The ultimate fate of every star that ever lived

Given enough time, every star will eventually die.

interior of a core collapsing supernova and element locations

Artist’s illustration (left) of the interior of a massive star in the final, pre-supernova stage of silicon combustion. (The combustion of silicon forms iron, nickel, and cobalt in the core.) A Chandra image (right) of Cassiopeia A supernova remnant today shows elements such as iron (blue), sulfur (green), and magnesium ( red). Ejected stellar material can glow for tens of thousands of years due to heat in the infrared, and the ejected particles from supernovae can be asymmetrical and contain separated elements, as shown here. In the right environment, this asymmetric material can be unevenly incorporated into future generations of stars.

Credit: NASA/CXC/M.Weiss (illustration, left) NASA/CXC/GSFC/U. Hwang & J. Laming (image right)

Stars are born when gaseous matter accumulates, fragments and collapses.

gas globules at the edge of the Orion Nebula

Here, evaporating gaseous globules are seen at the edge of a star-forming region in the Orion Nebula, containing newborn stars, Herbig-Haro objects and many fainter sources, including protostars, brown dwarfs and even planetary-mass objects. inside. As the gas continues to boil away, more and more of these lower-mass objects should be revealed.

Credit: MJ McCaughrean & SG Pearson, A&A submitted, 2023

Initiating hydrogen fusion in their cores officially leads to the birth of a star.

NASA's spacecraft investigates the birth of stars.

This ALMA observation of a high-mass protostar cluster, G351.77-0.54, has reached a spatial resolution of ~120 AU, which corresponds to 0.06 arcseconds at the distance of these protostars. The gaseous material fragments into at least four separate cores, an indication (now with further evidence) that core fragmentation, rather than anything related to a disk, plays an important role in determining how many stars form in these massive stars . -forming regions. When nuclear fusion reactions occur in these protostar nuclei, they will officially become full-fledged stars.

Credit: H. Beuther et al., Astronomy & Astrophysics, 2017

The external pressure from nuclear reactions keeps the star from collapsing due to gravity.

cut away sun

This exploded view shows different parts of the Sun’s surface and interior, including the core, the only location where nuclear fusion takes place. As time passes and hydrogen is consumed, the helium-containing region in the core expands and its maximum temperature increases, increasing the sun’s energy production. The balance between the inward pull of gravity and the outward push of radiation pressure determines the size and stability of a star.

Credit: Wikimedia Commons/KelvinSong

If insufficient pressure is created, the star immediately collapses into a black hole.

direct collapse immediately observed

Hubble’s visible/near-IR images show a massive star, about 25 times the mass of the Sun, disappearing from existence, with no supernova or other explanation. Direct collapse is the only reasonable candidate explanation, and is a known way, in addition to supernovae or neutron star mergers, to first form a black hole.

Credit: NASA/ESA/C. Kochanek (OSU)

The heaviest stars quickly burn their fuel and merge into heavier elements.

very massive star supernova

The anatomy of a very massive star throughout its life, culminating in a Type II (core collapse) Supernova when the core runs out of nuclear fuel. The final stage of fusion is usually the burning of silicon, producing iron and iron-like elements in the core for only a short time before a supernova occurs. The most massive supernovae that collapse typically result in the creation of black holes, while the less massive supernovae only create neutron stars.

Credit: Nicolle Rager Fuller/NSF

Eventually they will become a supernova and leave behind a black hole or neutron star remnant.

diagram of the anatomy of a supernova collapse

In the inner regions of a star undergoing a core-collapse supernova, a neutron star begins to form in the core, while the outer layers collide with it and undergo their own runaway fusion reactions. Neutrons, neutrinos, radiation, and extraordinary amounts of energy are produced, with neutrinos and antineutrinos carrying away most of the energy of the collapsing supernova. Whether the remnant ultimately becomes a neutron star or a black hole depends on how much mass is left in the core during this process.

Credit: TeraScale Supernova Initiative/Oak Ridge National Lab

Less massive stars, such as the Sun, cannot fuse elements beyond helium.

sun red giant

As the Sun becomes a true red giant, expanding to more than 100 times its current size as its interior contracts and heats to fuse helium, the Earth itself may be swallowed or engulfed, but will certainly be roasted like never before. The Sun’s outer layers will swell, but the exact details of its evolution, and how those changes will affect the planets’ orbits, still contain major uncertainties. Mercury and Venus will certainly be swallowed up by the Sun, but Earth will be very close to the edge of survival/engulfment.

