Universe Today

February 22, 2008December 26, 2015 by Fraser Cain

Milky Way is Twice as Thick as Previously Believed

Imagine suddenly realizing that your house was twice as big as you originally thought. Okay, maybe that’s a little out there, but astronomers from Australia have calculated that the Milky Way is actually twice as thick as previously believed – doubling from the originally estimated 6,000 light-years to 12,000 light-years.

The calculation was made by a couple of astronomers from the University of Sydney. They were working with the accepted numbers for the dimensions of our home galaxy (6,000 light years thick, and 100,000 light-years wide) when they thought it might make sense to double check those basic assumptions.

They used an accepted technique for calculating distance; measuring the light from pulsars. When light from distant pulsars moves through the background material of the Milky Way (known as the Warm Ionised Medium), it slows down. The redder pulses of light actually slow down more than the bluer pulses.

By measuring the change in light from the pulsar, astronomers can determine how much material the light has traveled through.

When they used the old calculations for 40 different pulsars inside and above it, they got the old numbers. But when they just looked at 17 pulsars which are above and below the galactic disk they got a new, more accurate, estimate.

“Of the thousands of pulsars known in and around our Galaxy, only about 60 have really well known distances,” said Professor Bryan Gaensler. “But to measure the thickness of the Milky Way we need to focus only on those that are sitting above or below the main part of the Galaxy; it turns out that pulsars embedded in the main disk of the Milky Way don’t give us useful information.”

Their results were presented in January at the annual meeting of the American Astronomical Society in Austin, Texas. Some of Dr. Gaensler’s colleagues appreciated the revised calculations, while others… not so pleased at the implications for their own research.

Original Source: University of Sydney

February 22, 2008December 26, 2015 by Fraser Cain

Send in Your Eclipse Pictures, Tell Your Stories

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How was your view of this week’s lunar eclipse? The skies actually opened up here in Vancouver, and we were able to see good portions of the eclipse. The kids were really excited, and got to stay up late watching the eclipse – it was all they were talking about the next day.

So send me your eclipse pictures, and I’ll run a quick gallery. Email them to me at [email protected], and I’ll try to post them in the next few days.

And to tide you over, here’s an image captured by ESA astronomers from Spain.

Post your eclipse stories in the comments below.

February 22, 2008December 29, 2015 by Fraser Cain

Carnival of Space #42

It’s time for another look around the space/astronomy community of websites. This week, the Carnival of Space is being hosted by celebrity blogger, Chris Lintott. Check this week’s collection of stories, including, the search for dark matter, the end of an important observatory, and a good long look at some of Saturn’s moons.

Click here to read the Carnival of Space #42

And if you’re interested in looking back, here’s an archive to all the past carnivals of space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let me know if you can be a host, and I’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the Carnival of Space. Help us get the word out.

February 22, 2008December 26, 2015 by Nancy Atkinson

Ulysses Spacecraft Dying of Natural Causes

“One equal temper of heroic heart
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.”
—from the poem “Ulysses” by Alfred, Lord Tennyson

The Ulysses spacecraft has been heroically studying our sun for more than 17 years, almost four times its expected lifetime. But now, the mission might be finally succumbing to the harsh environment of space. Mission managers say the spacecraft will likely “die” in the next month or two.

“Little remains; but every hour is saved
From that eternal silence, something more,
A bringer of new things;
To Follow knowledge like a sinking star,
Beyond the utmost bound of human thought.”
(more from “Ulysses”)

Ulysses is a joint mission between ESA and NASA that was launched in 1990 during space shuttle mission STS-41. Ulysses was the first mission to study the environment of space above and below the poles of the Sun. The spacecraft has returned a huge amount of data that has changed the way scientists view the Sun and its effect on the space surrounding it.

Ulysses is in a six-year orbit around the Sun. Its long orbital path carries it out to Jupiter’s orbit and back again. The further it ventures from the Sun, the colder the spacecraft becomes. If it drops to 2ºC, the spacecraft’s hydrazine fuel will freeze.

This has not been a problem in the past because Ulysses carries heaters to maintain a workable on-board temperature. The spacecraft is powered by the decay of a radioactive isotope and over the 17-plus years, the power it has been supplying has been steadily dropping. Now, the spacecraft no longer has enough power to run all of its communications, heating and scientific equipment simultaneously.

