Half a Million Galaxies, Yours to Explore

Move over, Hubble Deep Field.  The Canada-France-Hawaii Telescope has released a new deep-field image of as many as 500,000 galaxies out to a distance of 7 billion light years.  And you can surf the entire image at high resolution with an interactive zoom feature at the CFHT website.

This new image is the result of the accumulation of several hundreds of hours of light integration over five years (2003-2008) with the CFHT using the 340 megapixel camera called MegaCam. This field and three more like it from other parts of the sky were systematically observed every three nights to detect faint supernovae going off in distant galaxies to study the effect of the mysterious dark energy responsible for the observed accelerating expansion of the universe.

Stacking these individual MegaCam images reveals a dense wallpaper of distant galaxies.  An observing technique called “dithering” allows coverage of a larger field of view than that of the camera itself, leading to a sky coverage over 370 megapixels. Approximately half a million galaxies can be counted on the entire image.

As it covers a full square degree of sky (about 5 times greater than the size of the full moon), the entire image is impressive enough.  But the ultra-high resolution of the image, along with a nifty interactive tool on the CFHT website, allows you to zoom in on tiny subsets of the image to see an astonishing assortment of galaxies out to a distance of 7 billion light years, about half-way to the edge of the observable universe.  A few foreground stars of our own galaxy are visible.  But almost everything else you see in this image is a distant galaxy.

You can access the image and the interactive viewer at the CFHT website.

Source: Canada-France-Hawaii Telescope

Cosmic-Ray Intensity Hits 50-Year High

[/caption]

Planning a trip to Mars? Take plenty of shielding. According to sensors on NASA’s ACE (Advanced Composition Explorer) spacecraft, galactic cosmic rays have just hit a space-age high.

“In 2009, cosmic ray intensities have increased 19% beyond anything we’ve seen in the past 50 years,” says Richard Mewaldt of Caltech. “The increase is significant, and it could mean we need to re-think how much radiation shielding astronauts take with them on deep-space missions.”

The cause of the surge is solar minimum, a deep lull in solar activity that began around 2007 and continues today. Researchers have long known that cosmic rays go up when solar activity goes down. Right now solar activity is as weak as it has been in modern times, setting the stage for what Mewaldt calls “a perfect storm of cosmic rays.”

“We’re experiencing the deepest solar minimum in nearly a century,” says Dean Pesnell of the Goddard Space Flight Center, “so it is no surprise that cosmic rays are at record levels for the Space Age.”

Galactic cosmic rays come from outside the solar system. They are subatomic particles–mainly protons but also some heavy nuclei–accelerated to almost light speed by distant supernova explosions. Cosmic rays cause “air showers” of secondary particles when they hit Earth’s atmosphere.  They pose a health hazard to astronauts.  And a single cosmic ray can disable a satellite if it hits an unlucky integrated circuit.

The sun’s magnetic field is our first line of defense against these highly-charged, energetic particles. The entire solar system from Mercury to Pluto and beyond is surrounded by a bubble of solar magnetism called “the heliosphere.” It springs from the sun’s inner magnetic dynamo and is inflated to gargantuan proportions by the solar wind. When a cosmic ray tries to enter the solar system, it must fight through the heliosphere’s outer layers; and if it makes it inside, there is a thicket of magnetic fields waiting to scatter and deflect the intruder.

“At times of low solar activity, this natural shielding is weakened, and more cosmic rays are able to reach the inner solar system,” explains Pesnell.

Mewaldt lists three aspects of the current solar minimum that are combining to create the perfect storm:

(1) The sun’s magnetic field is weak. “There has been a sharp decline in the sun’s interplanetary magnetic field (IMF) down to only 4 nanoTesla (nT) from typical values of 6 to 8 nT,” he says. “This record-low IMF undoubtedly contributes to the record-high cosmic ray fluxes.”

