How will our Sun take care of itself after it dies? Scientists have made predictions about what the last days of our Solar System will be like and when it will happen. And we humans will not be around to see the curtain of the Sun.
Previously, astronomers thought the Sun would turn into a planetary nebula – a bright bubble of gas and cosmic dust – until evidence showed it should be more massive.
An international team of astronomers overturned it again in 2018 and found that a planetary nebula is indeed the most likely solar corpse.
The Sun is about 4.6 billion years old – measured by the age of other objects in the Solar System that formed around the same time. Based on observations of other stars, astronomers predict that it will reach the end of its life in about another 10 billion years.
There are other things that will happen along the way, of course. In about 5 billion years, the Sun is going to turn into a red giant. The star’s core will shrink, but its outer layers will expand into the orbit of Mars, engulfing our planet in the process. If it’s still there.
One thing is certain: Until that time, we will not be around. In reality, humanity only has about 1 billion years left unless we find a way off this rock. This is because the Sun increases in brightness by about 10 percent every billion years.
That doesn’t sound like much, but this increase in brightness will end life on Earth. Our oceans will evaporate and the surface will become too hot for water to form. We will be as strong as you can.
It is what comes after the red giant that has proven difficult to detect. Several previous studies have found that, for a bright planetary nebula to form, the original star must be up to twice the mass of the Sun.
However, the 2018 study used computer modeling to determine that, like 90 percent of other stars, our Sun is more likely to shrink from a red giant to become a white dwarf and then end up in a planetary nebula.
“When a star dies, it ejects a mass of gas and dust – known as its envelope – into space. The envelope can be as much as half the star’s mass. This reveals the star’s core, which at this point in its life of a star runs out of fuel, eventually dying out before finally dying,” explained astrophysicist Albert Zijlstra from the University of Manchester in the UK, one of the authors of the paper.
“Only then does the hot core make the ejecta envelope glow brightly for about 10,000 years – a short period in astronomy. This is what makes the planetary nebula visible. Some are so bright that they can be seen from extremely long distances, spanning tens of millions of years.” of light, where the star itself would be too faint to see.’
The data model the team created actually predicts the life cycle of different kinds of stars, to calculate the brightness of the planetary nebula associated with different star masses.
Planetary nebulae are relatively common throughout the observable Universe, with famous ones including the Helix Nebula, the Cat’s Eye Nebula, the Ring Nebula, and the Bubble Nebula.
They are called planetary nebulae not because they actually have anything to do with planets, but because, when first discovered by William Herschel in the late 18th century, they looked similar to planets through the telescopes of the time.
Nearly 30 years ago, astronomers noticed something strange: The brightest planetary nebulae in other galaxies are all about the same level of brightness. This means that, in theory at least, by looking at planetary nebulae in other galaxies, astronomers can estimate how far away they are.
The data showed this to be correct, but the models contradicted it, which has troubled scientists ever since the discovery was made.
“Old, low-mass stars should create much fainter planetary nebulae than young, more massive stars. This has become a source of conflict over the past 25 years,” Zijlstra said.
“The data said you could get bright planetary nebulae from low-mass stars like the Sun, the models said that wasn’t possible, anything less than twice the mass of the Sun would give a planetary nebula too faint to see.”
The 2018 models solved this problem by showing that the Sun is about the lower mass limit for a star that can produce a visible nebula.
Even a star less than 1.1 times the mass of the Sun will not produce a visible nebula. Larger stars up to 3 times the mass of the Sun, on the other hand, will create the brightest nebulae.
For all other stars in between, the predicted luminosity is very close to what has been observed.
“This is a nice result,” Zijlstra said. “Not only do we now have a way to measure the presence of stars a few billion years old in distant galaxies, which is a range that is extremely difficult to measure, we’ve even discovered what the Sun will do when it dies! “
The research was published in the journal Astronomy of Nature.
An earlier version of this article was first published in May 2018.