http://www.universetoday.com/guide-to-s ... -of-stars/
The least massive stars in the Universe are the red dwarf stars. These are stars with less than 50% the mass of the Sun, and they can be as small as 7.5% the mass of the Sun. This tiny mass is the minimum amount of gravitational force you need for a star to be able to raise the temperature in its core to the point that nuclear fusion can begin. If an object is less than this 7.5%, or about 80 times the mass of Jupiter, it can never get going; astronomers call these failed stars brown dwarfs. Instead of having nuclear fusion in their cores, brown dwarfs are heated by the gravitational friction of their ongoing collapse.
gary19702 wrote:firstly, how much would it possibly take to turn jupiter OR saturn for that fact, into suns? I'm not quite sure tht the entire nuclear arsenal on earth could acomplish such a thing, remember, these are two enormous gasious bodies, and even then if it is acomplished what gravitational havoc would ensue? certain death for life as we know it on earth.
This guy has a good point !
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.
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."
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.
= Since Dawn Of Time The Fate Of Man Is That Of Lice =
torofamily wrote:Lucifer Instrument Helps Astronomers See Through Darkness to Most Distant Observable Objects
By Rebecca Boyle Posted 04.23.2010
No, those aren't horns in the upper right
Courtesy of Lucifer This image depicts a stellar nursery in the Milky Way about 8,000 light years from Earth. Such clouds are typically opaque to visible light, but infrared light can penetrate them. The Lucifer instrument helps telescopes see that light. The E and N signify east and north. Anna Pasquali/via University of Arizona
A new instrument with an evil-sounding name is helping scientists see how stars are born. Lucifer, which stands for (deep breath) "Large Binocular Telescope Near-infrared Utility with Camera and Integral Field Unit for Extragalactic Research," is a chilled instrument attached to a telescope in Arizona. And yes, it's named for the Devil, whose name itself means "morning star." But it wasn't meant to evoke him, according to a spokesman for the University of Arizona, where it is housed.
The instrument is chilled to -213 Celsius, about -351 F, to allow for near-infrared observations. That wavelength is important for understanding star and planet formation, as well as observing very distant and very young galaxies. Lucifer has three interchangeable cameras for imaging and spectroscopy in different resolutions. It has a large field of view and high-res capabilities, which allow a wide range of observations.
Lucifer is part of the Large Binocular Telescope, which happens to be right next to the Vatican Observatory on Mt. Graham in Tucson. That's right, the Vatican has an observatory in Arizona, manned by Jesuit astronomers. Now its next-door neighbor is named for the Devil.
Scientists at five German universities designed the instrument, and they came up with the name, according to Daniel Stolte, a spokesman for the University of Arizona. Stolte -- who is German -- explained that the team was tossing around names, looking for an acronym that would fit all the technical terms.
"In Germany, they wouldn't have the same hesitation that Americans would have, since it's a very secular country," he said. "I may be completely off, but that's just my hunch -- for us Germans, Lucifer just sounds cool. It's more historical than emotional." No matter your religion, the photos are certainly cool.
Write your Congressman:
The American people vote once every 4 years and recycle and think they are politically correct, its the other 1459 days that f#&k us.
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