(2) The solar wind is flagging. “Measurements by the Ulysses spacecraft show that solar wind pressure is at a 50-year low,” he continues, “so the magnetic bubble that protects the solar system is not being inflated as much as usual.” A smaller bubble gives cosmic rays a shorter-shot into the solar system. Once a cosmic ray enters the solar system, it must “swim upstream” against the solar wind. Solar wind speeds have dropped to very low levels in 2008 and 2009, making it easier than usual for a cosmic ray to proceed.

(3) The current sheet is flattening. Imagine the sun wearing a ballerina’s skirt as wide as the entire solar system with an electrical current flowing along the wavy folds. That is the “heliospheric current sheet,” a vast transition zone where the polarity of the sun’s magnetic field changes from plus (north) to minus (south). The current sheet is important because cosmic rays tend to be guided by its folds. Lately, the current sheet has been flattening itself out, allowing cosmic rays more direct access to the inner solar system.

“If the flattening continues as it has in previous solar minima, we could see cosmic ray fluxes jump all the way to 30% above previous Space Age highs,” predicts Mewaldt.

Earth is in no great peril from the extra cosmic rays. The planet’s atmosphere and magnetic field combine to form a formidable shield against space radiation, protecting humans on the surface. Indeed, we’ve weathered storms much worse than this. Hundreds of years ago, cosmic ray fluxes were at least 200% higher than they are now. Researchers know this because when cosmic rays hit the atmosphere, they produce the isotope beryllium-10, which is preserved in polar ice. By examining ice cores, it is possible to estimate cosmic ray fluxes more than a thousand years into the past. Even with the recent surge, cosmic rays today are much weaker than they have been at times in the past millennium.

“The space era has so far experienced a time of relatively low cosmic ray activity,” says Mewaldt. “We may now be returning to levels typical of past centuries.”

NASA spacecraft will continue to monitor the situation as solar minimum unfolds. Stay tuned for updates.

A Prototype Detector for Dark Matter in the Milky Way

[/caption]

It doesn’t emit electromagnetic radiation and no one really knows what it is, but that hasn’t stopped a team of European researchers from developing a device which scientists will use to detect and determine the nature of the dark matter that makes up 1/4 of the mass of our universe.

The researchers from the University of Zaragoza (UNIZAR) and the Institut d’Astrophysique Spatiale (IAS, in France), made assumptions about the nature of dark matter based on theoretical studies, and developed device called a “scintillating bolometer” to detect the result of interaction of dark matter with material inside the detector.

“One of the biggest challenges in Physics today is to discover the true nature of dark matter, which cannot be directly observed – even though it seems to make up one-quarter of the matter of the Universe. So we have to attempt to detect it using prototypes such as the one we have developed”, Eduardo García Abancéns, a researcher from the UNIZAR’s Laboratory of Nuclear Physics and Astroparticles, tells SINC.

García Abancéns is one of the scientists working on the ROSEBUD project (an acronym for Rare Objects SEarch with Bolometers UndergrounD), an international collaborative initiative between the Institut d’Astrophysique Spatiale (CNRS-University of Paris-South, in France) and the University of Zaragoza, which is focusing on hunting for dark matter in the Milky Way.

The scientists have been working for the past decade on this mission at the Canfranc Underground Laboratory, in Huesca, where they have developed various cryogenic detectors (which operate at temperatures close to absolute zero: ?273.15 °C). The latest is a “scintillating bolometer”, a 46-gram device that, in this case, contains a crystal “scintillator”, made up of bismuth, germinate and oxygen (BGO: Bi4Ge3O12), which acts as a dark matter detector.

Naturally, to build any type of dark matter detector, the researchers had to make some assumptions about the nature of the dark matter itself.  The detection technique developed by the researchers is based on a number of theoretical studies which point to particles called WIMPs (Weakly Interacting Massive Particles) as the main constituent of dark matter.

“This detection technique is based on the simultaneous measurement of the light and heat produced by the interaction between the detector and the hypothetical WIMPs which, according to various theoretical models, explain the existence of dark matter”, explains García Abancéns.

