Posted on by Jerry Coffey

Mass of Jupiter

Jupiter and its moons. Image credit: NASA/JPL

The mass of Jupiter is 1.9 x 1027 kg. It is hard to fully understand a number that large, so here are a few comparisons to help. It would take 318 times Earth’s mass to equal Jupiter’s. Jupiter is 2.5 times more massive than all of the other planets in our Solar System combined. Jupiter is actually so massive that if it gained much more mass it would shrink.

How can additional mass cause a planet to shrink? Gravitational compression. Given that there is no more hydrogen or helium gas floating around for Jupiter to collect, it would gain mass through the accretion of rocky bodies like asteroids. Jupiter’s intense gravity would pull additional rock tightly together shrinking the diameter of the planet and increasing its density. As the density increased so would the gravity, further compressing the planet. Scientists estimate that Jupiter would have to accumulate 3-4 times its current mass in order to begin compressing. Since there isn’t that much material in our Solar System, it is a pretty good bet that Jupiter will never shrink.

But what if it did? There have been rumors floating around for decades that Jupiter could ignite fusion and become a star at any time. They are all false science and garbage at best. The mass of Jupiter is no where near enough for sustained nuclear fusion. Fusion requires high temperatures, intense gravitational compression, and fuel. Jupiter has the right fuels in abundance. There is plenty of hydrogen to be had, but the planet is too cold and lacks the density for a sustained reaction process. Scientists estimate that Jupiter needs 50-80 times its current mass to ignite fusion. As stated in the paragraph above, there isn’t enough material to be had, so Jupiter can not become a star.

At one time, scientists thought that Jupiter was the largest that a planet could become without igniting fusion and becoming a star. They discovered the fallacy of that belief once technology expanded their view of the universe. According to Dr. Sean Raymond, a post doctoral researcher at the Center for Astrophysics and Space Astronomy (CASA) at the University of Colorado, ”In terms of gaseous planets, once they reach 15 Jupiter masses or so there is enough pressure in the core to ignite deuterium fusion, so those are considered ‘brown dwarfs’ rather than planets.”

As you can see, the mass of Jupiter may seem awesome in comparison to Earth, it is a tiny fish in a world of sharks. Scientists have found a few hundred gas giants larger than Jupiter as they have surveyed the night sky. Who knows what is in store as telescope technology improves in the coming years.

Here’s an article from Universe Today explaining just how big planets can get, and an article about how Jupiter and the other gas giants might have gobbled up their moons while they were forming.

This site has more detailed information about the mass of Jupiter, and a page from NASA that helps you calculate the density of the planets.

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
http://planetquest.jpl.nasa.gov/news/tres4.cfm

Posted on by Nancy Atkinson

Just in Time for Summer: The Milky Way Loses Weight

The Milky Way and its dark matter halo. Image credit: Sloan Digital Sky Survey

Have you ever been surprised at your annual weigh-in at the doctor’s office to find that your bathroom scale at home was wrong? Or, bought a new scale that had a difference of opinion with your old one? That’s what has happened with our very own Galaxy, the Milky Way. “The Galaxy is slimmer than we thought,” said Xiangxiang Xue of the Max Planck Institute for Astronomy in Germany and the National Astronomical Observatories of China, who lead a research team using the Sloan Digital Survey to measure the mass of the stars in the galaxy. “We were quite surprised by this result,” said Donald Schneider, a member of the research team, from Penn State. The researchers explained that it wasn’t a Galactic diet that accounted for the galaxy’s recent slimming, but a more accurate scale.

The researchers used the motions of distant stars to make the new determination of the Milky Way’s mass. They measured the motions of 2,400 “blue horizontal branch” stars in the extended stellar halo that surrounds the disk of the galaxy. These measurements reach distances of nearly 200,000 light years from the Galactic center, roughly the edge of the region illustrated in the image above. Our Sun lies about 25,000 light years from the center of the Galaxy, roughly halfway out in the Galactic disk. From the speeds of these stars, the researchers were able to estimate much better the mass of the Milky Way’s dark-matter halo, which they found to be much ‘slimmer’ than thought before.

The discovery is based on data from the project known as SEGUE (Sloan Extension for Galactic Understanding and Exploration), an enormous survey of stars in the Milky Way. Using SEGUE measurements of stellar velocities in the outer Milky Way, a region known as the stellar halo, the researchers determined the mass of the Galaxy by inferring the amount of gravity required to keep the stars in orbit. Some of that gravity comes from the Milky Way stars themselves, but most of it comes the distribution of invisible dark matter, which is still not fully understood.

