A Distant Star Reveals The Future Of Our Sun

Stars are a lot like people–they are born, grow up, grow old, and finally and inevitably die. About 5.4 billion years from now, our own Star, the Sun, will have aged to the tragic point that it will enter what is termed the Red Giant stage of its evolution–this will begin once all of its necessary supply of hydrogen fuel is finally consumed in its seething-hot heart, and the inert helium that it has accumulated becomes unstable and collapses under its own powerful weight. This chain of events will cause our Star’s core to get hotter, and hotter, and hotter–and progressively more and more dense–causing our Sun to swell in size and undergo a hideous sea-change into an enormous, bloated Red Giant Star. But, what will happen to Earth when the inevitable happens, and our Sun grows a hundred times bigger than it is today? Using the most powerful radio telescope currently available, an international team of astronomers embarked on their quest to answer this profound question by watching L2 Puppis, a distant star, that five billion years ago was very similar to the way our Sun is today.

“Five billion years from now, the Sun will have grown into a Red Giant Star, more than a hundred times larger than its current size. It will also experience an intense mass loss through a very strong stellar wind. The end product of its evolution, about 7 billion years from now, will be a tiny white dwarf star. This will be about the size of the Earth, but much heavier: one teaspoon of white dwarf material weighs about 5 tons,” explained Dr. Leen Decin in a December 8, 2016 KU Leuven Press Release. Dr. Decin is at the KU Leuven Institute of Astronomy in Leuven, Belgium.

It has been calculated that the bloated future Sun will balloon to a size large enough to swallow both Mercury and Venus–and, possibly, even our Earth. But even if our planet does manage to survive being consumed by our Star on steroids, its new proximity to our Sun would broil our Earth, and make it absolutely impossible for life to survive on what has become a scorched, hostile ball of hell in orbit around a dying Star. On the brighter side, astronomers are aware that as our Sun expands, the orbit of our Earth is likely going to change as well.

When our Star reaches this advanced stage in its stellar evolution, it will hurl out a large amount of its mass into space through fierce stellar winds. As our Sun swells, it loses mass, and this will cause the planets to spiral outwards. The question is whether the expanding Sun will overtake the planets spiraling outwards, or will Earth (and maybe even Venus) escape the hideous fiery rage of its grasping flames? That is the question!

“The fate of the Earth is still uncertain. We already know that our Sun will be bigger and brighter, so that it will probably destroy any form of life on our planet. But will the Earth’s rocky core survive the Red Giant phase and continue orbiting the white dwarf,” Dr. Decin added in the December 8, 2016 KU Leuven Press Release.

Death Of A Star

Red Giants are elderly, evolved stars that are approaching their inevitable demise. However, they still have a little bit of life left in them. This is because they are still able to fuse their supply of hydrogen fuel into helium within a shell surrounding a degenerate core of helium. The closest Red Giant to Earth is Gamma Crucis, which is almost 90 light-years away.

Elderly and doomed to die, Red Giant stars have radii that are ten to hundreds of times larger than that of our Sun. Yellow-orange to red in color, the outer atmosphere of a Red Giant is not only puffed up and bloated, it also displays a surface temperature of only 5,000 Kelvin–or even lower. This means that Red Giants are cool by star-standards. These gigantic old stars evolved from small, still-“living” Sun-like stars, ranging from about 0.3 solar-masses to around 8 solar-masses, when they were still on the hydrogen-burning main-sequence of the Hertzsprung-Russell Diagram Of Stellar Evolution. The small Sun-like stars ballooned in size after having consumed their necessary supply of hydrogen fuel in their nuclear-fusing cores.

A baby star is born when an especially dense blob embedded within a dark, giant, molecular cloud collapses under its own weight. Molecular clouds, that float around our Milky Way Galaxy in huge numbers, are enormous, billowing, beautiful, and very, very cold–and they serve as nurseries for sparkling newborn stars (protostars). Molecular clouds are composed mostly of hydrogen and helium–with just a pinch of heavier atomic elements that are termed metals in the jargon of astronomers. For astronomers, a metal is defined as any atomic element that is heavier than helium. These metals are uniformly distributed throughout the forming star. The bouncing baby star finally attains true adult stardom when it reaches the hydrogen-burning main-sequence and its core grows hot enough to commence the process of nuclear fusion at the searing-hot temperature of a few million Kelvin. At this roasting temperature, the young, active star can at last fuse the hydrogen present in its core in order to establish hydrostatic equilibrium. Throughout its entire “life” on the main-sequence, the new star will gradually fuse the hydrogen in its hot heart into helium. The star’s “life” on the main-sequence comes to a sad conclusion when almost all of the hydrogen in its core has been fused into heavier things.

All of the 200 to 400 billion stars inhabiting our Milky Way Galaxy, including our own Sun, were born this way–from the gravitational collapse of an especially dense blob lodged secretively within the swirling, billowing, undulating folds of a cold molecular cloud. Today our Star is still on the hydrogen-burning main-sequence–it is a relatively small roiling, broiling sphere of searing-hot mostly hydrogen gas. Our Sun is currently almost 5 billion years of age, and it is enjoying an active middle-age–and it still has another 5 billion years to go before it goes gentle into that good night. As stars go, our Sun is nothing out of the ordinary–it does not stand out in the crowd of the billions of other stars inhabiting our Galaxy. There are planets, moons, and an assortment of smaller bodies circling our Sun. Our Solar System is situated in the far suburbs of our majestic, large, star-blazing, barred-spiral Galaxy, in one of its pinwheel-like arms.