The researcher explains that the difference in the scintillation of the various particles enables this method to differentiate between the signals that the WIMPs would produce and others produced by various elements of background radiation (such as alpha, beta or gamma particles).

In order to measure the miniscule amount of heat produced, the detector must be cooled to temperatures close to absolute zero, and a cryogenic facility, reinforced with lead and polyethylene bricks and protected from cosmic radiation as it housed under the Tobazo mountain, has been installed at the Canfranc underground laboratory.

“The new scintillating bolometer has performed excellently, proving its viability as a detector in experiments to look for dark matter, and also as a gamma spectrometer (a device that measures this type of radiation) to monitor background radiation in these experiments”, says García Abancéns.

The scintillating bolometer is currently at the Orsay University Centre in France, where the team is working to optimise the device’s light gathering, and carrying out trials with other BGO crystals.

This study, published recently in the journal Optical Materials, is part of the European EURECA project (European Underground Rare Event Calorimeter Array). This initiative, in which 16 European institutions are taking part (including the University of Zaragoza and the IAS), aims to construct a one-tonne cryogenic detector and use it over the next decade to hunt for the dark matter of the Universe.

Source: FECYT (Spain)

James Webb Space Telescope Begins To Take Shape

[/caption]

NASA’s James Webb Space Telescope is starting to come together. A major component of the telescope, the Integrated Science Instrument Module structure, recently arrived at NASA Goddard Space Flight Center in Greenbelt, Md. for testing in the Spacecraft Systems Development and Integration Facility.

The Integrated Science Instrument Module, or ISIM, is an important component of the Webb telescope. The ISIM includes the structure, four scientific instruments or cameras, electronics, harnesses, and other components.

The ISIM structure is the chassis, or “backbone” of the ISIM.  It supports and holds the four Webb telescope science instruments : the Mid-Infrared Instrument (MIRI), the Near-Infrared Camera (NIRCam), the Near-Infrared Spectrograph (NIRSpec) and the Fine Guidance Sensor (FGS). Each of these instruments were created and assembled by different program partners around the world.

When fully assembled, the ISIM will be the size of a small room with the structure acting as a skeleton supporting all of the instruments. Ray Lundquist, ISIM Systems Engineer, at NASA Goddard, commented that “The ISIM structure is truly a one-of-a-kind item. There is no second ISIM being made.”

Now that the structure has arrived at Goddard, it will undergo rigorous qualification testing to ensure it can survive the launch and extreme cold of space, and precisely hold the science instruments in the correct position with respect to the telescope. Once the ISIM structure passes its qualification testing, the process of integrating into it all of the other ISIM Subsystems, including the Science Instruments, will begin.

Each of the four instruments that will be housed in the ISIM is critical to the Webb telescope’s mission.

The MIRI instrument will provide information on the formation and evolution of galaxies, the physical processes of star and planet formation, and the sources of life-supporting elements in other solar systems.

The NIRCam will detect the first galaxies to form in the early universe, map the morphology and colors of galaxies; detect distant supernovae; map dark matter and study stellar populations in nearby galaxies.

NIRSpec’s microshutter cells can be opened or closed to view or block a portion of the sky which allows the instrument to do spectroscopy on many objects simultaneously, measuring the distances to galaxies and determining their chemical content.

The FGS is a broadband guide camera used for both “guide star” acquisition and fine pointing. The FGS also includes the scientific capability of taking images at individual wavelengths of infrared light to study chemical elements in stars and galaxies.

The ISIM itself is very complicated and is broken into three distinct areas

The first area involves the cryogenic instrument module. This is a critical area, because it keeps the instrument cool. Otherwise, the Webb telescope’s heat would interfere with the science instruments’ infrared cameras. So, the module keeps components as cold as -389 degrees Fahrenheit (39 Kelvin). The MIRI instrument is further cooled by a cryocooler refrigerator to -447 degrees Fahrenheit (7 Kelvin).

