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We're Talking Moons

The Solar System >

Tiny Mercury is happy with none. So is our bachelorette neighbor Venus. Our own planet has always been satisfied with just one. And macho Mars has pleasantly coexisted with its two feeble sycophants, Phobos and Deimos.

We're talking of moons, of course.

But those gas giants! They apparently have some obsessive desire to be surrounded by many, many moons. Whereas in the days of old we were taught in school that Jupiter and Saturn were surrounded by a mere brood of satellites --- just over a dozen each --- nowadays it seems they have a whole hive of hangers-on.

In only the last several years the moon total for Saturn has climbed to 31 and Jupiter's has skyrocketed to 39, with eleven of those found in just the last six months.

Now of course Jupiter and Saturn have always had those little guys buzzing around, but only recently have we had instruments sensitive enough to finally see them ourselves.

Galileo was first to peer through a telescope four centuries ago and see four star-like bodies actually orbiting Jupiter --- a complete and pleasant surprise back then. These are even today called the Galilean satellites in his honor.

As telescopes got bigger and better, satellite discoveries grew and grew. But with the introduction of charged-coupled devices, CCDs, things have changed dramatically.

These instruments are hypersensitive to light and, hooked up to a scope, can catch radiation from extremely faint objects out in space. It is with these that astronomers have been able to discover all those extra satellites.

Having nearly 40 moons doesn't mean that people living above the thick jovian clouds would feel they're always being mooned. Yes, the Galilean satellites are pretty weighty and close to Jupiter, not unlike our own Moon is to us. But the ones being discovered nowadays by the handful are miniature versions of Galileo's Quartet and very, very much further away.

Let's put things in perspective: Our Moon is over 2000 miles across, and is, on average, 240,000 miles away. These newfound satellites around Jupiter are 1000 times smaller (just a couple miles across) and 50 times further (over 12 million miles away). That, my friends, is a hard rock to pick up. Imagine looking for a golfball-sized dirt clod 180 miles away!

Because of their wacky, highly elliptical orbits, astronomers believe these little moons were probably not formed with Jupiter; they are most likely solar system debris captured early on by a more swollen, infantile Jupiter. In fact it is probable that a lot of Jupiter's and Saturn's satellites were just big rocks captured into orbit by the gas giants' intense gravities.

It is now thought that there may be over 100 of these little guys orbiting Jupiter; that it's just a matter now of finding them. Jupiter may get a big head out of all this and think that he's a record holder for Most Satellites. It would do Jupiter good to think twice before making that claim.

Saturn would be the record holder here. That spectacular ring system is composed of pieces of water ice, from baseball- to truck-sized. And the system is not just a couple hundreds of snowballs, oh no, but billions of them. And though small, they are all, by all rights, Saturn's satellites.

In my next column we'll dwell on our own Moon and examine in detail the Big Eclipse of 2002 --- what it is and how to watch it. Until next time, clear skies!

Mark Ritter can be reached here.

Posted by Administrator at 2002.05.25 02:54 PM | Comments (0)

The Most Massive Star Known

The Universe >

The Guinness Book of Universal Records has a new entry! The record setter's name: R136-38. The record: The most massive star known.

Admittedly, for most people this news is about as exciting as counting craters. But for astronomers, it is necessary information to help work out the details on just how big stars are born, live, and eventually die.

R136-38 is a star located in the Large Magellanic Cloud (LMC). The LMC is an irregular galaxy about 170,000 light years from us, a stone's throw away, just on the outskirts of our own Milky Way Galaxy.

Within the LMC lies a monstrous stellar nursery called the Tarantula Nebula (pictured). It is there, within this spider's web of gas and dust, that one can easily find a young star cluster on steroids with the mundane moniker of R136. And it is within this star cluster that astronomers have found our heavyweight champ with a name lifted right out of the Star Wars Book of Names --- R136-38.

