Posted on by Jerry Coffey

What is the Diameter of Jupiter?

Jupiter seen from Voyager. Image credit: NASA/JPL

The diameter of Jupiter at its equator is 142,984 km. Since it rotates very quickly, completing a full rotation in just 10 hours, it is an oblate spheroid and bulges at the equator. If you measure the diameter through the poles it is 9,276 km smaller at 133,708 km. Solely based on diameter, Jupiter is 11.2 times the size of the Earth and larger than any other body in our Solar System other than the Sun.

The diameter of Jupiter is amazingly large for our Solar System, but is easily eclipsed by some extrasolar planets. According to Dr. Sean Raymond at the Center for Astrophysics and Space Astronomy at the University of Colorado the largest terrestrial(rocky like Earth) planets can be up to 10 times the size of Earth. Since Jupiter is a gas giant, let’s compare apples to apples and talk about the largest known gas giant in the universe. As of this time(August, 2011) the largest gas giant known is TrES-4. This planet is 1,400 light years away in the constellation Hercules. It has been measured to be 1.4 times the size of Jupiter, but it only has 0.84 times Jupiter’s mass. A gas giant can get about 14 times more massive than Jupiter before they ignite fusion and become brown dwarf stars.

A common question that people ask is ”can Jupiter ever become a star?”. That is a reasonable question given its size and mass. Fortunately for humans, the answer is no. Jupiter would need to add about 80 times its current mass in order to ignite fusion. While the planet occasionally accretes more matter, there is not enough available in our Solar System to add that much mass. If it did ignite, it would scorch our world

Jupiter interests scientists for many reasons. Its moons are a major draw for research. The planet has 64 moons that have been confirmed and a few more that have rarely been observed. The moons in the Jovian system account for 50% of all of the moons in our Solar System. A few of those moons are larger than some dwarf planets and others show evidence of subsurface oceans. Scientist are not sure if they are oceans of water as we know it, but they do believe that they exist.

The diameter of Jupiter is an awesome number in itself, but, once you consider the planet as a whole, you see that knowing the diameter is just scratching the surface. Hopefully, it is enough to spark an interest in researching the planet further.

Here’s more information on the diameter of Earth, if you’d like to compare and see how big Jupiter really is. Jupiter’s big, but extrasolar planets are thought to be able to get even bigger. Here’s an article about how big planets can get.

As I’ve mentioned above, Jupiter is the biggest planet in the Solar System, and here’s Hubblesite’s News Releases about Jupiter.

We’ve also recorded an entire show just on Jupiter for Astronomy Cast. Listen to it here, Episode 56: Jupiter, and Episode 57: Jupiter’s Moons.

Sources:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=OverviewLong
http://planetquest.jpl.nasa.gov/news/tres4.cfm

Posted on by Nancy Atkinson

Super-Earths: How Much Are They Like Earth?

With yesterday’s announcement about finding a batch of so-called “super-Earths” – rocky alien worlds a few times more massive than our own – as well as another announcement back in May that 45 relatively low mass planets had been found, it’s obvious astronomers are constantly improving on their techniques to find new worlds. While the vast majority of the almost 300 previously discovered exoplanets are Jupiter-like gas giants, the new discoveries of large numbers of small planets – and especially that at least three of them orbit one star — suggests that they are abundant in our galaxy, and may outnumber Jupiter-sized giants by 3 to 1. But how much like Earth are these alien worlds?

Super-Earths are planets that have than ten times or less the mass of Earth. The three planets around the star HD 40307 have masses of 4.2, 6.7, and 9.4 times the mass of the Earth. They orbit their star with periods of 4.3, 9.6, and 20.4 days, respectively. That’s a short orbital period, meaning they are very close to the star. Since they are close to the star, astronomers believe its likely they are terrestrial, rocky-type planets rather than gas giants like Jupiter and Saturn. But also, being so close to the star means they are very warm – perhaps 1000 degrees Celsius. This would not be a pleasant or probable environment for life as we know it to take a foothold. But we don’t know for sure, and since we are curious creatures, we want to know more about these planets.

