Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff, Lauren Bolebaum. Here.
Speaker 1: When our Sun runs out of hydrogen fuel in roughly
Speaker 1: five billion years, it will swell into a huge, red
Speaker 1: giant star, violently shedding hot layers of plasma and cooking
Speaker 1: the inner planets to a crisp as it goes. All
Speaker 1: that will be left behind is an expanding bubble of
Speaker 1: cooling gas, creating a beautiful planetary nebula with a white
Speaker 1: dwarf in the middle, shining bright like a stellar diamond.
Speaker 1: Though we know this is the fate of our star,
Speaker 1: what of the planets in our Solar system? But what
Speaker 1: exactly will happen to Earth long after we're gone. Astronomers
Speaker 1: from the University of Warwick in the UK took a
Speaker 1: stab at answering this question back in twenty nineteen and
Speaker 1: came up with a rudimentary warning guide for planets that
Speaker 1: find themselves in this grim scenario. While our planet's fate
Speaker 1: isn't necessarily clear, the study, which is published in the
Speaker 1: journal Monthly Notices of the Royal Astronomical Society, revealed that
Speaker 1: when it comes to contending with a white dwarf star,
Speaker 1: only the tiniest worlds will survive. Why is that, Well,
Speaker 1: we know that many white dwarf star systems have quantities
Speaker 1: of dust surrounding them, and through spectroscopic measurements, dust has
Speaker 1: been found polluting these star's atmospheres. The implication is clear.
Speaker 1: These star systems used to have rocky planets, plus asteroids
Speaker 1: and comets and orbit, but through extreme tidal interactions with
Speaker 1: their white dwarf, were torn to shreds and ground to dust.
Speaker 1: But why do planetary bodies get blended when they're in
Speaker 1: the orbit of a white dwarf. These exotic stellar objects
Speaker 1: contain nearly the entire mass of the dead star that
Speaker 1: they came from, in a blob of degenerate matter only
Speaker 1: the size of Earth. With this extreme density comes an
Speaker 1: incredibly powerful gravitational field and tidal forces. Anything that strays
Speaker 1: too too close to a white dwarf will be pulled
Speaker 1: in by that powerful gravity. But there's a much wider
Speaker 1: zone of destruction around such a star within which planets
Speaker 1: or other orbiting bodies will be destroyed. Within this zone,
Speaker 1: a planet, for example, will experience a much more powerful
Speaker 1: tidal force on the star facing side than on the
Speaker 1: side facing away, depending on what that planet is made
Speaker 1: of and how well it holds together due to its
Speaker 1: own gravity and a number of other factors. At a
Speaker 1: certain distance, the tidal shear through the planet will be
Speaker 1: too much, and it will be literally pulled like taffy
Speaker 1: until it's pulled right apart. This is known as the
Speaker 1: destruction radiusmarked by an ominous dusty ring around a white dwarf.
Speaker 1: To understand where a variety of planets of different sizes
Speaker 1: might be safe, the researchers carried out dynamic simulations of
Speaker 1: different planets in orbit around a star like our Sun,
Speaker 1: as it dies and passes through the red giant phase
Speaker 1: to become a white dwarf. This violent phase of a
Speaker 1: star's life will disturb the orbit of the planets around it,
Speaker 1: possibly dragging them to their dusty deaths or flinging them
Speaker 1: to wider orbits. Interestingly, the researchers found that it isn't
Speaker 1: just the mass and composition of planets that affect how
Speaker 1: sensitive they are to the tidal shear. It's also their
Speaker 1: viscosity or the resistance they have to being deformed. Think
Speaker 1: if you had a glass of water and a glass
Speaker 1: of nacho cheese, If you poked the surface of the water,
Speaker 1: it would easily deform around your finger. You'd feel basically
Speaker 1: no resistance at all. This is low viscosity. Now, if
Speaker 1: you poked the nacho cheese, I mean, you'd still be
Speaker 1: able to deform its surface, but it would give you
Speaker 1: a little bit more resistance because it has a higher viscosity. Now,
Speaker 1: think about if you poke the glass itself, It's not
Speaker 1: going to deform at all from a mere poking. Of
Speaker 1: the three, it has the highest viscosity under these particular circumstances. Anyway,
Speaker 1: the physics is complicated. But back to white dwarfs. The
Speaker 1: researchers found that if all other variables were controlled for
Speaker 1: low viscosity, exoplanets of a similar consistency to say, Saturn's
Speaker 1: moon Enceladus, which they called a relatively homogeneous dirty snowball
Speaker 1: because of its thick iso layers surrounding a small core,
Speaker 1: would be dragged to its doom if it resides within
Speaker 1: anywhere up to five times of the white dwarf's destruction radius.
Speaker 1: At the other extreme, a high viscosity world might live
Speaker 1: comfortably if it orbited the white dwarf at just twice
Speaker 1: its destruction radius. Recently, astronomers discovered a dense, heavy metal
Speaker 1: object around a white dwarf that's embedded inside a dusky disc.
Speaker 1: It's believed that this object, which isn't much bigger than
Speaker 1: a large asteroid, was the metal core of a larger
Speaker 1: planet that was destroyed by tidal shear, leaving its high
Speaker 1: viscosity metallic core behind. As the search for exoplanets, that
Speaker 1: is planet's orbiting other stars becomes more sophisticated, we're going
Speaker 1: to observe more worlds in white dwarf star systems, So
Speaker 1: the researchers hope that these simulations will act as a
Speaker 1: guide that will help us understand what those exoplanets are
Speaker 1: made of. Although this simulation has provided some key insights
Speaker 1: to what it takes to avoid being dragged to a
Speaker 1: dusty death, it only simulated relatively homogeneous objects. When it
Speaker 1: comes to our planet, the problem becomes more complex because
Speaker 1: of all the layers of atmosphere, water, rock, and inner
Speaker 1: metallic core that our planet contains. But in summary, it
Speaker 1: pays to be tiny and mighty and composed of heavy
Speaker 1: metals if you want to have a snug orbit around
Speaker 1: a white dwarf without being dragged to your death. As
Speaker 1: for Earth's fate, we'll have to wait and see, but
Speaker 1: in all honesty, you probably won't want to be there
Speaker 1: when our red giant sun switches to broil. A note
Speaker 1: that long before the Sun runs out of hydrogen and
Speaker 1: puffs up into a red giant let alone before it
Speaker 1: becomes a white dwarf, it will become a lot hotter
Speaker 1: than it is now, irradiating the inner planets. This, combined
Speaker 1: with powerful solar winds, will likely blast away our atmosphere,
Speaker 1: undoubtedly destroying any and all life that remains. So today's
Speaker 1: episode is based on the article white dwarfs can shred
Speaker 1: planets to pieces on HowStuffWorks dot com, written by Ian O'Neil.
Speaker 1: Brainstuff is production of iHeartRadio in partnership with hostuffworks dot
Speaker 1: Com and is produced by Tyler klang A. Four more
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