Today's journal article involves the mysterious case of PSR J1841-500, the pulsar that doesn't pulse
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According to Wikipedia, a Journal Club is a group of individuals who meet regularly to critically evaluate recent articles in the scientific literature. Since this is Universe Today if we occasionally stray into critically evaluating each other’s critical evaluations, that’s OK too.
And of course, the first rule of Journal Club is… don’t talk about Journal Club. So, without further ado – today’s journal article involves the mysterious case of PSR J1841-500, the pulsar that didn’t pulse.
Pulsars are neutron stars – with polar jets. They rotate quite fast and when one of those polar jets line up with Earth we detect a pulse of radio light. This is a very regular and very predictable pulse – although when measured over long time periods, the pulses slowly decline in frequency as magnetic forces create drag that slows the neutron star’s spin.
But PSR J1841-500 is an oddball – when first discovered, it pulsed every 0.9 seconds. Then for reasons unknown, it stopped pulsing for a period of over 500 days – after which it just picked up where it left off. There are at least two other pulsars known to have demonstrated such ‘switch on – switch off’ behaviour, although neither had anything like the switch-off duration of PSR J1841-500.
It is known that now and again neutron stars experience a ‘glitch’, a kind of a starquake, as the intense gravity of the star crunches its internal structure down to an even more compact state. This can change its spin and hence its pulse rate.
However, it’s not clear if glitch phenomena would help explain the extended ‘switch-off’ phenomenon observed in PSR J1841-500. Looking for other anomalies, the authors point to the unusual proximity of the magnetar IE 1841-045, which might be having some (unknown) effect on its neighbor.
The authors then conclude with the interesting suggestion that if this behavior is common, then we may be missing lots of pulsars that were in a ‘switched-off’ state when their particular region of the sky was last surveyed. This means we actually need to undertake repeated surveys – which should hopefully keep more astronomers in a job.
So – comments? Are the authors just building an overblown story out of a measurement error? Is there some weird magnetic dance going on between two proximal neutron stars? Want to suggest an article for the next edition of Journal Club?
The James Webb Space Telescope mirrors have completed deep-freeze tests and are removed from the X-ray and Cryogenic test Facility at Marshall Space Flight Center. Credit: Emmett Given, NASA Marshall
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The last of the 21 mirrors for the James Webb Space Telescope have come out of deep freeze – literally! – and are now approved for space operations, a major milestone in the development of the next generation telescope that’s being hailed as the “successor to Hubble.”
“The mirror completion means we can build a large, deployable telescope for space,” said Scott Willoughby, vice president and Webb program manager at Northrop Grumman Aerospace Systems. “We have proven real hardware will perform to the requirements of the mission.”
The all-important mirrors for the Webb telescope had to be cryogenically tested to make sure they could withstand the rigors and extreme low temperatures necessary for operating in space. To achieve this, they were cooled to temperatures of -387F (-233C) at the X-ray and Cryogenic Test Facility at Marshall Space Flight Center.
When in actual use, the mirrors will be kept at such low temperatures so as not to interfere with deep-space infrared observations with their own heat signatures.
JWST engineers anticipate that, with such drastic cooling, the mirrors will change shape. The testing proved that the mirrors would achieve the shapes needed to still perform exactly as expected.
“This testing ensures the mirrors will focus crisply in space, which will allow us to see new wonders in our universe,” said Helen Cole, project manager for Webb Telescope mirror activities.
Planned for launch in 2018, the JWST will be the premier observatory of the next decade, serving thousands of astronomers worldwide. It will study every phase in the history of the Universe, ranging from the first luminous glows after the Big Bang to the formation of solar systems capable of supporting life on Earthlike planets.
Learn more about the James Webb Space Telescope here.
A Soyuz 2-1b rocket that launched successfully on November 27, 2011; a similar rocket failed on Dec. 23, 2011. Credit: Space Launch Report
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A day of highs and lows for the Russian space program: while the Soyuz TMA-03M capsule docked safely at the International Space Station, a Soyuz-2 rocket carrying a communications satellite failed shortly after launch from the Plesetsk spaceport. Reports say the Meridian satellite, which can be used by the military or for civilian purposes, did not reach orbit and crashed near the city of Tobolsk in Siberia, about 2,300 km from Moscow. A combustion chamber burn-through is suspected in today’s launch, another failure in what is becoming an alarmingly long list of problems for the Russian space program.
Roscosmos director Vladimir Popovkin admitted that Russian spaceflight is “in crisis” after today’s launch failure.
An update from RussianSpaceweb.com says an analysis of available telemetry on the fuel line pressure before the entrance to the engine’s injection system indicated a possible wall bulging of the combustion chamber No. 1, leading to its burn through and a catastrophic fuel leak. (RD-0124 engine has four combustion chambers).
The Interfax news agency reported the Meridian failure could delay the launch of Progress cargo craft to the ISS, scheduled for January.
Today’s rocket failure was a Soyuz-2.1b, the latest version of the rocket that has been in service in various forms since the 1960s.
