Posted on by Fraser Cain

Saturn’s Southern Atmosphere

Cassini captured intriguing cloud structures on Saturn as it neared its rendezvous with the gas giant. Notable is the irregularity in the eastern edge of the dark southern polar collar. The image was taken with the narrow angle camera on May 21, 2004, from a distance of 22 million kilometers (13.7 million miles) from Saturn through a filter sensitive to absorption and scattering of sunlight in the near infrared by methane gas (centered at 727 nanometers). The image scale is 131 kilometers (81 miles) per pixel. No contrast enhancement has been performed on this image.

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 Office of Space Science, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Posted on by Fraser Cain

The Search for More Earths

Until a decade ago, astronomers weren’t even sure there were any planets outside the Solar System. You’d be hard-pressed to find anyone who believed we had the only planets in the entire Universe, but we still didn’t have any direct evidence they existed. That all changed in October 5, 1995 when Michel Mayor and Didier Queloz announced they had discovered a planet half the mass of Jupiter orbiting furiously around a star called 51 Pegasi. The discoveries came fast; at last count, there are 122 confirmed extrasolar planets.

But these extrasolar systems generally look nothing like our own Solar System. Many contain massive planets which orbit extremely close to their parent star; no chance for life there. Planets roughly the size and orbit of Jupiter have been uncovered, but it’s impossible for the current technology to see anything the size of our own Earth.

Fortunately, there’s a series of ground and space-based observatories in the works that should be capable of detecting Earth-sized planets around other stars. NASA and the ESA are working towards the goal of being able to directly photograph these planets and measure the composition of their atmospheres. Find large amounts of oxygen, and you’ve found life.

Corot – 2006
The European Space Agency will be the first off the mark in the hunt for rocky planets with the launch of Corot in 2006. It’ll carefully monitor the brightness of stars, watching for a slight dimming that happens in regular intervals. These dimmings are called “transits”, and happen when a planet passes in between the Earth and a distant star. The concept of a “transit” should be fresh in your mind – Venus performed one recently on June 8, 2004. Corot will be sensitive enough to detect rocky planets as small as 10 times the size of the Earth.

A follow on mission, Eddington, was originally scheduled for launch in 2007, would have been able to spot planets half the size of the Earth. But it was recently canceled, unfortunately.

Kepler – 2007
The first space observatory designed to find Earth-sized planets in orbit around other stars will be Kepler, named after the German astronomer who devised the laws of planetary motion. It’s scheduled to launch in 2007, and will also use the transit method to detect planets.

Kepler has an extremely sensitive photometer hooked up to its one-metre telescope. It’ll monitor the brightness of hundreds of thousands of stars in a chunk of sky about the same size as your outstretched hand, and watch for that telltale periodic “dimming”.

Over the course of its four year mission, Kepler should discover plenty of objects orbiting other stars, and its photometer is just sensitive enough that it should notice an Earth-sized planet as it crosses in front of a star for a few hours.

Space Interferometry Mission – 2009
Next up will be the Space Interferometry Mission, due for launch in 2009. Once in space, the SIM will take up a position in orbit that trails the Earth as it goes around the Sun, slowly drifting further and further away – this’ll give it a good, stable view of the heavens, without having the Earth around to block the view.

The observatory is designed to measure the distance to stars with incredible precision. It’s so precise, that it should be able to spot a star being moved through the gravitational interaction with its planets. For example, if you looked at the position of our own Sun from a distant point, it would look like it’s wobbling around thanks to the gravity of Jupiter, Saturn, and even the Earth. SIM will be able to detect a star’s interactions with planets down to the size of a few times the mass of the Earth. That’s precise.

Terrestrial Planet Finder – 2012-2015
Unlike the previous missions, which will detect Earth-sized planets indirectly, the Terrestrial Planet Finder (TPF) will “see” them. It’s scheduled for launch in 2012 and will nullify the light from distant stars by a factor of 100,000 times, revealing their planets. The final design is still in the works, but it could end up being a group of spacecraft flying in close formation, merging their light together to form a much larger virtual space telescope.

