Posted on by Tammy Plotner

The Cosmic Cocoon: IC 5146 by Tom V. Davis

IC 5146: The Cocoon Nebula by Tom V. Davis

Out in the deep reaches of space, a cocoon has formed. Here on Earth, a cocoon represents the casing of a pupae – the child/insect which is about to undergo a magnificent transformation into a beautiful moth or butterfly. So what does the cosmic cocoon, IC 5146, hide inside? Let’s take a look…

Roughly 4000 light years away in some of the richest star fields in the northern Cygnus Milky Way, lies IC 5146. Discovered by Thomas Espin, it has often been referred to as the “Cocoon” because it lay at the end of a long and fairly starless trail – like the proverbial worm who ate its way to the end of the leaf before time for change. Although IC 5146’s fanciful name fits wonderfully with its visual appearance, what you may not know is the moniker is also very indicative of the star-birth process going on inside!

Deep within the folds and rifts of the bright nebula are many regions of emission, absorption and reflection. According to studies done by Kramer (et al), “A submillimeter dust continuum study of a molecular ridge in IC 5146 consists of at least four dense cores which are likely to be prestellar in nature. A map of dust temperatures, constructed from the continuum flux ratios, shows strong temperature gradients. Several cores appear isothermal, while two have inwardly decreasing temperatures profiles, which is expected if the cores are externally heated. We find an inverse correlation which we interpret as signature of grain coagulation and the formation of ice mantles, in accordance with models of dust evolution in dense prestellar cores.”

The embryo is emerging stars.

According to recent measurements, the massive star in the center of the Cocoon opened its way into the existing molecular cloud – the flowing and glowing region also known as Caldwell 19. Even though the central star is perhaps 100,000 years old, it still provides the major energy source of the visible light – but what about what is invisible?

According to W.B. Samson: “The very young star cluster IC 5146 is studied using star counts, with a view to determining the distribution of interstellar matter in a region where star formation recently occurred. IC 5146 is embedded in a dark nebula which is very dense near its center.” A dense center which hides magnetic properties! “Polarization of starlight in IC 5146 is found to be very variable in both magnitude and direction, indicating the presence of complex magnetic fields within the cluster.”

While the dark dust trail of Barnard 168 may appear to be full of nothing – nothing could be further from the truth. According to Lada and Elmegreen: Millimeter-wave observations of the dark cloud complex immediately surrounding the young open cluster IC 5146 show two unusually intense oxygen sources… suggesting the presence of two or more obscured newly formed stars embedded in molecular gas at the periphery. The total mass of the dark cloud complex is estimated to be 2500 solar masses, and the origin of the star-forming molecular shell around IC 5146 is considered. It is noted that IC 5146 is located at the tip of an elongated filamentary molecular cloud and, in this respect, is similar to Rho Oph and M17, where regions of active star formation are also located in dense cores at the tips of elongated molecular cloud complexes.”

IC 5146 Locator ChartThe 10th magnitude Cocoon is easily revealed in mid-sized telescopes and can be found near Pi Cygni (RA 21 53 6 Dec. +47 16) and M39. Capturing this rare transformation is definately worth your time, for open cluster Collinder 470 is also ‘involved’ with IC 5146. Take the time to look it up! Small reflection nebula Van den Bergh 147 is also nearby and adds another treat to this comsic chrysalis!

This week’s awesome image was contributed by Advanced Optical / Radio Astronomers and International Associates member Tom Davis. Thanks for the spectacular image!

Posted on by Nancy Atkinson

Satellites Keep an Eye on Wildfires Around the World

Wildfire season is underway in the northern hemisphere, and with hot and dry conditions in many areas this summer, fires have been plentiful. Regions affected include central Canada, California in the US, Southeastern Russia and Norway. While wildfires are a natural part of Earth’s environment when sparked by lightning strikes, these fires consume a million or more square kilometers per year. Wildfires can also be started from volcano eruptions, but humans also start many fires -sometimes accidentally, but mostly deliberately. Both NASA and ESA have Earth-watching satellites that have been keeping an eye on wildfires around the world. Above, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image of wildfires in Central Canada, in the Saskatchewan and Manitoba Provinces on June 30, 2008. Places where the sensor detected actively burning fires are marked in red; a strong wind was blowing east-southeast and spreading thick plumes of gray-brown smoke.


Thunderstorms in California brought lightning but little rain, starting several wildfires. This natural-color image was captured by MODIS on July 2, 2008, and it shows the location of actively burning fires marked in red. The highest concentration of fires is in Northern California, where reportedly 68 uncontained large fires were burning as of July 3. Meanwhile, Southern California was battling the state’s two largest blazes, shown in the lower half of this image.

