Posted on by Fraser Cain

Sirius’ White Dwarf Companion Weighed by Hubble

Sirius and its tiny companion. Image credit: Hubble. Click to enlarge
For astronomers, it’s always been a source of frustration that the nearest white-dwarf star is buried in the glow of the brightest star in the nighttime sky. This burned-out stellar remnant is a faint companion of the brilliant blue-white Dog Star, Sirius, located in the winter constellation Canis Major.

Now, an international team of astronomers has used the keen eye of NASA’s Hubble Space Telescope to isolate the light from the white dwarf, called Sirius B. The new results allow them to measure precisely the white dwarf’s mass based on how its intense gravitational field alters the wavelengths of light emitted by the star. Such spectroscopic measurements of Sirius B taken with a telescope looking through the Earth’s atmosphere have been severely contaminated by scattered light from the very bright Sirius.

“Studying Sirius B has challenged astronomers for more than 140 years,” said Martin Barstow of the University of Leicester, U.K., who is the leader of the observing team. “Only with Hubble have we at last been able to obtain the observations we need, uncontaminated by the light from Sirius, in order to measure its change in wavelengths.”

“Accurately determining the masses of white dwarfs is fundamentally important to understanding stellar evolution. Our Sun will eventually become a white dwarf. White dwarfs are also the source of Type Ia supernova explosions that are used to measure cosmological distances and the expansion rate of the universe. Measurements based on Type Ia supernovae are fundamental to understanding ‘dark energy,’ a dominant repulsive force stretching the universe apart. Also, the method used to determine the white dwarf’s mass relies on one of the key predictions of Einstein’s theory of General Relativity; that light loses energy when it attempts to escape the gravity of a compact star.”

Sirius B has a diameter of 7,500 miles (12,000 kilometers), less than the size of Earth, but is much denser. Its powerful gravitational field is 350,000 times greater than Earth’s, meaning that a 150-pound person would weigh 50 million pounds standing on its surface. Light from the surface of the hot white dwarf has to climb out of this gravitational field and is stretched to longer, redder wavelengths of light in the process. This effect, predicted by Einstein’s theory of General Relativity in 1916, is called gravitational redshift, and is most easily seen in dense, massive, and hence compact objects whose intense gravitational fields warp space near their surfaces.

Based on the Hubble measurements of the redshift, made with the Space Telescope Imaging Spectrograph, the team found that Sirius B has a mass that is 98 percent that of our own Sun. Sirius itself has a mass of two times that of the Sun and a diameter of 1.5 million miles (2.4 million kilometers).

White dwarfs are the leftover remnants of stars similar to our Sun. They have exhausted their nuclear fuel sources and have collapsed down to a very small size. Sirius B is about 10,000 times fainter than Sirius itself, making it difficult to study with telescopes on the Earth’s surface because its light is swamped in the glare of its brighter companion. Astronomers have long relied on a fundamental theoretical relationship between the mass of a white dwarf and its diameter. The theory predicts that the more massive a white dwarf, the smaller its diameter. The precise measurement of Sirius B’s gravitational redshift allows an important observational test of this key relationship.

The Hubble observations have also refined the measurement of Sirius B’s surface temperature to be 44,900 degrees Fahrenheit, or 25,200 degrees Kelvin. Sirius itself has a surface temperature of 18,000 degrees Fahrenheit (10,500 degrees Kelvin).

At 8.6 light-years away, Sirius is one of the nearest known stars to Earth. Stargazers have watched Sirius since antiquity. Its diminutive companion, however, was not discovered until 1862, when it was first glimpsed by astronomers examining Sirius through one of the most powerful telescopes of that time.

Details of the work were reported in the October 2005 issue of the Monthly Notices of the Royal Astronomical Society. Other participants on the team include Howard Bond of the Space Telescope Science Institute, Baltimore, Md.; Matt Burleigh of the University of Leicester; Jay Holberg and Ivan Hubeny of the University of Arizona; and Detlev Koester of the University of Kiel, Germany.

Original Source: HubbleSite News Release

Posted on by Fraser Cain

Thousands of Auroras on Mars

Location of aurora on Mars. Image credit: ESA Click to enlarge
Auroras similar to Earth’s Northern Lights appear to be common on Mars, according to physicists at the University of California, Berkeley, who have analyzed six years’ worth of data from the Mars Global Surveyor.

The discovery of hundreds of auroras over the past six years comes as a surprise, since Mars does not have the global magnetic field that on Earth is the source of the aurora borealis and the antipodal aurora australis.
plot of the 13,000 auroral events on Mars

According to the physicists, the auroras on Mars aren’t due to a planet-wide magnetic field, but instead are associated with patches of strong magnetic field in the crust, primarily in the southern hemisphere. And they probably aren’t as colorful either, the researchers say: The energetic electrons that interact with molecules in the atmosphere to produce the glow probably generate only ultraviolet light – not the reds, greens and blues of Earth.

“The fact that we see auroras as often as we do is amazing,” said UC Berkeley physicist David A. Brain, the lead author of a paper on the discovery recently accepted by the journal Geophysical Research Letters. “The discovery of auroras on Mars teaches us something about how and why they happen elsewhere in the solar system, including on Jupiter, Saturn, Uranus and Neptune.”

