Universe Today

May 4, 2009September 15, 2016 by Fraser Cain

What is Intergalactic Space?

The space between stars is known as interstellar space, and so the space between galaxies is called intergalactic space. These are the vast empty spaces that sit between galaxies. For example, if you wanted to travel from the Milky Way to the Andromeda galaxy, you would need to cross 2.5 million light-years of intergalactic space.

Intergalactic space is as close as you can get to an absolute vacuum. There’s very little dust and debris, and scientists have calculated that there’s probably only one hydrogen atom per cubic meter. The density of material is higher near galaxies, and lower in the midpoint between galaxies.

Galaxies are connected by a rarefied plasma that is thought to posses a cosmic filamentary structure, which is slightly denser than the average density of the Universe. This material is known as the intergalactic medium, and it’s mostly made up of ionized hydrogen. Astronomers think that the intergalactic medium is about 10 to 100 times denser than the average density of the Universe.

This intergalactic medium can actually be seen by our telescopes here on Earth because it’s heated up to tens of thousands, or even millions of degrees. This is hot enough for electrons to escape from hydrogen nuclei during collisions. We can detect the energy released from these collisions in the X-ray spectrum. NASA’s Chandra X-Ray Observatory – a space telescope designed to search for X-rays – has detected vast clouds of hot intergalactic medium in regions where galaxies are colliding together in clusters.

We have written many articles about galaxies for Universe Today. Here’s an article about how intergalactic dust might be messing up observations, and here’s an article about a cosmic hurricane in a starburst galaxy.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 4, 2009December 24, 2015 by Fraser Cain

Quasars

When astronomers first started using radio telescopes in the 1950s to study the Universe, they discovered a strange phenomenon. They found objects that shone brightly in the radio spectrum, but they couldn’t see any visible object associated with them. They called them quasi-stellar radio sources, or “quasars” for short.

Within a decade of their discovery, astronomers learned that these quasars were moving away at tremendous velocities. This velocity, or red-shift of their light, indicated that they were billions of light-years away; beyond the capabilities of most optical telescopes. It wasn’t until the 1960s when a quasar was finally tied to an optical object, a distant galaxy.

Since then, thousands of quasars have been discovered, but astronomers had no idea what they were. Finally in the 1980s, astronomers developed unified models that identified quasars as active galaxies. The bright radiation coming from them is because of the accretion disks surrounding the supermassive black holes at their centers. We see a quasar when a supermassive black hole is actively feeding on the surrounding material.

Since our own Milky Way has a supermassive black hole, it’s likely that we have gone through many active stages, whenever material is falling into the black hole; our galaxy would be seen as a quasar. But other times, like now, the supermassive black hole is quiet.

With new powerful telescopes, astronomers have observed that some quasars have long jets of material firing out from the center of the galaxy. These are channeled by the magnetic fields created by the supermassive black hole’s rotation in the accretion disk. The most luminous quasars can exceed the radiation output of an average quasar.

We have written many articles about quasars for Universe Today. Here’s an article about the first triple quasar ever found, and some hidden quasars… found!

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 3, 2009December 24, 2015 by Ian O'Neill

2009 HC82: A Burnt-Out, Eccentric and Backward Near-Earth Asteroid

The Solar System often throws up surprises for astronomers, but the recent discovery of a 2- to 3-km wide asteroid called 2009 HC82 has sent observers in a spin. A retrograde spin to be precise.

This particular near-Earth asteroid (NEO) should have already been spotted as it has such a strange orbit. It is highly inclined, making it orbit the Sun backwards (when compared with the rest of the Solar System’s planetary bodies) every 3.39 years. What’s more, it ventures uncomfortably close (3.5 million km) to the Earth, making this NEO a potentially deadly lump of rock…

2009 HC82 was discovered on April 29th by the highly successful Catalina Sky Survey, and after independent observations by five different groups, it was determined that the asteroid has an orbit of 3.39 years and that its orbit is very inclined. So inclined in fact that the asteroid’s orbit takes it well out of the Solar System ecliptic at an angle of 155°. Inclined orbits aren’t rare in themselves, but if you find an asteroid with an inclination of more than 90°, you are seeing a very rare type of object: a retrograde asteroid.