The observatory that made the discovery of the 3 planets around HD40307, as well as the 45 planets that were announced back in May is the High Accuracy Radial Velocity Planet Searcher (HARPS) survey based at the European Southern Observatory in La Silla, Chile. Astronomers spotted them by recording how each planet’s gravitational tug makes its parent star wobble.

But now astronomers know these planets are there, they can try other methods of studying the planets to glean some detailed information about what these planets are like. For years, astronomers have been waiting for a super-Earth to be found with an orbit that “transits” its parent star: in other words, it passes directly in front of the star as viewed from Earth. When exoplanets have short orbital periods, the likelihood of being able to observing transits increases. These new planets fit that category.

Being able to observe transits would give astronomers data to help figure out many of the planet’s characteristics, from measuring its radius to deducing its internal structure to “seeing” its atmosphere.

Getting information about the planet’s atmosphere would be especially exciting. By watching for changes in a star’s spectrum as it filters a fraction of the star’s light during a transit, the presence of methane and water vapor in the gaseous atmosphere could be revealed.


A few satellites are capable of watching for a transit, among them the Canadian MOST satellite. Another is the recycled Deep Impact spacecraft that is hosting the EPOCh (Extrasolar Planet Observation and Characterization) mission. So far, 4 new planets have been found with this spacecraft, using the transit method, and the goal of the mission is to find an exoplanet smaller than Earth. Also, EPOCh hopes to be able to identify features on an exoplanet, such as continents and oceans. Exciting prospect, indeed.

It’s only a matter of time until astronomers will be able to tell us how Earth-like these newly found Super Earths are.

Sources: New Scientist, Bad Astronomy, EPOCh

Posted on by Tammy Plotner

Telescope Review – Celestron NexStar 102 SLT

Celestron NexStar 102 SLT

Are you looking for a sweet little telescope that can take abuse and keep coming back for more? Designed for the advanced beginner, or for those interested in a highly portable telescope referred to as “Grab and Go”, the Celestron NexStar 102 SLT automated telescope goes through a year-long Tammy Test and graduates with honors…

First off, I’m not too keen on the idea of a GoTo telescope – much less a refractor. In my early years I found refractors to be uncomfortable to use, easy to dew, and just plain not as much deep sky fun as a reflector. As for the GoTo? I genuinely feel you do yourself a disservice by not learning to use an equatorial mount and a star chart. Misgivings aside, it was time to take a look at new technology and see what a year’s worth of use would do to it.

Assembling the Celestron NexStar 102 SLT

Unlike the variety of telescopes I’ve used over the years with complicated equatorial mounts and drive units, the Celestron NexStar is swift and efficient. The tripod is lightweight aluminum, and stands up to time. Despite repeated uses and even overtightening, the legs extend quickly and lock securely using the hand turn knobs. No wing nuts here to get dropped and lost in the dark. The center accessory tray bracket is permanently connected and folds down when the tripod is opened. What’s more, the knob that connects the accessory tray is captive – it can’t get lost. Even though these particular parts are some type of polymer, they are extremely durable and even the occasional cross-threading doesn’t strip them out.

At the top of the tripod is the mount cradle. Again, extremely simple and captively elegant. There is simply no “wrong way” to attach the mount to the tripod and no way to lose the parts that connect it. The mount itself is fully contained. Nothing is exposed to chance or wear. As for durability? Surprise, surprise. The drive motors are contained inside the mount and despite being dropped hard enough to make the exterior cover come off, it popped right back on and absolutely no damage was done.

Once the mount is connected, the telescope optical tube assembly (OTA) comes next. Again, captive screws mean even arthritic hands will not fumble these parts. The OTA attaches to the mount with what is called a “clamshell”. It’s a hinged affair that you simply fold over the telescope body and tighten down.

Last, but not least, are the accessories. Supplied with the Celestron NexStar SLT is a red dot finder that slides on easily on a dovetail mount, a cheap – but serviceable – 1.25″ star diagonal, and two excellent SMA eyepieces. The controller is easily attached into a port on the side of the mount with what looks like a telephone jack and the battery pack is internal to stop cord wrap. Set up time? Twenty minutes the first time… Less than five when you get used to it.