In August, a Soyuz-U rocket failed carrying a Progress resupply ship; three Glonass navigation system satellites launched in December 2010 veered off course and crashed into the Pacific Ocean; and the Phobos-Grunt probe, which launched in November is currently stuck in Earth orbit and will likely re-enter and crash after its booster failed, and communications with the spacecraft haven’t been permanently established.
The next Soyuz launch, scheduled for December 26 from the Baikonur Cosmodrome may also be delayed. This flight is intended to put six communications satellites in orbit.
Three international travelers arrived safely at the International Space Station in their Soyuz TMA-03M spacecraft, docking just in time for the holidays, at 15:19 UTC on December 23, 2011. Oleg Kononenko from Russia, NASA astronaut Don Pettit and European Space Agency astronaut Andre Kuipers from The Netherlands docked at the Rassvet module on the Russian segment of the complex, and a few hours later were greeted by three other crew members on the outpost, station Commander Dan Burbank of NASA and Russian Flight Engineers Anton Shkaplerov and Anatoly Ivanishin, who have been aboard the orbital laboratory for just over a month. Continue reading “New Crew Arrives Safely at International Space Station”
On June 30th, 1908 “something” exploded over the Tunguska region of Siberia, flattening thousands of square kilometres of forest, and unleashing a force that rivaled the most powerful nuclear weapon ever detonated. What was it? What could unleash that kind of destructive energy? And will it happen again?
If you want to see one of the strangest places in the Solar System, look no further than Io, Jupiter’s inner Galilean moon. The immense tidal forces from Jupiter keep the moon hotter than hot, with huge volcanoes blasting lava hundreds of kilometers into space.
Crater in Shadow on Vesta. This new image from Dawn in its low altitude mapping orbit on Dec. 13 shows part of the rim of a fresh crater on Vesta located in an area known as the Heavily Cratered Terrain in the northern hemisphere at around 17 degrees latitude and 77 degrees longitude. It was obtained at an altitude of 119 miles (191 km) and covers an area 11 mi x 11 mi (18 km x 18 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
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NASA’s Dawn spacecraft has swooped down to the closest orbit above the monster asteroid Vesta that the craft’s cameras and spectrometers will ever glimpse and the probe has begun transmitting these highest resolution pictures to anxiously waiting scientists back on Earth.
Dawn arrived at its Low Altitude Mapping Orbit, known as LAMO, on Dec. 12, 2011 and will continue circling scarcely 130 miles (210 kilometers) above Vesta for at least the next 10 weeks. Each orbit takes about 4.3 hours.
NASA has now released the first batch of crisp new close-ups images taken by the Framing Camera on Dec. 13 showing the stippled and lumpy surface in an exquisitely fine detail never seen before.
The photo montage below shows side by side views of the same portion of the Vestan surface at ever increasing resolution and clarity from ever lower altitudes.
Closer and Closer to the Vesta Surface
NASA’s Dawn spacecraft has spiraled closer and closer to the surface of the giant asteroid Vesta since arriving in mid-2011. The two images on the left represent an identical area, first observed during Dawn's survey orbit (far left image). The picture in the center is from Dawn's high-altitude mapping orbit (HAMO) from an altitude of about 430 miles (700 km) with about 230 feet (70 meters-per-pixel) resolution. The image at right was obtained on Dec. 13 from the low altitude mapping orbit (LAMO) at an altitude of 124 miles (199 km) above the surface and has a resolution of 75 feet (23 m) per pixel. It shows small impact craters or slumping at the steep-flanked mountain in the image center that can be identified in the two images to the left. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The high resolution image gallery reveals fine scale highlights such as multitudes of small craters, grooves and lineaments, landslides and slumping, ejecta from past colossal impacts, and small outcrops of bright and dark materials.
The science team, led by Principal Investigator Prof Chris Russell of UCLA, believes that Vesta is actually more like a planet than an asteroid based on the data obtained thus far.
“Vesta is the smallest terrestrial planet in our Solar System”, Russell told Universe Today. “We do not have a good analog to Vesta anywhere else in the Solar System.”
The primary science objectives at the LAMO orbit are to measure the elemental abundances on the surface of Vesta with the US built gamma ray and neutron detector (GRaND) and to probe the interior structure of the asteroid by measuring the gravity field.
Vesta is a proto-planet formed just a few million years after the birth of the solar system whose evolution into a larger planet was stopped cold by the massive gravitational influence of the planet Jupiter.
Scientists are plowing through thousands of images and millions of spectral measurements to glean clues about the origin and evolution of the solar system that have been preserved on the hitherto unexplored world.
Buried Craters on Vesta
This Dec. 13 image from Dawn spacecraft in its low altitude mapping orbit shows many buried craters located within the equatorial trough region of Vesta. This area bears traces of the material thrown out by the impact that created the Rheasilvia basin in the asteroid’s south polar region. Lineated features are visible in a variety of shapes and sizes from an altitude of 117 miles (189 km) over an area of 11 mi x 11 mi (18 km x 18 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
“Vesta is a transitional body between a small asteroid and a planet and is unique in many ways,” says mission scientist Vishnu Reddy of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany. “Vesta is unlike any other asteroid we have visited so far.”