The last time I wrote about a retrograde asteroid was back in September 2008 (Kuiper Belt Object Travelling the Wrong-Way in a One-Way Solar System), when a University of British Columbia researcher spotted a rather unique retrograde Kuiper belt object (called 2008 KV42) that had a large looping orbit with an inclination larger than 90°. It was nicknamed “Drac” after Dracula’s ability to walk on walls.

2009 HC82 is therefore not only rare, it is also very strange. It orbits the Sun the wrong way (therefore making it very inclined), it is a potentially hazardous NEO (it is smaller than the 10 km asteroid that is attributed to wiping out the dinosaurs, but it would cause significant devastation on a global scale if it did hit us) and it is very eccentric.

All these orbital components have led to speculation that 2009 HC82 is in fact a “burnt out” comet. Comets originate from the Oort Cloud, a theoretical region cometary nuclei that occasionally gets nudged by gravitational disturbances when stars pass by. The Oort Cloud is not restricted to a belt along the ecliptic (like the asteroid belt or the Kuiper belt), it encapsulates our Solar System. Therefore, this may explain 2009 HC82’s bizarre trajectory; it was a comet, but all the ice has vaporized, leaving a rocky core to fling around the Sun on a death-defying orbit, buzzing the inner Solar System.

Brian Marsden of the Minor Planet Center agrees that some retrograde asteroids could be burnt-out comets. The size and shape of the new asteroid’s orbit “is very like Encke’s comet except for inclination,” he said, but the only difference is the fact that 2009 HC82 has no cometary tail.

More observations are needed before a definitive conclusion can be made, but Marsden is confused as to why this object has not been discovered before now. “It should have been easily observable in 2000,” says Marsden. “Why wasn’t it seen then?”

It is hoped further investigation may answer this question…

Source: New Scientist

May 2, 2009December 24, 2015 by Fraser Cain

Galaxy Pictures

Spiral galaxy M101. Image credit: Hubble

The best photographs captured from ground and the Hubble Space Telescopes. I could look at pictures of beautiful spiral galaxies all day. So let’s take a look at some of the most beautiful galaxy photos ever taken.

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This is a classic picture of the spiral galaxy M101, captured by the Hubble Space Telescope. Since this galaxy is seen almost face-on, it allows astronomers to see what a large spiral galaxy, like our own Milky Way, looks like. M101 is located in the constellation of Ursa Major and measures 170,000 light-years across; twice the diameter of the Milky Way.

This is the Andromeda Galaxy, also known as M31. It’s the closest large galaxy to the Milky Way; in fact, Andromeda is currently on a collision course with the Milky Way, and will collide with us in about 10 billion years. After that, the two galaxies will collect together into an enormous irregular galaxy, and our supermassive black holes will merge together.

Andromeda galaxy photo. Image credit: Spitzer

Here’s another Andromeda galaxy picture, but this time captured in the infrared spectrum by the Spitzer Space Telescope. By seeing Andromeda in infrared, astronomers can see regions that would normally be obscured by dust, like new star forming regions, or the center of the galaxy.

This is a photo of galaxy M81 captured by the Hubble Space Telescope. This is another example of a grand spiral galaxy, seen from a bit of an angle. This galaxy is located 11.6 million light-years away in the constellation Ursa Major.

Here’s a picture of the galaxy Centaurus A, located in the constellation of the same name. The huge sprays of material above and below the galaxy demonstrate the power of the supermassive black hole located at the heart of the galaxy. The jets of material extend more than 13,000 light-years away from the center of the galaxy.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 1, 2009December 24, 2015 by Nancy Atkinson

NASA Begins Job Layoffs As Shuttle Retirement Looms

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NASA began the first round of job layoffs today as the space agency prepares to retire its fleet of space shuttles. 160 people were notified today their jobs were being cut, the first of 900 jobs that will evaporate in the next five months. The first wave of layoffs will affect Lockheed Martin and ATK Thiokol, contractors that support the shuttle program building fuel tanks and rocket boosters in Louisiana and Utah. The shuttle program employs about 1,600 NASA civil servants across the space agency and 13,800 contractors around the country. Once the shuttle stops flying, as many as 6,500 jobs could be cut at the Kennedy Space Center alone.

NASA announced the first round of layoffs at a briefing Thursday, where they also announced the launch date for the Hubble Telescope repair mission as May 11, a day earlier than previously planned. Making the two divergent announcements at the same news conference was bittersweet.