Brain and Jasper S. Halekas, both assistant research physicists at UC Berkeley’s Space Sciences Laboratory, along with their colleagues from UC Berkeley, the University of Michigan, NASA’s Goddard Space Flight Center and the University of Toulouse in France, also reported their findings in a poster presented Friday, Dec. 9, at the American Geophysical Union meeting in San Francisco.

Last year, the European spacecraft Mars Express first detected a flash of ultraviolet light on the night side of Mars and an international team of astronomers identified it as an auroral flash in the June 9, 2005, issue of Nature. Upon hearing of the discovery, UC Berkeley researchers turned to data from the Mars Global Surveyor to see if an on-board UC Berkeley instrument package – a magnetometer-electron reflectometer – had detected other evidence of auroras. The spacecraft has been orbiting Mars since September 1997 and since 1999 has been mapping from an altitude of 400 kilometers (250 miles) the Martian surface and Mars’ magnetic fields. It sits in a polar orbit that keeps it always at 2 a.m. when on the night side of the planet.

Within an hour of first delving into the data, Brain and Halekas discovered evidence of an auroral flash – a peak in the electron energy spectrum identical to the peaks seen in spectra of Earth’s atmosphere during an aurora. Since then, they have reviewed more than 6 million recordings by the electron reflectometer and found amid the data some 13,000 signals with an electron peak indicative of an aurora. According to Brain, this may represent hundreds of nightside auroral events like the flash seen by the Mars Express.

When the two physicists pinpointed the position of each observation, the auroras coincided precisely with the margins of the magnetized areas on the Martian surface. The same team, led by co-authors Mario H. Acu?a of NASA’s Goddard Space Flight Center and Robert Lin, UC Berkeley professor of physics and director of the Space Sciences Laboratory, has extensively mapped these surface magnetic fields using the magnetometer/reflectometer aboard the Mars Global Surveyor. Just as Earth’s auroras occur where the magnetic field lines dive into the surface at the north and south poles, Mars’ auroras occur at the borders of magnetized areas where the field lines arc vertically into the crust.

Of the 13,000 auroral observations so far, the largest seem to coincide with increased solar wind activity.

“The flash seen by Mars Express seems to be at the bright end of energies that are possible,” Halekas said. “Just as on Earth, space weather and solar storms tend to make the auroras brighter and stronger.”
Depiction of surface magnetic fields on Mars

Earth’s auroras are caused when charged particles from the sun slam into the planet’s protective magnetic field and, instead of penetrating to the ground, are diverted along field lines to the pole, where they funnel down and collide with atoms in the atmosphere to create an oval of light around each pole. Electrons are a big proportion of the charged particles, and auroral activity is associated with a physical process still not understood that accelerates electrons, producing a telltale peak in the spectrum of electron energies.

The process on Mars is probably similar, Lin said, in that solar wind particles are funneled around to the night side of Mars where they interact with crustal field lines. The ultraviolet light is produced when the particles hit carbon dioxide molecules.

“The observations suggest some acceleration process occurs like on Earth,” he said. “Something has taken the electrons and given them a kick.”

What that “something” is remains a mystery, though Lin and his UC Berkeley colleagues lean towards a process called magnetic reconnection, where the magnetic field traveling with the solar wind particles breaks and reconnects with the crustal field. The reconnecting field lines could be what flings the particles to higher energies.

The surface magnetic fields, Brain said, are produced by highly magnetized rock that occurs in patches up to 1,000 kilometers wide and 10 kilometers deep. These patches probably retain magnetism left from when Mars had a global field in a way similar to what occurs when a needle is stroked with a magnet, inducing magnetization that remains even after the magnet is withdrawn. When Mars’ global field died out billions of years ago, the solar wind was able to strip the atmosphere away. Only the strong crustal fields are still around to protect portions of the surface.

“We call them mini-magnetospheres, because they are strong enough to stand off the solar wind,” Lin said, noting that the fields extend up to 1,300 kilometers above the surface. Nevertheless, the strongest Martian magnetic field is 50 times weaker than the field at the Earth’s surface. It’s hard to explain how these fields are able to funnel and accelerate the solar wind efficiently enough to generate an aurora, he said.

Brain, Halekas, Lin and their colleagues hope to mine the Mars Global Surveyor data for more information on the auroras and perhaps join with the European team operating the Mars Express to get complementary data on the flashes that could solve the mystery of their origin.

“Mars Global Surveyor was designed for a lifetime of 685 days, but it has been very valuable for more than six years now, and we are still getting great results,” Lin observed.

The work was supported by NASA. Coauthors with Brain, Halekas, Lin and Acu?a are Laura M. Peticolas, Janet G. Luhmann, David L. Mitchell and Greg T. Delory of UC Berkeley’s Space Sciences Laboratory; Steve W. Bougher of the University of Michigan; and Henri R?me of the Centre d’Etude Spatiale des Rayonnements in Toulouse.

Original Source: UC Berkeley News Release

Posted on by Fraser Cain

What’s Up This Week – December 12 – December 18, 2005

Credit: Roger Warner
Monday, December 12 – Let’s hope observers in Eastern Siberia had the chance to catch the Moon occulting Mars!

Be sure to at least take binoculars out tonight and have a look at the cold and beautiful Moon. Trace its wonderful bright ray systems – such as those that extend from Tycho, Copernicus and Kepler. There is no astronomical target out there able to compete with the details you’ll find on the lunar surface!