“We expect certain parts of the spacecraft to reach 2ºC pretty soon,”says Richard Marsden, ESA’s Ulysses Project Scientist and Mission Manager. This will block the fuel pipes, making the spacecraft impossible to maneuver.

The ESA-NASA project team had tried to solve this problem by temporarily shutting of the main spacecraft transmitter, which would provide 60 watts of extra power that could be channeled back to the heater and science instruments. Unfortunately, the transmitter failed to turn back on.

“The decision to switch the transmitter off was not taken lightly. It was the only way to continue the science mission,”says Marsden, who is a 30-year veteran of the project, having worked on it for 12 years before the spacecraft was launched.

After many attempts, the Ulysses project team now consider it highly unlikely that the X-band transmitter will be recovered. They believe the fault can be traced to the power supply, meaning that the extra energy they hoped to gain cannot be routed to the heater and science instruments after all.

So, the spacecraft’s fuel lines are gradually freezing. This spells the end of this highly successful mission.

“Ulysses is a terrific old workhorse. It has produced great science and lasted much longer than we ever thought it would,” says Marsden. “This was going to happen in the next year or two, it has just taken place a little sooner than we hoped.”

The team plan to continue operating the spacecraft in its reduced capacity for as long as they can over the next few weeks. “We will squeeze the very last drops of science out of it,” says Marsden.

“Death closes all; but something ere the end,
Some work of noble note, may yet be done…
‘Tis not too late to seek a newer world…
To sail beyond the sunset.”
—more from “Ulysses” by Tennyson

Original News Source: ESA Press Release

February 22, 2008December 26, 2015 by Nancy Atkinson

An Elegant Proposal for Near Earth Asteroid Deflection

Although the chances of an asteroid hitting Earth appear to be small for any given year, the consequences of such an event would be monumental. The science community has come up with some ideas and proposals for ways to mitigate the threat of an incoming asteroid hitting the Earth. Some proposals suggest almost Hollywood type theatrics of launching nuclear weapons to destroy the asteroid, or slamming a spacecraft into a Near Earth Object to blow it apart. But other ideas employ more simple and elegant propositions to merely alter the trajectory of the space rock. One such plan uses a two-piece solar sail called a solar photon thruster that draws on solar energy and resources from the asteroid itself.

Physicist Gregory Matloff has been working with NASA’s Marshall Spaceflight Center to study the two-sail solar photon thruster which uses concentrated solar energy. One of the sails, a large parabolic collector sail would constantly face the sun and direct reflected sunlight onto a smaller, moveable second thruster sail that would beam concentrated sunlight against the surface of an asteroid. In theory, the beam would vaporize an area on the surface to create a ‘jet’ of materials that would serve as a propulsion system to alter the trajectory of the Near Earth Object (NEO.)

Changing the trajectory of a NEO exploits the fact that both the Earth and the impactor are in orbit. An impact occurs when both reach the same point in space at the same time. Since the Earth is approximately 12,750 km in diameter and moves at about 30 km per second in its orbit, it travels a distance of one planetary diameter in about seven minutes. The course of the object would be altered, or either delayed or advanced and cause it to miss the Earth.

But of course, the arrival time of the impactor must be known very accurately in order to forecast the impact at all, and to determine how to affect its velocity.

Additionally, the solar photon thruster’s performance would vary depending on the unique makeup of each NEO. For example, asteroids with a greater density, radius or rate of rotation would cause decreased performance of the solar photon thruster in acceleration and deflection.

Even though the solar photon thruster appears to be efficient in its performance, Matloff said that more than half of the solar energy delivered to the “hotspot” on the NEO would not be available to vaporize and accelerate the jet due to other thermodynamic processes such as conduction, convection, and radiation. As expected, a larger collector sail radius would increase the amount of energy available, and would increase acceleration of the NEO. Matloff said this system allows the sail craft to “tack” against the solar-photon breeze at a larger angle than conventional single solar sails can achieve.

This system of sails would not be attached to the NEO, but would be kept nearby the NEO “on station” either with its own thrusting capability or by auxiliary electric propulsion. More studies would be needed to ascertain if a supplementary propulsion system would be necessary.

The sails used in the study were both inflatable. However, Matloff believes it might be worth considering a small rigid thruster sail, which might simplify deployment and reduce occultation.

Said Matloff, “Hopefully, future design studies will resolve these uncertainties before application of NEO-diversion technology becomes necessary.”

