October 21, 1999
2 min read
I have heard people call Jupiter a "failed star" that just did not get big enough to shine. Does that make our sun a kind of double star? And why didn't Jupiter become a real star?
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."
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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.
FAQs
"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.
Why do people say Jupiter is a failed star? ›
It may be the biggest planet in our Solar System but it would still need more mass to turn into a second Sun. Jupiter is often called a 'failed star' because, although it is mostly hydrogen like most normal stars, it is not massive enough to commence thermonuclear reactions in its core and thus become a 'real star'.
Why doesn't Jupiter become a star? ›
Jupiter took most of the mass left over after the formation of the Sun, ending up with more than twice the combined material of the other bodies in the solar system. In fact, Jupiter has the same ingredients as a star, but it did not grow massive enough to ignite.
Could Jupiter become a star if it was bigger? ›
Jupiter, while more massive than any other planet in our solar system, is still far too underweight to fuse hydrogen into helium. The planet would need to weigh 13 times its current mass to become a brown dwarf, and about 83 to 85 times its mass to become a low-mass star.
What is the name for a failed star something that doesn t quite have enough mass to sustain fusion in the core but is more massive than a jovian planet? ›
The true failed stars
These are the brown dwarfs, and they fill that gap between gas giants and stars. Starting at over about 13 times the mass of Jupiter, these objects are massive enough to support core fusion - not of normal hydrogen, but deuterium.
What is a failed star called? ›
Brown dwarfs are sometimes called failed stars, since they form like stars through gravitational collapse, but never gain enough mass to ignite nuclear fusion. The smallest brown dwarfs can overlap in mass with giant planets.
What if Jupiter suddenly became a star? ›
In the best case scenario Earth's atmosphere will be stripped away and its surface will be turned to a molten, hostile lava. In the worst case, the entire planet will be consumed and vaporized by our once-reliable star. But we won't have to wait 5 billion years to run into stellar trouble.
How long is the Sun expected to last? ›
Eventually, the fuel of the sun - hydrogen - will run out. When this happens, the sun will begin to die. But don't worry, this should not happen for about 5 billion years. After the hydrogen runs out, there will be a period of 2-3 billion years whereby the sun will go through the phases of star death.
Which is bigger, Sun or Jupiter? ›
The sun is ten times bigger than Jupiter. This is the required solution. Note: The Jupiter is the biggest planet in the solar system followed by Saturn, Uranus and Neptune.
Is Jupiter getting bigger? ›
Since these atoms become neutrally charged, they can easily escape Jupiter's magnetic field and float off into space. This slow but constant loss of mass from Jupiter's atmosphere is actually greater than the gain in mass from collisions so, overall, Jupiter is shrinking not growing in mass.
Venus is sometimes called Earth's twin because Venus and Earth are almost the same size, have about the same mass (they weigh about the same), and have a very similar composition (are made of the same material).
Will Jupiter's storm ever end? ›
No one knows for sure. Some research has hypothesized that the spot could disappear in a few decades, but because researchers don't fully understand how and why the spot is changing, it may also last for much longer, possibly many centuries.
Could Jupiter ever ignite? ›
Objects less massive than that can never achieve the core temperatures required for thermonuclear reactions. This corresponds to about 13 times the mass of Jupiter, meaning that Jupiter itself is incapable of ever 'igniting'.
Is Jupiter really a failed star? ›
Jupiter isn't a star
Jupiter is called a failed star because it contains the same gases as the Sun (hydrogen and helium). However, it is not as big as the Sun. Jupiter is lightweight compared to the Sun.
How big is Jupiter without gas? ›
Jupiter's density is 1.33 g/cm³, so 4.14 times less. It's diameter is 140000km, give or take. Radius 70000 km. Jupiter's new radius, while having Earth's density, would be 43750 km, diameter 87500 km.
Is Jupiter A Fallen star? ›
"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.
Why is Saturn a failed star? ›
It got large enough that it could pull down a significant amount of hydrogen and helium through sheer force of gravitational will, but not enough that it could kick that process into overdrive and really get going. So for all intents and purposes, Saturn is a failed gas giant, Helled says.
What does a negative Jupiter mean? ›
Jupiter, or Guru, plays a pivotal role in astrology, symbolizing wisdom and luck. A strong Jupiter brings prosperity and good fortune, but a weak one can lead to challenges such as laziness and health issues.
Are all gas giants failed stars? ›
An isolated gas giant is probably a failed star. A failed star has such a low mass that its core never gets hot enough to fuse hydrogen, although it might fuse other elements like lithium and deuterium. A planet has an even lower mass and thus never fuses anything.