Tuesday, December 13 – Set the alarm for 4:30 a.m. and bundle up to watch for your one good chance at the Geminid meter shower!
Today in 1920, the first stellar diameter was measured by Francis Pease with an interferometer at Mt. Wilson. His target? Betelgeuse! Tonight let’s defy the Moon and have a look at the giant star as we look towards the northeastern corner of Orion.

One of the largest known stars, the Hobbits called it “Borgil” – but in the ancient world the Arabs knew this star as “Beit Alguese.” Its bright variability was first noticed by Sir William Herschel in 1836, and followed through its near 6 year cycle of erratic changes. During the phases of expansion and contraction, at smallest Betelgeuse still exceeds the diameter of Earth’s orbit around our own Sun. For all of its size, you might think Betelgeuse to be massive – but it’s not. Although it exceeds Sol by 160 million times in volume, it has only about 20 times more physical mass!

Enjoy its red photons tonight…

Wednesday, December 14 – Today is a very busy day in the history of astronomy. Tycho Brahe was born in 1546. Brahe was a Danish pre-telescopic astronomer who established the first modern observatory in 1582 and gave Kepler his first job in the field. In 1962, Mariner 2 made a flyby of Venus and became the first successful interplanetary probe. And, in 1972, the last humans (so far) to have been on the lunar surface returned to Earth on this date. Eugene Cernan left the final bootprint at Taurus-Littrow and called it the “end of the beginning.”

Tonight will be one of the most hauntingly beautiful and mysterious displays of celestial fireworks all year – the Geminid meteor shower. First noted in 1862 by Robert P. Greg in England, and B. V. Marsh and Prof. Alex C. Twining of the United States in independent studies, the annual appearance of the Geminid stream was weak, producing no more than a few per hour, but it has grown in intensity during the last century and a half. By 1877 astronomers were realizing that a new annual shower was occurring with an hourly rate of about 14. At the turn of the century it had increased to an average of over 20, and by the 1930s to from 40 to 70 per hour. Only eight years ago observers recorded an outstanding 110 per hour during a moonless night… But this time we’re not so fortunate.

So why are the Geminids such a mystery? Most meteor showers are historic, documented and recorded for hundred of years, and we know them as being cometary debris. When astronomers first began looking for the Geminids’ parent comet, they found none. After decades of searching, it wasn’t until October 11, 1983 that Simon Green and John K. Davies, using data from NASA’s Infrared Astronomical Satellite, detected an orbital object which the next night was confirmed by Charles Kowal to match the Geminid meteoroid stream. But this was no comet, it was an asteroid.

Originally designated as 1983 TB, but later renamed 3200 Phaethon, this apparently rocky solar system member has a highly elliptical orbit that places it within 0.15 AU of the Sun about every year and half. But asteroids can’t fragment like a comet – or can they? The original hypothesis was that since Phaethon’s orbit passes through the asteroid belt, it may have collided with other asteroids, creating rocky debris. This sounded good, but the more we studied the more we realized the meteoroid “path” occurred when Phaethon neared the Sun. So now our asteroid is behaving like a comet, yet it doesn’t develop a tail.

So what exactly is this “thing?” Well, we do know that 3200 Phaethon orbits like a comet, yet has the spectral signature of an asteroid. By studying photographs of the meteor showers, scientists have determined that the meteors are more dense than cometary material but not as dense as asteroid fragments. This leads us to believe that Phaethon is probably an extinct comet that has gathered a thick layer of interplanetary dust during its travels, yet retains the ice-like nucleus. Until we are able to take physical samples of this “mystery,” we may never fully understand what Phaethon is, but we can fully appreciate the annual display it produces!

Thanks to the wide path of the stream, folks the world over get an opportunity to enjoy the show. The traditional peak time is tonight – as soon as the constellation of Gemini appears around mid-evening – and it lasts through tomorrow morning. The radiant for the shower is right around bright star Castor, but meteors can originate from many points in the sky. From around 2:00 a.m. until dawn (when our local sky window is aimed directly into the stream) it is possible that we can see about one “shooting star” every 30 seconds, but the Moon will significantly decrease the number of fainter meteors. The most successful of observing nights are ones where you are comfortable, so be sure to use a reclining chair or pad the ground while looking up. Best of luck spotting one of the incredible and mysterious Geminids!

Thursday, December 15 – Heads up for Australia and New Zealand! On this universal date, the Moon will occult bright star Beta Tauri. Please check with IOTA for times in your location. Clear skies, mates!

Today in 1970, Soviet Venera 7 performed a first as it made a successful soft landing on Venus and went into the history books as the first object to land on another planet.

Tonight why not take a few minutes after sunset to land your eyes on Venus? Even if you don’t use a telescope, you can’t miss its ultra-bright appearance to the southwest in the northern hemisphere. If you use a telescope – Power up! Can you tell what percentage of the planet is shadowed? Follow it to month’s end when it will only be 6% illuminated, because it will be a year and a half before we see it like that again!

Friday, December 16 – Today we celebrate the birth of the working-class hero astronomer, Edward Emerson (E.E.) Barnard, Born into hardship in 1857 in Nashville, Tennessee, he was home schooled and began work at age 9 as a photographer. His first telescope was made from a cardboard tube and discarded parts. Continuing to self-educate, he purchased his first telescope and supported himself through awards from comet discoveries. His reputation as an outstanding observer brought him a Fellowship to Vanderbilt College and eventually to the doors of Lick and Yerkes Observatory where his photographic and observational skills became unsurpassed.

