Posted on by Fraser Cain

Uncovering More Details About the Solar Wind

Image credit: SOHO

The ESA’s SOHO spacecraft has uncovered new details about the Sun’s solar wind which might overturn previously held theories about exactly how the wind is generated. Astronomers believed that the fast wind emanates from gaps between giant plumes found near the Sun’s polar regions. But the new theory, supported by data from SOHO is that it’s the plumes themselves which are hurling the particles of the fast wind into space. If this controversial theory turns out to be correct, it will clear up a big misunderstanding about the Sun.

We have known for 40 years that space weather affects the Earth, which is buffeted by a ‘wind’ from the Sun, but only now are we learning more about its precise origins. Solving the mystery of the solar wind has been a prime task for ESA’s SOHO spacecraft. Its latest findings, announced on 20 May 2003, may overturn previous ideas about the origin of the ‘fast’ solar wind, which occurs in most of the space around the Sun.

Earlier results from SOHO established that the gas of the fast wind leaks through magnetic barriers near the Sun’s visible surface. Straight, spoke-like features called plumes have also been seen rising from the solar atmosphere at the polar regions, where much of the fast wind comes from. According to previous ideas, the gas of the fast wind streams out in the gaps between the plumes.

“Not so,” says Alan Gabriel of the Institut d’Astrophysique Spatiale near Paris, France. Careful observations with SOHO now suggest that most of the fast wind leaves the Sun via the plumes themselves, which are denser than their surroundings. Gabriel and his team tracked gas rising at about 60 kilometres per second to a height of 250 000 kilometres above the Sun’s visible surface.

“If this controversial result is right, it will clear up a big misunderstanding,” says Bernhard Fleck, ESA’s Project Scientist for SOHO. “We need to know how the fast wind is subsequently accelerated to 750 kilometres per second. To find out, we’d better be looking in the right places.”

SOHO has also investigated the origin of a slower wind, half the speed of the fast wind, which comes from the Sun’s equatorial regions. The gas of the ‘slow’ wind leaks from triangular features called ‘helmets’, which are plainly protruding into the Sun’s atmosphere during a solar eclipse. Blasts of gas called ‘coronal mass ejections’ also contribute to the solar wind in the equatorial zone of the Sun.

The ESA/NASA Ulysses spacecraft has twice passed over the poles of the Sun and signalled the relative importance of these fast and slow winds. Its measurements show that the fast wind predominates in the heliosphere, which is a huge bubble blown into interstellar space by the Sun’s outpourings, and extending far beyond the outermost planets. In interplanetary space, the fast wind often collides with the slow wind. Like the mass ejections, the collisions create shock waves that agitate the Earth’s space environment.

The four satellites of ESA’s Cluster mission are now studying the interaction between the solar wind and our planet’s defences. The Earth’s magnetic field creates a bubble within the heliosphere, but it does not give us perfect protection from Sun’s storms. Ulysses, SOHO, and Cluster together provide an extraordinary overview of solar behaviour and its effects, both near and far in the Solar System.

Original Source: ESA News Release

Posted on by Fraser Cain

Researchers Stop Light in Its Tracks

Image credit: NASA

Researchers at Harvard University demonstrated that they can slow light and even completely stop it for several thousandths of a second. They built a chamber containing a cloud of sodium atoms cooled to almost absolute zero and then fired a light pulse into this cloud. The pulse slowed to a stop and even turned off ? the researchers were able to revive it again by firing a laser into the cloud. Although this breakthrough happened a couple of years ago, and an upcoming special edition of Scientific American called ?The Edge of Physics? will provide an update to the research.

NASA-funded research at Harvard University, Cambridge, Mass., that literally stops light in its tracks, may someday lead to breakneck-speed computers that shelter enormous amounts of data from hackers.

The research, conducted by a team led by Dr. Lene Hau, a Harvard physics professor, is one of 12 research projects featured in a special edition of Scientific American entitled “The Edge of Physics,” available through May 31.

In their laboratory, Hau and her colleagues have been able to slow a pulse of light, and even stop it, for several-thousandths of a second. They’ve also created a roadblock for light, where they can shorten a light pulse by factors of a billion.

“This could open up a whole new way to use light, doing things we could only imagine before,” Hau said. “Until now, many technologies have been limited by the speed at which light travels.”