For the record, R136-38 weighs in at a hefty 57 solar masses. One solar mass is the mass of the Sol, our sun. Fifty-seven of our suns add up to about 100,000 trillion trillion metric tons of hydrogen and helium; all in one star! That's a lot of sol, and enough gas to fill balloons for an eternity of birthday parties.

The problem with such a monster is that even though it may act the big bully on the street, its days are severely numbered. Sure, it will blow away surrounding dust and gas for trillions of miles and prevent neighboring stars from starting their own solar systems. And yes, it will be the brightest stellar object for lightyears around. But with this life in the fast lane comes a quick finale.

The big tradeoff in being a big star is this: You can't even go to the store without someone begging for an autograph! Sorry, wrong star. The trouble is that all that mass translates into a lot of gravity. All that gravity crushes the core to such incredible temperatures that it burns its fuel prodigiously. And when the core runs out of fuel after just millions of years --- just the twinkling of an eye in the cosmos --- it can't produce enough pressure to push the giant star outwards anymore. Long-patient gravity has the last say and collapse! --- the whole core implodes.

This leads, via a complicated and not-too-well-understood set of events, to a supernova explosion. It's bye-bye big guy.

These types of stars, the big ones, aren't exactly all over the place; they live and die so quickly. So it's a good thing for astronomy that astronomers are getting an accurate handle on their masses. It's just another puzzle piece that helps us see the Big Picture of the life and death of big stars.

And you think R136-38 is big? There are undoubtedly bigger ones. One prime suspect is eta Carina, also in the LMC. It's estimated that she weighs in at nearly 100 solar masses, at about the biggest a star can get, theoretically. But she is so unstable and is in such death throes that it's hard to nail down an accurate mass which would help us more deeply understand what's going on there.

Kind of makes you appreciate the relative dullness of our own star, doesn't it?

Until next time, clear skies!

Mark Ritter is a big star in his own mind and can be reached here.

Posted by Administrator at 2002.05.11 02:56 PM | Comments (0)