The TPF will pick up where SIM leaves off, surveying the habitable zone of stars 50 light years away from the Earth. Not only will it be able to see Earth-sized planets in these zones, it’ll be able to analyze the composition of their atmospheres. Here’s the key: the TPF will be able to spot the presence of oxygen, water vapour, methane and carbon dioxide in Earth-sized planets in the habitable zone of other stars. If could find the fingerprint for life in the atmospheres of these planets.

Find life on other planets, and you can assume that it’s probably common throughout our Milky Way galaxy, and maybe even the entire Universe.

Darwin – 2014
Shortly after the TPF gets to work, the European Space Agency is planning to launch Darwin; a flotilla of 8 spacecraft working together to find Earth-sized planets and search for the chemical signatures of life. Darwin will be the most powerful space-based observatory, providing images 10-times more detailed than even the James Webb Space Telescope (due for launch 2009).

Stars are billions of times brighter than the planets that orbit them, so Darwin will solve this problem by observing in the infrared spectrum, where this difference is much smaller. It’ll also be capable of canceling out starlight to reveal the much dimmer planets.

Darwin is similar enough to the Terrestrial Planet Finder, that the two agencies are considering combining their designs into a single mission funded by both groups.

Maybe we aren’t alone after all.
In just a decade, and less than 20 years after the discovery of the first planets orbiting other stars, astronomers should be able to supply us with an answer to one of the most fundamental questions humans have asked themselves… are we alone? If the Terrestrial Planet Finder hasn’t turned up evidence of life yet, then the answer will still be, “not yet”. But there’s a chance that in 10 years, you’ll be reading news that that life has been discovered orbiting another star.

But that won’t be the end of it. The scientists will press on, with new equipment, observatories and techniques to search even deeper into space. And the philosophers and theologians will get to work considering our place in a very crowded Universe.

Posted on by Fraser Cain

Zubrin on Terraforming Mars

As a former Martin-Marietta aerospace engineer, prolific author and founder of the non-profit Mars Society (1998), Robert Zubrin is regarded as the driving force behind the proposed Mars Direct mission to reduce the cost and complexity of interplanetary travel. The flight plan calls for a return journey fueled by rocket propellant harvested in situ, from the martian atmosphere itself.

As described in Zubrin’s book, The Case for Mars: The Plan to Settle the Red Planet, the Mars Direct concept eventually became a cornerstone of a frugal ‘living off the land’ approach to travel in NASA’s Design Reference Mission. The Design Reference Mission (DRM) covers Earth launch to Mars landing, Mars cruise to Mars launch, and Earth return. The mission entails sending cargo ahead, docking the crew at the space station, then meeting up with the stashed supplies once on Mars.

“For our generation and many that will follow, Mars is the New World,” writes Zubrin. The New York Times Book Review (Dennis Overbye) indicated how such an outline initially was greeted as breaking conventional wisdom about martian mission plans: “Part history, part call to arms, part technical manual, part wishful thinking, The Case for Mars … lays out an ingenious plan. ……one of the most provocative and hopeful documents I have read about the space program in 20 years.”

The Mars Society continues to grow across many countries with thousands of members interested in space advocacy, particularly how best to encourage the exploration and settlement of Mars. Notable among the Society’s members are science-fiction author, Greg Benford, and Academy Award winning director, James Cameron.

Astrobiology Magazine had the opportunity to talk with Robert Zubrin about the possibilities for terraforming Mars.

Astrobiology Magazine (AM): First off, should Mars be terraformed?

Robert Zubrin (RZ): Yes.

AM: Does Mars contain all of the elements needed to make the planet habitable, or will we have to import gases, chemicals, etc., from elsewhere? If so, then will Mars always need constant inputs to achieve habitability, or do you think that given enough inputs Mars would reach a tipping point and planetary processes would create a self-sustaining feed-back loop?

RZ: It appears that Mars does have all the elements needed for terraforming. The one outstanding question is nitrogen, whose inventory remains unknown. However theory suggests that Mars should have had an initial supply of nitrogen comparable to the Earth, and it seems likely that much of this is still there.

AM: How long will terraforming take? When you envision a terraformed Mars, what do you see?

