Posted on by Jerry Coffey

How Long is a Year on Saturn?

It takes Saturn 10,832 Earth days to complete one orbit around the Sun. That means the answer to ”how long is a year on Saturn” is 29.7 Earth years. The length of Saturn’s year is a direct effect of its orbital distance from the Sun. Saturn orbits at an average of 1.43 billion km, or 9.58 AU, from the Sun.

Knowing how long a year is on Saturn might make one wonder if the planet experiences seasons like we do here on Earth. Yes, Saturn experiences seasons. Saturn has an axial tilt of 26.73 degrees, allowing different hemisphere to experience varying levels of sunlight. Of course, the seasons only go from cold to a whole lot colder. Also, the seasons last nearly 30 times longer because of the length of the planet’s year. Can you imagine a seven year summer that never reaches higher than -23 C?

The length of a day on Saturn is 10.656 hours. While that number seems to be pretty precise, it took a lot of study to arrive at that figure. There is no way to observe the planet’s surface region, so a way had to be found to estimate the planets rotational speed. Scientists first turned to radio emissions for an estimate, then observation by space craft. They then found that the rotational period varied by as much as 1% over the span of a week. The current stated length of a day on Saturn is an average from all observations.

Saturn’s movement through its orbit occasionally causes its rings to disappear. The phenomenon is called ”ring plane crossing”. Ring plane crossings occur when the tilt of the planet and its position in its orbit combine to allow a side-on view of the rings. The rings seem to disappear, but, without the glare from the rings, the planet’s moons are more easily observed. Also, these crossings are the best time to see Saturn’s blue north pole.

29.7 Earth years is the answer to ”how long is a year on Saturn”, but it leads to many other questions about our mysterious neighbor. Direct observation is the answer, but there have only been four missions to visit the planet as of today(October, 2011). The Casinni-Huygens mission is currently in orbit sending data on a regular basis. Hopefully, it will expand our knowledge of Saturn beyond expectations.

Here’s an article that discusses how Saturn’s rings can seem to disappear, and here’s how long a day is on Saturn.

Here’s a great photo collage of Saturn’s rings seen at various angles to the Earth, and some general Saturn facts.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Sources:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Saturn
http://www2.jpl.nasa.gov/saturn/faq.html#what

Posted on by Jerry Coffey

Does Saturn Have a Solid Core?

Scientist know that Saturn is made up of 96% hydrogen and 3% helium with a few other elements thrown in. What they have never been able to confirm beyond a shadow of a doubt is the answer to does Saturn have a solid core.

According to the core accretion theory, the most widely accepted theory of planetary formation, Saturn would have had to form a rocky or icy core with a great deal of mass in order to capture such a high percentage of gasses from the early solar nebula. That core, like those of the other gas giants, would have had to form and become massive more quickly than those of the other planets in order to capture such a comparatively high percentage of primordial gasses. It is possible that atmospheric pressure and temperatures near the core region have allowed or caused some of the core material to be conveyed to the top of the atmosphere and lost into space, greatly reducing the current size of Saturn’s core.

While Saturn most likely formed from a rocky or icy core, it’s low density seems to point to more of a liquid metal and rock mixture at the core. Saturn is the only planet who’s density is lower than that of water. If anything the core region would be more like a ball of thick syrup with a few rocky chunks. There doesn’t seem to be any part of Saturn that is solid as we understand it. That is, there is no place that you could set foot on it and stand.

The metallic hydrogen core of Saturn does generate a magnetic field. A magnetic field created in this way is said to be generated through a metallic hydrogen dynamo. It’s magnetic field is slightly weaker that Earth’s and only extends to the orbit of its largest moon, Titan. Titan contributes ionized particles to Saturn’s magnetosphere which help create aurorae within Saturn’s atmosphere. Voyager 2 measured high solar wind pressure within the magnetosphere. According to measurements taken during the same mission, the magnetic field only extends to 1.1 million km.

The core region of Saturn may never be directly observed. Neither has the Earth’s. Despite that, scientists are fairly certain that, while Saturn has a core, it is not a solid mass of rock or metal, but a liquid metallic mixture similar to all of the gas giants.

Here’s an article about the core accretion theory of planetary formation, and how Saturn and Jupiter might have formed differently.

If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn, and here’s some research about how Saturn and Jupiter might have formed around their solid cores.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Sources:
http://abyss.uoregon.edu/~js/ast221/lectures/lec15.html
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Saturn

Posted on by Jerry Coffey

What is Saturn Made Of?

The rings around Saturn have captured the imagination of humans for hundreds of years. A natural offshoot of that observation has been a desire to know what is Saturn made of. Using various methods of testing, scientists believe that Saturn is composed of 96% hydrogen, 3% helium, and 1% various trace elements that include methane, ammonia, ethane, and hydrogen deuteride. Several of these gases can be found in gas, liquid, and molten states as you descend into the planet.

