What indeed is the difference between a big planet and a small star? The recent discovery of massive planets around other stars has aroused a lot of debate on this very point. Alan P. Boss of the Carnegie Institution of Washington is one of the theorists trying to clarify which bodies qualify as planets and which as so-called "brown dwarfs"-objects smaller than stars but fundamentally unlike planets. He answers the question as follows:
"Nearly all scientists who study the formation of planets believe that Jupiter formed in a very different manner than stars form, so that calling Jupiter a 'failed star' is misleading. Stars form directly from the collapse of dense clouds of interstellar gas and dust. Because of rotation, these clouds form flattened disks that surround the central, growing stars. After the star has nearly reached its final mass, by accreting gas from the disk, the leftover matter in the disk is free to form planets.
"Jupiter is generally believed to have formed in a two-step process. First, a vast swarm of ice and rock 'planetesimals' formed. These comet-sized bodies collided and accumulated into ever-larger planetary embryos. Once an embryo became about as massive as ten Earths, its self-gravity became strong enough to pull in gas directly from the disk. During this second step, the proto-Jupiter gained most of its present mass (a total of 318 times the mass of the Earth). Soon thereafter, the disk gas was removed by the intense early solar wind, before Saturn could grow to a similar size."
Boss explains further that brown dwarfs may look like planets but they form like stars--that is, they collapse directly from a gas cloud, rather than building up in the disk around a star. Brown dwarfs lack sufficient mass to shine, so they might more fairly be described as "failed stars."
Alex Rudolph of the physics department at Harvey Mudd College expands on this important point:
"Jupiter is called a failed star because it is made of the same elements (hydrogen and helium) as is the Sun, but it is not massive enough to have the internal pressure and temperature necessary to cause hydrogen to fuse to helium, the energy source that powers the sun and most other stars.
"However, Jupiter has only about 0.1 percent the mass of the sun, and as it is definitely not a star, we can't really call the solar system a double star. It is interesting to note, however, that more than half of all stars in the sky are part of a binary, triple, or higher multiple star system (binaries being the most common). So the Sun is unusual in being a loner.
"As for why Jupiter failed to become a star--it probably had to do with the accident of the sun grabbing most of the mass early in the formation of the solar system, while in other systems the mass was more equitably distributed; in binary star systems, for example, the masses of the stars are commonly roughly equal. Stellar formation is a hot topic of current research, as astronomers are trying to fathom the still-mysterious details of the birth process.
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10 Comments
Add Commentwill we be eventuly able to move to venus if we put like 100 thousand tonnes of algae on it
Reply | Report Abuse | Link to thisJUPITER MIGHT BE A STAR THAT DIED BEFORE IT STARTED TO SHINE AND MAYBE THE SUN IS A DOUBLE STAR U NEVER KNOW
Reply | Report Abuse | Link to thishey u cant just say it isn't a star maybe it is we dont know yet but i hope we get to figure it out soon because it is really interesting!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! maybe it is a star just heating up
Reply | Report Abuse | Link to thisOk, firstly none of you know anything about astrology or have apparently studied astronomy. If Jupiter was indeed a star previously in it's life. It would have been of very small mass and would be need a lot more hydrogen to be even a brown dwarf. Due to it's size it would be able to live for billions of years and out live Sol, our yellow sun. And once it died it would collapse on itself creating a very dense white star. Since it's apparent that Jupiter isn't a star or a high dense miniature star. Jupiter also isn't a very small star heating up, it would require a HUGE amount of hydrogen and helium to reach the status of a star (as I previously stated). The only remote way Jupiter could become a star is if a large cloud of the 1st two elements got trapped in it's gravitational pull. The only place that could logically come from would be the sun and if it began to die. While on it's last legs our Sun would expand to make Jupiter it's nearest planet and even then it's solar winds would blast away Jupiter's already small amount of Hydrogen and Helium. So no, it's not a star. It's a gas giant people. It's also very safe to safe it will never "heat up" and become a star
Reply | Report Abuse | Link to thisThoroughly useful and extremely lucid. Hard to improve upon indeed!
Reply | Report Abuse | Link to thisHow are you sure it will never "heat up" our universe is unperdictable anything could happen I love how sciencetist say stuff like the coldest place in the Uni* is (blah blah) How in the hell do they know there is so much we don't know i mean were on earth saying things i mean okay have you been to jupiter? im pretty sure u haven't and there is only so much our satelites can tell so,....its could "heat Up"....Im only 14 so i dont know much but im interst is Atronomy and jupiter is my fav planet!
Reply | Report Abuse | Link to thisI just wanna put this out there - All of you people saying that it "just heating up maybe" or that it become a star, your fucking stupid. A star is formed by immense amounts of gravity fusing hydrogen and helium together to burn at very high heats. JUPITER ISNT NEARLY BIGGER ENOUGH AND IF YOU THINK ITS "a star heating up" YOUR FUCKING STUPID. JUPITER IS NOT A FAILED STAR ITS JUST A LARGE PLANET.
Reply | Report Abuse | Link to thisif people would actually read the damn post, you would have noticed that Jupiter has the mass of about 0.1% of our Sun. That being coupled with the fact that our sun is relatively small means that there is NO chance that Jupiter will ever become a star.
Reply | Report Abuse | Link to thisRead a book, you stupid prats.
Yours,
A British person with a grasp is space
PS: Scientific America my arse with comments like most of the above.
your comment here is the only one with actual relevance. How are people so stupid?
Reply | Report Abuse | Link to thisPerhaps instead of logging on to Scientific American, you should log on to Scientific Whining Limey. Oh wait, there isn't a magazine with that name. You should get to work on that, write what you know I always say. Believe it or not, it is possible to educate or relay information to someone without sounding like a pretentious snob or a 12 year old brat with a broken caps lock button. People aren't stupid, just a little uninformed which is why they looked up a question they had in the first place and there's nothing wrong with the pursuit of knowledge. Any attempt to do so shouldn't be ridiculed with insults and prepubescent Nerd rage.
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