The second area is the ISIM Electronics Compartment, which provides the mounting surfaces and a thermally-controlled environment for the instrument control electronics.

The third area is the ISIM Command and Data Handling subsystem, which includes ISIM flight Software, and the MIRI cryocooler compressor and control electronics.

NASA Goddard will be assembling and testing the ISIM and its components over the next several years. The integrated ISIM will then be mounted onto the main Webb telescope.

Source: NASA

Magnetic Fields Have Key Influence on Star Formation

[/caption]

When a giant cloud of interstellar gas and dust collapses to form a new cluster of stars, only a small fraction of the cloud’s mass ends up in stars. Scientists have never been sure why.  But a new study provides insights into the role magnetic fields might play in star formation, and suggests more than the influence of gravity should be taken into account in computer models of stellar birth.

Gravity favors star formation by drawing material together, so if most material does not coalesce into stars, some additional force must hinder the process. Magnetic fields and turbulence are the two leading candidates. Magnetic fields channel flowing gas, making it hard to draw gas from all directions, while turbulence stirs the gas and induces an outward pressure that counteracts gravity.

“The relative importance of magnetic fields versus turbulence is a matter of much debate,” said astronomer Hua-bai Li of the Harvard-Smithsonian Center for Astrophysics. “Our findings serve as the first observational constraint on this issue.”

Li and his team studied 25 dense patches, or cloud cores, each one about a light-year in size. The cores, which act as seeds from which stars form, were located within molecular clouds as much as 6,500 light-years from Earth.

The degree of polarization of light from the clouds is influenced by the direction and strength of the local magnetic fields, so the researchers measured polarization to determine magnetic field strength. The fields within each cloud core were compared to the fields in the surrounding, tenuous nebula.

The magnetic fields tended to line up in the same direction, even though the relative size scales (1 light-year-sized cores versus 1000 light-year-sized nebulas) and densities were different by orders of magnitude. Since turbulence would tend to churn the nebula and mix up magnetic field directions, their findings show that magnetic fields dominate turbulence in influencing star birth.

“Our result shows that molecular cloud cores located near each other are connected not only by gravity but also by magnetic fields,” said Li. “This shows that computer simulations modeling star formation must take strong magnetic fields into account.”

In the broader picture, this discovery aids understanding of how stars and planets form and, therefore, how the universe has come to look the way it is today.

Source: Harvard-Smithsonian Center for Astrophysics

Is The Milky Way Doomed By Galactic Bombardment?

[/caption]

As scientists attempt to learn more about how galaxies evolve, an open question has been whether collisions with our dwarf galactic neighbors will one day tear apart the disk of the Milky Way.

That grisly fate is unlikely, a new study now suggests.

While astronomers know that such collisions have probably occurred in the past, the new computer simulations show that instead of destroying a galaxy, these collisions “puff up” a galactic disk, particularly around the edges, and produce structures called stellar rings.

The finding solves two mysteries: the likely fate of the Milky Way at the hands of its satellite galaxies — the most massive of which are the Large and Small Magellanic Clouds — and the origin of its puffy edges, which astronomers have seen elsewhere in the universe and dubbed “flares.”

The mysterious dark matter that makes up most of the universe plays a role, the study found.

Astronomers believe that all galaxies are embedded within massive and extended halos of dark matter, and that most large galaxies lie at the intersections of filaments of dark matter, which form a kind of gigantic web in our universe. Smaller satellite galaxies flow along strands of the web, and get pulled into orbit around large galaxies such as our Milky Way.

Ohio State University astronomer Stelios Kazantzidis and his colleagues performed detailed computer simulations of galaxy formation to determine what would happen if a satellite galaxy — such as the Large Magellanic Cloud and its associated dark matter — collided with a spiral galaxy such as our own.

