Universe Today

April 2, 2008December 24, 2015 by Tammy Plotner

Venus’ Variable Evolution

For every backyard astronomer, we know 4.5 billion years ago, both Venus and Earth were formed with nearly the same radius, mass, density and chemical composition. Venus is like Earth’s evil twin, but why is the climate on both worlds so widely varied? Scientists analysing the data from the orbiting European Venus Express spacecraft are finally putting the pieces of the geological and climatological puzzle together as they take a closer look at Venusian evolution.

Today, Professor Fred Taylor of Oxford University presented the scenario in a talk at the Royal Astronomical Society National Astronomy Meeting in Belfast. According to the studies, Venus appeared to have evolved very rapidly compared to the Earth during the early formation of the solar system. Thanks to data obtained from the Venus Express, it would appear our wicked sister planet once had significant volume of water covering the surface… Oceans which were lost in a very short geological timescale. As the water disappeared, the geological evolution of the surface of Venus slowed quickly – unable to develop plate tectonics like the Earth. Biological evolution could never happen. If, at one time, Venus mirrored Earth in climate and habitability terms, then it evolved too quickly at first, then too slowly.

‘They may have started out looking very much the same,’ said Professor Taylor, ‘but increasingly we have evidence that Venus lost most of its water and Earth lost most of its atmospheric carbon dioxide.’

Here on Earth, carbon dioxide is captive plant life, minerals and the crust itself. Not to harp on global warming, but the release CO2 back into the atmosphere is a source of climatic change. On Venus, the majority of the carbon dioxide resides it its atmosphere, leaving the surface temperature at a searing 450 degrees Celsius. This slows or stops geological as well as biological evolution.

‘The interesting thing is that the physics is the same in both cases’ said Prof Taylor. ‘The great achievement of Venus Express is that it is putting the climatic behaviour of both planets into a common framework of understanding.’

But, we haven’t heard the last from Venus Express just yet. Due to operate until May 2009, scientists involved in the project are already busy applying for an extension until 2011.

‘We have plans for joint operations with the Japanese spacecraft called Venus Climate Orbiter that will arrive in December 2010’, said Taylor. ‘Together, we can do things neither could do alone to crack some of the remaining puzzles about Venus.’

April 2, 2008December 24, 2015 by Tammy Plotner

The Sun’s Magnetic Fountains

For you solar observing fans, enjoy the beauty. Over the years both the public and astronomers alike have witnessed the Sun’s volatile and ever-changing atmosphere. Before our eyes huge geysers of hot gas spew into the solar corona at tens of thousands of km per hour. Every few minutes they erupt and reach dynamic proportions. Now a team of scientists have used the Hinode spacecraft to find the origin and progenitor of these fountains – immense magnetic structures that thread through the solar atmosphere.

Today at the Royal Astronomical Society National Astronomy Meeting in Belfast (NAM 2008), team leader Dr. Michelle Murray from the Mullard Space Science Laboratory (MSSL, University College London) presented the latest results from Hinode spacecraft combined with computer emulated solar conditions. Since its launch in October 2006, scientists have been using Hinode to examine the solar atmosphere in extraordinary detail. One of it’s premier instruments is the Extreme Ultraviolet Imaging Spectrometer. The EIS generates images of the Sun and gives information on the speed of the moving gases.

At the core of the solar magnetic field, immense jets of hot gas are forced to the surface through increases in pressure. Just like an earthly geyser, when the pressure releases the gases fall back towards the Sun’s surface. But what causes the pressure? Unlike the volcanic activity that drives the terrestrial phenomena, solar fountains are caused by rearrangements of the Sun’s magnetic field, a continual process that results in looping cycles of increasing and decreasing pressure.

“EIS has observed the Sun’s fountains in unprecedented detail and it has enabled us to narrow down the fountains’ origins for the first time”, comments team member and MSSL postgraduate student Deb Baker. “We have also been able to find what drives the fountains by using computer experiments to replicate solar conditions.”

The sun-observing Hinode satellite is now in a sun-synchronous orbit, which allows it to observe the sun for uninterrupted periods lasting months at a time. Using a combination of optical, EUV and X-ray instrumentation Hinode will study the interaction between the Sun’s magnetic field and its corona to increase our understanding of the causes of solar variability.

“The computer experiments demonstrate that when a new section of magnetic field pushes through the solar surface it generates a continual cycle of fountains”, explains Dr. Murray, “but new magnetic fields are constantly emerging across the whole of the solar surface and so our results can explain a whole multitude of fountains that have been observed with Hinode.”

April 2, 2008December 24, 2015 by Nancy Atkinson

New Search Technique May Lead to Discovery of Extra-solar Earth-Like Planets

The Holy Grail in the search for extra-solar planets would be to find an Earth-like world orbiting another star. A group of UK astronomers believe they have good chance of being the first to find such a planet with a revolutionary new camera called RISE. With RISE, scientists will search for extra-solar planets using a technique called â€œtransit timing,â€ which may provide a short-cut to discovering Earth-like planets with existing technology.

The two primary techniques to find extra-solar planets are usually only sensitive to massive, gas giant planets in close orbit around their parent star, so-called â€œHot Jupiters.â€ Firstly, planets can be found through their gravitational pull on the star they orbit – as the extra-solar planet moves the star wobbles back and forth, and by measuring this movement astronomers can deduce the presence of a planet. Secondly, the transit search technique looks for the changes in a starâ€™s brightness as a planet passes in front of it.

But neither of these techniques is currently good enough to find small extra-solar planets similar to the Earth. With the new transit timing technique, the RISE camera will look for Earth-mass planets in orbit around stars already known to host Hot Jupiters.

Transit timing works on the principle that an isolated hot Jupiter planet orbiting its host will have a constant orbital period (i.e. its ‘year’ remains the same) and therefore it will block out the light from its parent star in a regular and predictable way. During the planet’s transit events, RISE can very accurately measure the rise and fall in the amount of light reaching the Earth from the parent star – the camera can be used to pinpoint the time of the centre of the event to within 10 seconds. RISE is a fast-read camera. It has a fixed “V+R” filter and reimaging optics giving a 7 x 7 acrminute field of view to maximize the number of comparison stars available. An e2V frame transfer detector is used to obtain a cycle time of less than 1 second.

By observing and timing their transits, astronomers hope to detect small changes in the orbital periods of known hot Jupiters caused by the gravitational pull of other planets in the same system. In the right circumstances, even planets as small as the Earth could be found in this way.

â€œThe potential of transit timing is the result of some very simple physics, where multi-planet systems will gravitationally kick one another around in their orbits – an effect often witnessed in our own Solar System,â€ said PhD student Neale Gibson of Queen’s University Belfast. â€œIf Earth-mass planets are present in nearby orbits (which is predicted by current Hot-Jupiter formation theories) we will see their effect on the orbit of the larger transiting planets. RISE will allow us to observe and time the transits of extrasolar planets very accurately, which gives us the sensitivity required to detect the effect of even small Earth-mass planets.â€

RISE was designed by astronomers at Queen’s University in collaboration with Liverpool John Moores University and is now installed on the 2 meter Liverpool Telescope on the Canary Island of La Palma. For more information about the RISE Camera, see Neale Gibson’s homepage.

Original News Source: NAM Press Release

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