Why Isn't Jupiter a Star?

The smallest star in the main-sequence is a real thing.

It is a red dwarf 600 light-years away. It is the smallest known star to support hydrogen fusion in its core, the process that keeps stars burning until they run out of fuel.

There are two objects larger than this star in our Solar System. The Sun is one of them. Jupiter is a giant scoop of ice cream with a mean radius of 69,911 kilometers.

Jupiter is not a star.

The short answer is that Jupiter doesn't have enough mass. If it were any lower, it wouldn't be able to make hydrogen and light up the sky. Jupiter could have exploded into a star if our Solar System had been different.

Jupiter and the Sun are more alike than you know

Jupiter is still a big deal despite not being a star. Its mass is 2.5 times that of all the other planets. It has a low density of around 1.33 grams per cubic centimeter, which is four times lower than Earth.

There are similarities between Jupiter and the Sun. The Sun has a density of 1.41 grams. The two objects are very similar. The mass of the Sun is 71 percent hydrogen and 27 percent helium, with the rest being made up of trace amounts of other elements. Jupiter is composed of 73 percent hydrogen and 24 percent helium.

There is an illustration of Jupiter and its moon. NASA has a space flight center.

Jupiter is sometimes called a failed star because of this.

Jupiter is unlikely to become a star because it is left to the Solar System's own devices.

There are two different mechanisms for the birth of stars and planets. Stars are born when a dense knot of material collapses under its own gravity. As it spins, the material from the cloud around it becomes a stellar accretion disc.

The core of the baby star is squeezed tighter and hotter as the mass grows. It becomes so hot and compressed that the core ignites.

A lot of accretion disc is left over after a star has finished accretion material. The planets are made of this.

Astronomers think that Jupiter's pebble accretion process starts with tiny chunks of icy rock and dust in the disc. The bits of material are stuck together with static electricity. These clumps can attract more and more gas from the surrounding disc, eventually reaching a large-enough size.

Jupiter grew to its current mass about a thousand times the mass of Earth and a thousand times the mass of the Sun. It stopped growing once it had slurped up all the material that was available to it.

Jupiter was not close to becoming a star. Jupiter was born from the same cloud of gas that gave birth to the Sun.

There is a NASA/SwRI/MSSS/Gerald Eichst.

The true failed stars

There are different objects that can be considered failed stars. The brown dwarfs fill the gap between gas giants and stars.

These objects are 13 times the mass of Jupiter and can support a core fusion. Heavy hydrogen is an isotope of hydrogen with a protons and a neutron in the nucleus instead of a single protons. The fusion temperature and pressure are not as high as that of hydrogen.

Deuterium fusion is an intermediate step on the way to hydrogen fusion for stars because it occurs at a lower mass, temperature, and pressure. Some objects are known as brown dwarfs.

After their existence was confirmed in 1995 it was unknown if brown dwarfs were underachieving stars or overambitious planets, but several studies have demonstrated that they form just like stars from cloud collapse rather than core accretion. Some brown dwarfs are below the mass for deuterium burning, indistinguishable from planets.

The smallest cloud collapse object has an estimated Jupiter mass of about one Jupiter mass. Jupiter could be considered a failed star if it formed from the cloud collapse.

According to data from NASA's Juno probe, Jupiter had a solid core once upon a time, and that is more consistent with the core formation method.

The upper limit of a planet's mass is less than 10 times that of Jupiter, according to modeling.

Jupiter is not a failed star. It is possible to better understand how the universe works by thinking about why it is. Jupiter is a swirly wonder in its own right. We may not have been able to exist without it.

It is another story to be told again.

The first version of this article was published in January of 2021.