The most recent previous studies of the mass of the Milky Way used mixed samples of 50 to 500 objects. They implied masses up to two-trillion times the mass of the Sun for the total mass of the Galaxy. By contrast, when the SDSS-II measurement within 180,000 light years is corrected to a total-mass measurement, it yields a value slightly under one-trillion times the mass of the Sun.

“The enormous size of SEGUE gives us a huge statistical advantage,” said Hans-Walter Rix, director of the Max Planck Institute for Astronomy. “We can select a uniform set of tracers, and the large sample of stars allows us to calibrate our method against realistic computer simulations of the Galaxy.” Another collaborator, Timothy Beers of Michigan State University, explained, “The total mass of the Galaxy is hard to measure because we’re stuck in the middle of it. But it is the single most fundamental number we have to know if we want to understand how the Milky Way formed or to compare it to distant galaxies that we see from the outside.”

All SDSS-II observations are made from the 2.5-meter telescope at Apache Point Observatory in New Mexico. The telescope uses a mosaic digital camera to image large areas of sky and spectrographs fed by 640 optical fibers to measure light from individual stars, galaxies, and quasars. SEGUE’s stellar spectra turn flat sky maps into multi-dimensional views of the Milky Way, Beers said, by providing distances, velocities, and chemical compositions of hundreds of thousands of stars.

Source: Penn State, arXiv

Posted on by Jerry Coffey

Is There Life on Jupiter?

As an avid reader, I have come across many books that proposed the idea of life on Jupiter. Some even proposed that Jupiter is lifeless, but its moons harbor advanced life forms. Is there life on Jupiter? While there have been no samples taken that could test for microscopic life on the planet, there is quite a bit of compelling evidence that shows there is no possible way for life as we know it to exist anywhere on the planet. Try this link for one scientist’s take on finding life in the cosmos.

First, let’s look at the conditions on Jupiter that preclude the existence of life. The planet is a gas giant composed mainly of hydrogen and helium. There is virtually no water to support known life forms. The planet does not have a solid surface for life to develop anywhere except as a floating microscopic organism.

Free floating organisms could only exist at the very tops of the clouds due to atmospheric pressure that is progressively more intense than anything seen on Earth. While the cloud tops could harbor life that is resistant to solar radiation, the atmosphere is in constant chaos. Convection forces the lower atmosphere upwards and colder areas of the atmosphere are constantly being sucked closer to the core. The churning would eventually expose any organisms to the extreme pressures nearer the core, thus killing any that may develop.

Should an organism find a way to resist atmospheric pressure that reaches 1,000 times what it is here on Earth, there are the temperatures close to the planet’s core. Gravitational compression has heated areas near the core to over 10,000 degrees Celsius. It is so hot in some areas that hydrogen is in a liquid metallic state. While organisms on Earth live in areas near volcanoes, the temperatures there do not approach Jovian levels.

Jupiter is completely inhospitable to life as we understand it, but its moon Europa has been proposed as a possible habitable zone. It is thought to have a large amount of water ice on its surface. Some of which covers a proposed ocean of water slush. The conditions under the water ice could be harboring microscopic life according to some scientists.

The question ”is there life on Jupiter” seems pretty well decided. There is no way that life as we understand it could exist on the gas giant. The possibility of life within the Jovian system is still being explored. Some debate exists about Europa. NASA’s Jupiter Icy Moons Orbiter was set to answer those questions before it was canceled. Hopefully, another mission like it will be launched soon and end all of the debate.

Here’s an article about the search for life on Europa. Not so fast, though. Here’s an article about how Europa might be corrosive to life.

Here’s a classic article from Time Magazine in 1961 about the possibilities of life on Jupiter, and the search for life on Jupiter’s moon Europa.

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://www.nasa.gov/vision/universe/starsgalaxies/frozenworlds.html
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jup_Europa
NASA Jimo MIssion

Posted on by Ian O'Neill

Seals Use Astronomy as Navigation Aid

A baby Harp Seal, looking upward (Care2.com)

Yes, we’ve heard bees use the Earth’s magnetic field to navigate by. We’ve also heard about some bird species following the Sun to find the location of their evening roost. But what do we know about the animals living at sea? Do they use astronomical aids to help them find their way around the planet? Mammals such as whales are known to exhibit “skyhopping” behaviour when they surface from the water to have a look around, but seals go one step further; they can recognise and orientate themselves with the stars…

It was one of the first methods us humans used for navigation when sailing across the middle of a featureless ocean, we’d pick out known stars and constellations and relate them to our location on the planet’s surface. Explorers used astronomy to guide them to new lands, captains used the stars to direct their battleships toward the enemy and trade routes were repeatedly used thanks to star navigation. In its most basic form, star navigation could be carried out by linking stars with the location on the horizon when they rise, as was traditionally done by Polynesian sailors to colonize vast numbers of islands in the Pacific.