Aligning and Using the Celestron NexStar 102 SLT

So, here’s where my misgivings with GoTo units usually start. I’ve played with a lot of encoders and a lot of different units over the years and I’d usually get frustrated because it would take longer to get the units working than it took just to starhop. In the case of the Celestron NexStar, I was pleasantly surprised to find that it didn’t take a whole lot of learning to use the system. Simply use the keypad to level the scope pointed north (remotely close is fine), and set the date, time and location. Press Go, and the little beast is off and running on its own – seeking out an alignment star. Use the keypad to move the red dot center on the star and enter again. Now, go to the eyepiece, center the star as much as possible and enter. Guess what? That’s all it takes.

The more accurate you are with your time, location (latitude and longitude) and centering – the more accurate the scope becomes. Even loosely set, and I do mean loosely here, folks… A low power, wide field eyepiece will bring almost everything into the field of view on the first try. After that, it’s a joy ride of selecting objects from the data base. If it tries to go to something below the horizon? It will tell you. If it might tangle itself trying to go to what you tell it? It won’t let you. If you try to slew it towards the Sun? A little hand reaches right out of the keypad and slaps you upside the head. It knows better! And it learns… Oh, yes… It learns each time you center a new object up and corrects itself.

What Can You See With the Celestron NexStar 102 SLT?

Everything in the database? No way, Jose. Before you go getting all excited about a 4,000 celestial objects database, remember you are using a 4″ telescope here. We’re talking about a limiting stellar magnitude of around 12 here, so objects much fainter than about magnitude 10 or 11 under average skies are about as good as you’re going to get. However, if you ask it to go to an object, it says it’s there and you don’t see it? Try looking at the on-screen data. Chances are you’re trying for something that is beyond this sweet little telescope’s grasp.

Lunar and planetary performance is outstanding. Being a refractor, it could be no less. Because the Celestron NexStar 102 is driven, it’s possible to drop in some ridiculously high power and get a decent image. Double stars are crisp and clean, and here’s the kicker… Deep sky (nebulae, galaxies, and star clusters) are surprisingly well resolved for such small aperture. When I can pick out the dark dust lane in the Sombrero Galaxy with a 4″ aperture? I’m delighted. When open star clusters sparkle? I’m enchanted. When globular clusters try to resolve? I’m fascinated. When nebulae smoke out of the sky? I’m hooked. A little scope that can!

Final Words On The Celestron NexStar 102 SLT: What’s Good And What Isn’t

The supplied 1.25″ eyepieces are excellent – but the diagonal needs an upgrade. On a happy note, it comes with a 2″ focuser, so do yourself a favor when you’re ready to step up your optics to the next level and go with the bigger accessories. If you can’t afford the full 2″ line, at least start with the 2″ diagonal and use a reducer to accept the 1.25″ eyepieces. You’ll have this scope for a long time and the upgrade is worth it.

Word of warning… It’s a battery eater. Even the high buck batteries don’t last. Having battery power is great when you’re in the field where no electrical outlet is available, but it won’t be long until you’re purchasing a power tank. Happy note? You can connect it to your car battery via the lighter, and the AC converter is very inexpensive.

Dew? Yep. It’s a refractor’s worst enemy. But, surprisingly, Celestron thought of that and the dew shield is included. Just remember, that won’t keep the fog monster away from your eyepieces, but taking care to cover them during the critical point means being able to stay outside and play a lot longer.

Again, don’t ever forget this is a small aperture telescope and it’s not going to reveal every heavenly treasure you dream of and what you see is going to be small. It does rich field, so picture yourself looking at the Ring Nebula about as big as a Cheerio on a dinner plate, ok? But small aperture has it’s advantages… The whole thing only weighs 14 pounds, so it is incredibily easy to take with you as a carry on, or to sling over your shoulder and walk. There’s definitely something to be said about a scope that you can carry everything, including your eyepiece case, folding chair and cooler in one trip!

