Posted on by Jerry Coffey

How Far is Saturn from Earth?

Revisit the best of the best images of Saturn

[/caption]
The answer to ”how far is Saturn from Earth” has a different answer every day. As the planets move along their orbital paths they move nearer and further in comparison to each other. For the sake of simplicity, Saturn is 1.2 billion km, roughly 7 AU, from the Earth when the two are at their closest approach to one another. They are 1.67 billion km, around 11 AU, from each other when they are at their most distant. Saturn and Earth are the closest to each other when they are on the same side of the Sun and at similar points in their orbits. The are the most distant when on opposite sides of the Sun.

Here are some of the other orbital and physical characteristics of Saturn compared to those of Earth.

Equatorial Diameter… 120,536 km, 9.44 times that of Earth
Polar Diameter… 108,728 km, 8.55 times that of Earth
Surface Area…4.27×1010 km2, 83.7 times that of Earth
Volume…8.2713×1014 km3, 763.6 times that of Earth
Mass…5.6846×1026 kg, 95.2 times that of Earth
Density… 0.687 g/cm3, one tenth that of Earth…Saturn could float in water.

Here are a few other interesting facts about Saturn that may interest you:

Saturn has 60 moons. That means that about 40% of the moons in our Solar System orbit around the planet. Many of these moons are very small and can not be seen from Earth. The last four were discovered by the Cassini spacecraft and scientist fully expect to find more as more spacecraft make their way toward Saturn.

Saturn is known for its amazing set of rings, but did you know that the occasionally disappear? Well, they disappear from our point of view anyway. The planet is tilted on its axis very similar to Earth. AS it makes its way along its 30 Earth year orbit of the Sun we sometimes see the rings full on and other time they are edge on from our perspective and disappear. This will next happen in 2024-2025.

While Saturn is too hostile for any form of life that we know, its moon Enceladus has ice geysers. That means that some mechanism is keeping the moon warm enough for liquid water to exist. As you know, here on Earth where ever there is liquid water there is life. Some scientist think that there is a chance for some type of life to exist on Enceladus.

Now that you know the answer to ”how far is Saturn from Earth”, we here at Universe Today hope that you will be inspired to find out more about the ringed planet.

Here’s an article that has photos of Earth seen from other worlds, including Saturn, and an article about how far each of the planets are from the Sun.

Here’s Hubblesite’s News Releases about Saturn, and more facts on Saturn from Kid Cosmos.

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 Fraser Cain

Podcast: Humans to Mars, Part 2 – Colonists

Artist illustration of a Mars Habitat. Image credit: NASA

[/caption]
After astronauts make the first tentative steps onto the surface of Mars, a big goal will be colonization of the Red Planet. The first trailblazers who try to live on Mars will have their work cut out for them, being in an environment totally hostile to life. What challenges will they face, and how might they overcome them?

Click here to download the episode

Humans to Mars, Part 2 – Colonists – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Posted on by Jerry Coffey

Diameter of Saturn

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

Saturn has an equatorial diameter of 120,536 km, 9.44 times that of Earth. That makes it the second largest planet in our Solar System, trailing only Jupiter. Saturn, like all of the other planets, is an oblate spheriod. This means that its equatorial diameter is larger than is diameter measured through the poles. In the case of Saturn this distance is quite a bit different due to the planet’s high rotational speed. The polar diameter of Saturn is 108,728 km, meaning that it is flattened by a factor of 9.796%.

Scientist know that Saturn rotates very quickly, but the exact speed of that rotation has been hard to determine because of the thick clouds in the atmosphere. With terrestrial planets, scientists are able to find surface features and basically time how long it takes for that feature to reappear in the same position. This is a simplified description of how they determine rotational speed. The problem with Saturn is that the surface can not be observed. To make things even more difficult, the visible features of the planet’s atmosphere rotate at different speeds depending on their latitude.

The atmosphere of Saturn is broken down into systems. System I is the equatorial zone has a rotational period of 10 hours and 14 minutes. System II encompasses all other areas of Saturn and has a rotational speed of 10 hours 38 minutes and 25.4 seconds. System III is based on radio emissions and has mostly replaced the use of the term System II. It has a rotational speed of 10 hours 39 minutes and 22.4 seconds. Despite these numbers, the rotational speed of the planet’s interior is currently impossible to measure precisely. The Cassini spacecraft found the radio rotational speed of Saturn to be 10 hours 45 minutes and 45 seconds. In 2007, it was determined that the varying radio emissions from the planet did not match Saturn’s rotation rate. Some scientists think that the variance is due to geyser activity on the Saturnian moon Enceladus. The water vapor from these geysers enter Saturn’s orbit become charged, thus creating a drag effect on Saturn’s magnetic field. This slows the magnetic field’s rotation slightly compared to the rotation of the planet. The current estimate of Saturn’s rotation is based on various measurements from the Cassini, Voyager and Pioneer probes. That estimated speed is 10 hours 32 minutes and 35 seconds as of September 2007.

Again, the equatorial diameter of Saturn is 120,536 km and its polar diameter is 108,728 km. It is very important to understand why the difference in these diameters is so large, that is why so much detail is given on the rotational speed of the planet. You can take many of the same factors into account when thinking about all of the gas giants.

Here’s an article about how long a day is on Saturn, and another article about how the storms never end on Saturn.

Here’s Hubblesite’s News Releases about Saturn, and more information from Solar Views.

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

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 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