Pinpointing the Distance to a Pulsar

Image credit: NSF

Astronomers have used the accuracy of the National Science Foundation’s Very Long Baseline Array (VLBA) to pinpoint the distance to a pulsar. The object, called PSR B0656+14, was previously thought to be up to 2,500 light-years away but it was at the same location in the sky as a supernova remnant which is only 1,000 light years away. This was thought to be a coincidence, but the new measurement from the VLBA pegs the pulsar at 950 light years away; the same distance as the remnant – they were both created by the same supernova blast.

Location, location, and location. The old real-estate adage about what’s really important proved applicable to astrophysics as astronomers used the sharp radio “vision” of the National Science Foundation’s Very Long Baseline Array (VLBA) to pinpoint the distance to a pulsar. Their accurate distance measurement then resolved a dispute over the pulsar’s birthplace, allowed the astronomers to determine the size of its neutron star and possibly solve a mystery about cosmic rays.

“Getting an accurate distance to this pulsar gave us a real bonanza,” said Walter Brisken, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM.



Brisken and his colleagues used the VLBA to make precise measurements of the sky position of PSR B0656+14 from 2000 to 2002. They were able to detect the slight offset in the object’s apparent position when viewed from opposite sides of Earth’s orbit around the Sun. This effect, called parallax, provides a direct measurement of distance.

“Our measurements showed that the pulsar is about 950 light-years from Earth, essentially the same distance as the supernova remnant,” said Steve Thorsett, of the University of California, Santa Cruz. “That means that the two almost certainly were created by the same supernova blast,” he added.

With that problem solved. the astronomers then turned to studying the pulsar’s neutron star itself. Using a variety of data from different telescopes and armed with the new distance measurement, they determined that the neutron star is between 16 and 25 miles in diameter. In such a small size, it packs a mass roughly equal to that of the Sun.





“This pulsar is becoming a fascinating laboratory for studying astrophysics and nuclear physics,” Thorsett said.




Original Source: NRAO News Release

SMART-1 Launch Pushed Back

Image credit: ESA

The launch of the European Space Agency’s SMART-1 mission to explore the Moon was pushed back because of delays with its Ariane 5 launcher. The mission was originally scheduled for August 28, but now it’s been pushed into September. Once SMART-1 does get into space, it will use its ion engine to make larger and larger orbits around the Earth over the course of 16 months until it finally reaches the Moon. It will remain in orbit around the moon for over 2 years analyzing the surface and searching for evidence of water ice near the southern pole.

Europe is going to the Moon for the first time! In just over two weeks the European Space Agency’s (ESA) lunar probe, SMART-1, begins its journey to the Moon. Due to be launched from Kourou in French Guiana on 3rd September (12.04 a.m. 4th September BST) SMART-1 will be powered only by an ion engine which Europe will be testing for the first time as the main spacecraft propulsion. Onboard will be D-CIXS, an X-ray spectrometer built by scientists in the UK, which will provide information on what the Moon is made of.

SMART-1 represents a new breed of spacecraft. It is ESA’s first Small Mission for Advanced Research in Technology – designed to demonstrate innovative and key technologies for future deep space science missions. As well as the ion propulsion mechanism SMART-1 will test miniaturised spacecraft equipment and instruments, a navigation system which in the long term will allow spacecraft to autonomously navigate through the solar system, and a space communication technique whereby SMART-1 will establish a link with the Earth using a laser beam.

Once it has arrived at the Moon (expected to be in January 2005), SMART-1 will perform an unprecedented scientific study of the Moon- providing valuable information which will shed light on some of the unanswered questions. The spacecraft will search for signs of water-ice in craters near the Moon’s poles, provide data on the still uncertain origin of the Moon and reconstruct its evolution by mapping and the surface distribution of minerals and key chemical elements.

Commenting on the mission Prof. Ian Halliday, Chief Executive of PPARC said,” This mission to our only natural satellite is a masterpiece of miniaturisation and UK scientists have played a leading role in providing one of the spacecraft’s key instruments – testament to the UK’s expertise in space science.” Halliday added, “SMART-1 is packed with innovative technology that promises to revolutionise our future exploration of neighbouring planets whilst answering some fundamental questions about the Moon – how did the Moon form and how did it evolve?”