The state of the gases change with pressure and temperature. At the cloud tops, you would encounter ammonia crystals, but at the bottom of the clouds you would come across ammonium hydrosulfide and/or water. Beneath the clouds, atmospheric pressure increases causing an increase in temperature, so hydrogen moves into a liquid state. Pressure and temperature continue to increase as you close in on the core, causing hydrogen to become metallic. Saturn, much like Jupiter, is thought to have a loose core made up of relatively little rock and some metals.

It is hard to conceive that Saturn is made up of much more than gas based on its low density. Saturn has a density of 0.687 g/cm3. Earth, on the other hand, has a density of 5.513 g/cm3. That means that a planet that has 95 times more mass than Earth has barely 12% of its density. Saturn’s density is so low that it could float on water more easily than most boats.

Modern space based observation has led to many discoveries about the make up of Saturn. The missions began with a flyby of the Pioneer 11 spacecraft in 1979. That mission discovered the F ring. The following year Voyager 1 flew by sending back surface details of several of Saturn’s moons. It also proved that the atmosphere on the moon Titan was impenetrable by visible light. In 1981 Voyager 2 visited Saturn and discovered changes in the atmosphere and the rings as well as confirming the presence of the Maxwell Gap and the Keeler Gap, both first seen by Voyager 1.

After Voyager 2, Cassini–Huygens spacecraft performed a Saturn orbit insertion maneuver to enter orbit around the planet in 2004. The craft had been studying the system for some time before entering orbit. The discoveries made by the craft are numerous and best explained on NASA’s mission page.

Saturn has held the imagination of countless generations. Knowing the answer to ”what is Saturn made of” is a great beginning. Hopefully, you will dive right in and become a Saturnian expert.

Here’s an article about what Saturn’s rings are made of, and information about the planet’s radiation belts.

Here’s an overview of NASA’s Cassini mission to Saturn, and the story of Saturn.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Source: NASA

Posted on by Jerry Coffey

What are Saturn’s Rings Made Of?

Saturn is sometimes called the ”Jewel of the Solar System” because its ring system looks like a crown. The rings are well known, but often the question ”what are Saturn’s rings made of” arises. Those rings are made up of dust, rock, and ice accumulated from passing comets, meteorite impacts on Saturn’s moons, and the planet’s gravity pulling material from the moons. Some of the material in the ring system are as small as grains of sand, others are larger than tall buildings, while a few are up to a kilometer across. Deepening the mystery about the moons is the fact that each ring orbits at a different speed around the planet.

Saturn is not the only planet with a ring system. All of the gas giants have rings, in fact. Saturn’s rings stand out because they are the largest and most vivid. The rings have a thickness of up to one kilometer and they span up to 482,000 km from the center of the planet.

The rings are named in alphabetical order according to when they were discovered. That makes it a little confusing when listing them in order from the planet. Below is a list of the main rings and gaps between them along with distances from the center of the planet and their widths.

  • The D ring is closest to the planet. It is at a distance of 66,970 – 74,490 km and has a width of 7,500 km.
  • C ring is at a distance of 74,490 – 91,980 km and has a width of 17,500 km.
  • Columbo Gap is at a distance of 77,800 km and has a width of 100 km.
  • Maxwell Gap is at a distance of 87,500 km and has a width of 270 km.
  • Bond Gap is at a distance of 88,690 – 88,720 km and has a width of 30 km.
  • Dawes Gap is at a distance of 90,200 – 90,220 km and has a width 20 km.
  • B ring is at a distance of 91,980 – 117,580 km with a width: 25,500 km.
  • The Cassini Division sits at a distance of 117,500 – 122,050 km and has a width of 4,700 km.
  • Huygens gap starts at 117,680 km and has a width of 285 km – 440 km.
  • The Herschel Gap is at a distance of 118,183 – 118,285 km with a width of 102 km.
  • Russell Gap is at a distance of 118,597 – 118,630 km and has a width of 33 km.
  • Jeffreys Gap sits at a distance of 118,931 – 118,969 km with a width of 38 km.
  • Kuiper Gap ranges from 119,403 -119,406 km giving it a width of 3 km.
  • Leplace Gap is at a distance of 119,848 – 120,086 km and a width of 238 km.
  • Bessel Gap is at 120,305 – 120,318 km with a width of 10 km.
  • Barnard Gap is at a distance of 120,305 – 120,318 km giving it a width of 3 km.
  • A ring is at a distance of 122,050 – 136,770 km with a width of 14,600 km.
  • Encke Gap sits between 133,570-133,895 km for a width of 325 km.
  • Keeler Gap is at a distance of 136,530-136,565 km with a width of 35 km.
  • The Roche Division is at 136,770 – 139,380 km for a width 2600 km.
  • F ring is begins at 140,224 km, but debate remains as to whether it is 30 or 500 km in width.
  • G ring is between 166,000 – 174,000 km and has a width of 8,000 km.
  • Finally, we get to the E ring. It is between 180,000 – 480,000 km giving it a width of 300,000 km.

