What is the largest known star in the observable universe?

Compared to other stars, our Sun is fairly average in size. We will not complain. Without him, we wouldn’t be here. But what is the largest known star in the universe?

The largest star is not the most massive. In fact, the heaviest stars are often banal in terms of the bulk they take up, while the bulkiest stars are often just “featherweights.” In fact, as they age, these objects tend to expand and lose mass.

The heaviest and largest.

If we talk only about mass, the record holder is R136a1. You’ll find this star about 160,000 light-years from Earth in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. In diameter, this very young and luminous star is also thirty or forty times larger than the Sun, but above all it is more than 315 times more massive.

If we talk about volume, then the largest known star is probably Oops Scuti, located about 9,500 light-years away. The diameter of this red hypergiant is approximately 1700 times the one of the sun plus or minus 192 solar radii.

This margin of error is explained by two main factors. To determine the diameter of such an object, astronomers must know the amount of light it produces. However, the further away a star is, the less luminous it appears to us. Add that to the fact that red hypergiants are often “variable,” meaning their brightness changes a lot over time. They light up and fade in fact regularly.

Other stars come just behind UY Scuti, starting with WOH G64 and VY Canis Majoris, both of which are about 1500 times the diameter of the Sun. However, given the degree of uncertainty, both could ultimately be larger than UY Scuti. . Located in the center of our system, these stars would surround each inner planet, but also Jupiter.

oops scuti star
Comparison of UY Scuti with the Sun. Credits: Philip Park

The smallest known star

On the other side of the spectrum, there are also “small” stars. For now, the title of smallest known star remains with EBLMJ0555-57Ab. The object, which has a radius comparable to that of Saturnflirts with the theoretical limit of the smallest possible stars with a mass of about 0.084 solar mass. In other words, this star is capable of sustaining nuclear fusion in its core, which allows it to “shine”, but just barely. Below this, this object would be considered a brown dwarf.

Of course, we don’t know all the stars in the universe. Also, we can’t even measure the size of those on the other side of the Milky Way because of the dust. Therefore, it is quite likely that even more imposing giants lurk in the cosmos.

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