UK scientists have a lead role in the mission. D-CIXS, a compact X-ray Spectrometer, which will make the first ever global X-ray map of the Moon’s surface, has been built by a team led by Principal Investigator Professor Manuel Grande from the CCLRC Rutherford Appleton Laboratory near Oxford. Scientists from a number of other UK institutions are involved in D-CIXS (see notes to editors for further details).

Professor Grande explains how D-CIXS works,




“SMART-1 is an unprecedented opportunity to provide the most comprehensive study ever of the surface of the Moon. The UK is playing a key role in this important European mission by providing technology that demonstrates excellent collaboration between engineering and science in this country. This mission will also give the European Space Agency the opportunity to develop new technology for future missions, demonstrating once again the effectiveness of joint working between the UK and our European partners in space.”

Detector Will Measure the Mass of Neutrinos

Image credit: PPARC

On August 14, a new detector designed to determine the mass of neutrinos began operations in an old mine in Minnesota, USA. The Main Injector Neutrino Oscillation Search (MINOS) detector is 30-metres long and consists of 486 massive octagonal plates, each of which is 8-metres across. MINOS will initially measure neutrinos coming from Sun, but in August 2004 it will measure man-made neutrinos created in a laboratory more than 700 km away. If the experiment is successful it will help solve the mystery of dark matter, which some astronomers believe comes from the mass of neutrinos.

Today, (August 14th), sees the start of data collection on the Main Injector Neutrino Oscillation Search (MINOS) detector, situated in the Soudan iron mine, Minnesota, USA. UK particle physicists, working within an international collaboration, will use the MINOS detector to investigate the phenomenon of neutrino mass – a puzzle that goes to the heart of our understanding of the Universe.

Neutrinos are pointlike, abundant particles with very little mass. They exist in three types or ‘flavours’ and recent experiments (including those at SNO – the Sudbury Neutrino Observatory) have demonstrated that neutrinos are capable of oscillating between these flavours (electron, tau and muon). This can only happen if one or more of the neutrino flavours does have mass, in contradiction to the Standard Model of particle physics.

The MINOS detector will start measurements of cosmic ray showers penetrating the Earth. It is situated in the Soudan Mine, Minnesota. The 30-metre-long detector consists of 486 massive octagonal planes, lined up like the slices of a loaf of bread. Each plane consists of a sheet of steel about 8 metres high and 2 ? cm thick, covered on one side with a layer of scintillating plastic that emits light when struck by a charged particle.

“MINOS can separate neutrino interactions from their antimatter counterparts – the antineutrinos.” explains UK MINOS spokesperson, Jenny Thomas from University College London. “The data taken now from neutrinos produced in cosmic ray cascades may provide new insight into why the Universe is made of more matter than antimatter. At least, for the first time we will be able to compare the characteristics of neutrinos and anti-neutrinos coming from the atmosphere.”

However, MINOS has more ambitious plans in place for August 2004. Whilst most experiments like SNO measure neutrinos coming from the Sun, when complete, MINOS will instead study a beam of man-made neutrinos, all of the same type or ‘flavour’ – the muon neutrino flavour. This beam will be created at Fermi National Accelerator Laboratory (Fermilab) and sent straight through the Earth to Soudan – a distance of 735 kilometres. No tunnel is needed because neutrinos interact so rarely with matter. A detector is currently being built just outside Fermilab, known as the ‘near’ detector, similar but smaller than the now operational MINOS detector, known as the ‘far’ detector. The ‘near’ detector will act as a control, studying the beam as it leaves Fermilab, then the results will be compared with those from the ‘far’ detector to see if the neutrinos have oscillated into electron or tau neutrinos during their journey.

A million million neutrinos will be created at Fermilab each year, but only 1,500 will interact with the nucleus of an atom in the far detector and generate a signal; the others will pass straight through.

“The realisation that neutrinos oscillate, first demonstrated by the Super Kamiokande experiment in Japan, has been one of the biggest surprises to emerge in particle physics since the inception of the Standard Model more than 30 years ago.” says Jenny Thomas. “The MINOS experiment will measure the oscillation parameters of these neutrinos to an unprecedented accuracy of a few percent; an amazing feat considering neutrinos can usually pass directly through the Earth without interacting at all and that their inferred masses are estimated to be less than 1eV. (The weight ratio of a neutrino to a 1kg bag of sugar is the same as the ratio of a grain of sand to the weight of the earth!). The parameter measurement will open up an entire new field of particle physics, to understand what effect on the universe this tiny neutrino mass has.”