While we most commonly recognize Barnard’s discoveries of dark nebulae, did you know that he also did extensive work on objects that we can easily observe? The hauntingly nebulosity in the Pleiades belongs to Barnard, as well as a companion star in the Trapezium. Take a look at the Andromeda Galaxy while you’re out tonight – despite the Moon. While Edward Holden took credit for much of Barnard’s work, his ability to photograph this galaxy with second-hand equipment, and to discover comets in the same way, helped pave the way into a new era of observing.
Saturday, December 17 – Before the Moon rises tonight, let’s turn our attention towards a very beautiful and lesser known open cluster – NGC 663. You’ll find it about one fingerwidth northeast of Delta Cassiopeiae…

This magnificent tornado-shaped collection of stars will be quite noticeable in binoculars and will resolve out more than a dozen members to a small telescope. Larger telescopes will fully resolve this magnitude 7 cluster and reveal color amongst its many stars.
For southern hemisphere observers, look a little more than a fistwidth southeast of Canopus for the incredible NGC 2516. Visible to the unaided eye, this cluster should be spectacular in binoculars or a small telescope! Look for a red star in its center…

Sunday, December 18 – With the later rise of the Moon tonight, take the time to do a quick tour of the skies with binoculars. It would be a great time to try to spot M33 – the “Pinwheel Galaxy” – about three fingerwidths southeast of Beta Andromedae.
If you’re still around when the Moon rises, be sure to take a look at the Mare Crisium area. The terminator will show just how much of a curve we view this feature on!

Until next week, ask for the Moon but keep reaching for the stars! Light speed… ~Tammy Plotner

Posted on by Fraser Cain

Detailed Dark Matter Maps

Dwarf galaxy I Zwicky 18. Image credit: NASA. Click to enlarge
Clues revealed by the recently sharpened view of the Hubble Space Telescope have allowed astronomers to map the location of invisible “dark matter” in unprecedented detail in two very young galaxy clusters.

A Johns Hopkins University-Space Telescope Science Institute team reports its findings in the December issue of Astrophysical Journal. (Other, less-detailed observations appeared in the January 2005 issue of that publication.)

The team’s results lend credence to the theory that the galaxies we can see form at the densest regions of “cosmic webs” of invisible dark matter, just as froth gathers on top of ocean waves, said study co-author Myungkook James Jee, assistant research scientist in the Henry A. Rowland Department of Physics and Astronomy in Johns Hopkins’ Krieger School of Arts and Sciences.

“Advances in computer technology now allow us to simulate the entire universe and to follow the coalescence of matter into stars, galaxies, clusters of galaxies and enormously long filaments of matter from the first hundred thousand years to the present,” Jee said. “However, it is very challenging to verify the simulation results observationally, because dark matter does not emit light.”

Jee said the team measured the subtle gravitational “lensing” apparent in Hubble images ? that is, the small distortions of galaxies’ shapes caused by gravity from unseen dark matter ? to produce its detailed dark matter maps. They conducted their observations in two clusters of galaxies that were forming when the universe was about half its present age.

“The images we took show clearly that the cluster galaxies are located at the densest regions of the dark matter haloes, which are rendered in purple in our images,” Jee said.

The work buttresses the theory that dark matter ? which constitutes 90 percent of matter in the universe ? and visible matter should coalesce at the same places because gravity pulls them together, Jee said. Concentrations of dark matter should attract visible matter, and as a result, assist in the formation of luminous stars, galaxies and galaxy clusters.

Dark matter presents one of the most puzzling problems in modern cosmology. Invisible, yet undoubtedly there ? scientists can measure its effects ? its exact characteristics remain elusive. Previous attempts to map dark matter in detail with ground-based telescopes were handicapped by turbulence in the Earth’s atmosphere, which blurred the resulting images.

“Observing through the atmosphere is like trying to see the details of a picture at the bottom of a swimming pool full of waves,” said Holland Ford, one of the paper’s co-authors and a professor of physics and astronomy at Johns Hopkins.

The Johns Hopkins-STScI team was able to overcome the atmospheric obstacle through the use of the space-based Hubble telescope. The installation of the Advanced Camera for Surveys in the Hubble three years ago was an additional boon, increasing the discovery efficiency of the previous HST by a factor of 10.

The team concentrated on two galaxy clusters (each containing more than 400 galaxies) in the southern sky.

“These images were actually intended mainly to study the galaxies in the clusters, and not the lensing of the background galaxies,” said co-author Richard White, a STScI astronomer who also is head of the Hubble data archive for STScI. “But the sharpness and sensitivity of the images made them ideal for this project. That’s the real beauty of Hubble images: they will be used for years for new scientific investigations.”

The result of the team’s analysis is a series of vividly detailed, computer-simulated images illustrating the dark matter’s location. According to Jee, these images provide researchers with an unprecedented opportunity to infer dark matter’s properties.

The clumped structure of dark matter around the cluster galaxies is consistent with the current belief that dark matter particles are “collision-less,” Jee said. Unlike normal matter particles, physicists believe, they do not collide and scatter like billiard balls but rather simply pass through each other.