The researchers considered the impacts of many different smaller galaxies onto a larger, primary disk galaxy. They calculated the likely number of satellites and the orbital paths of those satellites, and then simulated what would happen during collision, including when the dark matter interacted gravitationally with the disk of the spiral galaxy.

The conclusion?  None of the disk galaxies were torn apart.  To the contrary, the primary galaxies gradually disintegrated the in-falling satellites, whose material ultimately became part of the larger galaxy.  The satellites passed through the galactic disk over and over, and on each pass, they would lose some of their mass, a process that would eventually destroy them completely.

Though the primary galaxy survived, it did form flared edges which closely resembled our galaxy’s flared appearance today.

Does that settle the question of the fate of the Milky Way?

Kazantzidis couldn’t offer a 100-percent guarantee.

“We can’t know for sure what’s going to happen to the Milky Way, but we can say that our findings apply to a broad class of galaxies similar to our own,” Kazantzidis said. “Our simulations showed that the satellite galaxy impacts don’t destroy spiral galaxies — they actually drive their evolution, by producing this flared shape and creating stellar rings — spectacular rings of stars that we’ve seen in many spiral galaxies in the universe.”

Source: Ohio State University

Astronomers Find World’s Best Observing Site

[/caption]

The search for the best observatory site in the world has lead to the discovery of what is thought to be the coldest, driest, calmest place on Earth. No human is thought to have ever been there, but it’s expected to yield images of the heavens three times sharper than any ever taken from the ground.

The joint US-Australian research team combined data from satellites, ground stations and climate models to assess the many factors that affect the quality of an observing site – cloud cover, temperature, sky-brightness, water vapour, wind speeds and atmospheric turbulence.

The researchers pinpointed a site on an Antarctic plateau with the prosaic name “Ridge A”.  At an elevation of 4,053 m, the ridge is not only remote but extremely cold and dry. The study revealed that Ridge A has an average winter temperature of -70 °C, and that the water content of the entire atmosphere in a vertical column above the ridge is equivalent to a layer of liquid water less than the thickness of a human hair.

The ridge is also extremely calm, which means that there is very little of the atmospheric turbulence elsewhere that makes stars appear to twinkle. “It’s so calm that there’s almost no wind or weather there at all,” says Dr. Will Saunders of the Anglo-Australian Observatory and visiting professor to the University of New South Wales, who led the study.

“The astronomical images taken at Ridge A should be at least three times sharper than at the best sites currently used by astronomers,” says Dr. Saunders. “Because the sky there is so much darker and drier, it means that a modestly-sized telescope there would be as powerful as the largest telescopes anywhere else on earth.”

They found that the best place in almost all respects was not the highest point on the Plateau – called Dome A – but 150km away along a flat ridge.

“Ridge A looks to be significantly better than elsewhere on the Antarctic plateau and far superior to the best existing observatories on high mountain tops in Hawaii and Chile,” says Dr. Saunders.

Ridge A is located within the Australian Antarctic Territory (81.5 °S 73.5 ºE), the site is 144km from an international robotic observatory and the proposed new Chinese ‘Kunlun’ base at Dome A (80.37 °S 77.53 °E).

Interest in Antarctica as a site for astronomical and space observatories has accelerated since 2004 when astronomers published a paper in the journal Nature confirming that a ground-based telescope at Dome C, another Antarctic plateau site, could take images nearly as good as those from the space-based Hubble telescope.  A detailed study by the Anglo-Australian Observatory suggests the cost of building and running the 2.5 m telescope PILOT optical/infrared telescope at Dome C would be US$8.5 million.

The finding is published today in the Publications of the Astronomical Society of the Pacific.

Source: University of New South Wales

Star-Birth Myth Shattered

[/caption]

An international team of astronomers has debunked a long-held belief about how stars are formed.

Since the 1950’s, astronomers believed groups of new-born stars obeyed the same rules of star formation, which meant the ratio of massive stars to lighter stars was pretty much the same from galaxy to galaxy.  For every star 20 times more massive than the Sun or larger, for example, there’d be 500 stars equal to or less than the mass of the Sun.