February 22, 2008December 26, 2015 by Ian O'Neill

The Mysteries Behind the Dynamic Global Weather of Venus

As if the cloudy planet couldn’t get any more mysterious, Venus and its global weather patterns are baffling European Space Agency (ESA) scientists. The ESA Venus Express mission is continuing to unearth the details of what lies in and under its thick atmosphere, but Venus’s dynamic global weather patterns are very quick to consume the whole planet, like nothing we experience on Earth…

The ESA Venus Express missions Venus Monitoring Camera (VMC) is a long-term data gathering experiment to monitor the long-term progression of weather systems on the planet. On numerous occasions, the VMC has observed massive clouds of bright, hazy sulphuric acid particles form from equator to pole in a matter of days, only for it to disappear just as quickly. This suggests that fast dynamical, chemical and microphysical processes are at work on the planet in scales never before realized.

“This bright haze layer is made of sulphuric acid […] the process is a bit similar to what happens with urban smog over cities.” – Dmitri Titov, VMC Co-Investigator and Venus Express Science Coordinator, Max Planck Institute for Solar System Research, Germany.

With over 600 orbits completed, the VMC is observing the effects that solar radiation has on the dynamics of Venus’s atmosphere. It is well known that Venus’s atmosphere is carbon dioxide-rich and also contains water molecules and gaseous sulphur dioxide. Should this mix be exposed to UV radiation, the molecules will break up, forming a mix of highly reactive chemicals. As these chemicals bond, droplets of sulphuric acid form, creating planetary-scale clouds of bright haze. However, the planets atmosphere is too thick for much of the solar radiation to penetrate. For the gases to be exposed to UV radiation, some powerful atmospheric process must force them aloft, above much of the dense atmosphere, allowing them to react.

Although the bright haze of Venus’s atmosphere has been identified, many dark patches have also been observed. So far, there is no explanation for these patches of atmospheric chemicals absorbing solar UV, but the presence of the orbiting Venus Express is hoped to shine light on the dark and bright atmospheric features and how the atmosphere is mysteriously driving them.

Source: ESA

February 21, 2008December 26, 2015 by Ian O'Neill

Pulsars are Exploding Unexpectedly and “Magnetars” Might be to Blame

Pulsars are fast-spinning, highly radiating neutron stars. Most pulsars emit radio, X-ray and gamma radiation at regular intervals (usually periods of a few milliseconds to a few seconds), in fact many pulses keep the accuracy of the most accurate atomic clocks on Earth. However, occasionally, these rapidly rotating bodies undergo a violent change, blasting massive quantities of energy into space. Although short-lived (a fraction of a second), the observed explosion packs a punch of at least 75,000 Suns. Is this a natural process in the life of a pulsar? Is it a totally different type of cosmic phenomena? Researchers suggest these observations may be a different type of neutron star: magnetars disguised as pulsars (and without an ounce of dark matter in sight!)…

Neutron stars are a product of massive stars after a supernova. The star isn’t big enough to create a black hole (i.e. less than 5 solar masses), but it is big enough to create a tiny, dense and hot mass of neutrons (hence the name). Due to the “Pauli exclusion principal” – a quantum mechanical principal that prevents any two neutrons from having the same quantum characteristics within the same volume – neutron stars are also predicted to be very hot. Intense gravity forces matter into a tiny volume, but quantum effects are repelling the neutrons. After theÂ star has gone supernova, as neutron stars are so small (a radius of only 10 to 20 km), the small mass preserves the starsÂ angular momentum, resulting in a fast-spinning, highly radiating body.

Much of theÂ stars magnetism is also preserved, but in a vastly increased dense state. Neutron stars are therefore expected to have an intense magnetic field. It is in fact this magnetic field that helps to generate jets of emission from the magnetic poles of the rotating body, creating a beam of radiation (much like a lighthouse).

However, one of these flashing lighthouses has surprised observers… it exploded, blasting vast amounts of energy into space, and then continued to spin and flash as if nothing had happened. This phenomenon has recently been observed by NASA’s Rossi X-ray Timing Explorer (RXTE) and has been backed up by data from the Chandra X-ray Observatory.

There are in fact other classes of neutron star out there. Slow-spinning, highly magnetic “magnetars” are considered to be a separate type of neutron star. They are distinct from the less-magnetic pulsar as they sporadically release vast amounts of energy into space and do not exhibit the periodic rotation we understand from pulsars. It is believed that magnetars explode as the intense magnetic field (the strongest magnetic field believed to exist in the Universe) warps the neutron star surface, causing extremely energetic reconnection events between magnetic flux, causing violent and sporadic X-ray bursts.

