Can Planets Become Stars?

We have known for some time now that stars, other than our sun, in our galaxy and beyond have planets revolving around them. But can any of these planets, in any way, turn into a star? This question arises due to a planet in our very own solar system. Jupiter is sometimes referred to as a failed star. It is quite misleading and we will see why later in this post. But can it turn into a star during some point? Can any planet that we know of in any star system turn into a star? We’ll look into that in this article.

Short answer, it is possible but highly improbable. Why? According to the definition of a star, it is an object with enough mass so as to produce nuclear reaction in its interior and produce energy in the form of light energy and hence is luminous. Theoretically, anything can be turned into a star by simply adding mass. Given enough mass, the pressure and temperature inside the planet can reach the minimum amount to initiate nuclear reactions. The main problem with the planets is that they do not have the required amount of mass.  

HOW MUCH MASS WOULD A PLANET NEED TO GAIN?

Planets would need a lot of mass to turn into a star. The most probable source of gaining this mass would be cosmic dust and gas. But the amount required can’t be supplied by this process.

Let us consider Jupiter as a possible candidate for turning into a star from this point on.

There are many different kinds of stars in universe. Some are really big and some are considerably small. So what does Jupiter need to meet minimum requirement. Our sun is a medium sized star. Jupiter would need 1000 times more mass than what it has now. One of the smallest kinds of stars are cooler ‘Red Dwarfs’. Only 80 Jupiter masses have to be added in this case. However, this number is still too high. There is another less massive star like object called ‘Brown Dwarf'. It is estimated to have a mass somewhere between the heaviest gas giant i.e. Jupiter and least massive star. In this case, you only need only about 13 Jupiter masses. This object (Brown Dwarf) isn’t massive enough to burn in true fusion but it is still massive enough to fuse deuterium, an isotope of hydrogen (deuterium has 2 neutrons as opposed to one in hydrogen). Even then it’s highly unlikely that Jupiter would gain such mass unless there is a catastrophic events resulting in it colliding with various objects.

ANOTHER REASON WHY JUPITER CANNOT BE A STAR

Despite what most people want Jupiter to turn to, it was always destined to be a planet. It is referred to as failed star just because it has abundance of hydrogen and helium, same as the stars, however, as we have already seen, it lacks the mass to initiate nuclear reaction due to internal pressure and temperature. In fact, if anything that can be described as ‘failed stars’ , it is brown dwarfs as they can’t shine or they lack enough mass to shine despite undergoing fusion.

Jupiter's chemical composition and structure is a consequence of how it was formed. It is still unclear whether gaining mass would make it a star or not because of how it was formed. Stars are formed when electrical charge and gravity attract clouds of gas and dust and they eventually start rotating when the cloud becomes dense enough causing the matter to flatten into a disc. Planets are formed when the residual dust and debris from the star formation clump together. Jupiter is believed to have formed in two step process. First, a huge quantity of ice and rock ‘planetesimals’ formed. They collided with other objects and when they gained mass of 10 earths, they pulled gas directly from the disc. Eventually, it became as big as it is today. Why couldn’t the other gas giants grow into that size? Intense solar winds blew the remaining gas before they could grow. The process of formation of both is very different indeed. This leads to different chemical composition and structure in Jupiter compared to a star such as Sun. This difference may prevent it from becoming a brown dwarf even if it were to gain enough mass.

CONCLUSION

We can conclude that it is very improbable for planets to turn into a star. Main reasons why it is so are that they lack enough mass and their formation is different from stars leading to different chemical compositions and structures. The only way for them to turn into a star is to gain a ridiculous amount of mass which is highly unlikely.