Usability factor? Don’t give the Celestron NexStar 102 to a small child – but do give it to anyone old enough to read and follow a few simple instructions. Durability factor? It’s been carried around in a car trunk for weeks at a time, strapped on the back of a motorcycle, knocked over at a public outreach event, and traveled to many star parties and still performs flawlessly. It is not a Takahashi, but Celestron produces quality optics and you will not be disappointed with your investment in this $500 telescope.

I wasn’t.

Posted on by Nancy Atkinson

NASA Says Launchpad Damage Shouldn’t Impact Shuttle Schedule

About 5,300 special heat-resistant bricks broke off a flame trench wall of launchpad 39 A at Kennedy Space Center during the space shuttle launch on May 31, hurling some bricks more than 1,800 feet. Engineers assessing the damage said on Monday they are confident the flame trench can be repaired in time for NASA’s next mission, the Oct. 8 launch of shuttle Atlantis on a flight to service the Hubble Space Telescope. NASA allowed journalists to survey the damage to the pad, as well as a heavily damaged security fence around the pad perimeter, with bricks scattered across a wide area around the pad.

The flame trench diverts exhaust to flow out both sides of the launchpad. The missing bricks exposed an irregular area of the concrete wall measuring roughly 20 feet by 75 feet. New bricks cannot be manufactured in time to support the Hubble mission, but engineers believe the trench can be repaired by stripping away additional bricks around the damage area, erecting a steel mesh framework and then spraying on a thick coating of a heat resistant covering.


NASA still does not know exactly what caused the flame trench to come apart and why it broke now, after decades of use. The launch pads were built by the U.S. Army Corps of Engineers in the 1960s for the Saturn rockets that sent the Apollo missions to the moon.

The space agency is inspecting its other launch pad, 39 B, to see whether it, too, has flaws. Both launchpads will be needed for the Hubble mission, as a second shuttle needs to be ready to go, as post-Columbia flight guidelines require a backup shuttle to serve as a recue ship for any mission not going to the International Space Station, where the crew could take refuge if any damage occurred that would prohibit the shuttle from landing.

Previously, NASA said, the worst damage to a launch pad was the loss of 800 bricks from the flame trench at Pad B during Challenger’s doomed liftoff in 1986.

News Sources: AP, CBS News Space Place

Posted on by Ian O'Neill

Phoenix Finds No Water on Mars Surface… So Far

Color-coded elevation map shows the "Dodo-Goldilocks" trench dug by the Robotic Arm on NASA's Phoenix Mars Lander (NASA/JPL-Caltech/University of Arizona/Texas A&M University/NASA Ames Research Center)

The results are now in from the first sample of Mars regolith to be baked in Phoenix’s oven. It’s not good news… there’s no water. After a difficult time of actually delivering the sample to the Thermal and Evolved Gas Analyzer (TEGA) – a.k.a. the “oven” – scientists were hopeful for a clear science run. They were finally able to sift the clumpy regolith through the TEGA screen last week. However, the sample was waiting on the deck of Phoenix for some time until tests could be carried out on the sample; it seems probable that any water ice will have sublimed into the thin atmosphere. This first null result by no means suggests the area is devoid of water, Phoenix has many more water-finding tricks up its sleeves yet…

On June 11th, Phoenix mission control breathed a sigh of relief as they found a solution to the problem of getting the clumpy Mars regolith through the oven screen. Over the weekend they were able to carry out the first tests on the sample and it appears that everything functioned as it should when the sample was heated to 35°C (95°F). At this temperature any water in the sample will have melted. In the second phase of the test, the sample was heated up to 175°C (350°F). No water vapour was detected.

“We saw no water coming off the soil whatsoever” – William Boynton, TEGA team leader, University of Arizona.

Scientists are in no way surprised or discouraged about this early result. The regolith sample sat atop the lander’s TEGA hatch for several days whilst scientists tried to find an answer as to why no particles had fallen into the oven. It is believed that any water ice in the sample will have quickly vaporized in the Martian sunlight and thin atmosphere. As the atmospheric pressure is so low on Mars, exposed water ice cannot melt into liquid water, it will sublime straight to water vapour (by-passing the liquid phase).

Over the coming days, scientists will instruct Phoenix to fire up the TEGA again to heat the sample to 1000°C (1800°F). This will vaporize minerals that might be chemically bound to H2O, CO2 or SO2 and then use instrumentation to measure the vented gases. Scientists are very confident that, although water has not been directly detected today, they will detect evidence of its existence in the next round of tests.

Whilst the drama unfolds in the lander’s oven, Phoenix continues its excavation work on the surface with its robotic arm. It has just expanded a trench (a 3D visualization can be seen at the top of this post) by linking the two trenches “Dodo” and “BabyBear” into a new united “Dodo-Goldilocks” trench. This is the location where scientists noticed white sediment last Friday, so they will be keen to learn whether this is water or salt.

Source: Space.com

Posted on by Matt Williams

What are Temperatures Like on Jupiter?

A true-color image of Jupiter taken by the Cassini spacecraft. The Galilean moon Europa casts a shadow on the planet's cloud tops. Credit: NASA/JPL/University of Arizona

Jupiter, which takes its name from the father of the gods in ancient Roman mythology, is the largest planet in our Solar System. It also has the most moon’s of any solar planet – with 50 accounted for and another 17 awaiting confirmation. It has the most intense surface activity, with storms up to 600 km/h occurring in certain areas, and a persistent anticyclonic storm that is even larger than planet Earth.

And when it comes to temperature, Jupiter maintains this reputation for extremity, ranging from extreme cold to extreme hot. But since the planet has no surface to speak of, being a gas giant, it’s temperature cannot be accurately measured in one place – and varies greatly between its upper atmosphere and core.

Currently, scientists do not have exact numbers for the what temperatures are like within the planet, and measuring closer to the interior is difficult, given the extreme pressure of the planet’s atmosphere. However, scientists have obtained readings on what the temperature is at the upper edge of the cloud cover: approximately -145 degrees C.

Because of this extremely cold temperature, the atmosphere at this level is composed primarily of ammonia crystals and possibly ammonium hydrosulfide – another crystallized solid that can only exist where conditions are cold enough.

However, if one were to descend a little deeper into the atmosphere, the pressure would increases to a point where it is ten times what it is here on Earth. At this altitude, the temperature is thought to increase to a comfortable 21 °C, the equivalent to what we call “room temperature” here on Earth.

Descend further and the hydrogen in the atmosphere becomes hot enough to turn into a liquid and the temperature is thought to be over 9,700 C. Meanwhile, at the core of the planet, which is believed to be composed of rock and even metallic hydrogen, the temperature may reach as high as 35,700°C – hotter than even the surface of the Sun.

Interestingly enough, it may be this very temperature differential that leads to the intense storms that have been observed on Jupiter. Here on Earth, storms are generated by cool air mixing with warm air. Scientists believe the same holds true on Jupiter.

A close-up of Jupiter's great red spot. Credit: NASA/JPL-Caltech/ Space Science Institute
A close-up of Jupiter’s great red spot, an anticyclonic storm that is larger than Earth. Credit: NASA/JPL-Caltech/ Space Science Institute

One difference is that the jet streams that drive storms and winds on Earth are caused by the Sun heating the atmosphere. On Jupiter it seems that the jet streams are driven by the planets’ own heat, which are the result of its intense atmospheric pressure and gravity.

During its orbit around the planet, the Galileo spacecraft observed winds in excess of 600 kph using a probe it deployed into the upper atmosphere. However, even at a distance, Jupiter’s massive storms can be seen to be humungous in nature, with some having been observed to grow to more than 2000 km in diameter in a single day.

And by far, the greatest of Jupiter’s storms is known as the Great Red Spot, a persistent anticyclonic storm that has been raging for hundreds of years. At 24–40,000 km in diameter and 12–14,000 km in height, it is the largest storm in our Solar System. In fact, it is so big that Earth could fit inside it four to seven times over.

Given its size, internal heat, pressure, and the prevalence of hydrogen in its composition, there are some who wonder if Jupiter could collapse under its own mass and trigger a fusion reaction, becoming a second star in our Solar System. There are a few reasons why this has not happened, much to the chagrin of science fiction fans everywhere!

This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen. Credit: Kelvinsong/Wikimedia Commons
This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen. Credit: Kelvinsong/Wikimedia Commons

For starters, despite its mass, gravity and the intense heat it is believed to generate near its core, Jupiter is not nearly massive or hot enough to trigger a nuclear reaction. In terms of the former, Jupiter would have to multiply its current mass by a factor of 80 in order to become massive enough to ignite a fusion reaction.

With that amount of mass, Jupiter would experience what is known as gravitational compression (i.e. it would collapse in on itself) and become hot enough to fuse hydrogen into helium. That is not going to happen any time soon since, outside of the Sun, there isn’t even that much available mass in our Solar System.

Of course, others have expressed concern about the planet being “ignited” by a meteorite or a probe crashing into it – as the Galileo probe was back in 2003. Here too, the right conditions simply don’t exist (mercifully) for Jupiter to become a massive fireball.

While hydrogen is combustible, Jupiter’s atmosphere could not be set aflame without sufficient oxygen for it to burn in. Since no oxygen exists in the atmosphere, there is no chance of igniting the hydrogen, accidentally or otherwise, and turning the planet into a tiny star.

Scientists are striving to better understand the temperature of Jupiter in hopes that they will eventually be able to understand the planet itself. The Galileo probe helped and data from New Horizons went even further. NASA and other space agencies are planning future missions that should bring new data to light.

To learn more about Jupiter, check out this article on how weather storms on Jupiter form quickly. Here’s Hubblesite’s News Releases about Jupiter, and NASA’s Solar System Explorer.

We’ve also recorded an entire show just on Jupiter for Astronomy Cast. Listen to it here, Episode 56: Jupiter, and Episode 57: Jupiter’s Moons.

Sources:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=OverviewLong
http://www.jpl.nasa.gov/news/news.cfm?release=2008-013

Posted on by Tammy Plotner

Simeis 147 by Davide De Martin

Simeis147 - By Davide De Martin

If you think we’re looking straight down the maul of the “Doomsday Machine”, you’d be pretty much correct. While the fictionalized Star Trek account had the planet killer slowly destroying a distant solar system, this particular “star eater” is very real and still exists along the Auriga-Taurus border…

Named Simeis 147, this ancient supernova remnant has expanded so much that it’s barely visible to larger telescopes. Why? Mostly because the diameter of the nebula is about 3-1/2 degrees, or about 7 times the size of the Moon – and the fact it’s one of the faintest objects in the night sky. Like many nebulous “sky scraps”, it is simply too large to be seen in its entirety – or beauty – except through the magic of astrophotograhy.

In this week’s image by Davide De Martin, we take an up close and personal look at Simeis 147. The intricate filaments of this faint supernova remnant spans over 160 light years of interstellar space and is around 3900 light years away. With an apparent age of about 100,000 years, this awesome explosion occurred around the time of Peking Man, and like our distant ancestor left more than one artifact behind. In this case, the expanding remnant is not all. Deep within the folds and rifts lay a spinning neutron star. This pulsar is all that’s left of the original star’s core.

Unlike many things unexplored, more study was indicated and newer estimated gauge Semeis 147’s age at about 30,000 years. The pulsar itself has recently been detected and has been cataloged as PSR J0538+2817. Imagine something that rotates completely on its axis seven times per second! And think about what happened… The outer layers of this exploding star initially carried outward at speeds of 10,000-20,000 km/s–a tremendous amount of energy released in a blast wave.

Supernovae are divided into classes based upon the appearance of their spectra: hydrogen lines are prominent in Type II supernovae; while hydrogen lines are absent in Type Ia supernovae. Put simply, this means the progenitor stars either had hydrogen in their outer envelopes or did not have hydrogen in their outer envelopes. Type II supernovae are the territory of massive stars while Type Ia supernovae more than likely originated with white dwarf binary star systems – a place where the accreting white dwarf is driven above the Chandrasekhar Mass Limit, collapses and explodes.

So how often do events like the Simeis 147 type happen? According to Rudolph Minkowski; “As regards the supernovae frequency, there are two types of supernovae. The Supernovae I seem to occur about every 400 or 500 years per galaxy and the Supernovae II about every 50 years per galaxy, with considerable leeway. But, the Supernovae II are certainly much more frequent than Supernova I.” In recent studies done the 610.5 MHz Contour Maps of the Supernova Simeis 147, by Dickel and McKinley, the integrated flux densities show that the radiation is probably non-thermal and incredibly old.

As old as the Star Trek “Doomsday Machine”? Its origins were also unknown and it produced mass destruction. Maybe Simeis 147 isn’t quite the same as the neutronium hulled, antiproton beam firing planet killer of Gene Roddenberry’s fictionalized story… But it is definitely as intriguing to the imagination!

This week’s awesome image was done by Davide De Martin.

Posted on by Jerry Coffey

How Long is a Year on Jupiter

The answer to ”how long is a year on Jupiter” is 11.86 Earth years. There is so much more to know about the Jovian system, that we can not just leave you with one fact, so here are some more interesting facts about Jupiter.

At perihelion Jupiter is 741 million km from the Sun(4.95 AU). At aphelion it is 817 million km from the Sun(5.46 AU). That gives Jupiter a semi-major axis of 778,340,821 km. Jupiter’s orbit varies by 76 million km, but it has one of the least eccentric orbits in the Solar System.

Jupiter has 2.5 times the mass of all of the other objects in the Solar System except the Sun. It is so massive that if it gained any more mass it would shrink. Gravitational compression would take over making the planet more dense instead of larger.

There are some conspiracy theorists who like to propose that Jupiter will become a star and destroy Earth. That can never happen. Jupiter would have to accrete about 80 times more mass than it has now and experience a huge increase in temperature in order to ignite fusion. The planet has the hydrogen it needs, but not the wherewithal to fuse it into helium and become a star.

Earth’s magnetic field is generated by its core through a dynamo effect. Scientist are not even sure that Jupiter has a rocky/metallic core, yet the planet has a magnetic field that is 14 times stronger than Earth’s. Astronomers think the magnetic field is generated by the churning of metallic hydrogen near the center of Jupiter. This magnetic field traps ionized particles from the solar wind and accelerates them to nearly the speed of light.

One of the most well known aspects of Jupiter is the Great Red Spot. Astronomers have been documenting it for nearly 350 years. It seems to grow and shrink over time. It is actually a giant storm that would totally engulf the Earth. At one time the storm covered an area that was 40,000 km long. It is slowly getting smaller, but astronomers do not know if it will ever disappear.

Knowing the answer to ”how long is a year on Jupiter” is just one minor detail about the planet. The others above are just a few facts that do not even scratch the surface of the Jovian mystery. None of Jupiter’s 67 moons or it ring system have been mentioned. Imagine the stories yet to be told.

Here’s a great image of Jupiter, captured by amateur astronomer Mike Salway, and an interesting hypothetical article about how Jupiter’s orbit could mess up the Solar System.

Here’s some general information on Jupiter from the Nine Planets, and more information from Solar Views.

We’ve also recorded an entire show just on Jupiter for Astronomy Cast. Listen to it here, Episode 56: Jupiter, and Episode 57: Jupiter’s Moons.

Sources:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=OverviewLong
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Facts

Posted on by Jerry Coffey

How Long is a Day on Jupiter

Jupiter and moon Io (NASA)

The Universe Today readers are always asking great questions. ”How long is a day on Jupiter?”, is one of them. A day on Jupiter, also known as the sidereal rotation period, lasts 9.92496 hours. Jupiter is the fastest rotating body in our Solar System. Determining the length of a day on Jupiter was very difficult, because, unlike the terrestrial planets, it does not have surface features that scientists could use to determine its rotational speed.

Scientists cast about for ways to judge the planet’s rotational speed. An early attempt was to do some storm watching. Jupiter is constantly buffeted by atmospheric storms, so the theory was that you could locate the center of a storm and get some idea of the length of a day. The problem scientists encountered was that the storms on Jupiter are very fast moving, making them an inaccurate source of rotational information. Scientist were finally able to use radio emissions from Jupiter’s magnetic field to calculate the planet’s rotational period and speed. While other parts of the planet rotate at different speeds, the speed as measured by the magnetosphere is used as the official rotational speed and period.

All of the planets are oblate spheroids with varying degrees of flattening. Jupiter’s extremely fast rotation flattens it more than any other planet. The diameter of the equator is 9275 km more than the distance from pole to pole. Another interesting effect of Jupiter’s rotational speed is that, because Jupiter is not a solid body, its upper atmosphere features differential rotation. The atmosphere above the poles rotates about five minutes slower than the atmosphere at the equator.

Jupiter is almost a solar system unto itself. Many astronomers believe the the planet is simply a failed star, just lacking the mass needed to ignite fusion. Many people are aware of its four largest moons, the Galilean moons Io, Europa, Ganymede, and Callisto, but few realize that Jupiter has 50 confirmed moons and at least 14 provisional moons. The four largest moons are all very interesting to scientists. Io is a volcanic nightmare. Europa is covered in water ice and may have oceans of slushy ice underneath. Ganymede is the largest moon in the Solar System, even bigger than Mercury, and is the only moon known to have an internally generated magnetic field like Earth’s. Callisto is interesting because its surface is thought to be very ancient; perhaps original material from the birth of the Solar System.

Knowing ”how long is a day on Jupiter” just scratches the surface of the intrigue that is the Jovian system. You could spend months researching the planet and its moons, yet have more to research to do.

Here’s an article on Universe Today that shows how Jupiter can be very flattened, and an article about how the powerful windstorms are generated from its rotation.

NASA’s Ask an Astronomer also has an answer for the question, “how long is a day on Jupiter?” And a cool video of Jupiter’s rotation.

We’ve also recorded an entire show just on Jupiter for Astronomy Cast. Listen to it here, Episode 56: Jupiter, and Episode 57: Jupiter’s Moons.

Sources:
NASA
Caltech Cool Cosmos

Posted on by Nancy Atkinson

New Radio Telescope to Help SETI Scan Unexplored Frequencies for Extraterrestrials

Since the 1960’s astronomers have been scanning the heavens, searching for radio signals beamed towards the vicinity of Earth by other intelligent beings. But so far, no ET signals have been found. However, no radio telescope has been able to search the very low frequency radio spectrum, which could possibly include “leakage” of extraterrestrial “everyday” signals that a distant civilization might emit, such as television and radio signals. But a new radio telescope called LOFAR (the Low Frequency Array), will have that ability. Currently being built by ASTRON, (the Netherlands Foundation for Research in Astronomy), LOFAR consists of about 25,000 small antennas that will receive signals from space, and offers the ability to search these low-frequency type of radio waves.

According to Professor Michael Garrett, General Director of ASTRON, LOFAR is well suited to SETI research. “LOFAR can extend the search for extra-terrestrial intelligence to an entirely unexplored part of the low-frequency radio spectrum, an area that is heavily used for civil and military communications here on Earth. In addition, LOFAR can survey large areas of the sky simultaneously – an important advantage if SETI signals are rare or transient in nature.”

Astronomers believe of the approximately 100 thousand million stars in the galaxy, most of these have planetary systems. Some of these planets might actually be suitable for life and many scientists believe that life is probably wide-spread across the galaxy. However, technically advanced civilizations might be relatively rare or at least widely separated from each other.

Despite the huge distances between stars, the next generation of radio telescopes, such as LOFAR, begin to offer the possibility of detecting radio signals associated with extraterrestrial radio and TV transmitters.

Dan Werthimer, a SETI@home project Scientist at the University of Berkeley said, “SETI searches are still only scratching the surface, we need to use as many different telescopes, techniques and strategies as possible, in order to maximize our chances of success.”

Professor Garrett thinks it is high time European scientists began to support their colleagues from the United States in this exciting area of research. “I cannot think of a more important question humanity can ask and perhaps now answer. Are we truly alone in the Universe or are there other civilizations out there waiting to be discovered? Either way, the implications are tremendous.”

LOFAR will begin its scans of low frequency radio waves when the array is completed in 2009.

Original News Source: ASTRON