The speed of light is approximately 300,000 kilometers per second (about 186,000 miles per second or 670 million miles per hour). Some substances, like water and diamonds, can slow light to a limited extent. More drastic techniques are needed to dramatically reduce the speed of light. Hau’s team accomplished “light magic” by laser-cooling a cigar-shaped cloud of sodium atoms to one-billionth of a degree above absolute zero, the point where scientists believe no further cooling can occur. Using a powerful electromagnet, the researchers suspended the cloud in an ultra-high vacuum chamber, until it formed a frigid, swamp-like goop of atoms.

When they shot a light pulse into the cloud, it bogged down, slowed dramatically, eventually stopped, and turned off. The scientists later revived the light pulse and restored its normal speed by shooting an additional laser beam into the cloud.

Hau’s cold-atom research began in the mid-1990s, when she put ultra-cold atoms in such cramped quarters they formed a type of matter called a Bose-Einstein condensate. In this state, atoms behave oddly, and traditional laws of physics do not apply. Instead of bouncing off each other like bumper cars, the atoms join together and function as one entity.

The first slow-light breakthrough for Hau and her colleagues came in March 1998. Later that summer, they successfully slowed a light beam to 38 miles per hour, the speed of suburban traffic. That’s 2 million times slower than the speed of light in free space. By tinkering with the system, Hau and her team made light stop completely in the summer of 2000.

These breakthroughs may eventually be used in advanced optical-communication applications. “Light can carry enormous amounts of information through changes in its frequency, phase, intensity or other properties,” Hau said. When the light pulse stops its information is suspended and stored, just as information is stored in the memory of a computer. Light-carrying quantum bits could carry significantly more information than current computer bits. Quantum computers could also be more secure by encrypting information in elaborate codes that could be broken only by using a laser and complex decoding formulas.

Hau’s team is also using slow light as a completely new probe of the very odd properties of Bose-Einstein condensates. For example, with the light roadblock the team created, they can study waves and dramatic rotating-vortex patterns in the condensates.

The Harvard research team includes Hau; Drs. Zachary Dutton, Chien Liu, Brian Busch and Michael Budde; and graduate students Christopher Slowe, Naomi Ginsberg and Cyrus Behroozi. More information about Hau’s research is available on the Internet, at http://www.physics.harvard.edu/fac_staff/hau.html.

For information about NASA’s Fundamental Physics Program on the Internet, visit http://spaceresearch.nasa.gov or http://funphysics.jpl.nasa.gov.

Hau conducts research under NASA’s Fundamental Physics in Physical Sciences Research Program, part of the agency’s Office of Biological and Physical Research, Washington. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., a division of the California Institute of Technology, Pasadena, manages the Fundamental Physics program.

Original Source: NASA News Release

Posted on by Fraser Cain

MARS-1 Humvee Rover Arrives at Devon Island

Image credit: Mars Institute

The Mars Institute confirmed today that the MARS-1 Humvee Rover successfully crossed the frozen Wellington Channel reaching NASA Haughton-Mars Project on Devon Island. The odd-looking vehicle is a converted Humvee military ambulance with widened tracks for the snow, and will be equipped with scientific equipment for exploring the region. Devon Island, in the Canadian Arctic, is barren and remote and makes a great testing ground for learning what it will take to send a human mission to Mars.

The Mars Institute today announced that its MARS-1 Humvee rover has reached Devon Island in the Canadian high Arctic after successfully crossing the Wellington Channel, a 23 mile (37 km) stretch of treacherous sea ice separating Cornwallis Island from Devon Island at 75?N. The vehicle was driven and escorted by a team of four expeditioners led by Dr Pascal Lee, Project Lead for the NASA Haughton-Mars Project (HMP) and Chairman of the Mars Institute.

“We are very happy everything went well,” said Lee. The successful arrival of the rover on Devon Island represents an important milestone in the research effort Lee and his colleagues on the HMP have developed in the Arctic since 1997. “The MARS-1 Humvee rover is a powerful new tool for our scientific investigations on Devon. It will serve as a long-distance roving field lab and will also allow us to study the design and operation of future large pressurized rovers for the human exploration of the Moon and Mars”.