“This was a really useful idea. Unfortunately it seems not to be true,” said team research leader Dr. Gerhardt Meurer of Johns Hopkins University in Baltimore.

This mass distribution of newly-born stars is called the ‘initial mass function’, or IMF.  Most of the light we see from galaxies comes from the highest mass stars, while the total mass in stars is dominated by the lower mass stars which can’t be seen, so the IMF has implications in accurately determining the mass of galaxies.  By measuring the amount of light from a population of stars, and making some corrections for the stars’ ages, astronomers can use the IMF to estimate the total mass of that population of stars.

Results for different galaxies can be compared only if the IMF is the same everywhere, but Dr. Meurer’s team has shown this ratio of high-mass to low-mass newborn stars differs between galaxies.  Small ‘dwarf’ galaxies, for instance, form many more low-mass stars than expected.

To arrive at this finding, Dr. Meurer’s team used galaxies in the HIPASS Survey (HI Parkes All Sky Survey) done with the Parkes radio telescope near Sydney, Australia.  A radio survey was used because galaxies contain substantial amounts of neutral hydrogen gas, the raw material for forming stars, and the neutral hydrogen emits radio waves.

The team measured two tracers of star formation, ultraviolet and H-alpha emissions, in 103 of the survey galaxies using NASA’s GALEX satellite and the 1.5-m CTIO optical telescope in Chile.

Selecting galaxies on the basis of their neutral hydrogen gave a sample of galaxies of many different shapes and sizes, unbiased by their star formation history.

H-alpha emission traces the presence of very massive stars called O stars, the birth of a star with a mass more than 20 times that of the Sun.

The UV emission, traces both O stars and the less massive B stars — overall, stars more than three times the mass of the Sun.

Meurer’s team found the ratio of H-alpha to UV emission varied from galaxy to galaxy, implying the IMF also did, at least at its upper end.

“This is complicated work, and we’ve necessarily had to take into account many factors that affect the ratio of H-alpha to UV emission, such as the fact that B stars live much longer than O stars,” Dr. Meurer said.

Dr. Meurer’s team suggests the IMF seems to be sensitive to the physical conditions of the star-forming region, particularly gas pressure.  For instance, massive stars are most likely to form in high-pressure environments such as tightly bound star clusters.

The team’s results allow a better understanding of other recently observed phenomena that have been puzzling astronomers, such as variation of the ratio of H-alpha to ultraviolet light as a function of radius within some galaxies.  This now makes sense as the stellar mix varies as the pressure drops with radius, just like the pressure varies with altitude on the Earth.

The work confirms tentative suggestions made first by Veronique Buat and collaborators in France in 1987, and then a more substantial study last year by Eric Hoversteen and Karl Glazebrook working out of Johns Hopkins and Swinburne Universities that suggested the same result.

Source: CSIRO

NASA Satellite Will Provide New Look At Cosmic X-Ray Sources

[/caption]

NASA has announced the development of a space-based observatory to give astronomers a new way to view X-rays from exotic objects such as black holes, neutron stars, and supernovae.  Called the Gravity and Extreme Magnetism Small Explorer (GEMS), the mission is part of NASA’s Small Explorer (SMEX) series of cost-efficient and highly productive space-science satellites, and will be the first satellite to measure the polarization of X-rays sources beyond the solar system.

Polarization is the direction of the vibrating electric field in an electromagnetic wave. An everyday example of polarization is the attenuating effect of some types of sunglasses, which pass light that vibrates in one direction while blocking the rest.  Astronomers frequently measure the polarization of radio waves and visible light to get insight into the physics of stars, nebulae, and the interstellar medium, but few measurements have every been made of polarized X-rays from cosmic sources.

“To date, astronomers have measured X-ray polarization from only a single object outside the solar system — the famous Crab Nebula, the luminous cloud that marks the site of an exploded star,” said Jean Swank, a Goddard astrophysicist and the GEMS principal investigator. “We expect that GEMS will detect dozens of sources and really open up this new frontier.”