“Collision-less particles do not bombard one another, the way two hydrogen atoms do. If dark matter particles were collisional, we would observe a much smoother distribution of dark matter, without any small-scale clumpy structures,” Jee said.

Ford said this study demonstrates that the ACS is uniquely advantageous for gravitational lensing studies and will, over time, substantially enhance understanding of the formation and evolution of the cosmic structure, as well as of dark matter.

“I am enormously gratified that the seven years of hard work by so many talented scientists and engineers to make the Advanced Camera for Surveys is providing all of humanity with deeper images and understandings of the origins of our marvelous universe,” said Ford, who is principal investigator for ACS and a leader of the science team.

The ACS science and engineering team is concentrated at the Johns Hopkins University and the Space Telescope Science Institute on the university’s Homewood campus in Baltimore. It also includes scientists from other major universities in the United States and Europe. ACS was developed by the team under NASA contract NAS5-32865 and this research was supported by NASA grant NAG5-7697.

Original Source: JHU News Release

Posted on by Fraser Cain

Dione and Rhea in the Same Frame

Saturn’s moons, Rhea and Dione. Image credit: NASA/JPL/SSI Click to enlarge
Saturn’s sibling moons, Rhea and Dione, pose for the Cassini spacecraft in this view.

Even at this distance, it is easy to see that Dione (below) appears to have been geologically active in the more recent past, compared to Rhea (above). Dione’s smoother surface and linear depressions mark a contrast with Rhea’s cratered terrain.

Sunlit terrain seen on Rhea (1,528 kilometers, or 949 miles across) is on the moon’s Saturn-facing hemisphere. Lit terrain on Dione (1,126 kilometers, or 700 miles across) is on that moon’s leading hemisphere. North is up.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 1, 2005, at a distance of approximately 1.8 million kilometers (1.1 million miles) from Rhea and 1.2 million kilometers (800,000 miles) from Dione. The image scale is 11 kilometers (7 miles) per pixel on Rhea and 7 kilometers (4 miles) per pixel on Dione.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Northern Lights on the Move

Earth’s northern lights. Image credit: Philippe Moussette.Click to enlarge
After some 400 years of relative stability, Earth’s North Magnetic Pole has moved nearly 1,100 kilometers out into the Arctic Ocean during the last century and at its present rate could move from northern Canada to Siberia within the next half-century.

If that happens, Alaska may be in danger of losing one of its most stunning natural phenomena – the Northern Lights.

But the surprisingly rapid movement of the magnetic pole doesn’t necessarily mean that our planet is going through a large-scale change that would result in the reversal of the Earth’s magnetic field, Oregon State University paleomagnetist Joseph Stoner reported at the annual meeting of the American Geophysical Union in San Francisco, Calif.

“This may be part of a normal oscillation and it will eventually migrate back toward Canada,” said Stoner, an assistant professor in OSU’s College of Oceanic and Atmospheric Sciences. “There is a lot of variability in its movement.”

Calculations of the North Magnetic Pole’s location from historical records goes back only about 400 years, while polar observations trace back to John Ross in 1838 at the west coast of Boothia Peninsula. To track its history beyond that, scientists have to dig into the Earth to look for clues.

Stoner and his colleagues have examined the sediment record from several Arctic lakes. These sediments – magnetic particles called magnetite – record the Earth’s magnetic field at the time they were deposited. Using carbon dating and other technologies – including layer counting – the scientists can determine approximately when the sediments were deposited and track changes in the magnetic field.

The Earth last went through a magnetic reversal some 780,000 years ago. These episodic reversals, in which south becomes north and vice versa, take thousands of years and are the result of complex changes in the Earth’s outer core. Liquid iron within the core generates the magnetic field that blankets the planet.

Because of that field, a compass reading of north in Oregon will be approximately 17 degrees east from “true geographic north.” In Florida, farther away and more in line with the poles, the declination is only 4-5 degrees west.

The Northern Lights, which are triggered by the sun and fixed in position by the magnetic field, drift with the movement of the North Magnetic Pole and may soon be visible in more southerly parts of Siberia and Europe – and less so in northern Canada and Alaska.

In their research, funded by the National Science Foundation, Stoner and his colleagues took core samples from several lakes, but focused on Sawtooth Lake and Murray Lake on Ellesmere Island in the Canadian Arctic. These lakes, about 40 to 80 meters deep, are covered by 2-3 meters of ice. The researchers drill through the ice, extend their corer down through the water, and retrieve sediment cores about five meters deep from the bottom of the lakes.

The 5-meter core samples provide sediments deposited up to about 5,000 years ago. Below that is bedrock, scoured clean by ice about 7,000 to 8,000 years ago.

“The conditions there give us nice age control,” Stoner said. “One of the problems with tracking the movement of the North Magnetic Pole has been tying the changes in the magnetic field to time. There just hasn’t been very good time constraint. But these sediments provide a reliable and reasonably tight timeline, having consistently been laid down at the rate of about one millimeter a year in annual layers.

“We’re trying to get the chronology down to a decadal scale or better.”

What their research has told Stoner and his colleagues is that the North Magnetic Pole has moved all over the place over the last few thousand years. In general, it moves back and forth between northern Canada and Siberia. But it also can veer sideways.

“There is a lot of variability in the polar motion,” Stoner pointed out, “but it isn’t something that occurs often. There appears to be a ‘jerk’ of the magnetic field that takes place every 500 years or so. The bottom line is that geomagnetic changes can be a lot more abrupt than we ever thought.”