RZ: If one considers the problem of terraforming Mars from the point of view of current technology, the scenario looks like this:

1. A century to settle Mars and create a substantial local industrial capability and population.
2. A half century producing fluorocarbon gases (like CF4) to warm the planet by ~10 C.
3. A half century for CO2 to outgas from the soil under the impetus of the fluorocarbon gases, thickening the atmosphere to 0.2 to 0.3 bar, and raising the planetary temperature a further 40 C. This will cause water to melt out of the permafrost, and rivers to flow and rain to fall. Radiation doses on the surface will also be greatly reduced. Under these conditions, with active human help, first photosynthetic microbes and then ever more complex plants could be spread over the planet, as they would be able to grow in the open. Humans on Mars in this stage would no longer need pressure suits, just oxygen masks, and very large domed cities could be built, as the domes would no longer need to contain pressure greater than the outside environment.
4. Over a period of about a thousand years, human-disseminated and harvested plants would be able to put ~150 mbar (millibars) of oxygen in the Martian atmosphere. Once this occurs, humans and other animals will be able to live on Mars in the open, and the world will become fully alive.

That’s the scenario, using current technological approaches. However technology is advancing, and 23rd Century humans will not conduct their projects using 21st Century means. They will use 23rd Century means and accomplish the job much faster than anyone today can suppose.

So if someone in the 24th Century, living on a fully terraformed Mars, should discover this interview, I believe that she will view it in much the same way as we today look at Jules Verne’s lunar mission design. We today look at Verne’s ideas and say “Amazing, a man living a hundred years before Apollo foresaw it — and not only that– launched his crew of three from Florida, and returned them in a capsule landing in the Pacific Ocean where they were picked up by a US warship, all as things actually happened. But launching people with heavy artillery – how 19th Century can you get?” So our 24th Century Martian historian studying this interview will smile and say; “Incredible. Here are people 300 years ago talking about terraforming Mars. But doing it with fluorocarbon gases and green plants –how 20th century can you get?”

AM: Who should the first human colonists to Mars be and how should they be chosen? Since Martian gravity is one-third of Earth’s, wouldn’t bone and muscle loss, along with radiation, make colonization a one-way journey? What are the implications of what, from an Earth-perspective, is exile?

RZ: Life is a one-way trip, and we are all permanently exiled from our past. In that sense Mars colonists, and all colonists, are no different from anyone else. It is just more apparent in their case, as in addition to leaving behind the time of their past, they also leave behind the place. But in so doing, they gain the opportunity to create a world where none existed before, and thus gain a form of immortality that is denied to those who are content to accept the world they are born in.

AM: If there’s life on Mars, how do we balance the Martian right to life with the human impulse to explore and extend our borders?

RZ: The basis of ethics needs to be of benefit to humanity. If there is life on Mars, it is microbial, and its interests can in no way be considered as commensurate with human interests. Those who argue otherwise strike a fashionable pose, but deny their arguments every day through their actions. If bacterial interests trump human interests, then mouthwash should be banned, chlorination of water supplies should be banned, and antibiotics should be banned. If bacterial interests trump human interests, then Albert Schweitzer and Louis Pasteur should be denounced for crimes against bacteria.

Now, in saying that ethics must be based in human benefit, we need not deny that preserving valuable environments in important. It is important to save the amazon rain forest, for example, because a world without an amazon rain forest would be a poorer inheritance for our descendants than one with one, and the degree of the impoverishment exceeds whatever value might be obtained in the short term from slash and burn agriculture. However, in the case of Mars, the calculation votes the other way, as a terraformed Mars, filled with life, cities, universities, used book stores, and yes, rain forests, would be a vastly richer gift to posterity than the current barren Red Planet. Clearly, just as anyone who proposed transforming the current Earth into a place like Mars would be considered mad, so those who, given the choice, would keep Mars dead rather than make it a place as wonderful as the Earth must have their sanity doubted.