Credit: Fsgregs/Wikimedia Commons

They are doomed to die in a planetary nebula, leaving behind white dwarfs.

planetary nebula

When our sun runs out of fuel, it becomes a red giant, followed by a planetary nebula with a white dwarf at its center. The Cat’s Eye Nebula is a visually spectacular example of this potential destiny, with the intricate, layered, asymmetrical shape of this particular nebula reminiscent of a binary star. At the center, a young white dwarf heats up as it contracts, reaching temperatures tens of thousands of Kelvin hotter than the surface of the red giant from which it emerged. The outer gas shells consist largely of hydrogen, which is returned to the interstellar medium at the end of a Sun-like star’s life.

Credit: Nordic Optical Telescope and Romano Corradi (Isaac Newton Group of Telescopes, Spain)

The least massive stars, meanwhile, only fuse hydrogen in their cores.

proton proton chain

The simplest and lowest energy version of the proton-proton chain, which produces helium-4 from initial hydrogen fuel. Note that only the fusion of deuterium and a proton produces helium from hydrogen; all other reactions produce hydrogen or make helium from other isotopes of helium. This reaction set takes place in the interior of all young, hydrogen-rich stars, regardless of their mass.

Credit: Sarang/Wikimedia Commons

They live the longest and become pure helium white dwarfs: without a counterpart of the planetary nebula.

convection within the sun

The energy produced in a star’s core must pass through large amounts of ionized material before reaching the photosphere, where it is radiated. Inside the Sun there is a large, non-convective zone of radiation around the core, but in lower mass stars the entire star can convect on timescales of tens or hundreds of billions of years, allowing red dwarf stars to merge 100% of the core. hydrogen in it. Red dwarfs cannot fuse elements heavier than hydrogen, so when all their hydrogen is fused together, they simply contract into a white helium dwarf.

Credit: APS/Alan Stonebraker

The merger of stars and brown dwarfs pushes them into larger masses, changing their fate.

moment of devouring star planet

When an orbiting body enters the photosphere of a massive star, the star will increase in size and brighten considerably, but will also stop spewing dusty material; that was only part of the pre-merger phase of the astronomical system in question. Stars often grow through mergers into more massive stars with a shorter lifespan.

Credit: K. Miller/R. Pain (Caltech/IPAC)

Black hole encounters destroy stars through tidal disruption: they are torn apart by gravity.

black hole hit the earth

This illustration of a tidal disruption shows the fate of a huge, large astronomical body that has the misfortune of coming too close to a black hole. It will be stretched and compressed in one dimension, fragmenting it, accelerating its matter and alternately devouring and expelling the resulting debris. Black holes with accretion disks are often very asymmetric in properties, but much brighter than inactive black holes that do not have them.

Credit: ESO/M. Kornmesser

Black holes eventually decay into radiation via the Hawking process.

Hawking radiation black hole decay

The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even light, can escape. But beyond the event horizon, the black hole is expected to emit radiation. Hawking’s 1974 work was the first to demonstrate this, and it was perhaps his greatest scientific achievement. Sun-mass black holes will decay after 10^67 years, while heavier black holes will survive longer.

Credit: NASA/Dana Berry, Skyworks Digital Inc.

White dwarf mergers create Type Ia supernovae: they are destroyed.

there are two ways to create a type Ia supernova

The two main ways to create a Type Ia supernova: the accretion scenario (left) and the merger scenario (right). Most white dwarfs that undergo supernovae are below the Chandrasekhar mass limit, which strongly favors the merger scenario for most Type Ia supernovae.

Credit: NASA/CXC/M. Weiss

Meanwhile, lonely white dwarfs and neutron stars simply fade to black: cold, non-luminous, but lasting forever.

An accurate size/color comparison of a white dwarf (left), Earth reflecting light from our sun (center), and a black dwarf (right). When white dwarfs finally radiate away their last energy, they will all eventually become black dwarfs. However, the degeneracy pressure between the electrons within the white/black dwarf will always be high enough, as long as it does not build up too much mass, to prevent it from collapsing further. A similar process, albeit on longer time scales, should occur in neutron stars.

Credit: BBC/GCSE(L)/SunflowerCosmos(R)

Only isolated, low-mass stellar bodies will last forever.

After the Sun dies, the remaining core will contract and become a white dwarf. On a time scale of 100 trillion years it will disappear and eventually become a black dwarf. Any surviving planets orbiting it must survive gravitational encounters in order to survive, where gravitational radiation will eventually cause them to be devoured by the black dwarf. Black dwarfs should be the last remaining stellar remnants of all.

Credit: Jeff Bryant/Vistapro

Mostly Mute Monday tells an astronomical story in images, visuals and no more than 200 words.

Leave a Reply

Your email address will not be published. Required fields are marked *