Astronomy Archives

July 8, 2008December 24, 2015 by Fraser Cain

What is the Second Biggest Planet in the Solar System?

Saturn captured by Voyager. Image credit: NASA/JPL

The biggest planet in the Solar System is Jupiter. But the title for the second biggest planet in our Solar System goes to Saturn.

Just for a comparison, Jupiter measures 142,984 km across its equator. Saturn for comparison is only 120,536. So Jupiter is only 1.18 times as big of Saturn. Saturn is big, but it has a much lower mass. Once again, Jupiter is 3.34 times as massive as Saturn.

Since Saturn is so big, but has so little mass, it has a very low density. In fact, if you had a pool big enough, Saturn would float. The density of Saturn is less than water. And this means that you wouldn’t experience a lot of gravity if you tried to walk on the “surface of Saturn”. If you were standing on the surface of Saturn (I know, that’s impossible), you would experience only 91% the force of Earth’s gravity.

If you wanted to compare Saturn to Earth, it’s 9.4 times as big as the Earth, and 95 times as massive. It it was just a hollow shell, you could pack 763 Earths inside Saturn, with a little room to spare.

Wanna see Jupiter? Here are amazing telescopes from Amazon.com which you can buy at reasonable prices:

Here’s the article about how Jupiter is the biggest planet. And here’s another article about just how big planets can get.

If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn, and another page on Saturn from NASA’s Solar System Exploration Guide.

We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.

July 8, 2008December 24, 2015 by Tammy Plotner

Planetary Alignment Dazzles Weekend SkyWatchers

July 6: Saturn, Mars, Regulus and Moon - Richard McCoy

We warned you it was about to happen! Even though you may have been clouded out of viewing this weekend’s awesome alignment of Regulus, Mars and Saturn dancing with the Da Vinci Moon, our friendly photographers around the world were happy to share the view with us. Unlike the many erroneous myths that often surround such occurrences, planetary alignments are nothing more than the visible clockwork mechanism of our natural skies.

While Saturn and Mars descend through the “Sacred Hoop”, we have to remember that such alignments are not rare – just natural. Rumors and myths of calamities and catastrophe have abounded since the beginning or oral history when they occur, and it is amazing just how quickly these stories dissipate once the alignment has passed and nothing happened! Without rehashing doomsday prophecies, we need to take a closer look at alignments for just what they are…

An awesome display of celestial mechanics.

Each and every planetary alignment holds an opportunity to expand awareness about astronomy. It is a proven fact that the human eye follows the Gestalt Laws of Organization – the study of how people perceive visual components as organized patterns or wholes, instead of many different parts. We develop a fixation on such patterns when we see them. Ask yourself if your own eye is not drawn to this image of the alignment! The parallax is so far and so slow, that we simply cannot attach anything more than a mystical sense of wonder at the visualization. And that is not a bad thing… It draws people to require an explanation for what they see.

Be a good astronomer and stop misinformation in its tracks. When people you know ask about what they have seen in the sky, tell them! Explain how the stars and planets work just like a clock, each following their gear and routine. Alignments happen every hour… 1:05 and five seconds… 8:40 and 40 seconds.. and the sky is no different. If our eyes were sensitive enough, just think of all the deep sky alignments that occur each month as the Moon and planets traverse the ecliptic plane! How many stars hidden behind blue skies does our own Sun align with each and every second of the day?

And stay tuned for the next awe inspiring event…

The two incredible images of this weekend’s planetary alignment belong to Advanced Optical and Radio Astronomers International Associates members, Richard McCoy (panoramic image) and Shevill Mathers (closeup). We appreciate the time and energy you put into these photos and thank you for sharing with us!

July 7, 2008December 24, 2015 by Fraser Cain

Pictures of Saturn

Cassini's image of Saturn and Earth. Image credit: NASA/JPL

Saturn is easily the most beautiful planet in the Solar System. To celebrate this natural wonder, lets look at some beautiful pics of Saturn.

But if you want to see Saturn by yourself, you can check out these cool telescopes that will help you see the beauty of planet Saturn.