Officials at the briefing stressed that without an infusion of money in 2010 — for which a detailed budget is expected to be released next week — they had no choice but to continue the gradual shutdown of shuttle operations.

Bill Gerstenmaier (left), NASAÂ?s associate administrator for space operations, and shuttle-program manager John Shannon announce job cuts Thursday at Kennedy Space Center. Credit: NASA

Shuttle program manager John Shannon said several hundred jobs will be lost to attrition and some employees will transfer to other contractors or projects. The rest will be layoffs.

“Only if we were directed to fly additional missions would we halt that activity,” Shannon said.

Bill Gerstenmaier, associate administrator for space operations, said that if $2.5 billion proposed recently by Congress budget planners materialized, it could allow a few shuttles to fly past the 2010 retirement date if some shuttle flights got delayed and NASA were unable to complete the construction of the international space station.

He added that, although the shuttle program’s plans were clear, it was less certain how quickly jobs would ramp up for the shuttle’s replacement, the Ares I rocket and Orion capsule.

The first launch of Ares I and Orion is planned for March 2015, but that date is not certain.

Source: Orlando Sentinel

May 1, 2009December 24, 2015 by Nancy Atkinson

Why Are Galaxies Smooth? Star Streams

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Look at the disk of any large spiral galaxy, and outwardly it appears smooth, with stars evenly distributed throughout. But when young stars are forming, they are clustered together in dense clouds of dust and gas. So what happens as the galaxy matures to allow for the smooth distribution seen in galaxies like the Milky Way? Using NASA’s Spitzer Space Telescope, an international team of astronomers has discovered streams of young stars flowing from their natal cocoons in distant galaxies. These distant rivers of stars provide an answer to one of astronomy’s most fundamental puzzles.

Astronomers know that the clusters where stars form begin to disappear when their ages reach several hundred million years. A few mechanisms are thought to explain this: some clusters evaporate when random internal motions kick out stars one by one, and other clusters disperse as a result of collisions among the clouds where they were born. Zooming out to mechanisms operating on larger scales still, shearing motions caused by the galaxy’s rotation around its center disperses the clusters of clusters of young stars.

“Our analysis now answers the grand puzzle. By finding a myriad of streams of young stars all over the disks of galaxies we studied, we see that the mechanism for pulling the clusters of young stars apart is shearing motions of the parent galaxy. These streams are the ‘missing link’ we needed to understand how the disks of galaxies evolve to look the way they do,” said team leader David Block of the University of the Witwatersrand in South Africa.

Crucial to this discovery was finding a way to image previously hidden young stellar streams in galaxies millions of light-years away. To do this the team used high-resolution infrared observations from the Spitzer.
Using infrared rather than visible light to look at the galaxies allowed the group to pick out stars at just the right age when the stars are just starting to spread out from their clusters.

“Spitzer observes in the infrared where 100-million-year-old populations of stars dominate the light,” noted co-author Bruce Elmegreen, from IBM’s Research Division in New York. “Younger regions shine more in the visible and ultraviolet parts of the spectrum, and older regions get too faint to see. So we can filter out all the stars we don’t want by taking pictures with an infrared camera.”

Infrared is also important because light in this part of the spectrum can penetrate the dense dust clouds surrounding the clusters where stars form.

“Dust blocks optical starlight very effectively,” said Robert Gehrz of the University of Minnesota, “but infrared light with its longer wavelength goes right around the dust particles blocking our view. This allows the infrared light from young stars to be seen more clearly.”

But even when the images are taken in the infrared, they are still dominated by the light from the smooth older disks of galaxies, not the faint tracks of young dispersing clusters. Special mathematical manipulations were needed to pick out the clusters, whose faint tracks can still be seen precisely because they are not smooth.

Team member Ivanio Puerari of the Instituto Nacional de Astrofisica, Optica y Electronica in Puebla, Mexico used a technique invented by mathematician Jean Baptiste Fourier in the early 1800’s. The technique is effectively a spatial filter that picks out structure on the physical scale where star formation occurs. “The structures cannot be seen on the original Spitzer images with the human eye,” noted Puerari.