Our Sun is still young and bouncy enough to comfortably burn hydrogen in its heart by way of the process of nuclear-fusion–which forms increasingly heavier and heavier atomic elements out of lighter ones (stellar nucleosynthesis). When our Sun–and other stars similar to it–have at last managed to fuse their necessary supply of hydrogen fuel in their hot hearts, their looks change. They are now stellar seniors. In the heart of an aging Sun-like star, a core of helium is surrounded by a shell in which hydrogen is still being fused into helium. Eventually, the shell expands outward, and the searing-hot helium heart grows larger–and larger–as the doomed star grows old. Alas, the helium heart itself ultimately shrivels under its own heavy weight and, as it does so, it becomes extremely hot. This triggers a new stage of nuclear burning, whereby the helium is being fused to form the even heavier atomic element, carbon.

In 5 billion years, our Sun will harbor a small, hot heart that will be hurling out more energy than it does today. Our Sun’s outer gaseous layers will have become red and bloated to grotesque proportions, and it will no longer be the lovely bright sphere that brings warmth and light to our small, blue planet. At this stage, our Sun will have evolved into a Red Giant that will likely incinerate one or two or possibly even three of its innermost, small, and rocky planet-children. The temperature at the surface of our bloated, swollen red Sun will be considerably cooler than it is today. However, our dying Star will still be sufficiently broiling that it may convert the currently frigid icy inhabitants of the distant Kuiper Belt, such as the dwarf planet Pluto, into tropical paradises–at least for a time.

The sad story continues as our dying Star shrivels even further, and because it can no longer churn out radiation via nuclear fusion, all further evolution will be the result of the force of gravity alone. In the end, our Star will cast off its outer gaseous layers. However, the core of our Sun will remain in one piece, and all of its material will ultimately collapse into this tiny relic body that is only about the same size as our own small planet. In this way, our Star will wind up as a type of stellar ghost called a white dwarf star. The new white dwarf will be surrounded by a beautiful, shimmering shroud of varicolored gases termed a planetary nebula.

A white dwarf is an extremely dense stellar relic that radiates away the energy of its collapse, and is made up of a bizarre brew of carbon and oxygen nuclei swimming around in a soup of degenerate electrons. Adding more mass to the white dwarf will only cause it to shrink even more than it already has, and its central density will also increase. The stellar ghost’s radius will ultimately shrink to only a few kilometers. At this tragic stage, our Star and others like it are doomed to become ever cooler and cooler as time goes by.

At the very end of this tragic story, our Star will likely evolve into an object termed a black dwarf. Black dwarf stars are hypothetical objects because it is generally thought that none exist in our Universe–at least, not yet! It requires hundreds of billions of years for a white dwarf to become cold enough to become a black dwarf–and our Universe is only about 13.8 billion years old. The cooling white dwarf will first emit yellow light, then red light, as it draws from its progenitor star’s reservoir of thermal energy. The stellar ghost’s atomic nuclei will be crushed together as tightly as the laws of physics will allow and, at this final phase, no further collapse can possibly occur. At last, this lingering relic of a star-that-was can send forth no light at all. In the end, as a carbon-oxygen-rich black dwarf, our Sun will continue to wander lost and alone within our Galaxy.

A Distant Star Reveals The Future Of Our Sun

Will Earth survive when our Sun finally undergoes a sea-change into a swollen Red Giant? In order to answer this question, the international team of astronomers that includes Dr. Decin, observed the elderly evolved star L2 Puppis. This star is 208 light-years from Earth–which makes it a close neighbor by cosmological standards. The team of astronomers used the ALMA Radio Telescope, located in the Atacama Desert in Chile. ALMA is composed of 66 individual radio antennas that work together to create a gigantic virtual telescope with a 16-kilometer diameter.

“We discovered that L2 Puppis is about 10 billion years old. Five billion years ago, the star was an almost perfect twin of our Sun as it is today, with the same mass. One third of this mass was lost during the evolution of the star. The same will happen with our Sun in the very distant future,” explained Dr. Ward Horman in the December 8, 2016 KU Leuven Press Release. Dr. Horman is in the Department of Astronomy at KU Leuven.

The astronomers detected an object in orbit around L2 Puppis. The object was about 300 million kilometers from the dying star–or double the distance between Earth and Sun in our own Solar System. In all probability, this object is a distant exoplanet that is in orbit around L2 Puppis, which is its parent-star–and it is providing a precious preview of what will happen to our own planet five billion years from now.

A greater understanding of the interactions between L2 Puppis and its planet will provide extremely valuable information about how our own Sun will be during its final stages of evolution–as well as its impact on the planets that circle our dying Star.

Whether our Earth will eventually survive the death of our Sun, or be destroyed, is still unknown. L2 Puppis may provide the answer to this question.

https://youtu.be/7KzPDdo4pRs