The distinctive orange MARS-1 Humvee rover is a unique experimental field exploration vehicle modified for the HMP by AM General, manufacturer of the famous High Mobility Multi-purpose Wheeled Vehicle (HMMWV) or Humvee. The refurbished four-wheel-drive all-terrain rover rolled out of AM General’s plant in Mishiwaka, Indiana, on May 14, 2002, bearing the one-of-a-kind serial number “MARS-1”. The vehicle configuration is based on a military ambulance HMMWV. To increase traction and tread lightly, the MARS-1 is equipped with wide tracks manufactured by Mattracks, Inc. The MARS-1 reached Resolute Bay on Cornwallis Island, high Arctic, the starting point of the expedition, on a C-130 transport plane of the United States Marine Corps.

“This rover will be a mobile all-terrain laboratory from which we will be able to access and deliver data as we go about our scientific field work on Devon Island. From that experience, we’ll learn how to do the same thing for planetary exploration” said Dr. Stephen Braham of Simon Fraser University (SFU), Vancouver, British Columbia, Chief Field Engineer and Canadian Principal Investigator for the HMP. Dr. Braham will lead a Canadian Space Agency (CSA) funded research program under the SFU-led MarsCanada CSA Support Study, totaling C$272,000, to develop the advanced power, computing, and communications systems for MARS-1, as a study of the technologies required for future robotic and crewed Mars rovers.

In addition to Lee who has spent five summers and a winter in Antarctica and was leading his eighth Arctic expedition, the team of four in the successful crossing comprised Mr. John W. Schutt, a veteran field guide of over thirty Arctic and Antarctic scientific research expeditions, and Mr. Joe Amarualik and Mr. Paul Amagoalik, two Inuit residents of Resolute Bay and highly experienced experts in Arctic land and sea travel working as a two-brother team. Joe Amarualik is a Master Corporal in the Resolute Bay Patrol of the Canadian Rangers, and Paul Amagoalik an expert in Arctic resources.

The team left Resolute Bay at 9:30 pm CDT on May 10, 2003, driving the MARS-1 and three snowmobiles with traditional Inuit komatik sleds on tow. After a 6-hour overland traverse under the midnight sun, they reached Read Bay on the east coast of Cornwallis Island (75?02’N, 94?36’W) and rested for the “night” inside the rover. The next day, May 11 at 3:30 pm CDT, the 8800 lb (4 metric ton) MARS-1 ventured onto the rugged sea ice off Read Bay, only to touch land again 3.5 hours later 23 miles (35 km) to the East, at Cape McBain, on the west coast of Devon Island (75?04’N, 92?13’W). The rover was driven in shifts by Lee and Schutt, both of whom received formal training in the operation and maintenance of military Humvees at the AM General plant prior to this Arctic trek.

“Things have come a long way since the ill-fated Franklin Expedition explored this area in the 1840s in search of the Northwest Passage. We planned our expedition carefully, but the Arctic remains an unforgiving environment and there was always some concern that disaster might befall us as well” said Schutt who, when not in the Arctic with the NASA HMP, is chief field guide for the National Science Foundation Antarctic Search for Meteorites (ANSMET) program. A geologist and experienced ice expert, Schutt was a member of the team that recovered the now-famous ALH84001 meteorite thought by some scientists to contain possible evidence of past life on Mars.

Original Source: Mars Institute News Release

Posted on by Fraser Cain

Supermassive Black Holes Contribute to Galaxy Growth

Image credit: Chandra

New images taken by the Chandra X-Ray Observatory show galaxies in an energetic phase in their development. Supermassive black holes at their centres are transferring a significant amount of energy into the gas surrounding the galaxies. Astronomers believe that this is just a stage in longer cycle where gas cools to form galaxies, which then merge and create a supermassive black hole. Jets of hot gas blast away from the black hole sweeping away all matter, giving the gas a chance to cool back down ? and then the cycle starts all over again.

Images made by NASA’s Chandra X-ray Observatory have revealed two distant cosmic construction sites buzzing with activity. This discovery shows how super massive black holes control the growth of massive galaxies in the distant universe.

X-rays were detected from vast clouds of high-energy particles around the galaxies 3C294 and 4C41.17, which are 10 and 12 billion light-years from Earth, respectively. The energetic particles were left over from past explosive events that can be traced through the X-ray and radio jets back to the super massive black holes located in the centers of the galaxies.