As you can see, a great deal of observation has been dedicated to understanding and defining Saturn’s rings. Hopefully, having the answer to ”what are Saturn’s rings made of” will inspire you to look more deeply into the topic.

We have written many articles about Saturn for Universe Today. Here’s an article about the orbit of Saturn, and here’s an article about the temperature of Saturn.

If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn. And here’s a link to the homepage of NASA’s Cassini spacecraft, which is orbiting Saturn.

We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.

Source: NASA

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 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

Posted on by Nancy Atkinson

Unusual Galaxies Eat Their Neighbors

Seyfert galaxies appear to be normal spiral galaxies, but they have fluctuating bright centers. And now, their deep-down, hidden nature has been revealed: they are cannibals. While visible-light images didn’t provide much evidence that these galaxies had any interaction with their neighbors, radio-telescope images from the Very Large Array revealed that Seyfert galaxies are snacking on neighboring galaxies, with the “meal” feeding the supermassive black hole at their centers. Astronomers had suspected this was the case, but until now, they didn’t have the evidence to support the idea.

One leading theory said that the fluctuations seen in Seyfert galaxies’ centers were caused by close encounters with neighboring galaxies. The gravitational encounters stirred up gas from the neighboring galaxies and brought it within reach of the black hole. However, when astronomers looked at Seyferts with visible-light telescopes, only a small fraction showed any evidence of such an encounter. Now, new images of hydrogen gas in Seyferts made using the National Science Foundation’s Very Large Array (VLA) radio telescope show the majority of them are, in fact, disturbed by ongoing encounters with neighbor galaxies.

“The VLA lifted the veil on what’s really happening with these galaxies,” said Cheng-Yu Kuo, a graduate student at the University of Virginia. “Looking at the gas in these galaxies clearly showed that they are snacking on their neighbors. This is a dramatic contrast with their appearance in visible starlight,” he added.

The effect of the galactic encounters is to send gas and dust toward the black hole and produce energy as the material ultimately is consumed. Black holes, concentrations of matter so dense that not even light can escape their gravitational pull, reside at the cores of many galaxies. Depending on how rapidly the black hole is eating, the galaxy can show a wide range of energetic activity. Seyfert galaxies have the mildest version of this activity, while quasars and blazars are hundreds of times more powerful.

The astronomers picked a number of relatively nearby Seyfert galaxies that had previously been observed with visible-light telescopes. They then carefully studied the Seyferts with the VLA, specifically looking for radio waves emitted by hydrogen atoms. The VLA images showed the vast majority of the Seyferts were disturbed by encounters with neighbor galaxies.

By comparison, similar VLA images of inactive galaxies showed that very few were disturbed. “This comparison clearly shows a connection between close galactic encounters and the black-hole-powered activity in the cores,” said Ya-Wen Tang, who began this work at the Institute of Astronomy & Astrophysics, Academia Sinica (ASIAA), in Taiwan and now is a graduate student at the National Taiwan University.

“This is the best evidence yet for the fueling of Seyfert galaxies. Other mechanisms have been proposed, but they have shown little if any difference between Seyferts and inactive galaxies,” Tang added.

Original News Source: National Radio Astronomy Observatory

Posted on by Nancy Atkinson

Rare Binary Pulsars Provide High Energy Physics Lab

For the first time, a spacecraft has detected signals from both stars of a binary pulsar system in X-rays. XMM-Newton is watching both stars radiate pulsating X-rays, providing scientist with the perfect laboratory for high energy physics and a never-ending source of intriguing physical problems. The binary pulsar PSR J0737-3039 was first spotted by astronomers in 2003 in radio wavelengths, but now X-rays can be used to investigate this system in greater detail.

Binary pulsars are extremely rare. Each star of the closely-packed system is a dense neutron star, spinning extremely fast, radiating X-rays in pulses. One pulsar (B) rotates slowly, what scientists call a ‘lazy’ neutron star, while orbiting a faster and more energetic companion (pulsar A).

Each pulsar or neutron star once existed as a massive star. “These stars are so dense that one cup of neutron star-stuff would outweigh Mt. Everest,” says Alberto Pellizzoni, who has been studying this system. “Add to that the fact that the two stars are orbiting really close to each other, separated by only 3 light-seconds, about three times the distance between Earth and the Moon.”

