created from direct solar observations.

“This is a breakthrough for scientists trying to understand the corona and the solar wind. We’ve been attempting to apply tomography to the solar corona for more than 30 years but it’s proved very difficult and very inaccurate until now. The new technique that I’ve developed is only in its infancy but shows great potential for areas of research like space weather,” said Dr Morgan, of the University of Aberystwyth.

The process has not been as easy one, nor is it a new idea. Without images of the coronal far side, researchers were left with only half the data. The near side produces its own difficulties as well, since the outermost areas of the corona are more than a thousand times fainter than the regions near the Sun. This factor introduces huge potential errors to observations. Thanks to Dr. Morgan, his new way of processing coronal images, called Qualitative Solar Rotational Tomography (QSRT), eliminates the steep drop in brightness and associated errors. With the help of SOHO’s LASCO instrument, Dr. Morgan applied the technique to a series of images taken as the Sun’s rotation brings the ‘missing’ areas into view. The result? Full coronal maps that are at least 5 times more detailed than previous tomographical studies of the Sun. And the future may hold far more. Says Morgan:

“I’ve now produced maps of the corona over almost a whole cycle of solar activity, so we can now see in unprecedented detail how structures develop and evolve in three-dimensions. The maps have produced some interesting results: for instance we’ve observed large areas of dense structures when the Sun is most active that are not predicted by current computer models. We’ve also found evidence that inner regions of the corona rotate at different speeds.”

According to the RAS press release, the technique is already being used by scientists at the Institute of Maths and Physics at Aberystwyth University to interpret their radio-wave observations of the solar wind. Dr. Morgan, together with colleagues at the Institute of Astronomy at the University of Hawaii, is also using the maps to interpret ultraviolet observations of the corona. Says Dr. Morgan:

“These maps will also prove useful in the important field of space weather. Explosions at the Sun travel through space and often hit the Earth. These energetic magnetic clouds can disrupt communication, power supplies and be a major health hazard for astronauts and airline pilots. Understanding and predicting these storms is a major goal of solar science. The ability to map the whole 3D structure of the corona is a critical step towards achieving this goal.”

April 1, 2008December 24, 2015 by Tammy Plotner

Old Galaxies Stick Together In A Young Universe

Can appearances be deceiving? According to the United Kingdom Infra-Red Telescope (UKIRT), galaxies that appear old in our Universe’s early history are positioned in huge clouds of dark matter. Using the most sensitive images ever taken, UKIRT scientists believe these galaxies will evolve into the most massive yet known.

Today University of Nottingham PhD student Will Hartley is speaking to the Royal Astronomical Society’s National Astronomy Meeting in Belfast. As the leader of the study, Hartley proposes the distant galaxies identified in the UKIRT images are considered elderly from their content of old, red stars. Because these systems are nearly 10 billion light years distant, the images are as the galaxies appeared about 4 billion years after the Big Bang. Fully evolved galaxies at that point in time are hard to explain and the answer has been puzzling astronomers who study galactic formation and evolution.

Hartley and his team used the deep UKIRT images to estimate the mass of the dark matter formed in a halo surrounding the old galaxies – a halo which collapses under its own gravity to form a even distribution of matter. By measuring their ability to form galactic clusters, astronomers can get a better sense of what causes older galaxies to stick together.

Hartley explains “Luckily, even if we don’t know what dark matter is, we can understand how gravity will affect it and make it clump together. We can see that the old, red galaxies clump together far more strongly than the young, blue galaxies, so we know that their invisible dark matter halos must be more massive.

The halos of dark matter surrounding the old galaxies in the early Universe are found to be extremely massive, containing material which is one hundred thousand billion times the mass of our Sun. In the nearby Universe, halos of this size are known to contain giant elliptical galaxies, the largest galaxies known.

“This provides a direct link to the present day Universe,” says Hartley, “and tell us that these distant old galaxies must evolve into the most massive but more familiar elliptical-shaped galaxies we see around us today. Understanding how these enormous elliptical galaxies formed is one of the biggest open questions in modern astronomy and this is an important step in comprehending their history.”