Within two years of turning on the neutrino beam, MINOS should produce an unequivocal measurement of the oscillation of muon neutrinos with none of the uncertainties associated with the atmospheric or solar neutrino source. If indeed the findings are positive, then a new era in particle physics will begin. Theorists will have to incorporate massive neutrinos into the Standard Model, which will have exciting implications. Furthermore cosmologists will have a strong candidate for the ‘missing mass’ of the Universe (which dynamical gravitational measurements show must exist). The experimental side will be just as exciting as we plan new experiments to measure precisely how the different neutrinos change their flavour.

Original Source: PPARC News Release

These Microbes Can Take the Heat


Chandra Sees Horseshoe Nebula

Image credit: Chandra




Infrared Close-Up of M17



Original Source: Chandra News Release

Three Fates for Hubble

Image credit: NASA

















Original Source: NASA News Release

Northeast Blackout Seen From Space

The National Oceanic and Atmospheric Administration posted satellite images online that showed the extent of the power blackout that affected more than 50 million people late last week. The photos show the areas both before and after the lights went out and demonstrate the dramatic change in power. The images were acquired by the agency’s Defense Meteorological Satellite Program (DMSP) on August 14 at 9:03 pm EDT.

Fuel Leak Delays Titan Launch

The launch of a Titan 4B rocket was delayed after 200 litres of toxic nitrogen tetroxide propellant spilled out and created a dangerous gas cloud. Fortunately, none of the workers were injured by the cloud, and it dissipated before it reached the adjacent Kennedy Space Center. It’s unknown when the Titan rocket will be ready again to launch its cargo of a National Reconnaissance Office satellite. Investigators are still determining what caused the accident.

Ultrasound is the Coolest Thing Ever

My wife and I went for our second ultrasound last week to see how our second child is coming along. We were originally booked into a terrible ultrasound clinic (we’d been there before) but we begged our midwife to get us into a place that would treat us a little better, so we ended up at a hospital without a maternity ward – they never get a chance to look at babies. We ended up giving the ultrasound technicians a welcome break from the more boring stuff they usually have to look at. They spent almost an hour with us, examining our next baby in detail; showing us the face, the heart, and every little part of the body. If you’ve never watched an ultrasound before, I can’t recommend it enough. A static photo doesn’t do justice to the little images you see of your unborn child squirming around in the womb.

Oh yeah… we’re having a boy. 🙂

Fraser Cain
Universe Today

P.S. I’m headed away for vacation on Friday and won’t be back until Tuesday afternoon so there’ll be a little break in the news.

Gamma Ray Bursts May Propel Fast Moving Particles

Image credit: NASA

Astronomers believe that gamma-ray bursts, the most powerful explosions in the Universe, may be generating ultrahigh-energy cosmic rays, the most energetic particles in the Universe. These cosmic rays have baffled astronomers because they’re moving faster than if they were thrown out of a supernova. Evidence gathered by NASA’s de-orbited Compton Gamma-Ray Observatory showed that in one instance of a gamma ray burst, these high-energy particles dominated the area giving a connection between them, but this is hardly enough evidence to say they’re conclusively linked.

The most powerful explosions in the universe, gamma-ray bursts, may generate the most energetic particles in the universe, known as the ultrahigh-energy cosmic rays (UHECRs), according to a new analysis of observations from NASA’s Compton Gamma-Ray Observatory.

Researchers report in the August 14 edition of Nature of a newly identified pattern in the light from these enigmatic bursts that could be explained by protons moving within a hair’s breadth of light speed.

These protons, like shrapnel from an explosion, could be UHECRs. Such cosmic rays are rare and constitute an enduring mystery in astrophysics, seemingly defying physical explanation, for they are simply far too energetic to have been generated by well-known mechanisms such as supernova explosions.

“Cosmic rays ‘forget’ where they come from because, unlike light, they are whipped about in space by magnetic fields,” said lead author Maria Magdalena Gonzalez of the Los Alamos National Laboratory in New Mexico and graduate student at the University of Wisconsin. “This result is an exciting chance to possibly see evidence of them being produced at their source.”

Gamma-ray bursts — a mystery scientists are finally beginning to unravel — can shine as brilliantly as a million trillion suns, and many may be from an unusually powerful type of exploding star. The bursts are common yet random and fleeting, lasting only seconds.

