The smallest known main serial star in the Milky Way is a true messenger of something.
It’s called EBLM J0555-57Ab, and it’s a red dwarf 600 light-years away. With an average radius of about 59,000 km, it’s just a simbridge Greater than Saturn. This makes it the smallest known star to support hydrogen fusion at its core, the process that keeps stars burning until they run out of fuel.
In our solar system, there is two Objects larger than this little star. Obviously, one of them is the sun. The other is Jupiter, which, like a huge scoop of ice cream, comes in a medium radius 69,911 km.
So why is Jupiter a planet and not a star?
The short answer is simple: Jupiter doesn’t have enough mass to fuse hydrogen into helium. The mass of EBLM J0555-57Ab is about 85 times the mass of Jupiter, equivalent to the light a star could be – if it were less than that, it wouldn’t be able to fuse hydrogen either. But if our solar system were different, could Jupiter turn into a star?
Jupiter and the sun are more alike than you know
The gas giant may not be a star, but Jupiter is still a big deal. Its mass 2.5 times That all other planets combined. It is only that, being a gaseous giant, it has a really low density: about 1.33 grams per cubic centimeter; Earth’s density, at 5.51 grams per cubic centimeter, is four times that of Jupiter.
But it is interesting to note the similarities between Jupiter and the sun. The sun has a density of 1.41 grams per cubic centimeter. The two objects are structurally very similar. From the blockThe sun is made up of about 71% hydrogen and 27% helium, and the rest is made up of trace amounts of other elements. Jupiter From the block About 73 percent hydrogen and 24 percent helium.
Illustration of Jupiter and Io. (NASA’s Goddard Space Flight Center / CI Laboratory)
That is why Jupiter is sometimes called a failed star.
But it is still unlikely, if left to the Solar System’s own devices, that Jupiter would soon be a star.
The stars and planets, you see, are generated by two very different mechanisms. Stars are born when a dense knot of matter collapses into an interstellar molecular cloud due to its gravitational pull. flomph! Spin as it goes through a process called cloud collapse. As it spins, it coils more material from the surrounding cloud into a stellar accretion disk.
As the mass – and thus gravity – grows, the young star’s core is compressed more tightly and tightly, causing it to get hotter and hotter. It eventually becomes extremely hot and compressed, the core ignites and thermonuclear fusion takes off.
According to our understanding of star formation, once a star has finished accumulating material, much of the accretion disk remains. This is what planets are made of.
Astronomers believe that for gas giants like Jupiter, this process (called pebble accumulation) begins with small chunks of icy rock and dust in the disk. As it orbits around the young star, these pieces of material begin to collide and stick together with static electricity. Ultimately, these growing lumps reach a large enough size – around 10 land blocks They can attract more and more gas from the disk surrounding gravity.
From that point on, Jupiter gradually grew to its present mass – about 318 times the mass of the Earth, and 0.001 times the mass of the Sun. Once it eats away all of the material at its disposal – quite far from the mass required for hydrogen fusion – it stops growing.
Therefore, Jupiter was not close to growing large enough to become a star. Jupiter has a similar composition to the Sun, not because it was a « failed star » but because it was born from the same cloud of molecular gas that gave birth to the sun.
(NASA / SwRI / MSSS / Gerald Eichstädt / Seán Doran / Flickr / CC-BY-2.0)
Real failed stars
There is a different class of organisms that can be considered « failed stars ». These are brown dwarfs, and they fill the gap between gas giants and stars.
The mass of these objects begins at about 13 times the mass of Jupiter, and is massive enough to support core fusion – not from regular hydrogen, but deuterium. This is also known as « heavy » hydrogen; It is an isotope of hydrogen with a proton and a neutron in the nucleus instead of just one proton. The fusion temperature and pressure are lower than the melting temperature and pressure of hydrogen.
Since it occurs at lower mass, temperature and pressure, deuterium fusion is an intermediate step on the hydrogen fusion pathway of stars, as it continues to aggregate in mass. But some things never reach this mass; These are known as brown dwarves.
For a while after they are Confirmed in 1995It was not known whether brown dwarfs were not achieving stars or over-ambitious planets. But Numerous studies They prove that they are taking shape Just like the stars, From cloud collapse rather than primary accumulation. Some brown dwarfs are less than mass due to burning deuterium, and are indistinguishable from planets.
Jupiter is located directly on the minimum mass of the cloud collapse; The smaller mass of the drag collapse object has been estimated Jupiter is about one mass. So if Jupiter was formed from collapsing clouds, it could be considered a failed star.
But Data from NASA’s Juno probe She points out that, at least once, Jupiter had a solid core – that’s more consistent with Primary accumulation Formation method.
The modeling indicates that the upper limit of the planet’s mass, formed by accretion of the nucleus, is Less than 10 times the mass of Jupiter Only a few of Jupiter’s clusters shy of deuterium fusion.
So, Jupiter is not a failed star. But thinking about why this hasn’t happened can help us better understand how the universe works. Plus, Jupiter is a striped, stormy, and whirling dessert wonder in its own right. Without it, we are humans It might not even be able to exist.
This is, however, another story, to tell again.