These false-color images of the Santa Lucia Range Mountains near Big Sur, California, was captured by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite on June 29, 2008. Vegetation is red, naturally bare ground is tan, burned ground is charcoal colored, and smoke is light blue. Clouds over the Pacific Ocean to the southwest are bright bluish white. Over 120,000 acres have been burned by the two large wildfires in this area.


With extremely hot weather conditions in Europe, Norway experienced its biggest forest fire in the last half century in June. ESA’s Envisat satellite images were used in the fire’s aftermath to get an overview of the damaged area for authorities and insurance companies. The Envisat Advanced Synthetic Aperture Radar (ASAR) image shows the burned area as a red cluster in the image center.

The fires (red dots) visible along the shoreline of Russia’s Khabarovsk Province at the upper left of this image are only a few of the forest fires responsible for the river of smoke spreading eastward over the Sea of Okhotsk and the Kamchatka Peninsula on July 2, 2008. This natural-color image of the area was captured by MODIS on NASA’s Aqua satellite. Like this image, many images area developed daily from orbiting satellites to to provide up-to-date satellite images of the Earth’s landmasses in near real time. The MODIS Rapid Response Team provides these images, many times with a few hours of being collected. This system is valuable resource for the international fire monitoring community, who use the images to track fires.

News sources: NASA’s Earth Observatory Natural Hazards site, ESA’s Observing the Earth site

Posted on by Fraser Cain

Missions to Saturn

Since Galileo first looked at Saturn in 1610, astronomers have wondered what Saturn would look like up close. We finally got the chance in 1979, when the first spacecraft reached Saturn. Here are the missions to Saturn.

Pioneer 11
Launched in 1973, Pioneer 11 made a flyby of Jupiter, and used the planet’s gravity to change its trajectory to intercept Saturn. It arrived at Saturn on September 1, 1979, passing just 22,000 km above the surface of Saturn. It took the first ever close up pictures of Saturn, and discovered a previously unknown ring.

Voyager 1
NASA’s Voyager 1 was the next mission to arrive at Saturn, passing the planet on November 12, 1980. It flew within 124,000 km of Saturn and sent back a torrent of pictures. It was also able to make a flyby of Saturn’s moon Titan, and returned stunning images of Saturn and its rings. After passing Saturn, Voyager 1 sped off into interstellar space, where it’s still going now, and still sending back data.

Voyager 2
Not long after Voyager 1 completed its mission to Saturn, Voyager 2 came along and did the same. It reached Saturn on August 26, 1981. In addition to seeing Saturn from an altitude of 100,800 km, Voyager 2 also made flybys of Saturn’s moons Enceladus, Tethys, Hyperion, Iapetus, Phoebe and several others. Voyager 2 received a gravitational boost from Saturn, and was able to swing into a path that took it past Uranus and Neptune, to complete the Grand Tour of the Solar System.

Cassini/Huygens
The previous flybys were helpful to scientists, but to really study Saturn, NASA sent the Cassini/Huygens mission, which arrived and went into orbit around Saturn in 2004. As part of its mission, the spacecraft delivered the Huygens probe to study Titan. Cassini has now completed its main mission, but will continue to orbit and study Saturn and its moons for years to come. So many discoveries have come out of Cassini/Huygens, such as the geysers on Enceladus, oceans and seas of hydrocarbons on Titan, new moons, and even new rings.

Here’s an article about seeing Cassini’s position in 3-dimensions, and another article about the completion of Cassini’s mission.

This page from NASA lists all the past, present and future missions to Saturn, and here’s NASA’s Saturn mission page.

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.

Reference:
NASA

Posted on by Fraser Cain

Tilt of Saturn

Collage showing the change in seasons on Saturn. Credit: NASA/ESA/Hubble

Saturn couldn’t be more different from Earth; it’s mostly made of hydrogen and helium and has nearly 100 times more mass. And those rings…

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

But Saturn’s axis is tilted, just like Earth. While Earth’s axis is tilted at an angle of 23.4°, Saturn’s tilt is 26.7°. That’s pretty close.

And just like Earth, Saturn’s axial tilt gives the planet seasons. In fact, we can see Saturn’s tilt by the position of the rings. When Saturn’s northern hemisphere is experiencing summer, we can see the rings at their widest point. And then, as Saturn works its way through its 30-year orbit around the Sun, the angle to the rings decreases until they’re almost invisible – just a line through the planet.

