Posted on by Fraser Cain

NASA Announces May 2005 For Shuttle Flight

The Space Shuttle fleet is housed and processed at NASA’s Kennedy Space Center (KSC), Fla. The order the Space Shuttles are listed does not necessarily reflect the chronological order of future missions.

Discovery (OV-103)
Powered-up orbiter system testing in the Orbiter Processing Facility continues to progress on schedule for Discovery’s Return to Flight mission (STS-114) to the International Space Station. The Space Flight Leadership Council met today and determined the new launch planning window is May 12 to June 3, 2005.

Technicians continue testing and checkout of both the Remote Manipulator System, or Space Shuttle robotic arm, and the starboard manipulator positioning mechanisms. Installation of the new wing leading edge sensors and relay units continues. Ku band target tracking tests are complete.

Atlantis (OV-104)
Atlantis remains in its extensive power-down period, during which technicians are performing Return to Flight modifications. The majority of the baseline wire inspections are complete. Structural inspections and arc track wire inspections continue throughout the vehicle.

With all radiators mounted for flight, technicians completed installations of the radiators’ flex hoses in support of orbiter power up. Work is progressing well with the flex hose conversion to hard lines in the waste water management system, and the flex hose modifications in the potable waste water system.

Flex hoses are used throughout the vehicle for numerous purposes where there is movement between two fixed ends, or where flexibility is desired for ease of installation and/or replacement.

Endeavour (OV-105)
Space Shuttle Endeavour is in its Orbiter Major Modification period, which began in December. Electrical modifications continue in the crew module. Three-String Global Positioning System wire routing in the avionics bay and flight deck continues.

Clean up continues from the bead blasting performed to remove minuscule corrosion from the wing leading edges. Bead blasting is a process using a pressurized pneumatic gun containing silica carbide, plastic pellets or glass beads to remove primer, paint and corrosion from orbiter vehicle surfaces.

Workers also are beginning to set up the protective tents in preparation for painting the wings prior to reinstallation of the Reinforced Carbon-Carbon panels.

Previous Space Shuttle processing status reports are available on the Internet at:
NASA KSC News

For information about NASA’s Return to Flight efforts on the Internet, visit:
http://www.nasa.gov/news/highlights/returntoflight.html

For information about NASA and agency programs on the Internet, visit:
http://www.nasa.gov

Original Source: NASA News Release

Posted on by Fraser Cain

Rovers Have Returned 50,000 Pictures

Image credit: NASA/JPL
A view of the sundial-like calibration target on NASA’s Mars Exploration Rover Spirit, with a bit of martian terrain in the background, is the 50,000th image from the twin rovers that have been exploring Mars since January.

The images stock a treasury of scientific information on scales from microscopic detail to features on the horizon scores of kilometers or miles away, and even include glimpses of Mars’ moons, Earth and the Sun. They also provide an always-current understanding of the surrounding terrain for use by the team of rover wranglers planning each day’s activities on Mars.

There are now more than twice as many images from the two rovers as from NASA’s three previous Mars surface missions combined: Viking Lander 1, Viking Lander 2 and Mars Pathfinder. “The cameras on Spirit and Opportunity have been reliable, sharp eyes for our adventure of exploring some amazing places on Mars,” said Dr. Justin Maki of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., an imaging scientist on the rover team. “The pictures continue to be stunning. One big difference from earlier Mars surface missions is that the rovers continue to show us new places and new sights.”

All raw images that reach Earth from the rovers are posted online at http://marsrovers.jpl.nasa.gov/gallery/all. Captioned pictures, including the 50,000th image and panoramas assembled from many individual raw images, are posted at http://marsrovers.jpl.nasa.gov/gallery/press/.

Both rovers have successfully completed their three-month primary missions and their first mission extensions. They began second extensions of their missions on Oct. 1.

Counting stereo instruments as separate right and left cameras, each rover carries nine cameras.

The stereo panoramic cameras have taken most of the images. Spirit’s accounts for 35 percent of the all images from the rovers so far; Opportunity’s, 32 percent. Color pictures from these cameras combine individual frames taken through different filters. Mosaic image products stitch together many contiguous frames for a larger view. A single 360-degree color panorama uses more than 100 individual images. Usually when a panoramic camera is used, it takes a series of shots of the calibration target through different filters to aid in accurate interpretation of the other shots it takes. It is no surprise that Spirit’s calibration target happened to be the subject in the 50,000th image, since it has become the single most photographed subject on Mars.