“These galaxies are revealing an energetic phase in which a super massive black hole transfers considerable energy into the gas surrounding the galaxies,” said Andrew Fabian of England’s Cambridge University, lead author of a paper on 3C294 to appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society. “This appears to be crucial in explaining the puzzling properties of present-day galaxies, especially those that group together in large clusters,” he said.

The picture that is emerging is of a grand cosmic cycle. A dense region of intergalactic gas cools to form several smaller galaxies, which merge to form a larger galaxy with a super massive black hole. The galaxy and its central black hole continue to grow until the energy generated by jets from the vicinity of the voracious black hole stops the fall of matter into the black hole. Millions of years after the jet activity subsides, matter will resume falling into the black hole and the cycle begins anew.

Both 3C294 and 4C41.17 reside in regions of space containing unusually high numbers of galaxies. The gas and galaxies surrounding these galaxies will eventually collapse to form galaxy clusters, some of the most massive objects in the universe. Although 3C294 and 4C41.17 will grow to gargantuan sizes, through the accumulation of surrounding matter that forms hundreds of billions of stars, their growth does not go unchecked.

“It’s as if nature tries to impose a weight limit on the size of the most massive galaxies,” said Caleb Scharf of Columbia University, New York, and lead author of a paper on 4C41.17 to be published in The Astrophysical Journal. “The Chandra observations have given us an important clue as to how this occurs. The high-energy jets give the super massive black holes an extended reach to regulate the growth of these galaxies,” he said.

In 3C294 and 4C41.17, the hot swirling infernos around their super massive black holes have launched magnetized jets of high-energy particles first identified by radio telescopes. These jets, which were also detected by Chandra, have swept up clouds of dust and gas and have helped trigger the formation of billions of new stars. The dusty, star-forming clouds of 4C41.17, the most powerful source of infrared radiation ever observed, are embedded in even larger clouds of gas.

Astronomers recently used the Keck Observatory to observe these larger clouds, which have a temperature of 10,000 degrees. These clouds are leftover material from the galaxy’s formation and should have cooled rapidly by radiation in the absence of a heat source.

“Significantly, the warm gas clouds coincide closely with the largest extent of the X-ray emission,” said Michiel Reuland of Lawrence Livermore National Laboratory, Livermore, Calif., a coauthor on the 4C41.17 paper and a paper describing the Keck Observatory work. “The Chandra results show that high-energy particles or radiation can supply the necessary energy to light up these clouds,” he said.

Most of the X-rays from 4C41.17 and 3C294 are due to collisions of energetic electrons with the cosmic background of photons produced in the hot early universe. Because these galaxies are far away, their observed radiation originated when the universe was younger and the background was more intense. This effect enhances the X-radiation and helps astronomers to study extremely distant galaxies.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program. TRW, Inc., Redondo Beach, Calif., is the spacecraft prime contractor. The Smithsonian’s Chandra X-ray Center controls science and flight operations from Cambridge, Mass., for the Office of Space Science, NASA Headquarters, Washington.

Original Source: NASA News Release

Posted on by Fraser Cain

Puzzling Jets Seen Blasting Out from a Nebula

Image credit: ESA

Astronomers from the European Space Agency have uncovered a bizarre mystery. They?ve found strange jets emerging from a planetary nebula called Henize 3-1475. Even more unusual is the shape of the jets, which curve back on opposite sides like water coming from a rotating garden sprinkler. Their theory is that a large star at the centre of the nebula is emanating the jets as it slowly turns, once every 1,500 years. Furthermore, the flow isn?t smooth, it?s all bubbled and knotted, leading the astronomers to believe new gas blasts out every 100 years or so.

There are many mysterious objects seen in the night sky which are not really well understood. For example, astronomers are puzzled by the ‘jets’ emerging from planetary nebulae. However, the S-shaped jet from Henize 3-1475 is the most perplexing of all.

‘Jets’ are long outflows of fast-moving gas found near many objects in the Universe, such as around young stars, or coming from black holes, neutron stars, and planetary nebulae, for example. The NASA/ESA Hubble Space Telescope has imaged the young planetary nebula Henize 3-1475 and its bizarre jet. Astronomers have nicknamed it the ‘Garden-sprinkler’ Nebula.

The origin of jets in the Universe is unclear, but they appear to originate in small regions of space where even Hubble’s sharp vision cannot penetrate. To produce a jet, you require some sort of nozzle mechanism. So far, these theoretical ‘nozzles’ remain hidden by dust that obscures our view of the centres of planetary nebulae.