Shifts in the North Magnetic Pole are of interest beyond the scientific community. Radiation influx is associated with the magnetic field, and charged particles streaming down through the atmosphere can affect airplane flights and telecommunications.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

Hayabusa Probably Didn’t Get a Sample After All

Artist’s impression of Hayabusa spacecraft. Image credit: JAXA Click to enlarge
As has been reported, it is estimated that part of a series of attitude and orbit control commands to restore the Hayabusa from its safe-hold mode have not gone well, and the functions of its major systems, including its attitude and communication network, have significantly deteriorated. However, on Nov. 29, a beacon line through a low gain antenna was restored.

On Nov. 30, we started a restoration operation by turning on and off the radio frequency modulation through the autonomous diagnostic function. Subsequently, on Dec. 1, telemetry data were acquired at 8 bits per second through the low gain antenna, although the line was weak and often disconnected. According to the data transmitted so far, the attitude and orbit control commands sent on Nov. 27 did not work well due to an unknown reason, and either major attitude control trouble or a large electric power loss seems to have occurred. It is estimated that the overall power switching systems for many pieces of onboard equipment were reset as their temperature dropped substantially due to the evaporation of leaked propellant, and also because of a serious discharge of electricity from the batteries of many sets of onboard equipment and systems due to declining power generation. Details are still under analysis.

On Dec. 2, we tried to restart the chemical engine, but, even though a small thrust was confirmed, we were not able to restore full-scale operations. Consequently, the cause of the anomaly on Nov 27 is still under investigation, and we suspect that one of the causes could be the malfunction of the chemical engine.

On Dec. 3, we found that the angles between the axis of the onboard high gain antenna (+Z angle) and the Sun, and also that with the earth, had increased to 20 to 30 degrees. As an emergency attitude control method, we decided to adopt a method of jetting out xenon for the ion engine operation. Accordingly, we immediately started to create the necessary operation software. As we completed the software on Dec. 4, we changed the spin speed by xenon jet, and its function was confirmed. Without delay, we sent an attitude change command through this function.

As a result, on Dec. 5, the angle between the +Z axis and the sun, and the earth, recovered to 10 to 20 degrees, and the telemetry data reception and acquisition speed was restored to the maximum 256 bits per second through the mid gain antenna.

After that, we found that there was a high possibility that the projectile (bullet) for sampling had not been discharged on Nov. 26, as we finally acquired a record of the pyrotechnics control device for projectile discharging from which we were not able to confirm data showing a successful discharge. However, it may be because of the impact of the system power reset; therefore, we are now analyzing the details including the confirmation of the sequence before and after the landing on Nov. 26.

As of Dec. 6, the distance between the Hayabusa and the Itokawa is about 550 kilometers, and that from the earth is about 290 million kilometers. The explorer is relatively moving from the Itokawa toward the earth at about 5 kilometers per hour.

We are now engaging in turning on, testing, and verifying onboard equipment of the Hayabusa one by one to start the ion engine. We currently plan to shift the attitude control to one using the Z-axis reaction wheel, and restart the ion engine. The restart is expected to happen no earlier than the 14th. We are currently rescheduling the plan for the return trip to earth. We need to study how to relax the engine operation efficiency. We will do our utmost to solve the problem with the attitude control (such as the restoration of the chemical engine), then find a solution for the return trip.

Original Source: JAXA News Release

Posted on by Fraser Cain

Women Wrap Up 60 Days of Simulated Spaceflight

WISE bed rest study participant Dorota. Image credit: ESA Click to enlarge
When the first women astronauts set foot on Mars, they may spare a thought for the 24 women who paved the way for lengthy space trips by giving three months of their lives to space science, two months of which involved staying in bed.

From March to May and from September to November, two different groups of 12 volunteers from eight European countries – the Czech Republic, Finland, France, Germany, the Netherlands, Poland, Switzerland, and the United Kingdom – took part in the Women International Space Simulation for Exploration (WISE) campaign on behalf of the European Space Agency (ESA), the French space agency (CNES), the Canadian Space Agency (CSA) and the US National Aeronautics and Space Administration (NASA).

The volunteers of the WISE femal bedrest study underwent numerous medical tests
They gathered at the MEDES Space Clinic in Rangueil Hospital in Toulouse, France, to take up an extraordinary challenge: a 60-day campaign of female bedrest. For two months, they had to lie down and undertake all daily activities in beds tilted at an angle of 6? below horizontal, so that their heads were slightly lower than their feet. This unusual position induces physiological changes similar to those experienced by astronauts in weightlessness.

The last volunteers of the second WISE campaign got up on 30 November, and are now undergoing rehabilitation and medical tests lasting until 20 December. Similar tests were conducted in the pre-bedrest period for comparison.

MEDES, the French Institute for Space Medicine and Physiology, organised the selection of the volunteers and provided medical, paramedical and technical staff to support the extensive science experiments.

The main objective of the WISE campaign has been to assess the roles of nutrition and physical exercise with adapted equipment in countering the adverse effects of prolonged microgravity conditions, in order to develop the counter-measures that will be required when future astronauts venture beyond the Earth orbit to explore other worlds.