The changing seasons on Saturn also affect the planet’s weather patterns. NASA’s Voyager spacecraft originally clocked wind speeds near Saturn’s equator at nearly 1,500 km/h. But when Cassini showed up 15 years later, they’d slowed down to only 1,100 km/h.

Here’s an article from Universe Today about long term changes on Saturn, and three views of Saturn over a long period of time.

Here’s a nice photograph from Astronomy Picture of the Day of Saturn, and another captured by Cassini, showing the planet’s southern hemisphere being illuminated.

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.

Posted on by Nancy Atkinson

“Starlight Zone” Interview Now Online

The interview that I (Nancy) did with the “Starlight Zone” radio show from station 2NUR FM in Newcastle, Australia back on June 19 is now online (or just listen below). It’s only five minutes long, so if you need a short diversion to your day…. We talked about the concept of a one-way trip to Mars and the Phoenix mission.

Col Maybury, who does the show was a very fun guy to talk with. Check out all the past interviews he’s done with various “spacey” people on 2NUR’s “Starlight Zone” website.

G’day!

Posted on by Tammy Plotner

WeekEnd SkyWatcher’s Forecast: July 4 – 6, 2008

Artist Impression of Deep Impact - Credit: NASA

Greetings, fellow SkyWatchers! If you’re enjoying a holiday weekend where you live, then start the fireworks off as we begin by remembering Deep Impact and journey towards a nearby star approaching the supernova phase. As things heat up towards one of the most spectacular conjunctions of the year, we’ll also take a look at another globular cluster study, lunar features and a binocular deep sky treat! Are you ready to step in the realm of a Barnard dark nebula? The grab your optics and let’s head out into the night…

Friday, July 4 – On this date in 2005, the Deep Impact mission entered the history books as its probe impacted Comet Tempel 1 successfully. The spacecraft relayed back to Earth a wealth of information about the material released from the surface. Thanks to this incredible mission (a collaboration between JPL, the University of Maryland, and Ball Aerospace Technologies), we’ve learned much more about the nature of comets and the protosolar nebula in which they formed.

This date in history also marks the 1947 founding of the Astronomical League – a worldwide organization with almost 15,000 members!

And did you know that celestial fireworks occurred in 1054, also on this day? It is believed the bright supernova recorded by Chinese astronomers happened at this point in history, and today we know its remnants as the Crab Nebula (M1).

Palomar Observatory, courtesy of CaltechBut could such an event happen again in our own celestial “backyard?” Look no further than HR 8210 (RA 21 26 26 Dec +19 22 32). It may be nothing more than a white dwarf star hiding out in late night Capricornus, but it’s a star that’s almost run out of fuel. This rather ordinary binary system has a companion white dwarf star that’s 1.15 times the mass of our Sun. As the companion also expends its fuel, it will add mass to HR 8210 and push it over the Chandrasekhar limit – the point of no return in mass. This will someday result in a supernova event located only 150 light-years away from our solar system…

And that’s 50 light-years too close for comfort!

470 light-years away in the Gould Belt, and roughly 1.5 million years ago, a similarly massive star exploded in the Upper Scorpius association. No longer able to fuel its mass, it unleashed a supernova event which left its evidence as a layer of iron here on Earth, and may have caused a certain amount of biological extinction when its gamma rays directly affected our ozone layer.

Take a long look at Antares tonight – for it is part of that association of stars and is no doubt also a star poised on the edge of extinction. At a safe distance of 500 light-years, you’ll find this pulsating red variable equally fascinating to the eye as well as to the telescope. Unlike HD 8210, Alpha Scorpii also has a companion which can be revealed to small telescopes under steady conditions. Discovered on April 13, 1819 during a lunar occultation, this 6.5 magnitude green companion isn’t the easiest to split from such a bright primary – but it’s certainly fun to try! And the best is yet to come, because Antares will be occulted again in a matter of days…

Saturday, July 5– Tonight the Moon has returned in a position to favor a bit of study. Start by checking IOTA information for a possible visible occultation of Regulus, and also look for Saturn quite nearby as the slender crescent graces the early evening skies.

Although poor position makes study difficult during the first few lunar days, be sure to look for the ancient impact crater Vendelinus just slightly south of central. Spanning approximately 150 kilometers in diameter and with walls reaching up to 4400 meters in height, lava flow has long ago eradicated any interior features. Its old walls give mute testimony to later impact events, which you can see when viewing crater Holden on the south shore; much larger Lame on the northeast edge; and sharp Lohse northwest. Mark your challenge list!

