Posted on by Fraser Cain

Temperature of Saturn

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

It’s almost impossible to say what is the temperature of Saturn. The highest cloud tops, right at the edge of space, are colder than -150 °C. But as you travel down into the planet, pressures and temperatures rise. At the very core, temperatures can reach 11,700 °C.

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

As I mentioned above, the internal core of Saturn gets as high as 11,700 °C. This comes from the huge amount of hydrogen and helium compressing down and heating up the core.

Saturn actually generates heat. In fact, it’s putting out 2.5 times as much energy as it receives from the Sun. This is because the planet’s gravity is slowly compressing it down, and generating heat as it does this.

Once you reach the cloud layers in Saturn’s atmosphere, temperatures drop quickly. The bottom of the clouds are made of water ice and have an average temperature of -23 °C. Above this is a layer of ammonium hydrosulfide ice, with an average temperature of -93 °C. Above this are the ammonia ice clouds that give Saturn its orange/yellow color. Temperatures at the very edge of Saturn can get as low as -150 °C.

Here’s an article about a hot spot on Saturn, and the temperature of its rings.

Here’s an article about Saturn from How Stuff Works, and more facts on Saturn from ESA.

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

What Color is Saturn?

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

Even through a small telescope, Saturn takes on a beautiful pale yellow with hints of orange. With a more powerful telescope, like Hubble, or images captured by NASA’s Cassini spacecraft, you can see subtle cloud layers, swirling storms mixing orange and white together.

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

But what gives Saturn its color?

Like Jupiter, Saturn is made almost entirely of hydrogen, a small amount of helium, and then trace amounts of other compounds, like ammonia, water vapor and hydrocarbons.

The colors we see come just from the upper cloud layers of Saturn, which are largely composed of ammonia crystals, and the lower level clouds are either ammonium hydrosulfide or water.

Saturn has a banded pattern in its atmosphere, similar to Jupiter, but they’re much fainter and wider near the equator. It also has long-lived storms – nothing like Jupiter’s Great Red Spot – which often occur when the planet nears the summer solstice for the northern hemisphere.

Some photographs of Saturn captured by NASA’s Cassini spacecraft make the planet look blue, similar to Uranus. But this is probably just because of how the light is scattering from Cassini’s perspective.

This article has a nice full-color image of Saturn, and another nice wallpaper of Saturn.

Here’s a beautiful image of Saturn from Solar Views, and a false color image from Hubble.

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 Ian O'Neill

Forget Neutron Stars, Quark Stars Might be the Densest Bodies in the Universe

The difference between a neutron star and a quark star (Chandra)

So neutron stars may not be the densest exotic objects in the cosmos after all. Recent observations of ultra-luminous supernovae suggest that these explosions may create an even more exotic remnant. Neutron stars can form after a star ends its life; measuring only 16 km across, these small but massive objects (one and a half times the mass of the Sun) may become too big for the structure of neutrons to hold it together. What happens if the structures of the neutrons inside a neutron star collapse? Quark stars (a.k.a. “Strange” stars) may be the result, smaller and denser than neutron stars, possibly explaining some abnormally bright supernovae observed recently…

Three very luminous supernovae have been observed and Canadian researchers are hot on the trail as to what may have caused them. These huge explosions occur at the point when a massive star dies, leaving a neutron star or black hole in their wake. Neutron stars are composed of neutron-degenerate matter and will often be observed as rapidly spinning pulsars emitting radio waves and X-rays. If the star was massive enough, a black hole might be formed after the detonation, but is there a phase between the mass of a neutron star and a black hole?

It appears there might be a smaller, more massive star on the block, a star composed not of hadrons (i.e. neutrons), but of the stuff that makes up hadrons: quarks. They are thought to be one step up the star-mass ladder, the point at which the mass of the supernova remnant is slightly too big to be a neutron star, but too small to form a black hole. They are composed of ultra-dense quark matter, and as neutrons break down it is thought some of their “up” and “down” quarks are converted into “strange” quarks, forming a state known as “strange matter.” It is for this reason that these compact objects are also known as strange stars.

