Category: red giant

Ask Ethan: Will The Earth Eventually Be Swallowed By The Sun?

“When the Sun eventually goes Red Giant, will the Earth simply be orbiting within the outer envelope of the sun, or will something more interesting happen?”

In 2008, a now-famous astronomy paper was published that purported to determine the fate of the Earth as the Sun swelled to become a red giant. In particular, it claimed that not only would Mercury and Venus definitely be engulfed, but that the Earth would be, too. Sure, the Sun loses mass, which causes the planets to spiral outward, but it also grows in size, which leads to both drag forces on the orbiting planets as well as tidal forces that can sap a planet’s orbital angular momentum. The authors concluded that Earth’s orbit would need to presently be about 15% larger in order for it to have a chance of surviving. But there are other important factors at play, and they legitimately could change the outcome. 

The smart money might still be on the Earth getting swallowed, but it’s far from a settled issue. Come learn where we are in our understanding of how the Solar System will evolve in the far future!

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. 

But the answer can also make you feel like you’re a part of the biggest, most meaningful thing of all. Here’s a version of the story we all should hear at least once.

Which Worlds Will Survive When The Sun Dies?

“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.

Who will survive, who will transform, and who will be annihilated when the Sun dies? The carnage is severe, but not complete. Get all the details here.

The Four Ways The Earth Will Actually End

3.) Reduction to a barren rock. You thought having our oceans boil was bad? How about the prospect of having every atom of atmosphere ejected from our world. Of everything that ever lived on the surface reduced to charred ash; of the record of everything that living creatures left behind turned into dust. With enough heat and energy, that’s exactly what would happen to any world, with Mercury, the closest planet to the Sun, being a prime example. In another five-to-seven billion years, this is exactly what will happen to Earth, as the Sun runs out of hydrogen fuel in its core. When that occurs, the core will contract, heat up, and begin fusing helium to release even more energy than before. In this state, the Sun turns into a helium-burning red giant, and nothing on Earth can withstand this.”

Here on Earth, we hear every so often about a conspiracy of how the world will come to an end. The end of the Mayan calendar; Y2K; an encounter with Nibiru; or a biblical prophesy come true are only a small selection of what people “predict” will bring a demise to our world, and soon. Yet even most of the egregious natural or human-caused disasters won’t bring an end to even our species, much less the entire world. Scientifically, the end of the world will happen in four stages. The first one is straightforward and inevitable: humanity will only continue to exist for so long. But the subsequent disasters that bring an end to our world are entirely predictable, and include the boiling of our oceans, the charring and evaporation of our atmosphere, and finally the loss of the remaining Earth-corpse to the vastness of the Universe in one of three possible ways. The world will indeed come to an end, but none of the conspiracy theories can stand up to the actual science.

Come get the full story on the four different ways, in order, that the Earth will someday come to an end!

Ask Ethan: Why Do Stars Come In Different Sizes?

“Why can suns grow to… many different sizes? That is, ranging from somewhat larger [than] Jupiter up to suns exceeding Jupiter’s orbit?”

“Bigger mass makes a bigger star,” you might be inclined to say. The smallest stars in size should be small because they have the least amount of material in them, while the largest ones of all are the largest because they’ve got the most material to make stars out of. And that’s a tempting explanation, but it doesn’t account for either the smallest stars or the largest ones in the Universe. As it turns out, neutron stars and white dwarfs are almost all larger in mass than our own Sun is, and yet the Sun is hundreds or even many thousands of times larger than they are. The most massive star known is only 30 times the physical size of our Sun, while the largest star of all is nearly 2,000 times our Sun’s size. As it turns out, there’s much, much more at play than mass alone.

Why do stars really come in different sizes, and how do we even know how big a star is at all? Find out on this week’s Ask Ethan!

The Scientific Story Of How Each Element Was Made

“Neutron star mergers create the greatest heavy element abundances of all, including gold, mercury, and platinum.

Meanwhile, cosmic rays blast nuclei apart, creating the Universe’s lithium, beryllium, and boron.

Finally, the heaviest, unstable elements are made in terrestrial laboratories.

The result is the rich, diverse Universe we inhabit today.”

When the Big Bang first occurred, the Universe was filled with all the various particles and antiparticles making up the Standard Model, and perhaps still others yet to be discovered. But missing from the list were protons, neutrons, or any of the atomic nuclei key to the life-giving elements in our Universe today. Yet the Universe expanded, cooled, antimatter annihilated away, and the first elements began to take shape. After billions of years of cosmic evolution, we arrived at a Universe recognizable today: full of stars, planets, and the full complement of elements populating the periodic table. More than 100 elements are known today, 91 of which are found to occur naturally on Earth. Some were formed in the Big Bang, others were formed in stars, still others were formed in violent cosmic cataclysms or collisions. Yet every one has an origin whose story is now known, giving rise to all we interact with today.

Come get the full story behind how all the elements were made in some fantastic pictures, visuals, and no more than 200 words on this edition of Mostly Mute Monday!