For all observers, let’s take a closer look at the fascinating constellation of Lupus southwest of brilliant Antares. While more northern latitudes will see roughly half of this constellation, it sits well at this time of year for those in the south. So why bother?

Cutting through our Milky Way galaxy at a rough angle of about 18 degrees is a disc-shaped zone called Gould’s Belt. Lupus is part of this area whose perimeter contains star forming regions which came to life about 30 million years ago when a huge molecular cloud of dust and gas was compressed – much like in the Orion area. In Lupus we find Gould’s Belt extending above the plane of the Milky Way!

Palomar Observatory, courtesy of CaltechReturn again to the beautiful Theta and head around five degrees west for NGC 5986 (RA 15 46 03 Dec 37 47 10), a 7th magnitude globular cluster which can be spotted with binoculars with good conditions. While this Class VII cluster is not particularly dense, many of its individual stars can be resolved in a small telescope.

Now sweep the area north of NGC 5986 (RA 17 57 06 Dec 37 05 00) and tell me what you see. That’s right! Nothing. This is dark nebula B 288 – a cloud of dark, obscuring dust which blocks incoming starlight. Look carefully at the stars you can see and you’ll notice they appear quite red. Thanks to B 288, much of their emitted light is absorbed by this region, providing us with a pretty incredible on-the-edge view of something you can’t see – a Barnard dark nebula.

NASASunday, July 6 – Celestial scenery alert! SkyWatchers… Mark your calendar and be sure to make this date with the western skyline as sunset marks one of the most picturesque views of the year! Regulus, Mars and Saturn will all dance with the da Vinci Moon. No special equipment is needed to see this event, and thanks to Leonardo da Vinci we can see the ghostly effect on the Moon as quite logical. He was the first to theorize that sunlight was reflecting off the Earth and illuminating the portion of the Moon not lit by the Sun. We more commonly refer to this as “Earthshine” – but no matter how scientific the explanations are for this phenomena, its appearance remains beautiful.

Today in 1687, Isaac Newton’s monumental Principia was published by the Royal Society with the help of Edmund Halley. Although Newton was indeed a very strange man with a highly checkered history, one of the keys to Newton’s work with the theory of gravity was the idea that one body could attract another across the expanse of space.

Now let’s have a look at some things gravitationally bound as we start at Eta Lupi, a fine double star which can even be resolved with binoculars. Look for the 3rd magnitude primary and 8th magnitude secondary separated by a wide 15″. You’ll find it by starting at Antares and heading due south two binocular fields to center on bright H and N Scorpii – then one binocular field southwest (RA 16 00 07 Dec 38 23 48).

Palomar Observatory, courtesy of CaltechWhen you are done, hop another roughly five degrees southeast (RA 16 25 18 Dec 40 39 00) to encounter the fine open cluster NGC 6124. Discovered by Lacaille and known to him as object I.8, this 5th magnitude open cluster is also known as Dunlop 514, as well as Melotte 145 and Collinder 301. Situated about 19 light-years away, it will show as a fine, round, faint spray of stars to binoculars and be resolved into about 100 stellar members to larger telescopes. While NGC 6124 is on the low side for northern observers, it’s worth the wait for it to hit its best position. Be sure to mark your notes, because this delightful galactic cluster is a Caldwell object and a southern skies binocular reward!

Wishing you an awesome weekend…

This week’s photos are courtesy of: Deep Impact Mission – Credit: JPL/NASA, HR 8210 – Credit: Palomar Observatory courtesy of Caltech, NGC 5986 – Credit: Palomar Observatory courtesy of Caltech, Da Vinci Moon – Credit: NASA and NGC 6124 – Credit: Palomar Observatory courtesy of Caltech.

Posted on by Fraser Cain

History of Saturn

Galileo

Saturn is easily visible with the unaided eye, so it’s hard to say when the planet was first discovered. The Romans named the planet after Saturnus, the god of the harvest – it’s the same as the Greek god Kronos.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Nobody realized the planet had rings until Galileo first turned his rudimentary telescope on the planet in 1610. Of course, Galileo didn’t realize what he was looking at, and thought the rings were large moons on either side of the planet.

It wasn’t until Christian Huygens used a better telescope to see that they were actually rings. Huygens was also the first to discover Saturn’s largest moon Titan.

Jean-Domanique Cassini uncovered the gap in Saturn’s rings, later named the Cassini Division, and he was the first to see 4 more of Saturn’s moons: Iapetus, Rhea, Tethys, and Dione.