Spirit’s front hazard-avoidance camera (also two cameras for stereo views) has the next highest fraction of the rovers’ image catalog at 9 percent. That signifies the importance of this low-slung camera in Spirit racking up 3.6 kilometers (2.3 miles) of driving so far. Opportunity has driven 1.6 kilometers (1 mile) and its front hazard-avoidance camera has taken 3 percent of all rover images. Totals for the rear hazard- avoidance cameras are about one-fifth of the number from the front cameras on each rover.

Each rover’s stereo navigation camera sits up on the mast with the panoramic camera but takes wider-angle images without filters. Spirit’s navigation camera has taken 7 percent, and Opportunity’s 6 percent, of all rover images.

Some days when Spirit was driving long distances, Opportunity was busy examining bedrock exposures and soil patches with its microscopic imager. That camera on Opportunity has taken 4 percent of all rover images; the one on Spirit, 2 percent. Each spacecraft had a 10th camera on the bottom of its lander, which contained the rover during the descent through Mars’ atmosphere. Those descent cameras each took three images, as planned, during the final minute before impact.

NASA’s Viking Lander 1 returned 3,542 images while it operated for 79 months beginning in 1976. Viking Lander 2 returned 3,043 images while it operated for 43 months, also beginning in 1976. Mars Pathfinder returned 16,635 images from its lander and 628 from its Sojourner rover during 12 weeks of operation in 1997.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Venus and Jupiter’s Upcoming Conjunction

A planetary conjunction occurs when two or more planets appear to be very close together in the night sky as seen from Earth. Conjunctions between Venus and Jupiter are fairly common, occurring as often as three times a year. But on the morning of November 5th, just before dawn, Venus and Jupiter will be less than one degree apart in the sky in the constellation of Virgo the Maiden. A degree is about the width of one finger held at arms distance. The pair will be at their closest at 1:58 UTC on the 5th, when they are 33 arc-minutes apart, or about 0.42 degrees.

This year’s conjunction is rare for two reasons. First, the two planets are less than one degree apart; and second, they are more than fifteen degrees from the sun. Large number conjunctions, such as the one that occurred in 1995, are less than fifteen degrees from the sun and therefore lost in the sun’s glare. The conjunction on November 5th is also special because it is the last close conjunction between Venus and Jupiter until September 1st 2005.

A conjunction very much like the one occurring on the 5th occurred in August of the year 3 B.C. This historic conjunction occurred on August 12th at 03:00 UTC and was widely visible from the Middle East. That year Venus and Jupiter were only 10 arc-minutes or 0.16 degrees apart in the constellation of Leo the Lion. With such a narrow separation, light reflected from the two would seem to merge into one as seen with the unaided eye.

Some scholars have speculated that this close conjunction may have been interpreted as a sign by a group known as the Magi. The Magi, or wise men, were priests of an ancient religion known as Zoroastrianism. Could this close conjunction have been what sent the wise men traveling to a far of city known as Bethlehem? Unfortunately we can’t draw any definitive conclusions. There are no known written records that tell exactly what the Magi saw, or how they interpreted it.

Regardless of what the Magi saw, modern computer software confirms that there was a very close conjunction between Venus and Jupiter in the year 3 B.C. The conjunction of 2004, while not as close, should be no less spectacular sight in the sky. Telescope or binocular users should have no difficulty fitting both planets into one field of view. This conjunction is also an excellent opportunity for aspiring (or seasoned) astro-photographers.

Exposures of from 1/15s to 1/60s are good for those using SLR’s with standard 50mm lenses. A zoom lens of 180mm can reduce the required shutter speed to a range of 1/60s to 1/250s depending on conditions. But as with any kind of astro-photography, the key is multiple exposures at various shutter speeds and apertures.

A planetary conjunction is a rare and beautiful sight. Because Venus and Jupiter are both so bright in the sky, the Venus-Jupiter conjunction of 2004 should not be missed. With a little imagination we can transport ourselves back in time to the Middle Eastern Skies before the Common Era, when a bright conjunction dominated the pre-dawn skies.

