What will our Sun look like after it dies? Scientists have made predictions about what the last days of our solar system will look like and when. And we humans won’t be there to see the reminder of the Sun.
Previously, astronomers thought the Sun would turn into a planetary nebula – a luminous bubble of cosmic gas and dust – until evidence suggested it might have to be a bit more massive.
An international team of astronomers flipped it in 2018 and discovered that a planetary nebula is indeed the most likely solar corpse.
The Sun is about 4.6 billion years old – measured on the age of other solar system objects 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 10 billion years.
There are other things that will happen along the way, of course. In about 5 billion years, the Sun should turn into a red giant. The star’s core will shrink, but its outer layers will expand to Mars’ orbit, engulfing our planet in the process. If he’s still there.
One thing is certain: at that time, we will no longer be here. In fact, humanity only has about 1 billion years left unless we find a way out of this rock. This is because the Sun’s brightness increases by about 10% every billion years.
It may not seem 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’ll be about as kaput as possible.
It’s what comes after the red giant that has proven difficult to pin down. Several previous studies have shown that for a bright planetary nebula to form, the initial star must have been up to twice as massive as the Sun.
However, the 2018 study used computer modeling to determine that, like 90% of other stars, our Sun is most likely to shrink from a red giant to a white dwarf and then terminate into a planetary nebula. .
“When a star dies, it ejects a mass of gas and dust – known as the envelope – into space. The envelope can be up to half the mass of the star. This reveals the core of the star, which at this point in the star’s life is running out of fuel, eventually shutting down and before finally dying,” explained astrophysicist Albert Zijlstra from the University of Manchester. in the UK, one of the authors of the article.
“Only then does the hot core cause the ejected envelope to glow for about 10,000 years – a brief period in astronomy. This is what makes the planetary nebula visible. Some are so bright that they can be seen at extremely large distances measuring tens of millions of light-years, where the star itself would have been far too faint to see.”
The data model the team created actually predicts the life cycle of different types of stars, to determine the planetary nebula brightness associated with different star masses.
Planetary nebulae are relatively common throughout the observable universe, with famous nebulae such as the Helix Nebula, Cat’s Eye Nebula, Ring Nebula, and Bubble Nebula.
Cat’s Eye Nebula (NASA/ESA)
They are called planetary nebulae not because they have anything to do with planets, but because when the first ones were discovered by William Herschel in the late 18th century, they looked like planets through the telescopes of the ‘era.
Almost 30 years ago, astronomers noticed something peculiar: the brightest planetary nebulae in other galaxies all have about the same level of brightness. This means that, theoretically at least, by observing planetary nebulae in other galaxies, astronomers can calculate how far away they are.
The data showed this to be correct, but the models contradicted it, which has vexed scientists ever since the discovery was made.
“Old, low-mass stars should produce much fainter planetary nebulae than younger, more massive stars. This has become a source of contention 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 it wasn’t possible, anything less than about twice the mass of the Sun would give a nebula planet too faint to be seen.”
The 2018 models solved this problem by showing that the Sun is around the lower mass limit of a star that can produce a visible nebula.
Even a star with a mass less than 1.1 times that of the Sun will not produce a visible nebula. Larger stars up to 3 times more massive than the Sun, on the other hand, will produce the brightest nebulae.
For all other intermediate stars, the predicted luminosity is very close to what has been observed.
“It’s a good result,” said Zijlstra. “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 remarkably difficult range to measure, but we have even discovered what the Sun will do when ‘he will die ! “
The research was published in the journal natural astronomy.
An earlier version of this article was first published in May 2018.
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