The data collected by the international science teams during the WISE study will improve our knowledge of muscle condition, blood parameters, cardiovascular condition, coordination of movements, changes in endocrine and immune systems, metabolism, bone status, as well as psychological wellbeing. This will serve not only the future of human spaceflight, but our everyday lives on Earth too, by providing clues as to how to deal with osteoporosis, fight the ”metabolic syndrome?, which affects millions of sedentary workers who take insufficient physical exercise, assist recovery of bedridden patients, or prevent some cardiovascular conditions.

Twelve scientific teams from 11 countries – Belgium, Canada, Denmark, France, Germany, Italy, the Netherlands, Sweden, Switzerland, the United Kingdom and the United States – are involved in the study. It will take them several months to analyse their data and start publishing their findings. In order to answer certain scientific questions, a follow-up of the volunteers will continue for three more years.

?The WISE campaign has now come to a successful conclusion and I look forward to further campaigns in the future where there is this degree of international involvement and complexity?, said Didier Schmitt, Head of the Life Sciences Unit in ESA?s Directorate of Human Spaceflight, Microgravity and Exploration. ?Planning for future research is already under way with a programme of bedrest campaigns being prepared, covering the next three years. This will be a combination of short-term, intermediate and long-term bedrest studies, lasting 5, 21 and 60 days, respectively. A research announcement covering this period is due to be released in the near future as part of the European programme for Life and Physical Sciences and Applications using the ISS (ELIPS). A further two bedrest studies are planned, one in Berlin and the other at the DLR in Cologne and they have already been selected as part of the ESA Microgravity Applications Programme (MAP). These studies are currently awaiting the necessary funding, also from the ELIPS Programme.?

To mark the completion of the WISE 2005 campaigns, ESA, CNES and MEDES are to hold a press conference, together with representatives from NASA and CSA, science teams and volunteers from the second WISE campaign, at the “Cit? de l?Espace” in Toulouse on 13 December.

Media representatives wishing to attend this press conference are requested to apply using the attached form, which should be returned to the address shown at the bottom of the form.

For additional information, ESA has created a website on the WISE study at:
http://www.spaceflight.esa.int/wise

Original Source: ESA Portal

Posted on by Fraser Cain

Hopping Microrobots

Planetary MicroBots. Image credit: NASA Click to enlarge
Interview with Penny Boston, Part I

If you want to travel to distant stars, or find life on another world, it takes a bit of planning. That’s why NASA has established NIAC, the NASA Institute for Advanced Concepts. For the past several years, NASA has been encouraging scientists and engineers to think outside the box, to come up with ideas just this side of science fiction. Their hope is that some of these ideas will pan out, and provide the agency with technologies it can use 20, 30, or 40 years down the road.

NIAC provides funding on a competitive basis. Only a handful of the dozens of proposals submitted are funded. Phase I funding is minimal, just enough for researchers to flesh out their idea on paper. If the idea shows merit, it then may get Phase II funding, allowing the research to continue from the pure-concept to the crude-prototype stage.

One of the projects that received Phase II funding earlier this year was a collaboration between Dr. Penelope Boston and Dr. Steven Dubowsky to develop “hopping microbots” capable of exploring hazardous terrain, including underground caves. If the project pans out, hopping microbots may some day be sent to search for life below the surface of Mars.

Boston spends a lot of time in caves, studying the microorganisms that live there. She is the director of the Cave and Karst Studies Program and an associate professor at New Mexico Tech in Socorro, New Mexico. Dubowsky is the director of the MIT Field and Space Robotics Laboratory at MIT, in Cambridge, Massachusetts. He is known in part for his research into artificial muscles.

Astrobiology Magazine interviewed Boston shortly after she and Dubowsky received their Phase II NIAC grant. This is the first of a two-part interview. Astrobiology Magazine (AM): You and Dr. Steven Dubowsky recently received funding from NIAC to work on the idea of using miniature robots to explore subsurface caves on Mars? How did this project come about?

Penny Boston (PB): We’ve been doing quite a lot of work in caves on Earth with an eye to looking at the microbial inhabitants of these unique environments. We think they can serve as templates for looking for life forms on Mars and other extraterrestrial bodies. I published a paper in 1992, with Chris McKay and Michael Ivanov, suggesting that the subsurface of Mars would be the last refuge of life on that planet as it became colder and drier over geological time. That got us into the business of looking into the subsurface on Earth. When we did, we discovered that there is an amazing array of organisms that are apparently indigenous to the subsurface. They interact with the mineralogy and produce unique biosignatures. So it became a very fertile area for us to study.

Getting into difficult caves even on this planet is not that easy. Translating that to robotic extraterrestrial missions requires some thought. We have good imaging data from Mars showing distinct geomorphological evidence for at least lava-tube caves. So we know that Mars has at least that one type of cave that could be a useful scientific target for future missions. It’s plausible to think that there are also other types of caves and we have a paper in press in an upcoming Geological Society of America Special Paper exploring unique cave-forming (speleogenetic) mechanisms on Mars. The big sticking point is how to get around in such rigorous and difficult terrain.

AM: Can you describe what you did in the first phase of the project?

