The smallest star known to us in the main sequence in the deer leap is one simple pixel in the full picture.
It is called EBLM J0555-57Ab, is a red dwarf and is located 600 light years from us. Its average radius is 59,000 kilometers and in this respect it is slightly larger than Saturn. As a result, it is the smallest star known to us, in the nucleus of which hydrogen is synthesized – a process that shines on a star before it runs out of fuel.
In the solar system, these tiny stars are two objects larger in size. Of course, one of them is our sun. The second is Jupiter with a radius of 69,911 kilometers.
So why is Jupiter a planet and not a star?
The short answer is simple – Jupiter does not have enough mass to synthesize hydrogen as helium. The mass of the star EBLM J0555-57Ab is 85 times that of Jupiter and is at the lower end of the mass of stars; Had it had less mass than this, it would not have been able to synthesize hydrogen. However, if our solar system were different, would Jupiter be able to ignite as a star?
Jupiter and the Sun are more similar to each other than we can imagine
This gas giant may not be a star, but it is still a fairly important object. Its mass is 2.5 times the mass of all the other planets in the solar system. However, because it is a gas giant, it has a very low density – about 1.33 grams per cubic centimeter; The density of the Earth is 5.51 grams per cubic centimeter, or four times that of Jupiter.
However, it is interesting to note the similarities between Jupiter and the Sun. The density of the sun is 1.41 grams per cubic centimeter. The composition of these two objects is very similar. In terms of mass, 71 percent of the sun is hydrogen, 27 percent is helium, and the rest is other elements. 73 percent of Jupiter is hydrogen and 24 percent is helium.
This is why Jupiter is sometimes called a failed star.
However, it is unlikely that Jupiter will ever even come close to a star.
Stars and planets are born with very different mechanisms. A star is born when a dense knot of matter in its interstellar molecular cloud collapses by its own gravity. It then begins to rotate and absorbs more matter from the cloud into the accretion plate.
With increasing mass and consequently gravity, the nucleus of the infant star becomes more and more dense, which makes it more and more heated. Gradually, it becomes so compressed and hot that the nucleus ignites and thermonuclear fusion begins.
According to the current notion of star formation, once a star completes the joining of matter, a fairly large portion of the accretion disk remains around it. This is where the following planets are born.
Astronomers think that for Jupiter-like gas giants, this process begins in the disk with icy debris and dust. As they move around a newborn star, these tiny pieces of matter collide and collide with each other with static electricity. Gradually, these growing piles reach a mass of about 10 Earths, and by gravity they attract more and more gas from the surrounding plate.
From this point on, Jupiter gradually reached its current mass – 318 times that of Earth, but only 0.001 solar masses. Once the available matter has been completely assimilated, growth has stopped, and this mass is not sufficient for the synthesis of hydrogen.
Consequently, Jupiter has never been even close to becoming a star. It has a sun-like composition not because it is a failed star, but because it was born from the same molecular gas cloud from which our sun came.
Real failed stars
There are different classes of objects that can be considered as “failed stars”. These are brown dwarfs that fluctuate between gas giants and stars.
The mass of these objects exceeds Jupiter at least 13 times, which is enough to start the synthesis of deuterium, not ordinary hydrogen, in the nucleus. Deuterium is also called heavy hydrogen and is a hydrogen isotope that has protons and neutrons instead of one proton in its nucleus. The temperature and pressure of its synthesis are less than that required for the synthesis of hydrogen.
Because it occurs at low mass, temperature, and pressure, deuterium synthesis is an intermediate step in the path of hydrogen synthesis in stars when they continue to join mass again. However, some objects can never gain this mass and they are called brown dwarfs.
The existence of brown dwarfs was confirmed in 1995, but it remained unknown whether they were failed stars or overly “ambitious” planets; Several studies have shown that they are born exactly like stars as a result of the collapse of a molecular cloud. Some brown dwarfs do not have enough of it to synthesize deuterium and are indistinguishable from the planets.
Jupiter is placed on the lower edge of the mass required for the collapse of the cloud; The smallest mass required for an object to emerge from a cloud collapse is estimated to be about the mass of about one Jupiter; Consequently, if Jupiter appeared as a result of a cloud collapse, it would be considered a failed star.
However, data from NASA’s Juno spacecraft indicate that at least once, Jupiter had a solid nucleus, which fits well with the accretion formation method.
As modeling indicates, when generated by nuclear accretion, the upper limit of the planet’s mass is less than 10 Jupiter mass, i.e. Jupiter is separated by several of its own masses from deuterium synthesis.
Therefore, Jupiter is not a failed star, but it really is an object that helps us better explore the cosmos. Finally, without it, humans may not exist at all.