There remains only the question of science. Surely we should avail ourselves of the opportunity to study native Martian life before we terraform the place. We surely will. Terraforming Mars will be a long term project, and should native Martian microbes exist, there will be ample opportunity to study it before terraforming takes place. There will also be opportunity to study how it adapts to warmer, wetter conditions and the presence of terrestrial microbes after terraforming takes place. Furthermore, if Mars actually is terraformed, there will be much more people on Mars to study every aspect of Mars, including both its native and immigrant life. So in fact, our knowledge of Martian biota will be increased by terraforming, not decreased.

AM: Humans sent to live on Mars will bring with them ideas on how to govern themselves, rules of conduct for living in society, economic motivations, and personality conflicts. How should the colonization of Mars be managed, and how should Mars be governed? Should the colonization of Mars be a cooperative effort among every nation, or should only those that financial contribute be in charge of the operation?

RZ: The Founding Fathers of the United States called our infant republic a “Noble Experiment,” a place where the grand liberal ideas of the Enlightenment could be given a run, and the idea of a government based on the rights on man could be tested to see if it could succeed in practice. Their Noble Experiment did succeed, and as a result became the model for a new and better form of human social organization worldwide.

Mars can, should, and will be a place for numerous new Noble Experiments. The well of human social thought has not yet run dry, nor do I believe that we have yet discovered the ultimate and most humanistic form of society possible. In the 22nd Century, as in the 18th, there will always be people who think they have discovered a better way, and need a place to go where the rules haven’t been written yet so they can give their ideas a try. For these, the Martian frontier will beckon. Many of their ideas will prove impractical, and their colonies will fail. But some of those who really have a better idea will succeed, and in doing so, light the way forward for all humanity.

So, to answer your question, I say that the colonization of Mars should not be managed at all, but be done through the joyful chaos of human freedom.

AM: Taking a leap into the future, let’s assume the technology, biology, sociology, and politics have all combined to create a unique sub-race of humanity on Mars. Generations of human beings have now been born, grown, bred and died on Mars. Who are these Martians?

RZ: In 1893, the great historian Frederick Jackson Turner wrote:

“To the frontier the American intellect owes its striking characteristics. That coarseness of strength combined with acuteness and inquisitiveness; that practical inventive turn of mind, quick to find expedients; that masterful grasp of material things, lacking in the artistic but powerful to effect great ends; that restless, nervous energy; that dominant individualism, working for good and evil, and withal that buoyancy and exuberance that comes from freedom — these are the traits of the frontier.”

I think that says it all. The pioneers of the Martian frontier will be the Americans of the future.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Observatory Finds Its First Planet

McDonald Observatory astronomers Bill Cochran, Michael Endl, and Barbara McArthur have exploited the Hobby-Eberly Telescope’s (HET’s) capabilities to rapidly find and confirm, with great precision, the giant telescope’s first planet outside our solar system. The event serves as proof-of-concept that HET, combined with its High Resolution Spectrograph instrument, is on track to become a major player in the hunt for other worlds. The research has been accepted for publication in an upcoming edition of Astrophysical Journal Letters.

With a mass 2.84 times that of Jupiter, the newly discovered planet orbits the star HD 37605 every 54.23 days. HD 37605 is a little smaller and little cooler than the Sun. The star, which is of a type called “K0” or “K-zero,” is rich in heavy chemical elements compared to the Sun.

Of the approximately 120 extrasolar planets found to date, this new planet has the third most eccentric orbit bringing it in close in to its parent star like a “hot Jupiter,” and swinging it back out. The planet’s average distance from its star is 0.26 Astronomical Units (AU). One AU is the Earth-Sun distance.

The team used the “radial velocity” technique, a common planet-search method, to find the planet. By measuring changes in the star’s velocity toward and away from Earth –its wobble– they deduced that HD 37605 is orbiting the center of mass of a star-planet system.

“In 100 days of observations –less than two full orbits– we were able to get a very good solution for this planet’s orbit,” Cochran said. The quick results were due to HET’s “queue scheduling” system. Astronomers do not travel to the observatory to operate the telescope themselves. Rather, a telescope operator at McDonald Observatory has a list of all HET research projects and selects the ones best suited to any given night’s weather conditions and Moon phase. This way, many targets for different research projects can be observed each night, and any particular target can be observed dozens of nights in a row. According to Cochran, “queue scheduling is the ideal way to do planet searching. If the HET had a normal scheduling system, it would have taken us a year or two to confirm this planet.”

Endl added that “with the queue scheduling mode, we can put every candidate star BACK into the queue at a high priority to secure follow-up telescope observations immediately.”

Cochran added that the high precision of the team’s radial velocity measurements “proves that the HET and the High Resolution Spectrograph have met their design specs.” He explained that the total error (called “root-mean-square deviation”) in the team’s velocity measurements was 3 meters per second — state of the art for planet searching. Many of the team’s measurements had even lower errors. The High Resolution Spectrograph that made this research possible was built by Phillip MacQueen, Robert Tull, and John Good of The University of Texas at Austin.

The Hobby-Eberly Telescope is a joint project of The University of Texas at Austin, The Pennsylvania State University (Penn State), Stanford University, Ludwig-Maximilians-Universitat Muenchen, and Georg-August- Universitat Goettingen.

This planet detection research is supported by the National Aeronautics and Space Administration.”

Original Source: University of Texas at Austin News Release

Posted on by Fraser Cain

Blue Moon on July 31

When you hear someone say “Once in a Blue Moon?” you know what they mean: Rare. Seldom. Maybe even absurd. After all, when was the last time you saw the moon turn blue?

On July 31st, you should look, because there’s going to be a Blue Moon.

According to modern folklore, a Blue Moon is the second full moon in a calendar month. Usually months have only one full moon, but occasionally a second one sneaks in. Full moons are separated by 29 days, while most months are 30 or 31 days long; so it is possible to fit two full moons in a single month. This happens every two and a half years, on average.

July has already had one full moon on July 2nd. The next, on July 31st, is by definition a Blue Moon.

But will it really be blue? Probably not. The date of a full moon, all by itself, doesn’t affect the moon’s color. The moon on July 31st will be pearly-gray, as usual. Unless….

There was a time, not long ago, when people saw blue moons almost every night. Full moons, half moons, crescent moons–they were all blue, except some nights when they were green.

The time was 1883, the year an Indonesian volcano named Krakatoa exploded. Scientists liken the blast to a 100-megaton nuclear bomb. Fully 600 km away, people heard the noise as loud as a cannon shot. Plumes of ash rose to the very top of Earth’s atmosphere. And the moon turned blue.

Krakatoa’s ash is the reason. Some of the ash-clouds were filled with particles about 1 micron (one millionth of a meter) wide–the right size to strongly scatter red light, while allowing other colors to pass. White moonbeams shining through the clouds emerged blue, and sometimes green.

Blue moons persisted for years after the eruption. People also saw lavender suns and, for the first time, noctilucent clouds. The ash caused “such vivid red sunsets that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration,” according to volcanologist Scott Rowland at the University of Hawaii.

Other less potent volcanos have turned the moon blue, too. People saw blue moons in 1983, for instance, after the eruption of the El Chichon volcano in Mexico. And there are reports of blue moons caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.

The key to a blue moon is having in the air lots of particles slightly wider than the wavelength of red light (0.7 micron)–and no other sizes present. This is rare, but volcanoes sometimes spit out such clouds, as do forest fires:

“On September 23, 1950, several muskeg fires that had been quietly smoldering for several years in Alberta suddenly blew up into major–and very smoky–fires,” writes physics professor Sue Ann Bowling of the University of Alaska. “Winds carried the smoke eastward and southward with unusual speed, and the conditions of the fire produced large quantities of oily droplets of just the right size (about 1 micron in diameter) to scatter red and yellow light. Wherever the smoke cleared enough so that the sun was visible, it was lavender or blue. Ontario and much of the east coast of the U.S. were affected by the following day, but the smoke kept going. Two days later, observers in England reported an indigo sun in smoke-dimmed skies, followed by an equally blue moon that evening.”

In the western U.S., there will be wildfires burning on July 31st. If any of those fires produce ash or oily-smoke containing lots of 1-micron particles, the Blue Moon there could be blue.

