“During the red giant phase, Mercury and Venus will certainly be engulfed by the Sun, while Earth may or may not, depending on certain processes that have yet to be fully worked out. The icy worlds beyond Neptune will likely melt and sublimate, and are unlikely to survive the death of our star.
Once the Sun’s outer layers are returned to the interstellar medium, all that remains will be a few charred corpses of worlds orbiting the white dwarf remnant of our Sun. The core, largely composed of carbon and oxygen, will total about 50% the mass of our present Sun, but will only be approximately the physical size of Earth.”
Looking forward in time, the death of our Sun is easy to envision, as we’ve seen Sun-like stars in their dying phases and immediately afterwards plenty of times. But what happens after that, in the far future? Will our Sun’s corpse remain a white dwarf forever? Will it simply cool down, radiating heat away? Or will something exciting happen?
Maybe we’ll get ejected from the galaxy. Maybe we’ll get devoured by a black hole. Maybe we’ll merge with another object, or experience an interaction that forever changes us from what we were. Maybe we’ll even experience a cataclysm that destroys our stellar corpse entirely!
This Is How The Sun Moves In The Sky Throughout The Year
“It’s easy to see that the topmost point corresponds to the summer solstice, while the lowest point corresponds to the winter solstice, but there is no special astronomical significance to the “crossing-point” in the Sun’s analemma as seen from Earth. Occurring approximately on April 14th and August 30th, those dates are only determined by the way our seasons, determined by axial tilt, align with our planet’s orbit around the Sun.
If our perihelion and aphelion were aligned with the equinoxes, rather than the solstices, we’d have a teardrop-shaped analemma, rather than a figure-8, which is how the Sun appears from Mars! The analemma is the beautiful, natural shape traced out by the Sun over time, creating a figure-8 as both our orbit and axial tilt dictate. Enjoy the Sun’s motion through our skies, as its unique cosmic pirouette is due to our planet’s one-of-a-kind motion through space!”
You might notice that the Sun is changing its position in the sky, while sunset and sunrise times also change. But did you know that you’d get this bizarre, pinched, figure-8-like shape if you took a picture of the Sun every day throughout the year at 24-hour intervals? It’s true! The shape is known as Earth’s analemma, and it’s determined by a variety of factors that you must consider all of in order to get the explanation right.
“If it weren’t for the quantum nature of every particle in the Universe, and the fact that their positions are described by wavefunctions with an inherent quantum uncertainty to their position, this overlap that enables nuclear fusion to occur would never have happened. The overwhelming majority of today’s stars in the Universe would never have ignited, including our own. Rather than a world and a sky alight with the nuclear fires burning across the cosmos, our Universe would be desolate and frozen, with the vast majority of stars and solar systems unlit by anything other than a cold, rare, distant starlight.
It’s the power of quantum mechanics that allows the Sun to shine. In a fundamental way, if God didn’t play dice with the Universe, we’d never win the Powerball three times in a row. Yet with this randomness, we win all the time, to the continuous tune of hundreds of Yottawatts of power, and here we are.”
In the core of our Sun, where temperatures cross the threshold of 4 million K (and rise all the way up to 15 million K), nuclear fusion occurs, driving the energy output of our Sun. Yet if you looked at what was going on at a particle level, that first step towards fusion is where two protons collide to form a deuteron. Only, there are two immediate problems: a deuteron is made out of a proton and neutron, not two protons, and that the two protons don’t even have enough energy to overcome the electrostatic repulsion between them! Thankfully, the Universe is quantum in nature, meaning weak interactions do occur, changing a quark’s flavor type, and particle positions are defined by quantum wavefunctions, which can overlap.
The Sun Will Someday Die, And That’s Why You’re Alive
“It’s true: death comes for us all. It comes for everyone we know and don’t know; it comes for everyone that will ever live. After we’re all dead for billions of years, the Sun will die, too.