Looking for something?	« April 2002 \| Main \| June 2002 » We're Talking Moons The Solar System > Tiny Mercury is happy with none. So is our bachelorette neighbor Venus. Our own planet has always been satisfied with just one. And macho Mars has pleasantly coexisted with its two feeble sycophants, Phobos and Deimos. We're talking of moons, of course. But those gas giants! They apparently have some obsessive desire to be surrounded by many, many moons. Whereas in the days of old we were taught in school that Jupiter and Saturn were surrounded by a mere brood of satellites --- just over a dozen each --- nowadays it seems they have a whole hive of hangers-on. In only the last several years the moon total for Saturn has climbed to 31 and Jupiter's has skyrocketed to 39, with eleven of those found in just the last six months. Now of course Jupiter and Saturn have always had those little guys buzzing around, but only recently have we had instruments sensitive enough to finally see them ourselves. Galileo was first to peer through a telescope four centuries ago and see four star-like bodies actually orbiting Jupiter --- a complete and pleasant surprise back then. These are even today called the Galilean satellites in his honor. As telescopes got bigger and better, satellite discoveries grew and grew. But with the introduction of charged-coupled devices, CCDs, things have changed dramatically. These instruments are hypersensitive to light and, hooked up to a scope, can catch radiation from extremely faint objects out in space. It is with these that astronomers have been able to discover all those extra satellites. Having nearly 40 moons doesn't mean that people living above the thick jovian clouds would feel they're always being mooned. Yes, the Galilean satellites are pretty weighty and close to Jupiter, not unlike our own Moon is to us. But the ones being discovered nowadays by the handful are miniature versions of Galileo's Quartet and very, very much further away. Let's put things in perspective: Our Moon is over 2000 miles across, and is, on average, 240,000 miles away. These newfound satellites around Jupiter are 1000 times smaller (just a couple miles across) and 50 times further (over 12 million miles away). That, my friends, is a hard rock to pick up. Imagine looking for a golfball-sized dirt clod 180 miles away! Because of their wacky, highly elliptical orbits, astronomers believe these little moons were probably not formed with Jupiter; they are most likely solar system debris captured early on by a more swollen, infantile Jupiter. In fact it is probable that a lot of Jupiter's and Saturn's satellites were just big rocks captured into orbit by the gas giants' intense gravities. It is now thought that there may be over 100 of these little guys orbiting Jupiter; that it's just a matter now of finding them. Jupiter may get a big head out of all this and think that he's a record holder for Most Satellites. It would do Jupiter good to think twice before making that claim. Saturn would be the record holder here. That spectacular ring system is composed of pieces of water ice, from baseball- to truck-sized. And the system is not just a couple hundreds of snowballs, oh no, but billions of them. And though small, they are all, by all rights, Saturn's satellites. In my next column we'll dwell on our own Moon and examine in detail the Big Eclipse of 2002 --- what it is and how to watch it. Until next time, clear skies! Mark Ritter can be reached here. Posted by Administrator at 2002.05.25 02:54 PM \| Comments (0) The Most Massive Star Known The Universe > The Guinness Book of Universal Records has a new entry! The record setter's name: R136-38. The record: The most massive star known. Admittedly, for most people this news is about as exciting as counting craters. But for astronomers, it is necessary information to help work out the details on just how big stars are born, live, and eventually die. R136-38 is a star located in the Large Magellanic Cloud (LMC). The LMC is an irregular galaxy about 170,000 light years from us, a stone's throw away, just on the outskirts of our own Milky Way Galaxy. Within the LMC lies a monstrous stellar nursery called the Tarantula Nebula (pictured). It is there, within this spider's web of gas and dust, that one can easily find a young star cluster on steroids with the mundane moniker of R136. And it is within this star cluster that astronomers have found our heavyweight champ with a name lifted right out of the Star Wars Book of Names --- R136-38. For the record, R136-38 weighs in at a hefty 57 solar masses. One solar mass is the mass of the Sol, our sun. Fifty-seven of our suns add up to about 100,000 trillion trillion metric tons of hydrogen and helium; all in one star! That's a lot of sol, and enough gas to fill balloons for an eternity of birthday parties. The problem with such a monster is that even though it may act the big bully on the street, its days are severely numbered. Sure, it will blow away surrounding dust and gas for trillions of miles and prevent neighboring stars from starting their own solar systems. And yes, it will be the brightest stellar object for lightyears around. But with this life in the fast lane comes a quick finale. The big tradeoff in being a big star is this: You can't even go to the store without someone begging for an autograph! Sorry, wrong star. The trouble is that all that mass translates into a lot of gravity. All that gravity crushes the core to such incredible temperatures that it burns its fuel prodigiously. And when the core runs out of fuel after just millions of years --- just the twinkling of an eye in the cosmos --- it can't produce enough pressure to push the giant star outwards anymore. Long-patient gravity has the last say and collapse! --- the whole core implodes. This leads, via a complicated and not-too-well-understood set of events, to a supernova explosion. It's bye-bye big guy. These types of stars, the big ones, aren't exactly all over the place; they live and die so quickly. So it's a good thing for astronomy that astronomers are getting an accurate handle on their masses. It's just another puzzle piece that helps us see the Big Picture of the life and death of big stars. And you think R136-38 is big? There are undoubtedly bigger ones. One prime suspect is eta Carina, also in the LMC. It's estimated that she weighs in at nearly 100 solar masses, at about the biggest a star can get, theoretically. But she is so unstable and is in such death throes that it's hard to nail down an accurate mass which would help us more deeply understand what's going on there. Kind of makes you appreciate the relative dullness of our own star, doesn't it? Until next time, clear skies! Mark Ritter is a big star in his own mind and can be reached here. Posted by Administrator at 2002.05.11 02:56 PM \| Comments (0)
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