“The combination of the Fourier filtering and infrared images highlighted regions of just the right size and the right age. To then unveil so many star streams in the disks of galaxies was unimaginable a year ago. This discovery continues to highlight the enormous potential of the Spitzer Space Telescope to make contributions none of us could have dreamed possible,” commented Giovanni Fazio from the Harvard-Smithsonian Center for Astrophysics, project leader for the Spitzer Infrared Array Camera team used to take the pictures, and co-author of the discovery.

“Galileo, as both astronomer and mathematician, would have been proud. It is a wonderful interplay between the use of astronomical observations and mathematics and computers, exactly 400 years since Galileo used his telescope to examine our Milky Way galaxy in 1609,” Fazio said

Source: Spitzer

May 1, 2009December 24, 2015 by Nancy Atkinson

Coastal Formations Not Result of Asteroid Impact

The black arrows indicate the orientation of chevrons along the southern coast of Madagascar, but the white arrows indicate what computer models say should have been the orientation if they were caused by the impact of a space body in the Indian Ocean. Credit: Robert Weiss

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Coastal formations called chevrons, large U- or V-shaped features found on coastlines around the world were originally thought to be evidence of ancient “megatsunamis” caused by asteroids or comets slamming into the ocean. However, new research using Google Earth and computer models to recreate large wave action refutes that school of thought.

The theory of chevrons being created by tsunamis was proposed in 2006 after the structures were found in Egypt and the Bahamas. Some were, at places, between several hundred meters- and a kilometer-wide. Since they were also found to exist in Australia and Madagascar, some geologists formed the hypothesis that they were sediment cones left behind by large tsunamis, perhaps up to ten times stronger than the devastating tsunami in the Indian Ocean in December 2005.

The theory propsed the only source for such a megatsunami was a meteor impact, occurring about 5,000 years ago.

But a new study, led by Jody Bourgeois, a geologist and tsunami expert at the University of Washington, argues that this theory is simply “nonsense. For example, she said, there are numerous chevrons on Madagascar, but many are parallel to the coastline. Models created by Bourgeois’ colleague Robert Weiss show that if they were created by tsunamis they should point in the direction the waves were travelling, mostly perpendicular to the shore.

Landsat image of the Fenambosy Chevrons in Madagascar by USGS. The open side of these chevrons point directly at a crater at the bottom of the Indian Ocean. They suggest a gigantic meteor impact occurred about 4800 years ago. But new research says chevrons were likely formed by wind.

“And if it really was from an impact, you should find evidence on the coast of Africa too, since it is so near,” she said.

By using Google Earth, Bourgeois and her team searched for chevrons and surprisingly they found some in desert areas, well inland and away from the shores.

“The extraordinary claim of ‘chevron’ genesis by megatsunamis cannot withstand simple but rigorous testing. There are the same forms in the Palouse in eastern Washington state, and those are clearly not from a tsunami,” Bourgeois said.

She believes the structures were formed by wind.

The discovery of marine fossils in some chevron formations seems to support the idea that a wave created the deposit, but Bourgeois discounts that evidence also.

“Marine fossils can get into non-marine deposits. It’s not uncommon. You only have to change sea level a little bit or have them wash up on a beach in a storm,” she said. “And some marine organisms can be carried by the wind. I am convinced these are largely wind-blown deposits.”

She noted that similar deposits have been seen on the Kamchatka Peninsula on Russia’s east coast, where she has conducted research for more than a decade.

“Those are made of volcanic ash, and they are not near the coast at all, yet they look very similar to these coastal chevrons,” Bourgeois said.

Source: Newswise

May 1, 2009December 24, 2015 by Fraser Cain

Spiral Galaxy

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When you think of a galaxy, you’re probably thinking of a spiral galaxy. You know, with the central bulge and grand sweeping arms that spiral outward from the center. In fact, our own Milky Way is a spiral galaxy, and there are many others out there in the Universe. But have you ever thought about how they form in such a beautiful shape?

A spiral galaxy is shaped like a flat disk with a thicker bulge in the center. Bright spiral arms start from the center and then coil outward like a pinwheel. All spiral galaxies rotate, but very slowly; our own Milky Way completes a single revolution once every 250 million years or so.

The spiral arms are actually density waves that move around the disk of the spiral galaxy. As the density wave passes over a region, masses are pulled together, and you get bright pockets of star formation. Then the density wave moves on, and encourages another region to begin star formation.