Cosmic rays are atomic particles (for example, electrons, protons or neutrinos) moving close to light speed. Lower-energy cosmic rays bombard the Earth constantly, propelled by solar flares and typical star explosions. UHECRs, with each atomic particle carrying the energy of a baseball thrown in the Major Leagues, are a hundred-million times more energetic than the particles produced in the largest human-made particle accelerators.

Scientists say the UHECRs must be generated relatively close to the Earth, for any particle traveling farther than 100 million light years would lose some of its energy by the time it reached us. Yet no local source of ordinary cosmic rays seems powerful enough to generate a UHECR.

The Gonzalez-led paper focuses not specifically on UHECR production but rather a new pattern of light seen in a gamma-ray burst. Digging deep into the Compton Observatory archives (the mission ended in 2000), the group found that a gamma-ray burst from 1994, named GRB941017, appears different from the other 2,700-some bursts recorded by this spacecraft. This burst was located in the direction of the constellation Sagitta, the Arrow, likely ten billion light years away.

What scientists call gamma rays are photons (light particles) covering a wide range of energies, in fact, over a million times wider than the energies our eyes register as the colors in a rainbow. Gonzalez’s group looked at the higher-energy gamma-ray photons. The scientists found that these types of photons dominated the burst: They were at least three times more powerful on average than the lower-energy component yet, surprisingly, thousands of times more powerful after about 100 seconds.

That is, while the flow of lower-energy photons hitting the satellite’s detectors began to ease, the flow of higher-energy photons remained steady. The finding is inconsistent with the popular “synchrotron shock model” describing most bursts. So what could explain this enrichment of higher-energy photons?

“One explanation is that ultrahigh-energy cosmic rays are responsible, but exactly how they create the gamma rays with the energy patterns we saw needs a lot of calculating,” said Dr. Brenda Dingus of LANL, a co-author on the paper. “We’ll be keeping some theorists busy trying to figure this out.”

A delayed injection of ultrahigh-energy electrons provides another way to explain the unexpectedly large high-energy gamma-ray flow observed in GRB 941017. But this explanation would require a revision of the standard burst model, said co-author Dr. Charles Dermer, a theoretical astrophysicist at the U.S. Naval Research Laboratory in Washington. “In either case, this result reveals a new process occurring in gamma-ray bursts,” he said.

Gamma-ray bursts have not been detected originating within 100 million light years from Earth, but through the eons these types of explosions may have occurred locally. If so, Dingus said, the mechanism her group saw in GRB 941017 could have been duplicated close to home, close enough to supply the UHECRs we see today.

Other bursts in the Compton Observatory archive may have exhibited a similar pattern, but the data are not conclusive. NASA’s Gamma-ray Large Area Space Telescope (GLAST), scheduled for launch in 2006, will have detectors powerful enough to resolve higher-energy gamma-ray photons and solve this mystery.

Co-authors on the Nature report also include Ph.D. graduate student Yuki Kaneko, Dr. Robert Preece, and Dr. Michael Briggs of the University of Alabama in Huntsville. This research was funded by NASA and the Office of Naval Research.

UHECRs are observed when they crash into our atmosphere, as is illustrated in the figure. The energy from the collision produces an air shower of billions of subatomic particles and flashes of ultraviolet light, which are detected by special instruments.

The National Science Foundation and international collaborators have sponsored instruments on the ground, such as the High Resolution Fly’s Eye in Utah ( and the Auger Observatory in Argentina ( In addition, NASA is working with the European Space Agency to place the Extreme Universe Space Observatory ( on the International Space Station. The proposed OWL mission would, from orbit, look downward towards air showers, viewing a region as large as Texas.

These scientists record the flashes and take a census of the subatomic shrapnel, working backward to calculate how much energy a single particle needs to make the atmospheric cascade. They arrive at a shocking figure of 10^20 electron volts (eV) or more. (For comparison, the energy in a particle of yellow light is 2 eV, and the electrons in your television tube are in the thousand electron volt energy range.)

These ultrahigh-energy particles experience the bizarre effects predicted by Einstein’s theory of special relativity. If we could observe them coming from a remote corner of the cosmos, say a hundred million light years away, we’d have to be patient — it will take a hundred million years to complete the journey. However, if we could travel with the particles, the trip is over in less than a day due to the dilation of time of rapidly moving objects as measured by an observer.