Rod Kennedy is a technician and education outreach coordinator at the Casper Planetarium, Wyoming’s first planetarium. He received his Chemistry degree from the University of Northern Colorado, and has been interested in astronomy for 10 years.

Posted on by Fraser Cain

More Findings About Methane on Mars

A University of Michigan scientist is part of a European Space Agency team that has detected methane gas on Mars, and the findings will be published in the online Web journal Science Express today.

Sushil Atreya, professor and director of the Planetary Science Laboratory in the College of Engineering says the detection of methane is the clearest indicator of the possibility of life on the Red Planet yet.

“Biologically produced methane is one of many possibilities,” Atreya said. “Methane is a potential biomarker, if a planet has methane we begin to think of the possibility of life on the planet. On Earth, methane is almost entirely derived from biological sources.”

Mars resembles Earth more than any other planet in our solar system, and studying its atmosphere gives us a greater understanding of our own.

How the methane got to Mars is the big question, and there are several possible sources, Atreya said. The most exciting scenario is that methanogens?microbes that consume the Martian hydrogen or carbon monoxide for energy and exhale methane?dwell in colonies out of sight beneath the surface of the red planet.

“These are anaerobic so they don’t need oxygen to survive, if they are there,” Atreya said. “If they are there, they would be underground.”

Speculation is tempting, but many more experiments are necessary before drawing any conclusions.

“While it’s tantalizing to think there are living things on Mars, we aren’t in a position to say that is what is causing the methane,” Atreya said.

A comet could have struck the planet, which would leave methane behind, but that only happens once every 60 million years or so, Atreya said. A more likely scenario is hydrothermal process involving chemical interaction between rock and water in aquifers below the Martian permafrost.

The instrument that sniffed out the methane is called a planetary Fourier spectrometer, and it is one of seven instruments on board the Mars Express spacecraft. The spectrometer measures the Sun’s infrared light that has been absorbed, emitted and scattered by the molecules in the Martian atmosphere. Every molecule has a unique spectral property?think of it as an infrared fingerprint?including methane.

The spectrometer detected an average 10 parts per billion by volume (ppbv) of methane on Mars, a small amount compared to the approximately 1700 ppbv on Earth. The methane gas was distributed unevenly over Mars’ surface, which tends to support the theory that an internal, on-site source, rather than a comet, is the source generating the methane, said Atreya.

Mars Express launched in June 2003, and it is the first Western European trip to another planet.

Original Source: University of Michigan News Release

Posted on by Fraser Cain

Hibernate on a Trip to Mars

Manned missions beyond the Moon are no longer wild dreams. For example, the objective of ESA’s Aurora programme, after exploring Mars with robotic missions, is to send astronauts to the red planet.

Engineers are already considering the space systems that will be required, from the spacecraft and propulsion systems to the life support systems, for journeys that will last 6-9 months.

With automatic systems in control, astronauts would face the challenge of living in a confined space with not much to do for an extremely long period. “Might as well sleep it off!”

Studies initiated by ESA’s Advanced Concepts Team have gone one step further. Wouldn’t it be nice if astronauts could hibernate!

Euronews has met two biologists who are conducting, as ESA consultants, investigations into the physiological mechanisms that mammals use to hibernate.

There are marked differences between species. A dormouse goes into a deep sleep with its body temperature dropping close to zero and its metabolism dramatically suppressed. During its ‘winter sleep’, a brown bears hibernates at near normal body temperature. Its heart rate drops by a quarter and it will spend 3-7 months in a state of torpor, neither eating, drinking, defecating or urinating.

For the past two years, Prof. Marco Biggiogera, at the Animal Biology Department at the University of Pavia in Italy has been studying how an opiate derivative inhibits the activity of living cells.

“The molecule DADLE is similar to others we have in the human brain and resembles one of the hibernation triggering proteins in hibernators. It can reduce the energy required by cells, whether isolated in cultures, or present in other animals or organisms,” explains Prof. Biggiogera.

“We would very much like to understand its basic mechanisms, and with this knowledge attempt to recreate a state of hypo-metabolism in an animal, and perhaps even one day in a human, although this is really far away.”

Also involved in this study is the University of Verona. There the DADLE molecule is injected in a rodent, specially equipped with sensors to measure its body temperature, heart rate and other vital activities. After comparing the animal’s behaviour with that of a normal rat, the test subject’s main organs are scanned to observe any changes.