Quark stars may be hypothetical objects, but the evidence is stacking up for their existence. For example, supernovae SN2005gj, SN2006gy and SN2005ap are all approximately 100 times brighter than the “standard model” for supernova explosions, leading the Canadian team to model what would happen if a heavy neutron star were to become unstable, crushing the neutrons into a soup of strange matter. Although these supernovae may have formed neutron stars, they became unstable and collapsed again, releasing vast amounts of energy from the hadron bonds creating a “Quark-Nova”, converting the oversized neutron star into a quark star.

If quark stars are behind these ultra-luminous supernovae, they may be viewed as super-sized hadrons, not held together by the nuclear strong force, but by gravity. Now there’s a thought!

Source: NSF

Posted on by Fraser Cain

What is the Closest Planet to Saturn?

What is the closest planet to Saturn? That depends on where Saturn is in its orbit, and the position of the other planets.

But for the majority of its orbit, the closest planet to Saturn is Jupiter. When the two planets are lined up perfectly, so that it goes: Sun, Jupiter, Saturn, the two planets are separated by only 655 million km.

Of course, when the planets are on opposite sides of the Sun (Jupiter – Sun – Saturn), they’re separated by 2.21 billion km, and all of the inner planets are closer to Saturn than Jupiter.

In fact, Uranus sometimes gets closer to Saturn than Jupiter. At their closest, Uranus and Saturn can be 1.43 billion km apart.

In case you were wondering, the closest planet to Jupiter is Mars, and the closest planet to Mars is Earth.

Here’s Hubblesite’s News Releases about Saturn, and NASA’s Solar System Exploration guide.

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

Gravity on Saturn

Saturn doesn’t have a solid surface, so it’s impossible to actually walk on the surface and feel the gravity of Saturn. But let’s pretend that you could. What kind of force would you feel if you could actually stand on the surface of Saturn and walk around.

Even though Saturn has much more mass than Earth, second in the Solar System only to Jupiter, it also has the lowest density of all the planets in the Solar System. When you spread that mass across the entire volume of Saturn, the actual gravity pulling at any spot on the surface is only 91% of Earth’s gravity. In other words, if your bathroom scale said 100 kg on Earth, it would say 92 kg on the “surface” of Saturn.

Just for comparison, if you wanted to walk on the “surface” of Jupiter, you would experience 2.5 times the gravity of Earth. And if you walked on the surface of Mars, you would experience about 1/3rd the gravity of Earth. You would have 1/6th your weight on the Moon.

What contributes to all this Saturn gravity? Saturn is largely comprised of hydrogen and helium, which came together at the beginning of the Solar System, gathered by their mutual mass. It’s the same composition as Jupiter and the Sun. These primordial elements were formed at the beginning of the Universe in the Big Bang.

Here’s more information about the gravity of Jupiter, and the gravity on Mars.

This page will help you calculate the gravity on Saturn, and this cool site lets you calculate gravity on all the planets.

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

Density of Saturn

Saturn has the lowest density of all the planets in the Solar System. The actual number is 0.687 grams per cubic centimeter. This is actually less dense than water; if you had a large enough pool of water, Saturn would float.

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

Just for comparison, Jupiter has an average density of 1.33 grams per cubic centimeter. So it wouldn’t float on water. And Earth, the densest planet in the Solar System, measures 5.51 grams/cubic centimeter.

If you’d like to calculate the density of Saturn for yourself, grab a calculator, and then divide the mass of Saturn (5.6846×1026 kg) by its volume (8.2713×1014 cubic kilometers. This gives you a final number of 0.687 g/cubic centimeter.

Here’s an article about a fluffy extrasolar planet, even less dense than Saturn, and more information about the density of Jupiter.

Here’s a textbook that helps you make the density calculations for yourself, and more information here.

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 Tammy Plotner

Cosmic Mystery: NGC 7008 by Dietmar Hager

NGC 7008 by Dietmar Hager

Over the weeks we’ve taken a look at some very curious objects which have often raised some wonderful questions. One such question dealt with what could be observed should a supernova event involve a planetary system. In this case, it’s not quite the explosive mass destruction scenario – but a planetary nebula that consumed its planets…

Veteran sky observers have long been aware of the unique structure of planetary nebula NGC 7008. Located about 2800 light years distant in the constellation of Cygnus, report after report shows even amateur telescopes easily resolve out the central star and unusual bright areas in the outer shell. We might wonder about it when we see it, but what lay within is quite unique.