Let’s start with one of the most beautiful photos of Saturn ever taken. This image of Saturn was taken by NASA’s Cassini spacecraft when it was behind Saturn. In other words, the Sun is completely obscured by Saturn, and illuminating it from behind. The tiny speck in the upper, left-hand side of Saturn’s rings is our own home planet Earth.

This is a picture of Saturn taken by the ground-based Keck telescope, located atop Mauna Kea in Hawaii. It’s one of the most powerful telescopes on Earth. The Saturn photo was taken in infrared, and shows the strange hot spot located at Saturn’s south pole.

It’s not the best picture, but you’re looking at one of the first ever images of Saturn captured up close by NASA’s Pioneer 11. During its mission, Pioneer 11 passed just 20,000 km above the cloud tops of Saturn, and captured the first close-up images of Saturn.

This is an example of a beautiful picture of Saturn taken by NASA’s Voyager 1 spacecraft in 1980. As you can see, the quality has improved significantly over the image captured by Pioneer 11. Both Voyager 1 and Voyager 2 made quick flybys of Saturn and then sped off into space. When Voyager 1 completed its flyby of Saturn, it sped off into the depths of space, while Voyager 2 went on to visit Uranus and Neptune as part of its Grand Tour of the Solar System.

Here’s another image of Saturn captured by NASA’s Cassini spacecraft. This photograph was taken in May 2004, when Cassini had almost arrived at Saturn. The spacecraft spent another 4 years orbiting Saturn as part of its primary mission, and at the time of this writing, it’s still going strong.

We have written many articles about Saturn for Universe Today. Here are some facts about Saturn.

July 7, 2008December 24, 2015 by Fraser Cain

Saturn for Kids

Color view of Saturn. Image credit: NASA/JPL/SSI

Want to help your kids learn more about Saturn? There are many great resources out there, which I’ll get to in a second.

But first, have you – or your kids – ever actually looked at Saturn with your own eyes? Many amateur astronomers say that seeing Saturn through a telescope was the moment that turned them onto the hobby that lasts a lifetime.

Chances are you’ve seen Saturn many times in the past, but you just didn’t realize it. When Saturn is high in the sky, it looks like a very bright star, easily visible with the unaided eye.

But to really appreciate it, you’ve got to see Saturn in a telescope. Find a friend with a telescope, or find your local astronomy club, and learn when they’re having an open telescope night. Ask to see Saturn, and then anything else they’re able to find for you.

Build a scale model of the Solar System
We’ve got a tutorial here on Universe Today that helps you build a miniature version of the Solar System. The Sun fits on a piece of paper, and then the rest of the planets fit within about 1 km from the Sun – easy walking distance for the kids. We even made little rings for our Saturn.

Learn about Saturn’s density
Saturn’s the only planet in the Solar System that would float if you could find a pool of water large enough. The density of Saturn is very close to the density of apples. So put some rings around an apple, and toss it into the tub.

Learn about their weight on Saturn
The gravity of Saturn is about 90% the gravity on Earth. Have your child stand on a bathroom scale, and then support them to the point that they’re 90% of their weight. Now let them walk around the room with you supporting a little of their weight. What does it feel like?

Draw Saturn
Take a look at some pictures of Saturn, and then try drawing your own. See the different bands on the planet, ranging in color from white to yellow to orange. And draw the rings, with different colors, and gaps in between. Try drawing completely different planets with rings.

Want more information about the Solar System for kids? Here’s some material on the Moon for kids, and Jupiter for kids.

And there are more great resources for kids on the Internet. Check out Kids Astronomy. From grown-ups, here’s Hubblesite’s News Releases about 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.

July 7, 2008December 24, 2015 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.”

The 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!

July 5, 2008December 24, 2015 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

July 5, 2008December 24, 2015 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 23.4Â°, Saturn’s tilt is 26.7Â°. 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.

July 5, 2008March 24, 2012 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!

July 4, 2008December 24, 2015 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).

But 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!

Return 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.

Sunday, 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).

When 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.

July 3, 2008April 26, 2016 by Fraser Cain

History of Saturn

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.