“Our preliminary results show that four hours after a DADLE injection, the body temperature drops notably and the rat is considerably less active,” says Prof. Carlo Zancanaro.

“Eventually we could adapt these hibernation triggering processes, using chemicals or by other means, to animals such as rats who do not normally hibernate. But concerning humans, we are still at an extremely early stage.”

The research could also lead to far-reaching applications in the medical field such as prolonging the useful life of a transplant organ or even heart-transplant operations while patients are in a state of hypo-metabolism.

Reducing the physical and psychological requirements of an astronaut crew to a minimum without jeopardising its safety would greatly simplify many aspects of a long-duration space mission.

For instance, less food and water would be required, as would the amount of pressurised space and other environmental features the astronauts would require to maintain their psychological health. This would allow large reductions in spacecraft mass, relaxing the requirements on the propulsion subsystem.

Additionally, the astonaut’s ability to hibernate would have a significant benefit in abort and emergency scenarios. Of course, a suitable and lightweight ‘hibernaculum’ to shelter astronauts during their ‘long sleep’ would have to be designed.

Hibernation for humans is an ethically controversial concept, and critics may consider it as a mad scientist’s dream. Prof. Biggiogera replied with a smile: “Without such dreamers, humanity would still be in the Middle Ages.”

Original Source: ESA News Release

Posted on by Fraser Cain

Detailed Image of Titan’s Surface

This radar image of the surface of Saturn’s moon Titan was acquired on October 26, 2004, when the Cassini spacecraft flew approximately 1,600 kilometers (994 miles) above the surface and acquired radar data for the first time.

Brighter areas may correspond to rougher terrains and darker areas are thought to be smoother. This image highlights some of the darker terrain, which the Cassini team has nicknamed “Si-Si the Cat” after a team member’s daughter, who pointed out its cat-like appearance. The interconnected dark spots are consistent with a very smooth or highly absorbing solid, or could conceivably be liquid.

The image is about 250 kilometers (155 miles) wide by 478 kilometers (297 miles) long, and is centered at 50 N, 54 W in the northern hemisphere of Titan, over a region that has not yet been imaged optically. The smallest details seen on the image vary from about 300 meters (984 feet) to 1 kilometer (.62 mile).

The data were acquired in the synthetic aperture radar mode of Cassini’s radar instrument. In this mode, radio signals are bounced off the surface of Titan. 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 Cassini-Huygens 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 instrument team is based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

For the latest news about the Cassini-Huygens mission visit http://www.nasa.gov/cassini . For more information about the mission visit http://saturn.jpl.nasa.gov .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Share Your Eclipse Experience

Well, how did it go? Did you get a chance to see the eclipse from your part of the world? Did you share it with your friends and family, and maybe build a little astronomy enthusiasm in your loved ones? One eye on the sky and one eye on the game? Come to the forum and share your experiences from last night. I’ll let you know how my night went. If you got pictures from last night, join the forum and post your photos into the Astrophotography forum and enjoy the “ooohs and ahhhs” from jealous rained out (or geographically challenged) forum members from around the world. Next eclipse is in 2007.

Fraser Cain
Publisher
Universe Today

Posted on by Mark Mortimer

Book Review: Space Tourism – Do You Want to Go?

Given the chance, most people would be off vacationing in space at a moment’s notice. Spencer’s plan is to make the holiday a lot more enjoyable than a weekend spent bouncing about Mir’s functional but restrictive interior. He has visions of space yachts in races similar to the America’s Cup; sentinel robots with self aware artificial intelligence maintain the yacht and keep the passengers happy; lunar dune buggies provide for excursions outside the yacht, much like excursions for cruise ships; and simulation centres on Earth train and condition people to their out-of-this-world holiday. With all this at hand, space vacationing would be very popular.

And popularity is a key condition for Spencer. He expects more than 800 people per month will be vacationing, once the infrastructure is in space. For example, a significant portion of the text describes the design of his own yacht, the Destiny. This yacht allows for a small group of passengers to mingle or enjoy solitary relaxation. Rooms, suites and common areas are created by self inflating structures. Environments are conditioned by service robots running on batteries. Safety is ensured by the afore mentioned AI sentinel. Self inflating space ports provide ‘harbours’ for the Destiny and her sister ships. There are even descriptions of coastguard like vessels that ensure the safety of the space lanes. All this is to allow the very rich to enjoy the Earth’s luxuries (wine, dining and dancing) while in the nouvelle regions of space. With this emphasis on pleasure, there should be no challenge meeting the monthly quota.