Because the central star of NGC 7008 is so prominent, the original lines of thinking on this nebula’s formation focused around the central star itself. Says Francesco Pala: “Much of the recent attention on primordial stars has focused on the properties of massive objects, considered the natural outcome of first structure formation. While there are reasons to believe that massive stars were common, but not unique, in the early universe, the question of their actual formation is still not adequately understood…. how unique must have been the physical conditions in primordial clouds to yield such an unusual distribution of stellar mass.”

In 1995, the Hubble Telescope was pointed towards NGC 7008. The primary aim of the survey was to find close, resolved main-sequence companions of the central stars, which through main-sequence fitting would provide excellent distance estimates for the nebulae. What they found was only the beginning of the end.

Scientist Mario Perniotto studies planetary nebulae and their gas dynamics. “I first recall the history of PNe which are generated from low and intermediate mass stars through successive mass loss processes starting in the Red Giant phase of evolution and continuing also after the termination of the pulsed AGB phase, where most of the nebular mass is believed to be ejected. The corresponding stellar winds are the ingredients of the nebula. Their initial properties and subsequent mutual interactions, under the action of the evolving stellar radiation field, are responsible for the properties of the nebula.” Through studies with the Hubble, the kinetic structure of NGC 7008 has been observed to have another unusual feature – Fast Low Ionization Emitting Regions.

Says Perinotto: “Attention is focused on FLIERs and on the proposed mechanisms to interpret them. Recent observations with the Hubble Space Telescope have provided us with a wealth of detailed (subarcsec) information on the nebular structures. The inner structure of FLIERs is here illustrated to consist of substructures of various shapes with an high degree of individually from object to object, also within the same planetary nebula. These new data call for deeper theoretical efforts to solve the problems of cosmic gas dynamics, posed by their observed properties.”

But the motions of the gas aren’t all that’s being observed – the dust itself plays an important role. According to studies done by Klaas and Walker, some of NGC 7008’s dynamic structure comes from dual layers of radically different dust which originated from two different sources. Could this be the result of a binary star taking its last twin breath? First the older star… And then the younger? Says Tylenda and Gorny: “Therefore we can conclude that the H-poor layers in these stars have been exposed shortly after the PN formation at the tip of AGB. This excludes, from our considerations, scenaria like that of a final helium shell flash which produced a H-poor, He-burning nucleus surrounded by an old, large nebula.”

But astronomer Noam Soker wasn’t taking that for an answer. “For NGC 7008, a deviation from symmetry is expected and indeed a departure is observed, but the main signature is on the outskirts of the nebula, and hence an interaction with the ISM (interstellar medium) is possible. If the companion is associated with the PN central star, as claimed… I put a question mark, since it is not clear if the morphology is compatible with the claimed companion or is solely due to an interaction with the ISM.”

Close-up on NGC 7008 - Dietmar Hager

Enter the Instituto de Astronomía in México. “We suggest that some of the structures observed in the envelopes of planetary nebulae are caused by the interaction of central star wind and radiation with preplanetary nebula debris: planets, moons, minor objects and ring and ring arcs. Recently considerable amount of planetary material has been reported to exist around solar type stars, this debris could be evaporated during the envelope ejection and alter the chemical abundance and produce some of the envelope inhomogeneities. If there are massive enough rings of material surrounding the progenitor and planets in their vicinity, arc rings could be formed. If the rings are viewed pole on when the envelope is detached from the central star, it will interact with the arc ring material and produce ansae and pedal and garden-hose-shape structures observed in some planetaries.”

Next time you visit NGC 7008 – take a closer look like Dr. Dietmar Hager did. There’s something more to this story than just another pretty cosmic face. Something he recognized and asked me to investigate. Not only does his image reveal the presence of FLIERS and the well resolved central region, but a structure that’s made scientists look again and again over the years. Of all the explanations and science that I’ve researched, I like Noam Soaker’s answer best:

“I propose that the destruction of brown dwarfs and massive planets inside the envelopes of asymptotic giant branch stars can lead to the formations of jets and ansae in elliptical planetary nebulae. Thick disks with jets on their two sides are the plausible outcome of this process. The process is likely to occur at late states of the AGB, and the jets push their way out of the envelopes in the course of a number of year. The Roche lobe overflow continues for several hundred years and destroys the secondaries. This scenario predicts that the same material will be contaminated by two sources. Once source is the AGB cores, from which material can be mixed into the jets and the other consists of the destroyed secondaries.”