But that’s not the full story, and it leaves out the best part. A star’s death brings a remarkable story of cosmic rebirth and possibilities for life to the Universe. It is a story of creation that goes hand-in-hand with destruction, and it follows just below. Give it a shot. It just might be the most remarkable, wonderful story an elementary schoolchild could hope to hear.”
It was a few years ago that I got one of those questions that has stuck in my mind ever since. In particular, it was a message from an elementary school teacher who had a distraught child. The teacher asked me:
“I need a good explanation for a third grader, whose Mom tells me is deeply concerned, that the sun will blow up.”
This is one of the toughest truths about the Universe that many of us will ever learn. The answers to it can make you feel small, inconsequential, and meaningless at times.
Our Sun Is Lighter Than Ever, And The Problem Is Getting Worse
“As time goes on, the amount of mass lost by the Sun will increase, particularly as it enters the giant phase of its life. But even at this relatively steady rate, the growth of helium in the Sun’s core means that we will heat up here on planet Earth. After about 1-to-2 billion years, the Sun will be burning hot enough that Earth’s oceans will boil away entirely, making liquid water impossible on the surface of our planet. As the Sun gets lighter and lighter, it will counterintuitively get hotter and hotter. Our planet has already used up approximately three-quarters of the time we have where Earth is habitable. As the Sun continues to lose mass, humanity and all life on Earth approaches its inevitable fate. Let’s make these last billion-or-so years count.”
As the Sun burns through its nuclear fuel, it loses mass in not one, but two ways. Sure, in its core, it’s fusing hydrogen in a chain reaction into helium, with the reduction in mass corresponding to a gain in energy: the energy that powers the Sun and gives life to all the planets. But it also blows off particles, including electrons, protons, and atomic nuclei, in a phenomenon called the solar wind. Even though more massive stars burn hotter and brighter than less massive ones, the Sun, perhaps paradoxically, will increase in temperature and luminosity as it loses mass to these two processes. The Sun is getting lighter and lighter, and the problem of its increasing energy output will eventually destroy all life on Earth.
“But the Sun will be so hot and so bright that much of the outer Solar System will be absolutely destroyed. Each of the gas giants has a ringed system; although Saturn’s is the most famous, all four of them have rings. These rings are mostly made of various ices, such as water ice, methane ice, and carbon dioxide. With the extreme energies given off by the Sun, not only will these ices melt/boil away, but the individual molecules will be so energetic that they will be ejected from the Solar System.”
When the Sun becomes a red giant, lots of changes are going to happen. Mercury and Venus will surely become engulfed; Earth and Mars will lose their atmospheres and oceans, becoming barren and charred. But even beyond that, the outer worlds and structures in the Solar System will melt and lose their volatiles. Asteroids will lose mass and become rocky/metallic cores; moons like Europa and Enceladus will melt away; the rings around the gas giants will disappear; even Pluto and the other large Kuiper Belt objects will lose their atmospheres and top layers, melting away until they’re only a rock-and-metal core.
Ask Ethan: How Do We Know The Age Of The Solar System?
“How do we know the age of our solar system? […] I have a loose grasp on the concept of dating the time elapsed since a rock was liquid, but 4.5 Billion years is roughly how long ago Theia hit proto-Earth liquefying a massive amount of everything. […] How do we know we’re actually dating the solar system and not just finding dozens of ways to date the Theia collision?”
You’ve probably heard the estimates before: that the Earth, the Sun, and the rest of the Solar System are all about 4.5 or 4.6 billion years old. But why be so imprecise? We don’t have to be! In fact, we know that there are slight variations, and based on the fact that we think that the Earth-Moon system formed from a giant impact tens of millions of years after the rest of the Solar System did, we shouldn’t get the same answer for everything! It turns out that we’ve now advanced to the point where we can actually give answers that are extremely accurate: the Earth-Moon system should be 4.51 billion years old; the oldest meteorites show an age for the rest of the Solar System of 4.568 billion years, and the Sun may be a little older at 4.6 billion years.