In a revealing study, researchers at the University of Southern Denmark in Odense have discovered that seals have the ability to recognise stars and groups of stars inside a modified planetarium. A five-metre round pool plus two harbour seals were covered with a dome with 6000 point light sources to simulate the Northern Hemisphere’s starry sky. Björn Mauck and his team found that if they selected an individual star with a laser pointer, they could train the seals to swim toward that star and then rewarded them with a treat if they did it correctly. Then the researchers would randomly orientate the dome, and without the help of a laser pointer, the seals would continue to swim toward the correct star.

“Seals and many other animals are exposed to the starry sky every clear night, and thus certainly have sufficient opportunities to learn the patterns of stars.” – Björn Mauck

This study strongly suggests that these two harbour seals have an amazing, natural ability to recognise the distribution of stars on a clear night.

So when you next see a seal popping to the ocean surface, it might not be simply checking out its surroundings, it might be trying to look for Sirius in the constellation of Canis Major…

Paper abstract: “Harbour seals (Phoca vitulina) can steer by the stars“, Mauck et al., 2008
Source: New Scientist

Posted on by Jerry Coffey

Orbit of Jupiter

Orbit of the planets. Image credit: NASA/JPL

The orbit of Jupiter, like that of all the planets, is elliptical instead of circular. At perihelion(closest approach) Jupiter comes within 741 million km, or 4.95 astronomical units(AU), of the Sun. An astronomical unit is the average distance from the Earth to the Sun and is used to make astronomical distances easier to communicate. At its most distant point, called aphelion, Jupiter is 817 million km, or 5.46 AU from the Sun. The average between perihelion and aphelion is called the semi-major axis. Jupiter’s semi-major axis is 778 million km, or 5.2 AU.

Jupiter is the fifth planet from the Sun, but it is the third brightest object in the night sky here on Earth. Since Jupiter is farther from the Sun, you would expect it to take longer to orbit, but did you know that it takes 11.86 Earth years, or 4331 Earth days for Jupiter to complete one orbit? Jupiter travels at 47,002 km/h through ts orbit. Its orbit is inclined 6.09 degrees from the the Sun’s equator. Several of the planets have seasons, similar to Earth’s, but Jupiter does not. It rotates too fast for seasonal variations(Jupiter rotates every 10 hours).

Jupiter has several companions in its orbit. By companions, I mean moons. There are 64 known moons in orbit around Jupiter with a few more being suspected. The largest four(Io, Europa, Ganymede, and Callisto) are are called the Galilean satellites. They are diverse and interesting worlds of their own. Io is the most volcanically active body in our Solar System. Europa is covered in water ice which may be covering an ocean of slushy water. Ganymede is larger than Mercury and it is the only moon in the Solar System that generates its own magnetic field. Callisto’s surface is heavily cratered and some of the larger craters may have been in place shortly after the creation of the Solar System, yet some small craters show indications of recent geologic activity. Four of Jupiter’s moons are thought to be the source of its rings. Adrastea and Metis contribute to the main ring and the halo ring. Amalthea and Thebe contribute to two separate gossamer rings.

The orbit of Jupiter is beyond comparison in our Solar System. The Jovian influence can be felt well beyond its orbit. There is so much within that orbit that scientists can make an entire career out of studying the Jovian system.

Here’s an article on Universe Today about how Jupiter might have caught one of its moons while orbiting the Sun, and more detailed information about how long a year is on Jupiter.

Here’s Hubblesite’s News Releases about Jupiter, and more information on Jupiter in NASA’s Solar System Exploration pages.

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.

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

Posted on by Jerry Coffey

Does Jupiter Have Rings

Jupiter's rings. Image Credit: University of Maryland

We all known that Saturn has rings, but does Jupiter have rings? Yes, it does. Four planets have a rings system: Saturn, Jupiter, Uranus, and Neptune. Saturn is best know because it has the brightest and most extensive rings system in the Solar System.

The rings around Jupiter had never been seen before Voyager 1 arrived in 1979. Since then the rings have been observed by the largest telescopes on Earth, the Hubble Space Telescope, and the New Horizons spacecraft. So far, only four rings have been observed: the halo ring, the main ring, the Amalthea gossamer ring, and the Thebe gossamer ring.

Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. These particles and fields comprise the Jovian magnetosphere or magnetic environment, which extends 3 to 7 million km toward the sun, and stretches in a windsock shape at least 750 million km, which puts it inside of Saturn’s orbit.

The main ring is about 7,000 km wide and has an abrupt outer boundary 129,130 km from the center of the planet. The main ring encompasses the orbits of two small moons, Adrastea and Metis, which may act as the source for the dust that makes up most of the ring. The ring needs a constant source of dust because small particles can only exist for 100 to 1000 years. The dust is thought to rise from moons within the rings due to micrometeoroid impacts. The main ring merges gradually into the Halo ring. The halo is a broad, faint torus of material about 20,000 km thick and extending halfway from the main ring down to the planet’s cloudtops.

On the outer edge of the main ring and opposite of the halo ring, is the broad and extremely faint Amalthea gossamer ring. This ring extends out beyond the orbit of the moon Amalthea. Scientists believe that it is composed of dust particles smaller than 10 microns. 10 microns is about the size of cigarette smoke particles. It extends to an outer edge of about 129,000 km from the center of the planet and inward to about 30,000 km. The origin of the ring is probably from micrometeorite bombardment of the tiny moons orbiting within the ring. Last, is the Thebe gossamer ring. This is the faintest of the Jovian rings and extended from the orbit of the moon Thebe at about 226,000 km towards the planet, ending at about 129,000 km. The exact inner edges of the two gossamer rings are hard to define because they overlap the brighter main ring.

So, the answer to ”does Jupiter have rings” is yes, it has four known rings. Be sure to read about the ring systems of Neptune and Uranus as well.

Here’s a news article from Universe Today about the rings of Jupiter, and information about New Horizon’s observations of Jupiter’s rings.

Here’s NASA’s Solar System explorer information about Jupiter’s rings, and a cool image from Astronomy Picture of the Day of Jupiter’s rings.

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.

Source:
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Rings

Posted on by Jerry Coffey

How Strong Is Jupiter’s Gravity?

Clouds on Jupiter. Image credit: NASA/JPL

Jupiter is the most massive planet in our Solar System and; therefore, the gravity of Jupiter is the most intense in the Solar System. The gravity of Jupiter is 2.5 times what it is here on Earth.

In the 1990s Jupiter’s gravity tore apart Comet P/Shoemaker-Levy 9 and pulled the broken pieces into the to planet. This marked the first time that humans had direct observation of two extraterrestrial Solar System bodies colliding. Jupiter had actually captured the asteroid between 20 and 30 years prior to impact and it had been orbiting the planet since. In 1992, the asteroid entered Jupiter’s Roche limit and was broken apart by the planet’s tidal forces. The asteroid resembled a string of pearls until its fragments impacted the surface July 16-22 of 1994. The fragments were as large as 2 km each and hit the surface at 60 km/s. The impacts allowed astronomers to make several new discoveries about Jupiter.

Astronomers found several chemicals within the Jovian atmosphere that had not been seen prior to the impacts. Diatomic sulfur and carbon disulfide were the most interesting. This was only the second time that diatomic sulfur had been detected in any astronomical object. Ammonia and hydrogen sulfide were detected for the first time on Jupiter. You can read up on other discoveries made during and shortly after these impacts by reading this article and this pdf from C.A. Olano.

Some scientists, including Jacques Laskar of the Paris Observatory, as well as Konstantin Batygin and Gregory Laughlin of the University of California, Santa Cruz believe that Jupiter’s gravity may lead to the destruction of Mercury. After running some simulations the group found that Jupiter is perturbing Mercury’s already eccentric orbit. They arrived at four possible end results: Mercury will crash into the Sun, Mercury will be ejected from the solar system altogether, Mercury will crash into Venus, or Mercury will crash into Earth. None is pleasant for Mercury and the last would be even less pleasant for humans. Not to fear though, none of these possible outcomes will happen in the next 5-7 billion years anyway.

The gravity of Jupiter affects every planet to one degree or another. It is strong enough to tear asteroids apart and capture 64 moons at least. Some scientist think that Jupiter destroyed many celestial objects in the ancient past as well as prevented other planets from forming. How’s that for a powerful neighbor?

Here’s an article from Universe Today about how Jupiter’s gravity might actually wreck the Solar System, and here’s an article about how big planets like Jupiter could get.

Use this site to calculate your weight on other worlds, and here’s more information about Comet P/Shoemaker Levy 9.

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://www2.jpl.nasa.gov/sl9/
http://adsabs.harvard.edu/full/1996EM%26P…73..147H

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 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.