Always look twice and think about what you’re observing… Because there is so much more there than what meets the eye!

These awesome images were done by Avanced Optical/ Radio Astronomers and International Associates member Dr. Dietmar Hager from StarGazer Observatory. Many thanks for the investigative challenge!

Posted on by Fraser Cain

Discovery of Saturn

Saturn is one of the 5 planets visible with the unaided eye. In fact, it often appears as one of the brightest stars in the sky, and so ancient people have known about Saturn for thousands of years. In fact, it’s impossible to know who made the Saturn discovery.

The Romans named Saturn after their god of the harvest and time, the same entity as the Greek God Chronos.

The first observation of Saturn through a telescope was made by Galileo Galilei in 1610. His first telescope was so crude that he wasn’t able to distinguish the planet’s rings; instead he thought the planet might have ears or two large moons on either side of it. When he looked at Saturn a few years later, the moons had disappeared, but this was just because the angle of Saturn had changed, and the rings were being seen edge on.

The Dutch astronomer Christiaan Huygens observed Saturn in 1659, and solved the mystery, realizing that the “arms” around Saturn were really a system of rings. He also was the first to observe Saturn’s moon Titan.

Better and better telescopes helped reveal that the rings were really a system of particles, and Jean-Dominique Cassini discovered 4 other major moons of Saturn: Iapetus, Rhea, Tethys and Dione.

The first close up observations of Saturn were made by NASA’s Pioneer 11 spacecraft, which made a flyby of the planet on September 1, 1979 at a distance of only 21,000 km above the planet’s cloud tops. It send back the first close-up images of Saturn.

Other spacecraft have visited Saturn, including NASA’s Voyager probes. And the Cassini has been orbiting Saturn since its arrival in July 2006.

Here’s an article about what Galileo might have seen, and an article about Cassini’s observations of Saturn.

Here’s a great history of Saturn from NASA, and more information from NASA’s JPL.

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 Jerry Coffey

How Long Does it Take to Get to Saturn?

How long does it take to get to Saturn? That is a great question that happens to have several answers. Just as it can take different amounts of time to get to a destination here on Earth depending on what route you take, it can take different amounts of time to get to Saturn based on how you travel.

In the past spacecraft have taken greatly different amounts of time to make it to Saturn. Pioneer 11 took six and a half years to arrive. Voyager 1 took three years and two months, Voyager 2 took four years, and the Cassini spacecraft took six years and nine months to arrive. The New Horizons spacecraft took a short two years and four months to arrive on the scene. Why such huge differences in flight time?

The first factor to consider is whether the spacecraft is launched directly toward Saturn or if the spacecraft is sent toward other celestial objects to uses their gravity to slingshot itself to Saturn. Another factor is consider is the type of engine propelling the spacecraft, and a third factor to think about is that it takes a great deal of time to slow down, so if a spacecraft is simply going to flyby, it need to slowdown, but if it is to orbit, its trip to Saturn will take longer.

With those factors in mind, lets look a the mission mentioned above. Pioneer 11 and Cassini used the gravitational influence of different planets before making their way to Saturn. These flybys of other planets added years to their trip. Voyager 1 and 2 did not meander around the Solar System so much and made their appearances near Saturn much more quickly. The New Horizons spacecraft had several distinct advantages over all of the other spacecraft mentioned. The two main being that it has the fastest, most advanced engine available and it was launched on a single trajectory past Saturn on its way to Pluto.

As you can see, the answer to ”how long does it take to get to Saturn” lacks a straightforward answer. Even with New Horizons flying past in just over two years, scientist are hoping to improve upon that speed with better engines and more efficient flight patterns.

Just in case you were wondering, here’s how long it takes to fly to Mars, and how long it takes to get to the Moon.

Here’s the same question answered at NASA’s Starchild, and information about how long each of NASA’s spacecraft took to make the journey.

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

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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.