After completing the LAMO measurements, Dawn will again spiral back to a higher altitude for further data gathering especially at the unseen North Pole which is in darkness now.
Dawn will continue orbiting Vesta until July 2012 when it will fire up its ion propulsion system and depart for Ceres, the largest body in the main Asteroid belt between Mars and Jupiter.
“What can be more exciting than to explore an alien world that until recently was virtually unknown!” Dr. Marc Rayman told Universe Today. Rayman is Dawn’s Chief Engineer from NASA’s Jet Propulsion Lab (JPL) in Pasadena, Calif.
Equatorial Trough in Dark and Bright on Vesta
This image was one of the first obtained by Dawn in its low altitude mapping orbit and shows a part of one of the long troughs at the equator of Vesta. Credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA
“Dawn continues to gather gamma ray spectra and neutron spectra,” Rayman reports. “The bonus imaging at LAMO is yielding pictures more than three times better than those acquired in the high altitude mapping orbit (HAMO). Every week at this low altitude, Dawn will use its ion propulsion system to fine tune its orbit. The first of these weekly orbit adjustments was performed on December 17.”
The framing cameras eere built by the Max Planck Institute for Solar System Research in Germany.
A treasure trove of spectacular Vesta close-ups are streaming at this moment to the home planet and we’ll have many more goodies to show.
The moons Titan and Dione are photographed with rings and Saturn in the background. Credit: NASA/JPL-Caltech/Space Science Institute
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“Hey! Look what our Santa at Saturn has sent our way!” said Carolyn Porco, the Cassini imaging team lead, in a post on Twitter. This wonderful collection of just-released colorful images from the Saturn system are a holiday gift from the Cassini and CICLOPS (Cassini Imaging Central Laboratory for Operations)team.
Above, Saturn’s third-largest moon, Dione, can be seen through the haze of the planet’s largest moon, Titan, in this view of the two posing before the planet and its rings from NASA’s Cassini spacecraft.
More treats below!
Saturn's moon Tethys, with its stark white icy surface, peeps out from behind the larger, hazy, colorful Titan in this view of the two moons obtained by NASA's Cassini spacecraft. Saturn's rings lie between the two. Credit: NASA/JPL-Caltech/Space Science InstituteThese views from NASA's Cassini spacecraft look toward the south polar region of Saturn's largest moon, Titan, and show a depression within the moon's orange and blue haze layers near the south pole. Credit: NASA/JPL-Caltech/Space Science InstituteThe colorful globe of Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science InstituteSaturn's largest moon, Titan, appears deceptively small paired here with Dione, Saturn's third-largest moon, in this view from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute
To see more details and larger versions of these images, visit the CICLOPS website. (And thanks, Carolyn and team for the beautiful gifts!)
Artist's conception of New Horizons during its flyby of Pluto in 2015. Credit:Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)
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First there was the recent story about evidence for a possible subsurface ocean on Pluto, of all places. Now there is a new report regarding evidence for complex molecules on its surface, from scientists at Southwest Research Institute and Nebraska Wesleyan University. Little enigmatic Pluto is starting to get even more interesting…
The findings come from the Hubble Space Telescope, using the new and highly sensitive Cosmic Origins Spectrograph which indicate that there is a strong ultraviolet-wavelength absorber on the surface. This absorbing material is thought to likely be complex hydrocarbons and/or nitriles. The results have been published in the Astronomical Journal.
Pluto’s surface is known to be coated with ices composed of methane, carbon monoxide and nitrogen (it is extremely cold there!). The putative molecules can be produced by sunlight or cosmic rays interacting with those ices.
“This is an exciting finding because complex Plutonian hydrocarbons and other molecules that could be responsible for the ultraviolet spectral features we found with Hubble may, among other things, be responsible for giving Pluto its ruddy color,” said project leader Dr. Alan Stern.
The team also found evidence for surface changes in the ultraviolet spectrum, comparing current observations to those from the 1990s. The cause may be an increase in the pressure of Pluto’s tenuous atmosphere or different terrain which is being viewed at different times.
In a unique first for Universe Today, Dr. Alan Stern was the first researcher to be asked questions from readers via the comments section of this recent interview article by Ray Sanders. His answers to the top five questions (as ranked by “likes” on the discussion posts) will be posted soon in a subsequent article. Stern is also the principal investigator for the New Horizons spacecraft currently en route to Pluto.
A copy of the paper by Stern et al. is available here.
With all of the new discoveries already being made about Pluto, it should be very interesting when New Horizons gets there in 2015, providing us with the first close-up look of this fascinating little world.
Comet Lovejoy is visible near Earth’s horizon in this nighttime image photographed by NASA astronaut Dan Burbank, Expedition 30 commander, onboard the International Space Station on Dec. 21, 2011. Credit: NASA
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*Now updated with video!*
We can’t get enough of Comet Lovejoy! But this latest image is off the charts for its beauty and it’s jaw-dropping to contemplate it was taken from space. Dan Burbank, Expedition 30 commander onboard the International Space Station took this image of Comet Lovejoy on Dec. 21, 2011. See more of Burbank’s shots of Lovejoy here.
NASA now has a timelapse video of Burbank’s observations of Comet Lovejoy:
