Posted on by Nancy Atkinson

Cassini Primary Mission Complete; Ready to Tackle New Assignments

An aurora dances on Saturn in this image from the Cassini orbiter. Credit: NASA/JPL/University of Arizona

Saturn’s gorgeous rings. Geysers on Enceladus. Methane lakes on Titan. These are just a few of the images that stand out from the Cassini mission’s four year survey of Saturn and its remarkable system of rings and moons. On June 30 the Cassini spacecraft completes its primary mission at the ringed planet, and now will embark on an extended two year mission, with hopes of studying more closely the most intriguing targets, Titan and Enceladus and the interaction between Saturn’s icy moons and rings.

“We’ve had a wonderful mission and a very eventful one in terms of the scientific discoveries we’ve made, and yet an uneventful one when it comes to the spacecraft behaving so well,” said Bob Mitchell, Cassini program manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We are incredibly proud to have completed all of the objectives we set out to accomplish when we launched. We answered old questions and raised quite a few new ones and so our journey continues.”
Mitchell said while its clear Cassini isn’t just driving off the showroom floor, considering how complex the nature of the mission has been and how long it’s been going, the spacecraft is doing remarkably well.

Cassini launched Oct. 15, 1997, taking seven years to traverse 3.5 billion kilometers (2.2 billion miles) to Saturn. The mission entered Saturn’s orbit on June 30, 2004, and began returning stunning data of Saturn’s rings almost immediately.

Mitchell said the spacecraft has made major discoveries about the dynamics of the rings, and how the moons gravity shapes the rings into the different gaps. “The geysers of Enceladus rank near the top of the excitement of the discoveries that we’ve made,” he said. “ Titan is very different than we expected it to be. It’s a lot like Earth, if you just replace water with methane there a lot of processes on Titan that look like Earth.”

The extended mission will allow for monitoring seasonal effects on Titan and Saturn, exploring new places within Saturn’s magnetosphere, and observing the unique ring geometry of the Saturn equinox in August of 2009 when sunlight will pass directly through the plane of the rings.

The next two years, Cassini will have 26 more encounters with Titan, seven close encounters with Enceladus, and one each with the icy moons Dione, Rhea and Helene.

And there’s sure to be other discoveries at Saturn as well. “There are a number of surprises yet waiting for us, as the seasons change, we’re bound to find exciting things we haven’t even thought of yet,” said Mitchell.

Original News Source: JPL

Posted on by Tammy Plotner

The Weekend SkyWatcher’s Forecast: June 27-29, 2008

Greetings, fellow SkyWatchers! It’s that time again and darker skies are in our favor for this weekend. Are you working towards Astronomical League studies? Then tag along as we seek out one of the most difficult of all targets – Palomar 5. But don’t despair – there’s just slightly easier ones to study, too! Come along for the double galaxy ride and the peak of two minor meteor showers as we head out into the night…

Friday, June 27 – As with all astronomical projects, there are sometimes difficult ones needed to complete certain fields of study – such as challenging globular clusters. Tonight we’ll take a look at one such cluster needed to complete your list and you’ll find it by using M5 as a guide.

Palomar Observatory, courtesy of CaltechPalomar 5 is by no stretch of the imagination easy. For those using GoTo systems and large telescopes, aiming is easy…but for star hoppers a bit of instruction goes a long way. Starting at M5 drop south for the double star 5 Serpentis and again south and slightly west for another, fainter double. Don’t confuse it with 6 Serpentis to the east. About half a degree west you’ll encounter an 8th magnitude star with 7th magnitude 4 Serpentis a half degree south. Continue south another half degree where you will discover a triangle of 9th magnitude stars with a southern one at the apex. This is home to Palomar 5 (RA 15 16 05 Dec 00 06 41).

Discovered by Walter Baade in 1950, this 11.7 magnitude, Class XII globular is anything but easy. At first it was believed to be a dwarf elliptical and possibly a member of our own Local Group of galaxies due to some resolution of its stars. Later studies showed Palomar 5 was indeed a globular cluster – but one in the process of being ripped apart by the tidal forces of the Milky Way.

75,000 light-years away from us and 60,000 light-years from the galactic center, Palomar 5’s members are escaping and leaving trails spanning as much as 13,000 light-years…a process which may have been ongoing for several billion years. Although it is of low surface brightness, even telescopes as small as 6″ can distinguish just a few individual members northwest of the 9th magnitude marker star – but even telescopes as large as 31″ fail to show much more than a faint sheen (under excellent conditions) with a handful of resolvable stars. Even though it may be one of the toughest you’ll ever tackle, be sure to take the time to make a quick sketch of the region to complete your studies. Good luck!

While you’re out, keep a watch for a handful of meteors originating near the constellation of Corvus. The Corvid meteor shower is not well documented, but you might spot as many as ten per hour.

Saturday, June 28 – Before you start hunting down the faint fuzzies and spend the rest of the night drooling on the Milky Way, let’s go globular and hunt up two very nice studies worthy of your time. Starting at Alpha Librae, head five degrees southeast for Tau, and yet another degree southeast for the splendid field of NGC 5897 (RA 15 17 24 Dec -21 00 36).

Palomar Observatory, courtesy of CaltechThis class XI globular might appear very faint to binoculars, but it definitely makes up for it in size and beauty of field. It was first viewed by William Herschel on April 25, 1784 and logged as H VI.8 – but with a less than perfect notation of position. When he reviewed it again on March 10, 1785 he logged it correctly and relabeled it as H VI.19. At a distance of a little more than 40,000 light-years, this 8.5 magnitude globular will show some details to the larger telescope, but remain unresolved to smaller ones. As a halo globular cluster, NGC 5897 certainly shows signs of being disrupted, and has a number of blue stragglers, as well as four newly-discovered variables of the RR Lyrae type.

Now let’s return to Alpha Librae and head about a fistwidth south across the border into Hydra and two degrees east of star 57 for NGC 5694 – also in an attractive field (RA 14 39 36 Dec 26 32 18).

Palomar Observatory, courtesy of CaltechAlso discovered by Herschel, and cataloged as H II.196, this class VII cluster is far too faint for binoculars at magnitude 10, and barely within reach of smaller scopes. As one of the most remote globular clusters in our galaxy, few telescopes can hope to resolve this more than 113,000 light-year distant ball of stars. Its brightest member is only of magnitude 16.5, and it contains no known variables. Traveling at 190 kilometers per second, metal-poor NGC 5694 will not have the same fate as NGC 5897…for this is a globular cluster which is not being pulled apart by our galaxy – but escaping it!

George E. HaleSunday, June 29 – Today we celebrate the birthday of George Ellery Hale, who was born in 1868. Hale was the founding father of the Mt. Wilson Observatory. Although he had no education beyond his baccalaureate in physics, he became the leading astronomer of his day. He invented the spectroheliograph, coined the word astrophysics, and founded the Astrophysical Journal and Yerkes Observatory. At the time, Mt. Wilson dominated the world of astronomy, confirming what galaxies were and verifying the expanding universe cosmology, making Mt. Wilson one of the most productive facilities ever built. When Hale went on to found Palomar Observatory, the 5-meter (200″) telescope was named for him, and was dedicated on June 3, 1948. It continues to be the largest telescope in the continental United States.

Tonight, while we have plenty of dark skies to go around, let’s go south in Libra and have a look at the galaxy pairing NGC 5903 and NGC 5898. You’ll find them about three degrees northeast of Sigma, and just north of a pair of 7th magnitude stars.

Palomar Observatory, courtesy of CaltechWhile northernmost NGC 5903 seems to be nothing more than a faint elliptical with a brighter concentration toward the center and an almost identical elliptical – NGC 5898 – to the southwest, you’re probably asking yourself… Why the big deal over two small ellipticals? First off, NGC 5903 is Herschel III.139 and NGC 5898 is Herschel III.138…two more to add to your studies. And second? The Very Large Array has studied this galaxy pair in the spectral lines of neutral hydrogen. The brighter of the pair, NGC 5898, shows evidence of ionized gas which has been collected from outside its galactic realm – while NGC 5903 seems to be running streamers of material toward its neighbor. A double-galaxy, double-accretion event!

But there’s more…

Look to the southeast and you’ll double your pleasure and double your fun as you discover two double stars instead of just one! Sometimes we overlook field stars for reasons of study – but don’t do it tonight. Even mid-sized telescopes can easily reveal this twin pair of galaxies sharing “their stuff,” as well as a pair of double stars in the same low power field of view. (Psst…slim and dim MCG 043607 and quasar 1514-241 are also here!) Ain’t it grand?

After the black of midnight and out of the blue comes a meteor shower! Keep watch tonight for the June Draconids. The radiant for this shower will be near handle of Big Dipper – Ursa Major. The fall rate varies from 10 to 100 per hour, and lack of lunacy means a great time for the offspring of comet Pons-Winnecke. On a curious note, today in 1908 was when the great Tunguska impact happened in Siberia. A fragment of a comet, perhaps?

Good luck and have a terrific weekend!

This week’s awesome image credits are: Palomar 5 (center of image) – Credit: Palomar Observatory, courtesy of Caltech, NGC 5897 – Credit: Palomar Observatory, courtesy of Caltech, NGC 5694 – Credit: Palomar Observatory, courtesy of Caltech, and the field of NGC 5903 and NGC 5898 – Credit: Palomar Observatory, courtesy of Caltech

Posted on by Nancy Atkinson

SOHO the Comet-Finder — And You Can Help

On June 25th, the ESA/NASA SOHO spacecraft discovered its 1,500th comet, making it more successful than all other comet discoverers throughout history, combined. But wait a minute, SOHO is the Solar and Heliospheric Observatory, designed to study solar physics. What’s it doing looking for comets? SOHO just happens to have a great vantage point to see comets as they approach the sun. Since its orbit is situated between the Sun and Earth, it has a unique view of the regions close to the sun that we can rarely see from Earth. But SOHO’s comet-finding success is just an added benefit to the extraordinary revelations this spacecraft has provided in its 13 years in space, observing the Sun and the near-Sun environment. “Catching the enormous total of comets has been an unplanned bonus,” said Bernhard Fleck, ESA SOHO Project Scientist.

About 85% of SOHO’s comet discoveries are fragments from a once-great comet that split apart in a death plunge around the Sun, probably many centuries ago. The fragments are known as the Kreutz group, which now pass within 1.5 million km of the Sun’s surface when they return from deep space.

That’s pretty close in celestial terms, and from Earth, we can only see those regions close to the Sun during an eclipse.

But that also puts them within sight of SOHO’s electronic eyes. Images of the comets are captured by the Large Angle and Spectrometric Coronograph (LASCO), one of 12 instruments on board.

Of course, LASCO itself does not make the detections; that task falls to an open group of highly-skilled volunteers who scan the data as soon as it is downloaded to Earth. Once SOHO transmits to Earth, the data can be on the Internet and ready for analysis within 15 minutes.

Enthusiasts from all over the world look at each individual image for a tiny moving speck that could be a comet. When someone believes they have found one, they submit their results to Karl Battams at the Naval Research Laboratory, Washington DC, who checks all of SOHO’s findings before submitting them to the Minor Planet Center, where the comet is cataloged and its orbit calculated.

From this mission, and with the public’s help, scientists have learned a great deal about comets.

“This is allowing us to see how comets die,” says Battams. When a comet constantly circles the Sun, it loses a little more ice each time, until it eventually falls to pieces, leaving a long trail of fragments. Thanks to SOHO, astronomers now have a plethora of images showing this process. “It’s a unique data set and could not have been achieved in any other way,” says Battams.

Most of the comet fragments are eventually destroyed when they get close enough to the Sun, evaporated by the Sun’s radiation.

Interested in helping search for SOHO’s comets? Visit the Sungrazing comets page.

Original News Source: ESA

Posted on by Nancy Atkinson

Launch Pad Repairs to Begin; Hubble Repair Mission Should Go As Scheduled

Work will begin on Friday to repair damaged sections of Kennedy Space Center’s launch pad 39A that was damaged during the last space shuttle launch on May 31. On Thursday, (June 26) NASA managers approved a plan that would complete the repairs by the third week of August. Therefore the mission schedule shouldn’t be impacted. The next space shuttle flight, the high-profile final mission to repair the Hubble Space Telescope is scheduled to launch on October 8, and if all goes well with the repairs, space shuttle Atlantis would crawl its way out to the pad on August 29. “We really like the plan,” said shuttle Program Manager John Shannon. “We expect to start moving out on it right away.”

During shuttle Discovery’s launch in May more than 3,500 fire-resistant bricks lining the northeast wall of the “flame trench” at pad 39A were blasted away. Radar tracking showed some of the bricks shot out of the trench at about 1,000 feet per second, or about 680 mph. But NASA officials said the incident did not pose a threat to the space shuttle. Computer simulations run by engineers showed that none of the bricks flew up near the pad surface, and therefore couldn’t have hit the shuttle.

“It’s not a flight [safety] issue at all,” said Rita Willcoxon, space shuttle processing manager, during a teleconference on Thursday.

The work is estimated to cost less than $2.7 million.
A detailed inspection found that many of the anchor plates used to secure the interlocking fire bricks to the 3-foot-thick concrete back wall were heavily eroded due to decades of exposure to severe pressures and acidic rocket exhaust. Additionally, epoxy used to help secure the bricks to the wall was degraded or not consistently applied when the pad was built in the mid 1960s. As a result, the outer brick wall was not tightly locked to the underlying concrete wall it was designed to protect.

To fix the trench, a two different sections of the trench wall will be stripped of bricks.. A steel mesh-like structure will be erected over the exposed backwall and then covered in sprayed-on Fondu Fyre, a material used to protect the massive flame deflector directly under the shuttle’s boosters and main engines.

Working two 10-hour shifts per day, the repair team expects to have the brick removed by July 19. After that, the mesh will be erected and the Fondue Fyre applied.
Officials said the repaired flame trench will be inspected after every launch, but is expected to hold up through the end of shuttle operations in 2010.

The other shuttle pad, 39B may have similar deficiencies in its flame trench. But no major repairs are scheduled for that pad, as all 10 remaining shuttle flights are scheduled to use pad 39A. NASA will have a shuttle ready at 39B for a rescue mission should Atlantis suffer major damage during the Hubble flight, since the shuttle couldn’t reach the International Space Station as a safe haven, which is in a different orbit than Hubble.

News Sources: CBS News Space Place, Space.com

Posted on by Ian O'Neill

Phoenix: Mars Soil Can Support Life

Phoenix delivers regolith to the wet lab (NASA/UA)

Another groundbreaking discovery from Mars: Phoenix has analysed martian regolith containing minerals more commonly found in soil here on Earth, and the acidity is not a hindrance for life to thrive. These new and very exciting results come after preliminary analyses of a scoop of regolith by the landers “wet lab” known as the Microscopy, Electrochemistry and Conductivity Analyzer (MECA) instrument. Although more data collecting needs to be done, trace levels of nutrients have already been detected. This, with the recent discovery of water ice, has amazed mission scientists, likening these new results to “winning the lottery.”

The MECA instrument is carrying out the first ever wet-chemical analysis on a planet other than Earth, and these first results are tantalisingly close to providing answers for the question: “Can Mars support life?” Taken from a scoop of top-soil, the robotic digger managed to excavate a 2 cm deep ditch, delivering the sample to the MECA where analysis could be carried out. The first results from the two-day wet-lab experiment are flooding in and mission scientists are excited by the results. “We are awash in chemistry data,” said Michael Hecht of NASA’s Jet Propulsion Laboratory and lead scientist for the MECA.

The salts discovered contain magnesium, sodium, potassium and chlorine, indicating these minerals had once been dissolved in water. The knowledge that these elements exist in martian regolith is nothing new, but the fact that they would be soluble in water means they would have been available for life to form. In fact, there are some strong similarities between the mineral content and pH level of the martian surface and soils more commonly found here on Earth.

“This soil appears to be a close analog to surface soils found in the upper dry valleys in Antarctica. The alkalinity of the soil at this location is definitely striking. At this specific location, one-inch into the surface layer, the soil is very basic, with a pH of between eight and nine. We also found a variety of components of salts that we haven’t had time to analyze and identify yet, but that include magnesium, sodium, potassium and chloride.” – Sam Kounaves, Phoenix co-investigator, Tufts University.

From the question “Has Mars supported life?” to “Can Mars support life?” – The answer seems to be an overwhelming “Yes.” Although nitrates have yet to be detected, the Mars soil appears to have an alkalinity commonly found in terrestrial soils. At a pH of eight or nine, a zoo of bacteria and plants can live comfortably. Vegetables such as asparagus and turnips are farmed in soils to this degree of alkalinity. Besides, extreme forms of bacteria have been discovered in environments that resemble the alkalinity of bleach, exceeding a pH of 12. The martian surface has suddenly become a little more hospitable for life to thrive.

“Over time, I’ve come to the conclusion that the amazing thing about Mars is not that it’s an alien world, but that in many aspects, like mineralogy, it’s very much like Earth.” – Kounaves.

Although these first results are very exciting, mission scientists are staying realistic. This is only one of several tests, plus it is a sample from a single location. As the digger only scooped a sample 2 cm deep, scientists are keen to see if the regolith deeper down has similar chemistry, so the intention is to dig deeper into the same location, possibly including ice.

Aside: The term “Mars soil”, up to this point, hasn’t been technically accurate. If we look at the definition of “soil” we get:

The material on the surface of the ground in which plants grow; earth
– Cambridge Dictionaries.
The top layer of the earth’s surface, consisting of rock and mineral particles mixed with organic matter.
– Answers.com

The stuff with a red hue on Mars is actually regolith, pulverized grains of rock from hundreds of millions of years of meteorite impacts, geological activity and weathering. Until Phoenix produced these new findings, the most accurate way to describe Mars “soil” was to call it regolith. But now, it seems, Mars regolith fulfils most of the characteristics of being a soil. It contains rock, it contains minerals and it appears to have a pH capable of sustaining plant growth. But does it already contain organic matter? Whether it contains anything “organic” now is open to debate, but it might do in the future…

Sources: Phoenix (UA), New Scientist

Posted on by Fraser Cain

Carnival of Space #60

The Pantheon.

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This week the Carnival of Space moves to Slacker Astronomy.

Click here to read the Carnival of Space #60

And if you’re interested in looking back, here’s an archive to all the past carnivals of space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let me know if you can be a host, and I’ll schedule you into the calendar.

Finally, if you run a space-related blog, please post a link to the Carnival of Space. Help us get the word out.

Posted on by Ian O'Neill

LCROSS Passes Pre-Flight Tests Before Kamikaze Mission to Find Water on Moon

LCROSS separation above the Moon (NASA)

The Lunar Crater Observation and Sensing Satellite (LCROSS) is a very exciting mission for lunar exploration. Since the discovery of water on Mars by Phoenix last week, focus is turning on other planetary bodies and natural satellites for the possibility they may hold a supply of water too. First stop for any manned mission will be our return trip to the Moon by 2020, so it would be very advantageous if we could find a frozen reservoir of H2O hiding within the craters of the lunar surface. LCROSS is going to hitch a ride with the Lunar Reconnaissance Orbiter (LRO) later this year on board an Atlas V rocket. It has just passed some gruelling pre-launch tests before it sets out on a suicide mission that will end in collision with the lunar surface…

To make sure LCROSS can stand up to the huge temperature gradients it will experience during its lunar adventure, engineers have subjected it to rigorous heating and cooling cycles at the Northrop Grumman facility in Redondo Beach, California. These tests come after successful completion of thermal vacuum testing at the start of this month. LCROSS has also been given the thumbs up after passing a launch acoustic vibration simulation intended to see how the integrity of the spacecraft copes with the violence of an Atlas V blast-off.

This new round of tests heated the spacecraft to 230°F (110°C) and then cooled it to -40°F (-40°C) over 13.5 days to simulate the extremes of temperature it will experience en-route to the Moon and flyby.

“The spacecraft steadily has taken shape since Ames delivered the science payload in January. It is a testament to the hard work, perseverance and expertise of the NASA and Northrop Grumman teams that the spacecraft has completed these critical tests ahead of schedule.” – Daniel Andrews, LCROSS project manager, NASA’s Ames Research Center, California.

When in orbit around the Moon in 2009, LCROSS will create two impact plumes in the lunar surface. The target will be a crater near the lunar polar region that is constantly in shadow. This is the perfect location for water ice to form, if there’s any at all.

The Atlas V’s Centaur upper stage rocket will carry LCROSS to the Moon and execute a lunar flyby. It will then enter an elongated Earth orbit, putting the probe in the correct trajectory, ready for LCROSS-Centaur separation. The Centaur stage will then be instructed to carry out a suicidal plunge into the surface so the resulting plume of dust and gas that will rise into the orbital path for LCROSS to analyse. Once data about the plume is relayed to Earth, LCROSS itself will make the ultimate sacrifice, ploughing into the Moon’s surface, creating a second plume of debris for Earth-based observatories to analyse.

It is hoped this trailblazer mission will unlock some of the lunar secrets as to whether water ice is present in any great quantities inside this polar crater, possibly the source for a future manned lunar base.

Source: LCROSS, Physorg

Posted on by Nicholos Wethington

Dark Matter is Denser in the Solar System

Dark matter was theorized to exist relatively recently, and we’ve come a long way in understanding what makes up a whopping 23% of our Universe. Our own galaxy is surrounded by a halo of dark matter that adds to its mass. A recent paper on the dark matter closer to home – right here in our own Solar System – reveals that it is denser and more massive than in the galactic halo.

Dark matter is just plain weird stuff. It doesn’t give off light, has mass and reacts gravitationally with “normal” matter – the stuff that we and our planet and the stars are composed of. Just like normal matter, it “clumps” up, or accretes, because of this gravitational attraction; we find more dark matter near galaxies than in the vast expanses between them.

Dark matter isn’t just far off in the Milky Way or somewhere on the other side of the Universe, though: it’s right here at home in our Solar System. In a recent paper submitted to Physical Review D, Ethan Siegel and Xiaoying Xu of the University of Arizona analyzed the distribution of dark matter in our Solar System, and found that the mass of dark matter is 300 times more than that of the galactic halo average, and the density is 16,000 times higher than that of the background dark matter.

Over the history of the Solar System, Xu and Siegel calculate that 1.07 X 10^20 kg of dark matter have been captured, or about 0.0018% the mass of the Earth. To get a handle on this number, the mass of Ceres – the largest object in the asteroid belt between Mars and Jupiter – is about 9 times this amount.

Siegel and Xu calculated how much dark matter the Solar System has swept up over it’s 4.5 billion-year lifespan by modeling the composition of the background dark matter halo in the orbit of the Solar System around the galaxy, and calculating just how much dark matter would be trapped by the Solar System as it moves through this halo. They ran this calculation for the Sun and each one of the eight planets separately, giving the distribution of the matter throughout the Solar System, as well as the total amount captured.

Much like when you drive your car through a light snowfall, dark matter “sticks” to the Solar System when it is gravitationally bound by the Sun and planets. Just as some of the snow melts on your windshield (hopefully), some doesn’t stick to the hood and most just flies right by, dark matter isn’t distributed evenly throughout our Solar System, either. Some planets have more dark matter surrounding them than others, depending on where they are. Shown below is the density distribution of the dark matter in the Solar System

The first spike is Mercury, and the next two spikes are Venus and Earth (Mars doesn’t show up). The next is Jupiter, followed by a small bump from Saturn and finally Uranus and Neptune combined create the last small bump.

How does the local dark matter effect interactions in the Solar System? Well,it doesn’t have a large effect on the orbits of the planets, nor does it slow down the Solar System in its orbit around the galactic center appreciably.

“Planetary orbits, if there were enough dark matter present, would have their perihelia precess faster than if there were no dark matter. The amount of dark matter allowed from these observations is considerably greater than the amount I predict. The errors on the measurements of perihelion precession are in units of hundredths of an arc second per century…Even if you assume the dark matter is at rest with respect to the galaxy that the Solar System moves through (which is the extreme example), the Sun is of order 10^30 kg; capturing a 10^20 kg clump of dark matter will slow you down by about 20 microns/second over the lifetime of the Solar System. So that would be small.” – Ethan Siegel in an email interview.

And, alas, the mystery of the Pioneer anomaly is not going to be solved by this revelation, as the mass of the captured dark matter is not enough to explain the odd motions of that spacecraft.

The discovery of a higher density and mass of dark matter in our neighborhood may aid in the study and detection of dark matter, though. Knowing the mass and density distribution of the local dark matter – and thus knowing how much and where to look for it – will provide astronomers looking into solving exactly what it’s made up of with more information .

“Our determination of the local dark matter density and velocity distribution are of great importance to direct detection experiments. The most recent calculations that have been carried out assume that the properties of dark matter at the Sun’s location are derived directly from the galactic halo. By comparison, we find that terrestrial experiments should also consider a component of dark matter with a density 16,000 times greater than the background halo density,” wrote Xu and Siegel.

Source: Arxiv, email interview with Ethan Siegel

Posted on by Tammy Plotner

Reaching for the Ring: M57 by Dietmar Hager

M57 Close-up - Dr. Dietmar Hager

For those of us old enough to remember riding on an old fashioned carousel, there was once a quaint custom where the operator would hold a brass ring out and the lucky contestant who captured it could ride again for free. Before you dismiss this astrophotograph as just another colorful look at a Messier, perhaps you better step inside the workings of the merry-go-round to learn more about what you’re really seeing here… Because this ring is pure gold.

Discovered by Antoine Darquier de Pellepoix in January of 1779 and independently discovered and cataloged by Charles Messier just a few days later, the famous comet hunter himself described it as being “a dull nebula, but perfectly outlined; as large as Jupiter and looks like a fading planet.” Perhaps it was that very description which coaxed Uranus’ discoverer – Sir William Herschel – to have a look for himself and class such objects as “planetary nebula“. Fortunately, Herschel’s telescope resolved M57 to a far greater degree and his descriptions were “a perforated ring of stars… none seems to belong to it.” Since that time, astronomers have been turning an eye towards this “curiosity of the heavens” in a great effort to not only understand its cause – but to capture it as well.

In 1800, German astronomer Friedrich von Hahn was the first to resolve out the Ring’s central star – a planet-sized white dwarf variable star which has an average magnitude of 15. At one point in its Mira-like life, it began shedding its outer layers in what we now believe to be a cylindrical shape and what we see is the bright torus of light from our point of view. Of course, none of this is particularly new news about the 2,300 light year distant M57. Nor is the knowledge when we are looking down this tunnel of expelled gas that we are seeing a decreasing ionization level as the distance from the central star increases. For all who have seen the Ring with their own eyes the innermost region appears dark – the result of only ultra-violet radiation. What we can capture visually is the inner ring, glowing brightly with the greenish forbidden light of doubly ionized oxygen and nitrogen. Where the true prize lay is much like a carousel – it’s just outside where only the red light of hydrogen can be excited.