Despite decades of intense effort, there is no single example of a jet whose origin is clearly understood. The curious S-shape and extreme high speed of its gaseous outflow gives Henize 3-1475 a special place in the study of planetary nebulae.

Henize 3-1475 is located in the constellation of Sagittarius around 18 000 light-years away from us. The central star is more than 12 000 times as luminous as our Sun and weighs three to five times as much. With a velocity of around 4 million kilometres per hour, the jets are the fastest ever discovered. Scientists are also intrigued by the converging, funnel-shaped structures that connect the innermost ‘knots’ and the core region.

A group of international astronomers led by Angels Riera from Universitat Polit?cnica de Catalunya, Barcelona, Spain, have combined observations from Hubble’s Wide Field and Planetary Camera 2, the Space Telescope Imaging Spectrograph and ground-based telescopes. Their work suggests that the nebula’s S-shape and hypervelocity outflow is created by a central source that ejects streams of gas in opposite directions and precesses once every 1500 years. It is like an enormous, slowly rotating garden sprinkler.

The flow is not smooth, but rather episodic with an interval of about 100 years, creating clumps of gas moving away at velocities up to 4 million kilometres per hour. The reason for these intermittent ejections of gas is not known. It may be due to either cyclic magnetic processes in the central star (similar to the Sun’s 22-year magnetic cycle), or to interactions with a companion star.

Original Source: ESA News Release

Posted on by Fraser Cain

New Site Design

I’ve been frustrated with the previous design of Universe Today for the better part of a year now, so I finally got some time together and redesigned the site from top to bottom. While I was at it, I also took better advantage of the publishing system I’m using (Article Manager from interactivetools.com) to tie in links to other resources on the site.

I also changed my webhost. My previously fabulous webhost (Communitech) was bought by another service provider whose technical support wasn’t nearly as good (that’s me putting it delicately). So, I switched to a new provider called Blue Virtual. It’s way faster, cheaper, and has a bunch of new software that I’m going to be taking advantage of.

Instead of majordomo, my new server uses a service called Mailman, which seems to be 100x better. It’s got a handy web interface so you can all manage your subscribe/unsubscribe stuff yourself.

So, thanks for your patience, please give me any feedback you can ([email protected]): either on the design or any problems you find with the new site (I’m still fixing older articles so they work in the new format, some of their links will be broken).

Take care,

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Foam Does Seem to Be the Culprit in the Columbia Disaster

Investigators said today that they believe chunks of foam have torn off shuttle fuel tanks in the past, and that this is still the mostly likely cause of the destruction of Columbia. By analyzing launch videos, the investigators found instances in six previous flights where foam peeled off the tanks and struck the shuttle. The group?s final report is expected to be delivered later this summer, and is expected to include recommendations for NASA?s management practices, safety programs and culture.

Posted on by Fraser Cain

Countdown for Mars Express Begins

Image credit: ESA

Controllers at the European Space Agency officially began the countdown clock for the launch of the Mars Express spacecraft today. If everything goes according to plan, the spacecraft will launch from the Baikonur cosmodrome in Kazakhstan on June 2, and it will arrive at Mars around December 25th. On board the spacecraft is the Beagle 2 lander, which will search for signs of past and present life on the surface of Mars.

On 2 June 2003, the first European mission to Mars will be launched. It will also be the first fully European mission to any planet. Mars Express has been designed to perform the most thorough exploration ever of the Red Planet.

Mars Express has the ambitious aim of not only searching for water, but also understanding the ‘behaviour’ of the planet as a whole. But maybe the most ambitious aim of all – Mars Express is the only mission in more than 25 years that dares to search for life.

Mars has always fascinated human beings. No other planet has been visited so many times by spacecraft. It has not been easy to unveil its secrets. Martian mysteries seem to have increased in quantity and complexity with every mission. When the first spacecraft were sent – the Mariner series in 1960s – the public was expecting an Earth ?twin?, a green, inhabited planet full of oceans. Mariner shattered this dream by showing a barren surface. This was followed by the Viking probes which searched for life unsuccessfully in 1976. Mars appeared dry, cold and uninhabited: the Earth?s opposite.

Now, two decades later, modern spacecraft have changed that view, but they have also returned more questions. Current data show that Mars was probably much warmer in the past. Scientists now think that Mars had oceans, so it could have been a suitable place for life in the past.