More likely, it’ll be red. Ash and dust clouds thrown into the atmosphere by fires and storms usually contain a mixture of particles with a wide range of sizes. Most are smaller than 1 micron, and they tend to scatter blue light. This kind of cloud makes the Moon turn red; indeed, red Blue Moons are far more common than blue Blue Moons.

Absurd? Yes, but that’s what a Blue Moon is all about. Step outside at sunset on July 31st, look east, and see for yourself.

Original Source: NASA Science Article

Posted on by Fraser Cain

Forum Reaches its First Birthday

Exactly one year today I was nagged into setting up the Universe Today forum as a way for space enthusiasts to come together and discuss all things space and astronomy. Despite my initial reluctance, it’s been incredibly successful, becoming one of the larger communities of this topic on the Internet – I wish I’d done it sooner. As I’m looking right now, we have 2422 members who’ve written 34354 posts. So, I’d like to make a special thanks to all the contributors, moderators, and experts who have participated so far, I really appreciate all your hard work.

If you have questions about space, want to explore any topic deeper, or just make friends who share your interests in space, come and join us.

Fraser Cain
Publisher
Universe Today

P.S. If you’ve had problems accessing the forum, or setting up an account, let me know, and I’d be happy to help you out. I know it can be a little confusing if you’ve never joined one before.

Posted on by Fraser Cain

Wallpaper: Saturn’s Rings in Ultraviolet

The best view ever of Saturn’s rings in the ultraviolet indicates there is more ice toward the outer part of the rings, hinting at ring origin and evolution, say two University of Colorado at Boulder researchers involved in the Cassini mission.

Researchers from CU-Boulder’s Laboratory for Atmospheric and Space Physics, Joshua Colwell and Larry Esposito, said the UV spectra taken during the Cassini spacecraft’s orbital insertion June 30 show definite compositional variation in the A, B and C rings.

Esposito, who discovered the F ring around Saturn in 1979 using Pioneer 11 data, is the team leader for Cassini’s Ultraviolet Imaging Spectrograph, or UVIS, a $12.5 million instrument riding on the spacecraft. A UVIS team member and ring expert, Colwell created the color-enhanced images from the spectra.

The CU-Boulder built UVIS instrument is capable of resolving the rings to show features up to 60 miles across, roughly 10 times the resolution obtained by the Voyager 2 spacecraft. The instrument was able to resolve the “Cassini division,” discovered by Giovanni Domenico Cassini in the 17th century, which separates the A and B rings of Saturn, proving the rings are not one contiguous feature.

The ring system begins from the inside out with the D, C, B and A rings followed by the F, G and E rings. The red in both images indicates sparser ringlets likely made of “dirty,” and possibly smaller, particles than in the denser, icier turquoise ringlets.

Original Source: University of Colorado News Release

Posted on by Fraser Cain

SpaceShipOne Problem Resolved

Wired News is reporting that Burt Rutan has resolved the nearly catastrophic problems that cropped up during SpaceShipOne’s historic flight into space last flight. After his flight, pilot Mike Melvill said that a control malfunctioned, caused the rocket plane to roll 90 degrees over to the left, and then 90 degrees to the right when he tried to compensate. Melvill was able to use a backup system, and still reach 100 km of altitude. Rutan said that the problem was traced to an actuator that had ?run against a stop?, limiting its movement. With the problem fixed, SpaceShipOne’s next flight will be an attempt to win the $10 million X-Prize.

Posted on by Fraser Cain

Brown Dwarf Pair Discovered

Today at the 13th Cambridge Workshop on “Cool Stars, Stellar Systems, and the Sun,” Dr. Kevin L. Luhman (Harvard-Smithsonian Center for Astrophysics) announced the discovery of a unique pair of newborn brown dwarfs in orbit around each other. Brown dwarfs are a relatively new class of objects discovered in the mid-1990s that are too small to ignite hydrogen fusion and shine as stars, yet too big to be considered planets. “Are brown dwarfs miniature failed stars, or super-sized planets, or are they altogether different from either stars or planets?” asks Luhman. The unique nature of this new brown dwarf pair has brought astronomers a step closer to the answer.