The highest energy cosmic rays cannot even reach us if produced from distant sources, because they collide and lose energy with the cosmic microwave photons left over from the big bang. Sources of these cosmic rays must be found relatively close to us, at a distance of several hundred million light years. Stars that explode as gamma-ray bursts are found within this distance, so intensive observational efforts are underway to find gamma-ray burst remnants distinguished by radiation halos made by the cosmic rays.

Few kinds of celestial objects possess the extreme conditions required to blast particles to UHECR speeds. If gamma-ray bursts produce UHECRs, they probably do so by accelerating particles in jets of matter ejected from the explosion at close to the speed of light. Gamma-ray bursts have the power to accelerate UHECRs, but the gamma-ray bursts observed so far have been remote, billions of light years away. This doesn’t mean they can’t happen nearby, within the UHECR cutoff distance.

A leading contender for long-lived kinds of gamma-ray bursts like GRB941017 is the supernova/collapsar model. Supernovae happen when a star many times more massive than the Sun exhausts its fuel, causing its core to collapse under its own gravity while its outer layers are blown off in an immense thermonuclear explosion. Collapsars are a special type of supernova where the core is so massive it collapses into a black hole, an object so dense that nothing, not even light, can escape its gravity within the black hole’s event horizon. However, observations indicate black holes are sloppy eaters, ejecting material that passes near, but does not cross, their event horizons.

In a collapsar, the star’s core forms a disk of material around the newly formed black hole, like water swirling around a drain. The black hole consumes most of the disk, but some matter is blasted in jets from the poles of the black hole. The jets tear through the collapsing star at close to the speed of light, and then punch through gas surrounding the doomed star. As the jets crash into the interstellar medium, they create shock waves and slow down. Internal shocks also form in the jets as their leading edges slow and are slammed from behind by a stream of high-speed matter. The shocks accelerate particles that generate gamma rays; they could also accelerate particles to UHECR speeds, according to the team.

“It’s like bouncing a ping pong ball between a paddle and a table,” said Dingus. “As you move the paddle closer to the table, the ball bounces faster and faster. In a gamma-ray burst, the paddle and the table are shells ejected in the jet. Turbulent magnetic fields force the particles to ricochet between the shells, accelerating them to almost the speed of light before they break free as UHECRs.”

Detection of neutrinos from gamma-ray bursts would clinch the case for cosmic ray acceleration by gamma-ray bursts. Neutrinos are elusive particles made when high-energy protons collide with photons. Neutrinos have no electrical charge, so still point back to the direction of their source.

The National Science Foundation is currently building IceCube (, a cubic kilometer detector located in the ice under the South Pole, to search for neutrino emission from gamma-ray bursts. However, the characteristics of nature’s highest-energy particle accelerators remain an enduring mystery, though acceleration by the exploding stars that make gamma-ray bursts has been in favor ever since Mario Vietri (Universita di Roma) and Eli Waxman (Weizmann Institute) proposed it in 1995.

The team believes that while other explanations are possible for this observation, the result is consistent with UHECR acceleration in gamma-ray bursts. They saw both low-energy and high-energy gamma rays in the GRB941017 explosion. The low-energy gamma rays are what scientists expect from high-speed electrons being deflected by intense magnetic fields, while the high-energy rays are what’s expected if some of the UHECRs produced in the burst crash into other photons, creating a shower of particles, some of which flash to produce the high-energy gamma rays when they decay.

The timing of the gamma-ray emission is also significant. The low-energy gamma rays faded away relatively quickly, while the high-energy gamma rays lingered. This makes sense if two different classes of particles – electrons and the protons of the UHECRs – are responsible for the different gamma rays. “It’s much easier for electrons than protons to radiate their energy. Therefore, the emission of low-energy gamma rays from electrons would be shorter than the high-energy gamma rays from the protons,” said Dingus.

The Compton Gamma Ray Observatory was the second of NASA’s Great Observatories and the gamma-ray equivalent to the Hubble Space Telescope and the Chandra X-ray Observatory. Compton was launched aboard the Space Shuttle Atlantis in April 1991, and at 17 tons, was the largest astrophysical payload ever flown at that time. At the end of its pioneering mission, Compton was deorbited and re-entered the Earth’s atmosphere on June 4, 2000.

Original Source: NASA News Release