There is now speculation that known periodic pulsars that suddenly exhibit magnetar-like explosions are actually the highly magnetic cousins of pulsars disguised as pulsars. Pulsars simply do not have enough magnetic energy to generate explosions of this magnitude, magnetars do.

Fotis Gavriil of NASA’s Goddard Space Flight Center in Greenbelt, and his colleagues analysed a young neutron star (called PSR J1846-0258 in the constellation Aquila). This pulsar was often considered to be “normal” due to its fast spin (3.1 revolutions per second), but RXTE observed five magnetar-like X-ray bursts from the pulsar in 2006. Each event lasted no longer than 0.14 seconds and generated the energy of 75,000 Suns. Follow up observations by Chandra confirmed that over the course of six years, the pulsar had become more “magnetar-like”. The rotation of the pulsar is also slowing down, suggesting a high magnetic field may be braking its rotation.

These findings are significant, as it suggests that pulsars and magnetars may be the same creature, just at different periods of a pulsars lifetime, and not two entirely different classes of neutron star…

Results of this research will be published in todayâ€™s issue of Science Express.

Source: AAAS Science Express

February 21, 2008December 26, 2015 by Ian O'Neill

Solar Variability Most Likely Not the Cause of Global Warming

The gradual increase in global temperatures is getting harder and harder to pin on the Sun and its energy output variability. The Sun hasÂ a variationÂ in how much energy it outputs but this variability is only about one tenth of one percent. The pattern of atmospheric heating since the 1960s is showing an increase with the increase inÂ human activity (industry, transportation, power generation)Â and neither are showing signs of slowing down…

At the American Association for the Advancement of Science (AAAS) meeting in Boston, many talks are focusing on climate change and the human impact on the Earth. Experts in solar science, climate modeling, and atmospheric science are exploring the issues surrounding what the main culprit behind the rapid rate of change in global temperatures could be. The sole energy input into the Earths atmosphere comes from the Sun; so many scientists have looked toward our star for the answers. The Sun does vary its output of energy (historically, this is obvious during long periods of solar inactivity, such as the Maunder Minimum in the 1600’s where hardly any sunspots were observed on the Sun – this reduction in activity has been linked to the “Little Ice Age” experienced during this time), but generally speaking, the net energy increase or decrease is very small.

The link between solar variability and global warming has taken another blow from analysis of historical samples of sediment containing radioactive carbon-14 and a beryllium isotope. Quantities of carbon-14 and beryllium-10 reflect solar activity as they are greatly affected by solar magnetic field strength. The Sun’s magnetic field is directly related to solar activity (and therefore sunspot population). These radioactive isotopes are created by the impact of cosmic rays in the Earths atmosphere, and should the solar magnetic field be strong (i.e. during periods of high activity), cosmic rays will be blocked, reducing the quantity of isotopes in the sediment.

However, results from this analysis appear inconclusive and no strong link can be found in favour of increased solar activity during periods of atmospheric heating.

Linking any atmospheric phenomenon with solar variability is a difficult task. Attempts to connect monsoons with the 11-year solar cycle for instance have failed in 150 years of trying. It would seem that, for now at least, any connection between increased solar energy output and global warming is tenuous at best.

Casper M. Ammann, climate modeler at the National Center for Atmospheric Research in Boulder, Colorado, points out that global temperatures are rising at a historic rate, and there remains no link between solar variability and global warming. He states that global warming has “nothing to do with changes in solar activity. Itâ€™s greenhouse gases. Itâ€™s not the sun that is causing this [climate] trend.”

Perhaps the only answer is to drastically cut back our dependence on fossil fuels to slow the rate of carbon dioxide production. Even if the Sun should decide to become inactive, as there appears to be very little relationship between solar output and global warming, we will not be able to escape the greenhouse gases heating up our climate.

Source: Physorg.com

February 20, 2008December 26, 2015 by Ian O'Neill

US Cruiser Strikes Dead Spy Satellite

Officials have confirmed that the US spy satellite, USA 193, has been hit by an anti-satellite missile fired from USS Lake Erie positioned west of the Hawaiian Islands in the mid-Pacific at 10.30pm (US Eastern Time) Wednesday night. Fears of the propellant hydrazine being released into the atmosphere prompted the military response. Although plans for the missile strike were hampered by bad weather, the launch appears to have gone ahead regardless.