One possible explanation for the origin of brown dwarfs is that they are born in the same way as stars. Stars form in huge interstellar clouds in which gravity causes clumps of gas and dust to collapse into “seeds,” which then steadily pull in more and more material until they grow to become stars. However, when this process is studied in detail by computer, many simulations fail to produce brown dwarfs. Instead, all the seeds grow into full-fledged stars. This result led some astronomers to wonder if brown dwarfs and stars are created in different ways.

“In one alternative that has been proposed recently,” explains Luhman, “the seeds in an interstellar cloud pull on each other through their gravity, causing a slingshot effect and ejecting some of the seeds from the cloud before they have a chance to grow into stars. These small bodies are what we see as brown dwarfs, according to that hypothesis.”

Testing these ideas for the birth of brown dwarfs is hampered by the fact that brown dwarfs are normally extremely faint and hard to detect in the sky. For most of their lives, they are not hot enough to ignite hydrogen fusion, so they do not shine brightly like stars, and instead are relatively dim like planets. However, for a short time immediately following their birth, brown dwarfs are relatively bright due to the leftover heat from their formation. As a result, brown dwarfs are easiest to find and study at an age of around 1 million years, which is newborn compared to the 4.5 billion year age of our Sun.

Taking advantage of this fact, Luhman searched for newborn brown dwarfs in a cluster of young stars located 540 light-years away in the southern constellation of Chamaeleon. Luhman conducted his search using one of the two 6.5-meter-diameter Magellan telescopes at Las Campanas Observatory in Chile, which are among the largest telescopes in the world.

Of the two dozen new brown dwarfs found, most were isolated and floating in space by themselves. However, Luhman discovered one pair of brown dwarfs orbiting each other at a remarkably wide separation. All previously known pairs of brown dwarfs are relatively close to each other, less than half the distance of Pluto from the Sun. But the brown dwarfs in this new pair are much farther apart, about six times the distance of Pluto from the Sun.

Because these brown dwarfs are so far apart, they are very weakly bound to each other by gravity, and the slightest tug would permanently separate them. Therefore, Luhman concludes, “The mere existence of this extremely fragile pair indicates that these brown dwarfs were never subjected to the kind of violent gravitational pulls that they would undergo if they had formed as ejected seeds. Instead, it is likely that these baby brown dwarfs formed in the same way as stars, in a relatively gentle and undisturbed manner.”

Dr. Alan P. Boss (Carnegie Institution) agrees, stating, “Luhman’s discovery strengthens the case for the formation mechanism of brown dwarfs being similar to that of stars like the Sun, and hence for brown dwarfs being worthy of being termed ‘stars,’ even if they are too low in mass to be able to undergo sustained nuclear fusion.”

The discovery of this binary brown dwarf will be published in an upcoming issue of The Astrophysical Journal. The discovery paper currently is online in PDF format at http://cfa-www.harvard.edu/~kluhman/paper.pdf

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

The Magellan telescopes are operated by the Carnegie Institution of Washington, the University of Arizona, Harvard University, the University of Michigan, and the Massachusetts Institute of Technology.

Las Campanas Observatory is operated by the Carnegie Observatories, which was founded in 1904 by George Ellery Hale. It is one of six departments of the private, nonprofit Carnegie Institution of Washington, a pioneering force in basic scientific research since 1902.

Original Source: Harvard CfA News Release

Posted on by Fraser Cain

Heavy Galaxies Evolved Early

Current theories of the formation of galaxies are based on the hierarchical merging of smaller entities into larger and larger structures, starting from about the size of a stellar globular cluster and ending with clusters of galaxies. According to this scenario, it is assumed that no massive galaxies existed in the young universe.

However, this view may now have to be revised. Using the multi-mode FORS2 instrument on the Very Large Telescope at Paranal, a team of Italian astronomers have identified four remote galaxies, several times more massive than the Milky Way galaxy, or as massive as the heaviest galaxies in the present-day universe. Those galaxies must have formed when the Universe was only about 2,000 million years old, that is some 12,000 million years ago.

The newly discovered objects may be members of a population of old massive galaxies undetected until now.

