While the researchers said Earth would probably be swallowed by our host star, the sun, before it becomes a white dwarf, the rest of our solar system, including asteroids between Mars and Jupiter, as well as moons of Jupiter, ultimately may be shredded by the sun in a white star form

It’s the end of the world, not quite as we know it.

Scientists from the University of Warwickand other universities have studied the impact white dwarfs – end-of-state stars that have burned all their fuel – have on planetary systems such as our own solar system.

When asteroids, moons and planets get close to a white dwarf, the latter’s huge gravity rips them into smaller and smaller pieces, which continue to collide, eventually being ground to dust

Dr Amornrat Aungwerojwit of Naresuan University in Thailand, who led the study, said: “Previous research had shown that when asteroids, moons and planets get close to white dwarfs, the huge gravity of these stars rips these small planetary bodies into smaller and smaller pieces.”

In a couple billion years, our Sun will be unrecognizable. It will swell up and become a red giant, then shrink again and become a white dwarf. The inner planets aren’t expected to survive all the mayhem these transitions unleash, but what will happen to them? What will happen to the outer planets?

The Sun will be a red giant for about one billion years. After that, it will undergo a series of more rapid changes, shrinking and expanding again. But the mayhem doesn’t end there.

The unpredictable nature of these transits can drive astronomers crazy—one minute they are there, the next they are gone.”Professor Boris Gaensicke, University of Warwick

Which white dwarf will mark the end of the solar system? 

Now, you must be wondering where this white dwarf will emerge from. Well, the white dwarf will not appear from thin air, but will be none other than our host star, the Sun. 

When a star burns all its fuel, it is converted into a white dwarf. This is the end state of each star. Therefore, when all the fuel in the Sun, which is composed of hydrogen atoms, is exhausted, it will become a white dwarf.

As part of the study, the researchers analysed what happens to asteroids, moons and planets that pass close to white dwarfs. 

The scientists studied transits, which are dips in the brightness of stars caused by objects passing in front of them. Transits caused by orbiting planets around stars are predictable, but transits caused by debris are chaotic, disorderly, and oddly shaped. 

When asteroids, moons and planets come close to white dwarfs, they are ripped apart into smaller pieces due to the huge gravity of the stars.

When the Sun becomes a white dwarf, asteroids and moons in the solar system are likely to be shredded into smaller pieces.

Quadrillions of years from now, when the Sun has faded to a white dwarf then black dwarf and eventually cooled completely, would we be able to land on its surface? What would it consist of?

A white dwarf is an object structured like an atom with discrete, filled electron orbitals, but rather than a nucleus, it has a cloud of free protons flying around and still behaving classically, seemingly unaware of the weird situation. The bigger, puffier electrons are not behaving this way- they’re stacked up with no room to spare, like the electrons in a large neutral atom. The star can’t collapse because it’s held up by electron degeneracy pressure- if you squeeze the star, you’re squeezing these filled electron orbitals too, making them smaller, so that the electrons need more energy to occupy them. That extra energy must come from you squeezing. (Ordinary individual atoms are hard to “squeeze” for the same reason.) The heavy protons in the star would love to collapse further, maybe to the size of a city, but the electrons won’t accompany them down. The weight of the protons is counterbalanced by electron degeneracy pressure only at a certain radius, and if the mass increases, this equilibrium radius decreases. The star will actually shrink if it gets heavier.Electron degeneracy pressure is fundamentally different than what currently exists in the sun. Its core has a density ten times larger than solid lead, but gravity is still countered with ordinary PV=nRT pressure. (It’s weird, but the ideal gas law you learn in high school still works in the Sun’s core. It’s so hot down there that the energetic particles have deBroglie wavelengths that are small even compared to the minuscule mean free path of a particle in such a dense material.) In a white dwarf, the core density is 100,000 times that of solid lead. You can’t use PV=nRT anymore- the mean free paths are too short for classical physics. Degeneracy pressure doesn’t have a thermal origin; it’s a quantum effect. It persists even at a temperature of zero once the star enters its dark era.(If the temperature and density are high enough, the electrons with the highest energies can engage in the uphill p + e => n + neutrino reaction. The neutrinos leave, the neutrons sink, their gravity squeezes the star, electron orbitals get tighter, their energy rises, more neutrons form and fall to the center, and you get what a stellar climatologist would call a “positive feedback loop”. This is an oversimplification, since there are similar uphill reactions involving carbon and oxygen that require less energy, and these are what provide the actual ignition. The supernova starts as a scattered flash deflagration in the core that spreads outward, in a process known as carbon detonation that triggers all Type Ia supernovas.)