Pellizzoni added, “One cup of neutron star-stuff would outweigh Mt. Everest. Add to that the fact that they’re orbiting really close, separated by only about three times the distance between Earth and the Moon.”

Pulsar B is an oddity, in that it is very different from a ‘normal’ pulsar. Additionally, the amount of X-rays coming from the system is greater that the scientists predicted. But how the two pulsars work together is still not understood.

“One possible solution for the mystery could be mutual interaction between the two stars, where the lazy star derives energy from the other,” says Pellizzoni.

Watch video of how the two pulsars may interact

The fundamental physical processes involved in these extreme interactions are a matter of debate among theoretical physicists. But now, with XMM-Newton’s observations, scientists have gained new insight, providing a new experimental setting for them. In X-rays, it will be possible to study the subsurface and magnetospheres of the stars as well as the interaction between the two in that close, heated environment.

This system also provides the study of strong-field gravity, given how close and dense the two stars are. Future tests of general relativity by radio observations of this system will supersede the best Solar System tests available. It is also a unique laboratory for studies in several other fields, ranging from the equation of state of super-dense matter to magneto-hydro dynamics.

Original News Source: ESA

Posted on by Tammy Plotner

NGC 6302 by Don Goldman

NGC 6302 by Don Goldman

Over the weeks we’ve looked at a lot of curious objects and today is no exception. NGC 6302 is often called the “Bug Nebula”, but its resemblance to an insect isn’t what makes it unique – it’s the complex structure. Deep inside this bipolar planetary nebula lay an unseen star… One of the hottest objects in the galaxy.

Residing about 4,000 light years away in the constellation of Scorpius, NGC 6302 is the end remains of an enormous dying star. With a surface temperature of an estimated 200,000 K, its central star exceeds our own Sun’s mean temperature output by nearly 35 times – yet has never been observed. Why? Because it is shielded from view at all wavelengths by an impossibly dense equatorial disc composed of gas and dust… One that may have restricted the star’s outflow into the unusual bipolar structure we can see.

But the hidden central star isn’t what’s bugging scientists, it’s the chemical composition!

Filled with ionization walls, edges and lobes, this dust is both oxygen and carbon-rich – a dual chemistry which means it has undergone recent changes and alternate formation processes in its 10,000 year life. Studies done by the European Space Agency’s Infrared Space Observatory (ISO) have shown that the dusty torus contains hydrocarbons, carbonates such as calcite, as well as water ice and iron. If the word carbonates made you raise an eyebrow, it should because carbonates form when carbon dioxide dissolves in liquid water and forms sediments.

Says Albert Zijlstra from UMIST: “What caught our interest in NGC 6302 was the mixture of minerals and crystalline ice – hailstones frozen onto small dust grains. Very few objects have such a mixed composition.”

Yet NGC 6302 is even more complex, displaying evidence that a second pair of lobes may have formed during a previous phase of the star’s mass loss. The visible northwest lobe is believed to have been created some 1,900 years ago and shows some signs that it may have once collided with pre-existing globules of gas which changed its outflow. According to studies done by Groves, Doptia, Williams and Hua; “We find that for NGC 6302, the visible to IR extinction law is indistinguishable from `standard’ interstellar reddening, but that the UV extinction curve is much steeper than normal, suggesting that more small dust grains had been ejected into the nebula by the PN central star.”

Kinematical studies done by Minkowski and Johnson suggest that NGC 6302 originated in some type of explosive event. It exhibits a rich spectrum of lines, indicating rich deposits of helium and nitrogen – far more than an ordinary planetary nebula. What the Bug Nebula seems to lack in its diet, however, is iron and calcium – two elements which may very well be tied up as solid grains.

So what’s next for this extreme, high-excitation planetary nebula? According to Wright, Barlow, Ercolano and Rauch; “We use the 3D photoionisation code to model the emission from the gas and dust. We have produced a good fit to the optical emission-line spectrum, from which we derived a density distribution for the nebula. A fit to the infrared coronal lines places strong constraints on the properties of the unseen ionising source. We find the best fit comes from using a 220,000 K hydrogen-deficient central star model atmosphere, indicating that the central star of this PN may have undergone a late thermal pulse.”

ngc 6302 mapBut don’t you be late observing the Bug Nebula yourself! NGC 6302 is located in Scorpius (RA 17 13 44 Dec -37 06 15). At around magnitude 9, this surprisingly bright planetary is well within the reach of a mid-size telescope and a treat to larger aperture. NGC 6302 was discovered by James Dunlop in 1826 with a handmade reflecting telescope he had constructed himself and the earliest known study of NGC 6302 is Edward Emerson Barnard who, in 1907, drew and described it.

Seek it out… And enjoy!

This week’s awesome image was taken by Don Goldman from Macedon Ranges Observatory.