Though Spencer’s image of space tourism is wonderful, his tie-ins to the practicalities is not. He expects space tourism to be well established by the year 2050, in spite of today’s obvious challenges of building and maintaining the International Space Station. Because of this, his book reads a little too much like science fiction. Almost every aspect of his infrastructure requires large leaps in current scientific and engineering knowledge. For example, his space vessel windows will have material that, on verbal command, changes to allow different sun/radiation intensities into the cabin. This would be more believable if there were an estimate of the effort to get to the required state. Another example is that his vessels include a squad of specialized robots. However, there are no trade off assessments made between the cost and effectiveness of robots to people. Perhaps most telling is his reliance on a low cost orbital access vehicle for which we’re all waiting. In consequence when regarding practicalities, the book is much more of a marketing flyer than it is a business plan.

I think that to get the most out of this book, you must set aside the practical and pessimistic side of your mind and let your free thinking self take over. A particularly rewarding is a first hand account of a lottery winner taking a space holiday in the future. This person starts with describing their training and conditioning through simulation centres on Earth. Next are meetings with fellow passengers at the launch area, safety drills, and the launch to an orbiting port. From there, the winner heads into the space yacht and spends a few luxurious days watching the Earth spin beneath them and the stars twinkle all about. Onboard and off board, activities keep everyone happy and entertained. Upon completion and debarkation, the lottery winner becomes an outspoken advocate for space tourism. In summary, this chapter is the most entertaining and the highlight of the text.

In conclusion, the supposition of the authors is that, today, there is a valid space tourism movement that can lead to a real industry in the near future. The people of this movement believe that by continually highlighting the potential benefits and applauding any steps made in this direction, they will have eventual success. Dennis Tito’s self-paid trip is the landmark they often cite. Also, one complete chapter is dedicated to the progress in space tourism from the mid-1960’s to now. Though this chapter appears to be the summary of the author’s day timer or diary, it still is an interesting and unique view into the progression of space tourism movement from a nascent bottom feeder to today being an oft seen marketing tool and front page head liner. Perhaps, the subtitle would have been more accurate as, ‘do you want to tour in space, then jump on the band wagon!’.

Space tourism, to some people, will be the final industry to succeed in the thrust to the stars. John Spencer and Karen Rugg in their book Space Tourism – Do You Want to Go? show how space tourism can lead the way. They present plans and ideas to build upon the existing space tourism movement so that a full fledged bit of fun can happen in space. Just think what your longest drive might be during a friendly golf game on the moon!

To get your own copy, visit Countdown Creations.

Review by Mark Mortimer

Posted on by Fraser Cain

Most Active Sun in 8,000 Years

The activity of the Sun over the last 11,400 years, i.e., back to the end of the last ice age on Earth, has now for the first time been reconstructed quantitatively by an international group of researchers led by Sami K. Solanki from the Max Planck Institute for Solar System Research (Katlenburg-Lindau, Germany). The scientists have analyzed the radioactive isotopes in trees that lived thousands of years ago. As the scientists from Germany, Finland, and Switzerland report in the current issue of the science journal “Nature” from October 28, one needs to go back over 8,000 years in order to find a time when the Sun was, on average, as active as in the last 60 years. Based on a statistical study of earlier periods of increased solar activity, the researchers predict that the current level of high solar activity will probably continue only for a few more decades.

The research team had already in 2003 found evidence that the Sun is more active now than in the previous 1000 years. A new data set has allowed them to extend the length of the studied period of time to 11,400 years, so that the whole length of time since the last ice age could be covered. This study showed that the current episode of high solar activity since about the year 1940 is unique within the last 8000 years. This means that the Sun has produced more sunspots, but also more flares and eruptions, which eject huge gas clouds into space, than in the past. The origin and energy source of all these phenomena is the Sun’s magnetic field.