Cracks on Mars suggest the presence of water
“We do not know what happened to the planet in the past. Which process turned Mars into the dry, cold world we see today?” says Agustin Chicarro, ESA’s Mars Express project scientist. “With Mars Express, we will find out. Above all, we aim to obtain a complete global view of the planet – its history, its geology, how it has evolved. Real planetology!”

Mars Express will reach the Red Planet by the end of December 2003, after a trip of just over six months. Six days before injection into its final orbit, Mars Express will eject the lander, Beagle 2, named after the ship on which Charles Darwin found inspiration to formulate his theory of evolution. The Mars Express orbiter will observe the planet and its atmosphere from a near-polar orbit, and will remain in operation for at least a whole Martian year (687 Earth days). Beagle 2 will land in an equatorial region that was probably flooded in the past, and where traces of life may have been preserved.

The Mars Express orbiter carries seven advanced experiments, in addition to the Beagle 2 lander. The orbiter’s instruments have been built by group of scientific institutes from all over Europe, plus Russia, the United States, Japan and China. These instruments are a subsurface sounding radar; a high-resolution camera, several surface and atmospheric spectrometers, a plasma analyzer and a radio science experiment.

The high-resolution camera will image the entire planet in full colour, in 3D, at a resolution of up to 2 metres in selected areas. One of the spectrometers will map the mineral composition of the surface with great accuracy.

The missing water
Data from some of the instruments will be key to finding out what happened with the water which was apparently so abundant in the past. For instance, the radar altimeter will search for subsurface water and ice, down to a depth of a few kilometres. Scientists expect to find a layer of ice or permafrost, and to measure its thickness.

Other observations with the spectrometers will determine the amount of water remaining in the atmosphere. They will also tell whether there is a still a full ‘water cycle’ on Mars, for example how water is deposited in the poles and how it evaporates, depending on the seasons.

“These data will determine how much water there is left. We have clear evidence for the presence of water in the past, we have seen dry river beds and sedimentary layers, and there is also evidence for water on present-day Mars. But we do not know how much water there is. Mars Express will tell us,” says Chicarro.

The search for life
The instruments on board Beagle 2 will investigate the geology and the climate of the landing site. But, above all, it will look for signs of life.

Contrary to the Viking missions, Mars Express will search for evidence for both present and past life. Scientists are now more aware that a few biological experiments are not enough to search for life – they will combine many different types of tests to help discard contradictory results.

To ‘sniff’ out direct evidence of past or present biological activity, Beagle 2’s ‘nose’ is a gas analysis package. This will determine whether carbonate minerals, if they exist on Mars, have been involved in biological processes. Beagle?s nose will also detect gases such as methane, which scientists believe can only be produced by living organisms.

Beagle 2 will also be able to collect samples from below the surface, whether under large boulders or within the interiors of rocks – places that the life-killing ultraviolet radiation from the Sun cannot reach. These samples will be collected with a probe called the ‘mole’, which is able to crawl short distances across the surface, at about 1 centimetre every six seconds, and to dig down to 2 metres deep.

Mars Express will add substantial information to the international effort to explore Mars. “Mars Express is crucial for providing the framework within which all further Mars observations will be understood,” says Chicarro.

The Mars Express spacecraft is now in Baikonur, Kazakhstan, being prepared for its launch in early June 2003.

Original Source: ESA News Release

Posted on by Fraser Cain

Newly Discovered Star Could Be the Third Closest

Image credit: NASA

NASA astronomers have discovered what they believe could be the third closest star to our own Sun. The star, now called SO25300.5+165258, is a faint red star estimated to be about 7.8 light years away in the constellation of Aries. This is just beyond Alpha Centauri (which is actually a group of three stars) and Bernard?s Star. This new star hasn?t been discovered until now because it only has 7% of the mass of our own Sun, and is 300,000 times fainter.

The local celestial neighborhood just got more crowded with a discovery of a star that may be the third closest to the Sun. The star, “SO25300.5+165258,” is a faint red dwarf star estimated to be about 7.8 light-years from Earth in the direction of the constellation Aries.

“Our new stellar neighbor is a pleasant surprise, since we weren’t looking for it,” said Dr. Bonnard Teegarden, an astrophysicist at NASA’s Goddard Space Flight Center, Greenbelt, Md. Teegarden is lead author of a paper announcing the discovery to be published by the Astrophysical Journal. This work has been done in close collaboration with Dr. Steven Pravdo of NASA’s Jet Propulsion Laboratory (JPL).