The star’s temperature is extremely high, so there are a large number of unfilled electron orbitals. As the “atom” relaxes to its ground state over trillions of years, electrons in higher energy states fall into these unoccupied orbitals and the star emits photons. The surface is extremely hot and bright, and most of the radiation is UV and soft X-rays rather than visible light. If a white dwarf had the sun’s angular radius in the sky, you would be less impressed than vaporized. Radiative cooling obviously proceeds really slowly because the star only has the surface area of the Earth to shine with now. Once the parking lot of electrons is completely full, the star is in thermodynamic equilibrium with the rest of the universe and goes dark

A white dwarf

A white dwarf is a stellar core remnantcomposed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun‘s, while its volume is comparable to Earth‘s. A white dwarf’s low luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. ¹ The name white dwarf was coined by Willem Luyten in 1922.

White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the stars in the Milky Way.^[4]: §1 After the hydrogen–fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant during which it fuses helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon (around 1 billion K), an inert mass of carbon and oxygen will build up at its center. After such a star sheds its outer layers and forms a planetary nebula, it will leave behind a core, which is the remnant white dwarf. Usually, white dwarfs are composed of carbon and oxygen (CO white dwarf). If the mass of the progenitor is between 7 and 9 solar masses (M_☉), the core temperature will be sufficient to fuse carbon but not neon, in which case an oxygen–neon–magnesium (ONeMg or ONe) white dwarf may form. Stars of very low mass will be unable to fuse helium; hence, a helium white dwarf may form by mass loss in binary systems.

The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. As a result, it cannot support itself by the heat generated by fusion against gravitational collapse, but is supported only by electron degeneracy pressure, causing it to be extremely dense. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the Chandrasekhar limit — approximately 1.44 times M_☉ — beyond which it cannot be supported by electron degeneracy pressure. A carbon–oxygen white dwarf that approaches this mass limit, typically by mass transfer from a companion star, may explode as a type Ia supernova via a process known as carbon detonation; SN 1006 is thought to be a famous example

White dwarf discovery

The first white dwarf discovered was in the triple star system of 40 Eridani, which contains the relatively bright main sequencestar 40 Eridani A, orbited at a distance by the closer binary system of the white dwarf 40 Eridani B and the main sequencered dwarf40 Eridani C. The pair 40 Eridani B/C was discovered by William Herschel on 31 January 1783. In 1910, Henry Norris Russell, Edward Charles Pickering and Williamina Fleming discovered that, despite being a dim star, 40 Eridani B was of spectral type A, or white. In 1939, Russell looked back on the discovery:

Habitability

It has been proposed that white dwarfs with surface temperatures of less than 10,000 Kelvins could harbor a habitable zoneat a distance of c. 0.005 to 0.02 AU that would last upwards of 3 billion years. This is so close that any habitable planets would be tidally locked. The goal is to search for transits of hypothetical Earth-like planets that could have migrated inward or formed there. As a white dwarf has a size similar to that of a planet, these kinds of transits would produce strong eclipses. Newer research casts some doubts on this idea, given that the close orbits of those hypothetical planets around their parent stars would subject them to strong tidal forces that could render them uninhabitable by triggering a greenhouse effect. Another suggested constraint to this idea is the origin of those planets. Leaving aside formation from the accretion disksurrounding the white dwarf, there are two ways a planet could end in a close orbit around stars of this kind: by surviving being engulfed by the star during its red giant phase, and then spiralling inward, or inward migration after the white dwarf has formed. The former case is implausible for low-mass bodies, as they are unlikely to survive being absorbed by their stars. In the latter case, the planets would have to expel so much orbital energy as heat, through tidal interactions with the white dwarf, that they would likely end as uninhabitable embers.

The sun gave spark of life to the earth and will take it away by fire 🔥

The habitable zone, the Goldilocks zone of the Sun will gradually move farther away as the red giant expansion continues. Once the sun has expanded to its maximum size, there is some uncertainty as to the fate of Jupiter, which would be much closer to the Sun than it is today. It could lose vast quantities of its mass because it is a gas giant. However, gas giant exoplanets have been observed quite near their red giant stellar hosts, and they are holding themselves together, so the future of Jupiter is somewhat uncertain, as well as that of Saturn.

Jupiter will be in a habitable zone. Examine the following illustration to see the significant changes which will take place during the Sun’s evolution to a red giant.

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