Is Jupiter A Failed Star?
Jupiter and the sun are made of virtually the same stuff. Both objects are primarily composed of hydrogen and helium, along with trace amounts of various other chemicals and elements. All that separates stars from gas giants like Jupiter is the fact that stars are powered by the process of nuclear fusion, wherein hydrogen nuclei are fused together to form heavier nuclei. Any object that can sustain nuclear fusion for extended periods of time is defined as a star. In order for nuclear fusion to occur, an object must be massive enough and hot enough for individual atoms to overcome the repulsive forces between them. Jupiter is the most massive planet in the solar system, and its interior is thousands of degrees. Is there a chance that Jupiter may be a failed star?
Did Jupiter Almost Become a Star?
As was stated before, all that separates Jupiter from the sun is mass and temperature. Theoretically, if Jupiter were to increase its mass by a large enough factor, the hydrogen in its core would undergo nuclear fusion and Jupiter would become a star. However, there is no evidence in our solar system that Jupiter almost became a star. Although Jupiter is often referred to as a failed star, this is not technically true. There simply was not enough material where Jupiter formed for it to grow massive enough to become a star.
How Massive Would Jupiter Have to be?
Jupiter is the most massive planet in our solar system, yet it is still very far off from becoming a true star. Jupiter may be gigantic, yet even the sun makes it look tiny. The sun is over 1,000 times the mass of Jupiter, and so in order to become a star like our sun, Jupiter would need to increase its mass by a factor of over 1,000. However, the sun is not among the lowest mass stars in the universe. The lowest mass stars in the universe are red dwarf stars, the smallest of which is only 7.5% the mass of the sun. If Jupiter were to become a star, it is much closer in mass to a red dwarf than the sun. Jupiter would need to increase its mass by a factor of around 80 to become a small red dwarf. Interestingly, there is one stellar-type object that Jupiter is much closer in mass to. Brown dwarfs are true failed stars, and they represent the state between a planet and a star. Brown dwarfs are not small enough to be a gas giant, yet they are also not quite massive enough to become a star, either. Brown dwarfs range from 15 Jupiter masses to 75 Jupiter masses. Around 80 Jupiter masses is when a brown dwarf becomes a red dwarf. If anything, Jupiter is closer to being a failed brown dwarf than it is a failed star.