The central bulge at the center of a spiral galaxy contains older stars, similar to an elliptical galaxy. And at the very center, there’s always a supermassive black hole containing millions of times the mass of the Sun.

Spiral galaxies are also surrounded by a vast spheroidal halo of stars. These stars might not have formed in the galaxy, but were stolen through successive mergers with other galaxies. This galactic halo also contains many globular star clusters.

Astronomers think that spiral galaxies are slowly built over time through the merger of smaller galaxies. As these tiny galaxies came together, their total momentum set the merged galaxy spinning. This spin flattened out the galaxy and set the spiral arms in motion.

We have written many articles about the galaxies for Universe Today. Here’s an article with twin spiral galaxies interacting, and here’s spiral galaxy NGC 2403.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

May 1, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – May 1-3, 2009

Greetings, fellow StarGazers! Let’s start the weekend off right by taking on a lunar club challenge and then kicking back to enjoy yet another spring meteor shower! (After all, if April showers bring May flowers, you do know what May flowers bring, don’t you? That’s right… Pilgrims!) Now that I’ve got you at least smiling, take out your binoculars, too… Because there’s two asteroids that are ripe for plucking – Hebe and Ceres. If you feel like being a little more serious about your lunar studies, why not do a little photographic map work? Just match the picture to what you see in the eyepiece and log your studies! Are you ready? Then I’ll see you in the back yard…

Friday, May 1, 2009 – This date is a rather special one in history. In 1543 on this date, Copernicus published and distributed the ‘‘ The Little Commentary ,’’ which described his heliocentric beliefs. In 1949, Gerard Kuiper discovered Nereid, a 150-kilometer-wide satellite of Neptune. It’s so distant from the planet that it requires almost one Earth year (360 days) to complete an orbit! At magnitude 18.7, Nereid is beyond the detection point of most average telescopes but can be ‘‘seen’’ using long exposure charge coupled AQ1 device (CCD) image stacking devices. Other sights that can’t be seen are the Van Allen Radiation Belts of our Earth, the discovery of which was announced in 1958 in this day’s copy of the Washington Evening Star. Thanks to James A. Van Allen’s use of the data from the Explorer I and Pioneer III space probes, we know that Earth’s magnetosphere contains concentrations of electrically charged particles. Say Happy Birthday to American astronaut M. Scott Carpenter, who was born on this date in 1925 and was one of the original seven Mercury astronauts to reach space in 1962.

Tonight’s outstanding lunar feature will be crater Maurolycus , just southwest of the three rings of Theophilus, Cyrillus, and Catharina. This Lunar Club Challenge spans 114 kilometers and goes below the lunar surface by 4,730 meters. Be sure to look for Gemma Frisius just to its north!

Now, relax and enjoy the peak of the Phi Bootid meteor shower, whose radiant is near the constellation Hercules. The best time to view most meteor showers is around 2:00 a.m. local time, but you may have good success watching for these meteors as soon as the Moon westers. The average fall rate is only about 6 per hour, but it’s a great way to spend a spring evening out under the stars!

Saturday, May 2, 2009 – Today, let’s start with the 1868 birth on this date of Robert Williams Wood. Although Wood’s primary research was on sound waves, he devised a ‘‘zone plate’’ that could replace the objective lens of a telescope! He also improved the diffraction grating, did research in spectroscopy, and made photographs showing both infrared and ultraviolet radiations. Also, take a moment to note the 1925 passing of the star cataloger, Johann Palisa. Palisa remains the most successful visual discoverer in the history of minor planet research, discovering 122 asteroids with a 600 telescope and no photographic plates!

Why not salute his achievements by looking for the asteroid Hebe, which reaches opposition tonight? Hebe is the 13th largest asteroid by mass and the 5th brightest to observe. If you collect meteorites and have an H chondrite, chances are good you have a physical piece of Hebe, since it is thought to have contributed up to 40% of all recovered chrondites! Hebe is now coming in at 6th magnitude and given its prime location shouldn’t make it fairly easy for even those with just binoculars to find this cool asteroid.

Now, let’s have a look at the Moon! Tonight’s challenges are craters Cassini and Cassini A, which come into view just south of the black slash of the Alpine Valley. The major crater spans 57 kilometers and reaches a floor depth of 1,240 meters. Your assignment, should you decide to accept it, is to spot the central crater A. It only spans 17 kilometers, yet drops down another 2,830 meters below the primary crater’s floor!