In 1935 an astronomer named J.C. Duncan discovered something a bit more about the Ring than we knew – an extended halo of material which is all the remains of the star’s earlier stellar winds. It took the power of the Hubble telescope to resolve out dust filaments and globules, but now I invite you to take a closer look at which took 40,000 years in the making and spans 500 times the size of our own solar system.

M57 Closeup - Dr. Dietmar Hager

It took Dr. Dietmar Hager a full month of work to compile some 12 hours of exposure time to reveal what you see here, but the results from StarGazer Observatory are nothing less than amazing. Like the Hubble Telescope images of M57, this image reveals small clouds of dark dust which have flowed out from the central star and are captured in silhouette against the glowing walls of the planetary shell. According to what we know, “These small, dense dust clouds are too small to be seen with ground-based telescopes, but are easily revealed by Hubble.” What’s more, the outer filaments only recently came to public light as ” The Spitzer Space Telescope’s powerful infrared vision detected this material expelled from the withering star.”

Congratulations, Dr. Hager. You have managed with a 9″ Earth-based refractor to capture for us what took two space telescopes to first reveal – along with a distant background galaxy in the full sized image. At least in my book, that means you’ve done far more than just reach for the brass ring…

You’ve captured pure gold.

Posted on by Nancy Atkinson

Twin Spiral Galaxies Dance Together

This incredible image looks like space art, or a trick done with Photoshop, but its an actual image of twin galaxies dancing together in the sky. The image was obtained, appropriately enough by the Gemini South telescope in Chile using GMOS, the Gemini Multi-Object Spectrograph. These two nearly identical spiral galaxies are in Virgo, 90 million light years distant, in the early stages of a gentle gravitational embrace.

Like two dancers grabbing hands while passing, NGC 5427 (the nearly open-faced spiral galaxy at lower left) and its southern twin NGC 5426 (the more oblique galaxy at upper right), are in the throes of a slow but disturbing interaction – one that could take a hundred million years to complete.

At a glance, these twin galaxies — which have similar masses, structures, and shapes and are together known as Arp 271 – appear undisturbed. But recent studies have shown that the mutual pull of gravity has already begun to alter and distort their visible features.

Typically, the first sign of a galaxy interaction is the formation of a bridge-like feature. Indeed, the two spiral arms on the western (upper) side of NGC 5426 appear as long appendages that connect with NGC 5427. This intergalactic bridge acts like a feeding tube, allowing the twins to share gas and dust with one other across the 60,000 light years (less than one galaxy diameter) of space separating them.

Colliding gases caused by the interaction may have also triggered bursts of star formation (starbursts) in each galaxy. Star-forming, or HII, regions appear as hot pink knots that trace out the spiral patterns in each galaxy. HII regions are common to many spiral systems, but the giant ones in NGC 5426 are curiously knotted and more abundant on the side of the galaxy closest to NGC 5427. Starburst activity can also be seen in the galaxy’s connecting bridge.

Once thought to be unusual and rare, gravitational interactions between galaxies are now known to be quite common (especially in densely populated galaxy clusters) and are considered to play an important role in galaxy evolution. Most galaxies have probably had at least one major, if not many minor, interactions with other galaxies since the advent of the Big Bang some 13 billion years ago. Our own Milky Way, a spiral galaxy like those in this image, is, in fact, performing its own stately dance. Both with the nearby dwarf galaxy, called the Large Magellanic Cloud and a future interaction with the large spiral galaxy M-31 or the Great Andromeda Galaxy, which is now located about 2.6 million light years away from the Milky Way. This new Gemini image is possibly a preview of things to come for our own galaxy. Ultimately the end result of these types of collisions will be a large elliptical galaxy.

Original news source: Gemini Observatory