The 10.30pm time window was chosen by the US so that should the first attempt fail, a second and then a third attempt could be carried out. The window was only 10 seconds long, and BBC correspondent Jonathan Beale, based in Washington, says this operation was hugely ambitious and likened it to “trying to fire a missile through the eye of a needle.”

It is hoped that the modified Standard Missile-3 (SM-3) successfully destroyed the large orbiting mass, containing 450kg (1,000lbs) of the poisonous propellant hydrazine. The SM-3 does not carry a warhead; it depends on its high velocity and weight to destroy the target. Travelling at a velocity of over 17,000 mph, on impact the missile and satellite should break up, creating debris and hopefully destroying the full fuel tank. Most of the debris is expected to burn up in the Earths atmosphere over the next 15 hours (or two Earth orbits), and all of it is expected to have re-entered over the next 40 days, eliminating the risk of the poisonous fuel falling to Earth. However, at least 24 hours will be needed to assess how successful the strike has been.

In an official statement, the Department of Defence has said, “A network of land-, air-, sea- and space-based sensors confirms that the U.S. military intercepted a non-functioning National Reconnaissance Office satellite which was in its final orbits before entering the Earth’s atmosphere […] At approximately 10:26 p.m. EST today, a U.S. Navy AEGIS warship, the USS Lake Erie, fired a single modified tactical Standard Missile-3, hitting the satellite approximately 247 kilometers (133 nautical miles) over the Pacific Ocean as it traveled in space at more than 17,000 mph.”

The missile strike has prompted anger from both Russia and China, as the nations see it as a provocative manoeuvre by the US, but US officials insist that the missile strike was not intended to showcase their anti-satellite technology and was not used to destroy any top-secret orbital weapon.

Sources: CNN, BBC

February 20, 2008December 26, 2015 by Ian O'Neill

Mysterious Mars Formation May be Caused by Bursts of Water

Many basin-like features observed on the Martian surface appear to have a fanned feature around possible inlets. Much like river deltas, scientists believe these Mars inlets have similar properties as their terrestrial counterparts, where the flow of water would slow into a basin reservoir, dropping suspended material and depositing it as silt, forming deltas. However, some Martian delta features have a stepped structure. This is not observed on the Earth, so how were they formed on Mars? Researchers suggest sudden flows of water may be to blame…

More and more evidence for ancient Mars water appears to be accumulating every day as images continue to be sent back from the numerous orbiting satellites and two rovers, Mars Explorer Rovers Opportunity and Spirit. Although recent findings suggest the water may have been poisonous to life on early Mars, reducing the likelihood of finding ancient microbial life, the nature and mechanics of water storage and release will be of tremendous value to understanding the evolution of the planets and perhaps helping future Mars colonies when tapping into a source of H₂O.

Using a laboratory experiment intended for science students, researchers from Utrecht University, in the Netherlands, were able to reproduce stepped river deltas by pouring water through a flume, filled with a hollowed out sand basin. On pouring water in bursts, sand sediment was eroded from the inlet channel and deposited in the basin reservoir. As the bursty water input continued, steps in the sediment were created as the sand was deposited in layers.

The research to be published in Nature (Feb. 21, 2008), “Martian stepped-delta formation by rapid water release,” is able to draw some parallels with images being sent back from the Mars Orbiter Laser Altimeter (MOLA) on board the Mars Global Surveyor (MGS) and characterize this one source of Martian water. Based on MOLA observations of fans of 20 kilometers in basins of 100 kilometer-scale on Mars, they calculated the conditions for the creation of a stepped fan and found that by comparing with sediment transportation models, that these stepped features would only take a few tens of years to form. This is in striking contrast to other hydrologic features on Mars that take anywhere between hundreds to millions of years to form. Stepped delta features would therefore require large volumes of fast-flowing water to be created.

One possible reason for this sudden release of water could be from sub-surface pressures, as explained by Erin R. Kraal, now a geosciences research scientist at Virginia Tech, “We suggest the water was released internally, such as hydrothermal water suddenly pushed to the surface.”

Although the search for life may have taken a serious blow, future Mars settlement planners will be enthusiastic about finding sites for aquifers to sustain future human exploration of the Red Planet.

Source: Physorg.com