Since the invention of the telescope in the early 17th century, astronomers have observed sunspots on a regular basis. These are regions on the solar surface where the energy supply from the solar interior is reduced owing to the strong magnetic fields that they harbour. As a consequence, sunspots are cooler by about 1,500 degrees and appear dark in comparison to their non-magnetic surroundings at an average temperature of 5,800 degrees. The number of sunspots visible on the solar surface varies with the 11-year activity cycle of the Sun, which is modulated by long-term variations. For example, there were almost no sunspots seen during the second half of the 17th century.

For many studies concerning the origin of the active sun and its potential effect on long-term variations of Earth’s climate, the interval of time since the year 1610, for which systematic records of sunspots exist, is much too short. For earlier times the level of solar activity must be derived from other data. Such information is stored on Earth in the form of “cosmogenic” isotopes. These are radioactive nuclei resulting from collisions of energetic cosmic ray particles with air molecules in the upper atmosphere. One of these isotopes is C-14, radioactive carbon with a half life of 5730 years, which is well known from the C-14 method to determine the age of wooden objects. The amount of C-14 produced depends strongly on the number of cosmic ray particles that reach the atmosphere. This number, in turn, varies with the level of solar activity: during times of high activity, the solar magnetic field provides an effective shield against these energetic particles, while the intensity of the cosmic rays increases when the activity is low. Therefore, higher solar activity leads to a lower production rate of C-14, and vice versa.

By mixing processes in the atmosphere, the C-14 produced by cosmic rays reaches the biosphere and part of it is incorporated in the biomass of trees. Some tree trunks can be recovered from below the ground thousands of years after their death and the content of C-14 stored in their tree rings can be measured. The year in which the C-14 had been incorporated is determined by comparing different trees with overlapping life spans. In this way, one can measure the production rate of C-14 backward in time over 11,400 years, right to the end of the last ice age. The research group have used these data to calculate the variation of the number of sunspots over these 11,400 years. The number of sunspots is a good measure also for the strength of the various other phenomena of solar activity.

The method of reconstructing solar activity in the past, which describes each link in the complex chain connecting the isotope abundances with the sunspot number with consistent quantitative physical models, has been tested and gauged by comparing the historical record of directly measured sunspot numbers with earlier shorter reconstructions on the basis of the cosmogenic isotope Be-10 in the polar ice shields. The models concern the production of the isotopes by cosmic rays, the modulation of the cosmic ray flux by the interplanetary magnetic field (the open solar magnetic flux), as well as the relation between the large-scale solar magnetic field and the sunspot number. In this way, for the first time a quantitatively reliable reconstruction of the sunspot number for the whole time since the end of the last ice age could be obtained.

Because the brightness of the Sun varies slightly with solar activity, the new reconstruction indicates also that the Sun shines somewhat brighter today than in the 8,000 years before. Whether this effect could have provided a significant contribution to the global warming of the Earth during the last century is an open question. The researchers around Sami K. Solanki stress the fact that solar activity has remained on a roughly constant (high) level since about 1980 – apart from the variations due to the 11-year cycle – while the global temperature has experienced a strong further increase during that time. On the other hand, the rather similar trends of solar activity and terrestrial temperature during the last centuries (with the notable exception of the last 20 years) indicates that the relation between the Sun and climate remains a challenge for further research.

Original Source: Max Planck Society News Release

Posted on by Fraser Cain

Survivor Found From Tycho’s Supernova

An international team of astronomers is announcing today that they have identified the probable surviving companion star to a titanic supernova explosion witnessed in the year 1572 by the great Danish astronomer Tycho Brahe and other astronomers of that era.

This discovery provides the first direct evidence supporting the long-held belief that Type Ia supernovae come from binary star systems containing a normal star and a burned-out white dwarf star. The normal star spills material onto the dwarf, which eventually triggers an explosion.

The results of this research, led by Pilar Ruiz-Lapuente of the University of Barcelona, Spain, are being published in the Oct. 28 British science journal Nature. “There was no previous evidence pointing to any specific kind of companion star out of the many that had been proposed. Here we have identified a clear path: the feeding star is similar to our Sun, slightly more aged,” Ruiz-Lapuente says. “The high speed of the star called our attention to it,” she added.