The existence of such systems shows that the build-up of massive elliptical galaxies was much faster in the early Universe than expected from current theory.

Hierarchical merging
Galaxies are like islands in the Universe, made of stars as well as dust and gas clouds. They come in different sizes and shapes. Astronomers generally distinguish between spiral galaxies – like our own Milky Way, NGC 1232 or the famous Andromeda galaxy – and elliptical galaxies, the latter mostly containing old stars and having very little dust or gas. Some galaxies are intermediate between spirals and ellipticals and are referred to as lenticular or spheroidal galaxies.

Galaxies are not only distinct in shape, they also vary in size: some may be as “light” as a stellar globular cluster in our Milky Way (i.e. they contain about the equivalent of a few million Suns) while others may be more massive than a million million Suns. Presently, more than half of the stars in the Universe are located in massive spheroidal galaxies.

One of the main open questions of modern astrophysics and cosmology is how and when galaxies formed and evolved starting from the primordial gas that filled the early Universe. In the most popular current theory, galaxies in the local Universe are the result of a relatively slow process where small and less massive galaxies merge to gradually build up bigger and more massive galaxies. In this scenario, dubbed “hierarchical merging”, the young Universe was populated by small galaxies with little mass, whereas the present Universe contains large, old and massive galaxies – the very last to form in the final stage of a slow assembling process.

If this scenario were true, then one should not be able to find massive elliptical galaxies in the young universe. Or, in other words, due to the finite speed of light, there should be no such massive galaxies very far from us. And indeed, until now no old elliptical galaxy was known beyond a radio-galaxy at redshift 1.55 that was discovered almost ten years ago.

The K20 survey
In order to better understand the formation process of galaxies and to verify if the hierarchical merging scenario is valid, a team of Italian and ESO astronomers used ESO’s Very Large Telescope as a “time machine” to do a search for very remote elliptical galaxies. However, this is not trivial. Distant elliptical galaxies, with their content of old and red stars, must be very faint objects indeed at optical wavelengths as the bulk of their light is redshifted into the infrared part of the spectrum. Remote elliptical galaxies are thus among the most difficult observational targets even for the largest telescopes; this is also why the 1.55 redshift record has persisted for so long.

But this challenge did not stop the researchers. They obtained deep optical spectroscopy with the multi-mode FORS2 instrument on the VLT for a sample of 546 faint objects found in a sky area of 52 arcmin2 (or about one tenth of the area of the Full Moon) known as the K20 field, and which partly overlaps with the GOODS-South area. Their perseverance paid off and they were rewarded by the discovery of four old, massive galaxies with redshifts between 1.6 and 1.9. These galaxies are seen when the Universe was only about 25% of its present age of 13,700 million years.

For one of the galaxies, the K20 team benefited also from the database of publicly available spectra in the GOODS-South area taken by the ESO/GOODS team.

A new population of galaxies
The newly discovered galaxies are thus seen when the Universe was about 3,500 million years old, i.e. 10,000 million years ago. But from the spectra taken, it appears that these galaxies contain stars with ages between 1,000 and 2,000 million years. This implies that the galaxies must have formed accordingly earlier, and that they must have essentially completed their assembly at a moment when the Universe was only 1,500 to 2,500 million years old.

The galaxies appear to have masses in excess of one hundred thousand million solar masses and they are therefore of sizes similar to the most massive galaxies in the present-day Universe. Complementary images taken within the GOODS (“The Great Observatories Origins Deep Survey”) survey by the Hubble Space Telescope show that these galaxies have structures and shapes more or less identical to those of the present-day massive elliptical galaxies.

The new observations have therefore revealed a new population of very old and massive galaxies.

The existence of such massive and old spheroidal galaxies in the early Universe shows that the assembly of the present-day massive elliptical galaxies started much earlier and was much faster than predicted by the hierarchical merging theory. Says Andrea Cimatti (INAF, Firenze, Italy), leader of the team: “Our new study now raises fundamental questions about our understanding and knowledge of the processes that regulated the genesis and the evolutionary history of the Universe and its structures.”

Original Source: ESO News Release