If its distance estimate is confirmed, the newfound star will be the Sun’s third-closest stellar neighbor, slightly farther than the Alpha Centauri system, actually a group of three stars a bit more than four light-years away, and Barnard’s star, about six light-years away. One light-year is almost six trillion miles, or nearly 9.5 trillion kilometers.

The new star has only about seven percent of the mass of the Sun, and it is 300,000 times fainter. The star’s feeble glow is the reason why it has not been seen until now, despite being relatively close.

“We discovered this star in September 2002 while searching for white dwarf stars in an unrelated program,” said Teegarden. The team was looking for white dwarf stars that move rapidly across the sky. Celestial objects with apparent rapid motion are called High Proper Motion (HPM) objects. A HPM object can be discovered in successive images of an area of sky because it noticeably shifts its position while its surroundings remain fixed. Since either a distant star moving quickly or a nearby star moving slower can exhibit the same HPM, astronomers must use other measurements to determine its distance from Earth.

During its star search, the team used the SkyMorph database for the Near Earth Asteroid Tracking (NEAT) program. NEAT is a NASA program, run by the Jet Propulsion Laboratory (JPL), Pasadena, Calif., to search for asteroids that might be on a collision course for Earth. SkyMorph was separately supported by NASA’s Applied Information Systems Research Program. Like HPM stars, asteroids reveal themselves when they shift their position against background stars in successive images. Automated telescopes scan the sky, accumulating thousands of images for the NEAT program, which have been incorporated into SkyMorph, a web-accessible database, for use in other types of astronomical research.

Once the star revealed itself in the NEAT images, the team found other images of the same patch of sky to establish a rough distance estimate by a technique called trigonometric parallax. This technique is used to calculate distances to relatively close stars. As the Earth progresses in its orbit around the Sun, the position of a nearby star will appear to shift compared to background stars much farther away — the larger the shift, the closer the star.

The team refined their initial distance estimate with another technique called photometric parallax. They used the 3.5-meter Astrophysical Research Consortium telescope at the Apache Point observatory, Sunspot, N.M., to observe the star and separate its light into its component colors for analysis. This allowed the team to determine what kind of star it is. The analysis indicates it’s similar to a red dwarf star (spectral type M6.5) that’s shining by fusing hydrogen atoms in its core, like our Sun (called a main sequence star).

Once the type of star is known, its true brightness, called intrinsic luminosity, can be determined. Since all light-emitting objects appear dimmer as distance from them increases, the team compared how bright the new star appeared in their images to its intrinsic luminosity to improve their distance estimate.

Although the star resembles a M6.5 red dwarf, it actually appears three times dimmer than expected for this kind of star at the initial distance estimate of 7.8 light-years. The star could therefore really be farther than the rough trigonometric distance indicates; or, if the initial estimate holds, it could have unusual properties that make it shine less brightly than typical M6.5 red dwarfs. A more precise measurement of the new star’s position to establish an improved trigonometric parallax distance is underway at the U.S. Naval Observatory. This will confirm or refute its status as one of our closest neighbors by late this year. Either way, we might get even more company soon: “Since the NEAT survey only covered a band of the sky (+/- 25 degrees in declination), it is entirely possible that other faint nearby objects remain to be discovered,” said Teegarden.

Original Source: NASA News Release

Posted on by Fraser Cain

Hubble Sees Springtime on Neptune

Image credit: Hubble

New photos of Neptune taken by the Hubble Space Telescope seem to indicate that the planet is entering its version of Spring. By comparing photos taken in 1996, astronomers believe that bands across the planet are getting wider and brighter, which seems to be a response to increased sunlight. Like the Earth, Neptune is believed to have four seasons, but since the planet takes 165 years to orbit the Sun, they last decades, not months.

Springtime is blooming on Neptune! This might sound like an oxymoron because Neptune is the farthest and coldest of the major planets. But NASA Hubble Space Telescope observations are revealing an increase in Neptune’s brightness in the southern hemisphere, which is considered a harbinger of seasonal change, say astronomers.