Sunday, May 3, 2009 – How about starting the day with the bizarre and unusual? In 1375 BC, the oldest recorded total solar eclipse occurred—if we can believe eighth century Babylonian records! If you have a green laser pointer, or a telrad, you might want to wish Alfred Kastler a happy birthday. Born on this date in 1902, the physicist was very interested in what happened to atoms when excited by light or radio waves. Kastler developed a method called ‘‘optical pumping,’’ where atoms enter a higher energy state. Optical pumping is what makes your laser work!

Tonight notice just how close bright Regulus is to the Moon! If you’d like to try your hand at asteroid Ceres, you’ll find it approximately another 15 degrees north of the ‘‘Little King.’’

Tonight let’s take a long Moonwalk together and do some major crater exploration. Try using mid-range magnification in your telescope and see how many of the craters in this photograph you can identify!.

Ptolemaeus area: (1) Sinus Asperitatis, (2) Theophilus, (3) Cyrillus, (4) Catharina, (5) Rupes Altai, (6) Piccolomini, (7) Sacrobosco, (8) Abulfeda, (9) Almanon, (10) Taylor, (11) Abenezra, (12) Apianus (13) Playfair, (14) Aliacensis, (15) Werner, (16) Blanchinus, (17) Lacaille, (18) Walter, (19) Regiomontanus, (20) Purbach, (21) Thebit, (22) Arzachel, (23) Alphonsus, (24) Ptolemaeus, and (25) Albategnius.

Until next week? Ask for the Moon… But keep on reaching for the stars!

This week’s awesome images are (in order of appearance): M. Scott Carpenter (credit—NASA), Maurolycus (credit—Alan Chu), Johann Palisa (historical image), Hebe Chart (Your Sky), Cassini (credit—Wes Higgins), Alfred Kastler (historical image) and the Ptolemaeus area (credit—Greg Konkel). We thank you so much!

May 1, 2009December 24, 2015 by Anne Minard

Cosmic Rays too Wimpy to Influence Climate

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People looking for new ways to explain climate change on Earth have sometimes turned to cosmic rays, showers of atomic nuclei that emanate from the Sun and other sources in the cosmos.

But new research, in press in the journal Geophysical Research Letters, says cosmic rays are puny compared to other climatic influences, including greenhouse gases — and not likely to impact Earth’s climate much.

Jeffrey Pierce and Peter Adams of Carnegie Mellon University in Pittsburgh, Pennsylvania, point out that cycles in numerous climate phenomena, including tropospheric and stratospheric temperatures, sea-surface temperatures, sea-level pressure, and low level cloud cover have been observed to correlate with the 11-year solar cycle.

However, variation in the Sun’s brightness alone isn’t enough to explain the effects and scientists have speculated for years that cosmic rays could fill the gap.

For example, Henrick Svensmark, a solar researcher at the Danish Space Research Institute, has proposed numerous times, most recently in 2007, that solar cosmic rays can seed clouds on Earth – and he’s seen indications that periods of intense cosmic ray bombardment have yeilded stormy weather patterns in the past.

Others have disagreed.

“Dust and aerosols give us much quicker ways of producing clouds than cosmic rays,” said Mike Lockwood, a solar terrestrial physicist at Southampton University in the UK. “It could be real, but I think it will be very limited in scope.”

To address the debate, Pierce and Adams ran computer simulations using cosmic-ray fluctuations common over the 11-year solar cycle.

“In our simulations, changes in [cloud condensation nuclei concentrations] from changes in cosmic rays during a solar cycle are two orders of magnitude too small to account for the observed changes in cloud properties,” they write, “consequently, we conclude that the hypothesized effect is too small to play a significant role in current climate change.”

The results have met a mixed reception so far with other experts, according to an article in this week’s issue of the journal Science: Jan Kazil of the University of Colorado at Boulder has reported results from a different set of models, confirming that cosmic rays’ influence is similarly weak. But at least one researcher — Fangqun Yu of the University at Albany in New York — has questioned the soundness of Pierce and Adams’ simulations.

And so, the debate isn’t over yet …

Sources: The original paper (available for registered AGU users here) and a news article in the May 1 issue of the journal Science. See links to some of Svensmark’s papers here.