Type Ia supernovae are used to measure the history of the expansion rate of the universe and so are fundamental to helping astronomers understand the behavior of dark energy, an unknown force that is accelerating the expansion of the universe. Finding evidence to confirm the theory as to how Type Ia supernovae explode is critical to assuring astronomers that the objects can be better understood as reliable calibrators of the expansion of space.

The identification of the surviving member of the stellar duo reads like a crime scene investigation tale. Even though today’s astronomers arrived at the scene of the disaster 432 years later, using astronomical forensics they have nabbed one of the perpetrators rushing away from the location of the explosion (which is now enveloped in a vast bubble of hot gas called Tycho’s Supernova Remnant). For the past seven years the runaway star and its surroundings were studied with a variety of telescopes. The Hubble Space Telescope played a key role by precisely measuring the star’s motion against the sky background. The star is breaking the speed limit for that particular region of the Milky Way Galaxy by moving three times faster than the surrounding stars. Like a stone thrown by a sling, the star went hurtling off into space, retaining the velocity of its orbital motion when the system was disrupted by the white dwarf’s explosion.

This alone is only circumstantial evidence that the star is the perpetrator because there are alternative explanations to its suspicious behavior. It could be falling in at a high velocity from the galactic halo that surrounds the Milky Way’s disk. But spectra obtained with the 4.2-meter William Herschel Telescope in La Palma and the 10-meter W.M. Keck telescopes in Hawaii show that the suspect has the high heavy-element content typical of stars that dwell in the Milky Way’s disk, not the halo.

The star found by the Ruiz-Lapuente team is an aging version of our Sun. The star has begun to expand in diameter as it progresses toward a red-giant phase (the end stage of a Sun-like star’s lifetime). The star turns out to fit the profile of the perpetrator in one of the proposed supernova conjectures. In Type Ia supernova binary systems, the more massive star in the pair will age faster and eventually becomes a white dwarf star. When the slower-evolving companion star subsequently ages to the point where it begins to balloon in size, it spills hydrogen onto the dwarf. The hydrogen accumulates until the white dwarf reaches a critical and precise mass threshold, called the Chandrasekhar limit, where it explodes as a titanic nuclear bomb. The energy output of this explosion is so well known that it can be used as a standard candle for measuring vast astronomical distances. (An astronomical “standard candle” is any type of luminous object whose intrinsic power is so accurately determined that it can be used to make distance measurements based on the rate the light dims over astronomical distances).

“Among the various systems containing white dwarfs that receive material from a solar-mass companion, some are believed to be viable progenitors of Type Ia supernovae, on theoretical grounds. A system called U Scorpii has a white dwarf and a star similar to the one found here. These results would confirm that such binaries will end up in an explosion like the one observed by Tycho Brahe, but that would occur several hundreds of thousands of years from now,” says Ruiz-Lapuente.

An alternative theory of Type Ia supernovae is that two white dwarfs orbit each other, gradually losing energy through the emission of gravitational radiation (gravity waves). As they lose energy, they spiral in toward each other and eventually merge, resulting in a white dwarf whose mass reaches the Chandrasekhar limit, and explodes. “Tycho’s supernova does not appear to have been produced by this mechanism, since a probable surviving companion has been found,” says Alex Filippenko of the University of California at Berkeley, a co-author on this research. He says that, nevertheless, it is still possible there are two different evolutionary paths to Type Ia supernovae.

On November 11, 1572, Tycho Brahe noticed a star in the constellation Cassiopeia that was as bright as the planet Jupiter (which was in the night sky in Pisces). No such star had ever been observed at this location before. It soon equaled Venus in brightness (which was at -4.5 magnitude in the predawn sky). For about two weeks the star could be seen in daylight. At the end of November it began to fade and change color, from bright white to yellow and orange to faint reddish light, finally fading away from visibility in March 1574, having been visible to the naked eye for about 16 months. Tycho’s meticulous record of the brightening and dimming of the supernova now allows astronomers to identify its “light signature” as that of a Type Ia supernova.

Tycho Brahe’s supernova was very important in that it helped 16th-century astronomers abandon the idea of the immutability of the heavens. At the present time, Type Ia supernovae remain key players in the newest cosmological discoveries. To learn more about them and their explosion mechanism, and to make them even more useful as cosmological probes, a current Hubble Space Telescope project led by Filippenko is studying a sample of supernovae in other galaxies at the very time they explode.

Original Source: Hubble News Release