PB: In Phase I, we wanted to focus on robotic units that were small, very numerous (hence expendable), largely autonomous, and that had the mobility that was needed for getting into rugged terrains. Based on Dr. Dubowsky’s ongoing work with artificial-muscle-activated robotic motion, we came up with the idea of many, many, tiny little spheres, about the size of tennis balls, that essentially hop, almost like Mexican jumping beans. They store up muscle energy, so to speak, and then they boink themselves off in various directions. That’s how they move.

credit:Render by R.D.Gus Frederick
Planetary Setting For Large-Scale Planetary Surface & Subsurface Exploration. Click image for larger view.
Image Credit: Render by R.D.Gus Frederick

We’ve calculated that we could probably pack about a thousand of these guys into a payload mass the size of one of the current MERs (Mars Exploration Rovers). That would give us the flexibility to suffer the loss of a large percentage of the units and still have a network that could be doing recon and sensing, imaging, and perhaps even some other science functions.

AM: How do all these little spheres co-ordinate with each other?

PB: They behave as a swarm. They relate to each other using very simple rules, but that produces a great deal of flexibility in their collective behavior that enables them to meet the demands of unpredictable and hazardous terrain. The ultimate product that we’re envisioning is a fleet of these little guys being sent to some promising landing site, exiting from the lander and then making their way over to some subsurface or other hazardous terrain, where they deploy themselves as a network. They create a cellular communication network, on a node-to-node basis.

AM: Are they able to control the direction in which they hop?

PB: We have aspirations for them ultimately to be very capable. As we move into Phase II, we’re working with Fritz Printz at Stanford on ultra-miniature fuel cells to power these little guys, which would enable them to be able to do a fairly complex array of things. One of those capabilities is to have some control over the direction in which they go. There are certain ways that they can be built that can allow them to preferentially go in one direction or another. It’s not quite as precise as it would be if they were wheeled rovers just going on a straight path. But they can preferentially cant themselves more or less in the direction that they wish to go. So we’re envisioning that they will have at least crude control over direction. But a lot of their value has to do with their swarm motion as an expanding cloud.

As wonderful as the MER rovers are, for the kind of science I do, I need something more akin to the insect robot idea pioneered by Rodney Brooks at MIT. Being able to tap into the model of insect intelligence and adaptation for exploration had long appealed to me. Adding that to the unique mobility provided by Dr. Dubowsky’s hopping idea, I think, can enable a reasonable percentage of these little units to survive the hazards of subsurface terrain – that just seemed like a magical combination to me.

HB: So in Phase I, did any of these actually get built?

PB: No. Phase I, with NIAC, is a six-months-long brain-straining, pencil-pushing study, to scope out the state of the art of the relevant technologies. In Phase II, we’re going to do a limited amount of prototyping and field-testing, over a two-year period. This is far less than what one might need for an actual mission. But, of course, that is NIAC’s mandate, to examine technology 10 to 40 years out. We’re thinking this is probably in the 10- to 20-year range.

AM: What kinds of sensors or scientific equipment do you imagine being able to put on these things?

PB: Imaging is clearly something that we would like to do. As cameras become incredibly tiny and robust, there are already units in the size range that could be mounted on these things. Possibly some of the units could be fitted with magnification capability, so one could look at the textures of the materials that they are landing on. Integrating images taken by tiny cameras on lots of different little units is one of the areas for future development. That’s beyond the scope of this project, but that’s what we’re thinking of for imaging. And then, certainly chemical sensors, being able to sniff and sense the chemical environment, which is very critical. Everything from tiny laser noses to ion-selective electrodes for gases.

We are envisioning having them not all identical, but rather an ensemble, with enough of the different kinds of units fitted out with different kinds of sensors so that the probability would still be high, even given fairly high losses of numbers of units, that we would still have a complete suite of sensors. Even though each individual unit cannot have a giant payload of sensors on it, you could have enough so that it could give significant overlap with its fellow units.

AM: Will it be possible to do biological testing?

PB: I think so. Particularly if you imagine the time frame that we’re looking at, with the advances that are coming online with everything from quantum dots to lab-on-a-chip devices. Of course, the difficulty is getting sample material to those. But when we’re dealing with little ground-contacting units like our hopping microbots, you might be able to position them directly over the material that they wish to test. In combination with microscopy and wider-field imagery, I think that the capability is there to do some serious biological work.

AM: Do you have an idea of what the milestones are that you’re hoping to hit during your two-year project?

PB: We’re anticipating that by March we may have crude prototypes that have the relevant mobility. But that may be overly ambitious. Once we do have mobile units, our plan is to do field testing in real lava-tube caves that we are doing science on in New Mexico.

The field site’s already tested. As part of Phase I the MIT group came out and I taught them a little bit about caving and what the terrain was actually like. It was a big eye-opener for them. It’s one thing to design robots for the halls of MIT, but it’s another thing to design them for real-world rocky environments. It was a very educational experience for us all. I think they have a pretty good idea what the conditions are that they have to meet with their design.

AM: What are those conditions?

PB: Extremely uneven terrain, lots of crevices that these guys could get temporarily jammed in. So we’ll need modes of operation that will allow them to extricate themselves, at least with a reasonable chance of success. The challenges of line-of-sight communication in a highly rough surface. Getting over big boulders. Getting stuck in little cracks. Things of that sort.

Lava is not smooth. The interior of lava tubes is intrinsically smooth after they’re formed, but there is a lot of material that shrinks and cracks and falls down. So there are rubble piles to get around and over, and a lot of elevational change. And these are things that conventional robots don’t have the capability to do.

Original Source: NASA Astrobiology