Observations of Neptune made over six years by a group of scientists from the University of Wisconsin-Madison and NASA’s Jet Propulsion Laboratory (JPL) show a distinct increase in the amount and brightness of the banded cloud features located mostly in the planet’s southern hemisphere.

“Neptune’s cloud bands have been getting wider and brighter,” says Lawrence A. Sromovsky, a senior scientist at University of Wisconsin- Madison’s Space Science and Engineering Center and a leading authority on Neptune’s atmosphere. “This change seems to be a response to seasonal variations in sunlight, like the seasonal changes we see on Earth.”

The findings are reported in the current issue (May, 2003) of Icarus, a leading planetary science journal.

Neptune, the eighth planet from the Sun, is known for its weird and violent weather. It has massive storm systems and ferocious winds that sometimes gust to 900 miles per hour, but the new Hubble observations are the first to suggest that the planet undergoes a change of seasons.

Using Hubble, the Wisconsin team made three sets of observations of Neptune. In 1996, 1998, and 2002, observations of a full rotation of the planet were obtained. The images showed progressively brighter bands of clouds encircling the planet’s southern hemisphere. The findings are consistent with observations made by G.W. Lockwood at the Lowell Observatory, which show that Neptune has been gradually getting brighter since 1980.

Neptune’s near-infrared brightness is much more sensitive to high altitude clouds than its visible brightness. The recent trend of increasing cloud activity on Neptune has been qualitatively confirmed at near-infrared wavelengths with Keck Telescope observations from July 2000 to June 2001 by H. Hammel and co-workers. Near-infrared observations at NASA’s Infrared Telescope Facility on Mauna Kea, Hawaii are planned for this summer to further characterize changes in the high-altitude cloud structure.

“In the 2002 images, Neptune is clearly brighter than it was in 1996 and 1998,” Sromovsky says, “and is dramatically brighter at near infrared wavelengths. The greatly increased cloud activity in 2002 continues a trend first noticed in 1998.”

Like the Earth, Neptune would have four seasons: “Each hemisphere would have a warm summer and a cold winter, with spring and fall being transitional seasons, which may or may not have specific dynamical features,” the Wisconsin scientist explains.

Unlike the Earth, however, the seasons of Neptune last for decades, not months. A single season on the planet, which takes almost 165 years to orbit the Sun, can last more than 40 years. If what scientists are observing is truly seasonal change, the planet will continue to brighten for another 20 years.

Also like Earth, Neptune spins on an axis that is tilted at an angle toward the Sun. The tilt of the Earth, at a 23.5-degree inclination, is the phenomenon responsible for the change of seasons. As the Earth orbits the Sun over the course of a year, the planet is exposed to patterns of solar radiation that mark the seasons. Similarly, Neptune is inclined at a 29-degree angle and the northern and southern hemispheres alternate in their positions relative to the Sun.

What is remarkable, according to Sromovsky, is that Neptune exhibits any evidence of seasonal change at all, given that the Sun, as viewed from the planet, is 900 times dimmer than it is from Earth. The amount of solar energy a hemisphere receives at a given time is what determines the season.

“When the Sun deposits heat energy into an atmosphere, it forces a response. We would expect heating in the hemisphere getting the most sunlight. This in turn could force rising motions, condensation and increased cloud cover,” Sromovsky notes.

Bolstering the idea that the Hubble images are revealing a real increase in Neptune’s cloud cover consistent with seasonal change is the apparent absence of change in the planet’s low latitudes near its equator.

“Neptune’s nearly constant brightness at low latitudes gives us confidence that what we are seeing is indeed seasonal change as those changes would be minimal near the equator and most evident at high latitudes where the seasons tend to be more pronounced.”

Despite the new insights into Neptune, the planet remains an enigma, says Sromovsky. While Neptune has an internal heat source that may also contribute to the planet’s apparent seasonal variations and blustery weather, when that is combined with the amount of solar radiation the planet receives, the total is so small that it is hard to understand the dynamic nature of Neptune’s atmosphere.

There seems, Sromovsky says, to be a “trivial amount of energy available to run the machine that is Neptune’s atmosphere. It must be a well-lubricated machine that can create a lot of weather with very little friction.”

In addition to Sromovsky, authors of the Icarus paper include Patrick M. Fry and Sanjay S. Limaye, both of University of Wisconsin-Madison’s Space Science and Engineering Center; and Kevin H. Baines of NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

Original Source: Hubble News Release