There weren’t many more major discoveries about Saturn until the spacecraft flybys in the 70s and 80s. NASA’s Pioneer 11 was the first spacecraft to visit Saturn, getting within 20,000 km of the planet’s cloud layers. It was followed by Voyager 1 in 1980, and Voyager 2 in August 1981.

It wasn’t until July 2004 that NASA’s Cassini spacecraft arrived at Saturn, and began the most detailed exploration of the system. Cassini has performed multiple flybys of many of Saturn’s moons, and sent back thousands of images of the planet and its moons. It has discovered 4 new moons, a new ring, and saw liquid hydrocarbon seas on Titan.

This article was published when Cassini had finished half its primary mission, and discusses many of the discoveries made so far, and another article when its primary mission was complete.

This article has a timeline of Saturn history, and more history from NASA.

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.

Posted on by Fraser Cain

Formation of Saturn

Solar nebula. Image credit: NASA

Like the rest of the planets, Saturn formed from the solar nebula about 4.6 billion years ago. This solar nebula started out as a vast cloud of cold gas and dust which was disturbed somehow – perhaps by colliding with another cloud, or the shock wave from a supernova.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

The cloud compressed down, forming a protostar in the center, surround by a flattened disk of material. The inner part of this disk contained more heavier elements, and formed the terrestrial planets, while the outer region was cold enough for ices to remain intact.

These ices came together, forming larger and larger planetesimals. And these planetesimals collided together, merging into planets. At some point in Saturn’s early history, a moon roughly 300 km across might have been torn apart to create the rings that circle the planet today.

Since Saturn was smaller than Jupiter, it cooled down more quickly. Astronomers think that once its outer atmosphere reached about 15 K, helium condensed into droplets that fell towards its core. The friction from these droplets heated up the planet to the point that it gives off roughly 2.3 times the amount of energy it receives from the Sun.

Here’s an article from Universe Today about how the gas giant planets might have consumed their moons early on, and another article about how gas giant planets might form around other stars.

Here’s an article about the formation of Saturn’s rings, and an article about what Saturn’s moons might tell scientists about planet formation.

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.

Posted on by Fraser Cain

Radiation on Saturn

Radiation Belts on Saturn. Image credit: NASA/JPL/SSI

Just like Jupiter, Saturn radiates out more energy that it draws in from the Sun. In fact, Saturn radiates 2.3 times more energy than it receives from the Sun.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

This has been a bit of a mystery to scientists. But the solution lies in the fact that Saturn’s atmosphere is relatively poor in helium, compared to Jupiter. Scientists think it cooled faster than Jupiter after initial formation, and then helium droplets formed when the temperature of the atmosphere dropped below 15 K. These droplets have been falling down into the core of Saturn, heating it up, and generating the heat.

When NASA’s Cassini first arrived at Saturn, the spacecraft detected lightning storms and radiation belts around the planet. It even found a brand new radiation belt located inside the rings of Saturn. The belts extend from about 139,000 km from Saturn’s center out to 362,000, and contain highly charged particles.

Here’s an article about Cassini finding the radiation belts around Saturn, and another about strange radio emissions coming from Saturn, related to the belts.

Here’s more information on the radiation belts, and a nice photograph from NASA.

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.

Posted on by Fraser Cain

Storms on Saturn

Storms on Saturn. Image credit: NASA/JPL/SSI

Jupiter is well known for the storms that rage across its upper atmosphere, especially the Great Red Spot. But Saturn has storms too. They’re not as large, intense or large lived, but compared to Earth, they’re enormous. And Saturn has one of the big mysteries in the Solar System; a hexagon-shaped storms at its poles.

You can also check out these cool telescopes that will help you see the beauty of planet Saturn.

Winds blow hard on Saturn. The highest velocities are near the equator, where easterly blowing winds can reach speeds of 1,800 km/h. The wind speeds drop off as you travel towards the poles.

Like Jupiter, storms can appear in the bands that circle the planet. One of the largest of these was the Great White Spot, observed by the Hubble Space Telescope in 1990. These storms seem to appear once every year on Saturn (once every 30 Earth years).

NASA’s Cassini spacecraft discovered static hexagonal storm circling around Saturn’s north pole, including a clearly defined eyewall – just like a hurricane. Each side on the northern polar hexagon is approximately 13,800 km long, and the whole structure rotates once every 10 hours and 39 minutes; the same as a day on Saturn.

Here’s an article about a time when Cassini tracked a long-lived lightning storm on Saturn, and another about the strange “Dragon Storm” seen in the planet’s southern hemisphere.

Here’s an article about the northern hexagonal storm from MSNBC, and Astronomy Picture of the Day has an image of storm alley on 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.