Black holes will be high on the list of objects for GEMS to observe.  The extreme gravitational field near a spinning black hole not only bends the paths of X-rays, it also alters the directions of their electric fields. Polarization measurements can reveal the presence of a black hole and provide astronomers with information on its spin. Fast-moving electrons emit polarized X-rays as they spiral through intense magnetic fields, providing GEMS with the means to explore another aspect of extreme environments.

“Thanks to these effects, GEMS can probe spatial scales far smaller than any telescope can possibly image,” Swank said. Polarized X-rays carry information about the structure of cosmic sources that isn’t available in any other way.

“GEMS will be about 100 times more sensitive to polarization than any previous X-ray observatory, so we’re anticipating many new discoveries,” said Sandra Cauffman, GEMS project manager and the Assistant Director for Flight Projects at Goddard.

Some of the fundamental questions scientists hope GEMS will answer include: Where is the energy released near black holes? Where do the X-ray emissions from pulsars and neutron stars originate? What is the structure of the magnetic fields in supernova remnants?

GEMS will have innovative detectors that efficiently measure X-ray polarization. Using three telescopes, GEMS will detect X-rays with energies between 2,000 and 10,000 electron volts. (For comparison, visible light has energies between 2 and 3 electron volts.) The telescope optics will be based on thin-foil X-ray mirrors developed at Goddard and already proven in the joint Japan/U.S. Suzaku orbital observatory.

GEMS will launch no earlier than 2014 on a mission lasting up to two years.  GEMS is expected to cost $105 million, excluding launch vehicle.

Orbital Sciences Corporation in Dulles, Va., will provide the spacecraft bus and mission operations. ATK Space in Goleta, Calif., will build a 4-meter deployable boom that will place the X-ray mirrors at the proper distance from the detectors once GEMS reaches orbit. NASA’s Ames Research Center in Moffett Field, Calif., will partner in the science, provide science data processing software and assist in tracking the spacecraft’s development.

Source: NASA Goddard

Also see Proposed Mission Could Study Space-Time Around Black Holes

Sub-surface Oceans In Early Comets Suggest Possible Origin of Life

[/caption]

A new study claims early comets contained vast interior oceans of liquid water that may have provided the ideal conditions for early life to form.

In a paper published in the International Journal of Astrobiology, Professor Chandra Wickramasinghe and his colleagues at the Cardiff Centre for Astrobiology suggest the watery environment of early comets, together with the vast quantity of organics already discovered in comets, would have provided ideal conditions for primitive bacteria to grow and multiply during the first 1 million years of a comet’s life.

The Cardiff team has calculated the thermal history of comets after they formed from interstellar and interplanetary dust approximately 4.5 billion years ago. The formation of the solar system itself is thought to have been triggered by shock waves that emanated from the explosion of a nearby supernova. The supernova injected radioactive material such as Aluminium-26 into the primordial solar system and some became incorporated in the comets. Professor Chandra Wickramasinghe together with Drs Janaki Wickramasinghe and Max Wallis claim that the heat emitted from radioactivity warms initially frozen material of comets to produce subsurface oceans that persist in a liquid condition for a million years.

Professor Wickramasinghe said: “These calculations, which are more exhaustive than any done before, leaves little doubt that a large fraction of the 100 billion comets in our solar system did indeed have liquid interiors in the past.

Comets in recent times could also liquefy just below their surfaces as they approach the inner solar system in their orbits. Evidence of recent melting has been discovered in recent pictures of comet Tempel 1 taken by the “Deep Impact” probe in 2005.”

The existence of liquid water in comets gives added support for a possible connection between life on Earth and comets. The theory, known as cometary panspermia, pioneered by Chandra Wickramasinghe and the late Sir Fred Hoyle argues the case that life was introduced to Earth by comets.

Source: University of Cardiff