This is the Dumbbell Nebula, photographed from my driveway (1,200-,1400 light years away).
If you could look deep into the center of most stars, you would see hydrogen atoms. 99.99999999999% of a hydrogen atom consists of empty space... but at its core is 1 proton, 1 electron, and 0 neutrons. Because the forces and temperatures are SO BIG at the center of stars, these protons and electrons are squished together with protons and neutrons of other hydrogen atoms. This squishing process (a very scientific term) is called "nuclear fusion." "Nuclear Fusion" sounds intimidating, but it's just a process where two lighter nuclei come together to form a single heavier nucleus (and release energy).
As these ultra-lightweight hydrogen atoms are squished together, energy and helium (an element much heavier than hydrogen) are created. The energy is released outward as heat, while the helium sinks to the star's core. This *outward* release of energy balances out the *inward* pull of gravity from a star's core, preventing it from collapsing on itself.
Our closest star, the Sun, has been undergoing a form of "nuclear fusion" (here, turning hydrogen into helium) for about 5 billion years, and has 5 billion years worth of hydrogen left before it runs out.
Over time, the Sun's *core* will eventually turn to helium. This creates even more heat and causes a hydrogen shell to form around the helium core. This shell gets very hot (due to the nearby helium collapsing on itself) and this extra heat will cause the Sun to expand (x100) and cool. As the Sun cools, its color will change from a "hot" white to a cooler "red." This is why these dying stars are called "Red Giants" ... "Red" because the color shifts and "Giant" because they become larger.
The nuclear fusion that occurs in stars is absolutely fascinating, and is likely the cause of every element in the universe (including those on Earth). If you apply enough heat and pressure to Helium [periodic table #2], it fuses into carbon [periodic table #3]. For really big stars, the elements keep fusing together. Carbon [3] turns into oxygen [8], neon [10], and magnesium [12]. These ultimately turn into silicon [14], which fuses into iron [26]. Stars that get all the way to iron [26] sometimes explode (supernovae--whose core lives on as either a "neutron star" or black hole). Elements heavier than Iron [26] are likely to have come from supernova explosions.
As fusion occurs, shells of these various elements are formed around the star. Eventually, gravity can't hold on to these shells and they are ejected into space, forming rings around the now dead (small) star (referred to as a "white dwarf"). The star is "dead" because no fusion is taking place, although it continues to emit light. The white dwarf emits radiation for about a million years, which ionizes the gas between the star and the rings that were ejected, sending light photons to Earth that I can capture with my telescope!
The photo I took has a white dwarf in the center, and you can see the rings that exploded outward (and are still expanding outward). Scientists call these types of objects "planetary nebulae" even though they have nothing to do with planets. This could be what our Sun looks like in many billions of years.
Additional Thoughts: Hydrogen is the lightest element on Earth. We fill balloons with helium instead of hydrogen because hydrogen is flammable, and helium is not.
Full size photo here: https://astrob.in/full/c0dwi2/0/
If you could look deep into the center of most stars, you would see hydrogen atoms. 99.99999999999% of a hydrogen atom consists of empty space... but at its core is 1 proton, 1 electron, and 0 neutrons. Because the forces and temperatures are SO BIG at the center of stars, these protons and electrons are squished together with protons and neutrons of other hydrogen atoms. This squishing process (a very scientific term) is called "nuclear fusion." "Nuclear Fusion" sounds intimidating, but it's just a process where two lighter nuclei come together to form a single heavier nucleus (and release energy).
As these ultra-lightweight hydrogen atoms are squished together, energy and helium (an element much heavier than hydrogen) are created. The energy is released outward as heat, while the helium sinks to the star's core. This *outward* release of energy balances out the *inward* pull of gravity from a star's core, preventing it from collapsing on itself.
Our closest star, the Sun, has been undergoing a form of "nuclear fusion" (here, turning hydrogen into helium) for about 5 billion years, and has 5 billion years worth of hydrogen left before it runs out.
Over time, the Sun's *core* will eventually turn to helium. This creates even more heat and causes a hydrogen shell to form around the helium core. This shell gets very hot (due to the nearby helium collapsing on itself) and this extra heat will cause the Sun to expand (x100) and cool. As the Sun cools, its color will change from a "hot" white to a cooler "red." This is why these dying stars are called "Red Giants" ... "Red" because the color shifts and "Giant" because they become larger.
The nuclear fusion that occurs in stars is absolutely fascinating, and is likely the cause of every element in the universe (including those on Earth). If you apply enough heat and pressure to Helium [periodic table #2], it fuses into carbon [periodic table #3]. For really big stars, the elements keep fusing together. Carbon [3] turns into oxygen [8], neon [10], and magnesium [12]. These ultimately turn into silicon [14], which fuses into iron [26]. Stars that get all the way to iron [26] sometimes explode (supernovae--whose core lives on as either a "neutron star" or black hole). Elements heavier than Iron [26] are likely to have come from supernova explosions.
As fusion occurs, shells of these various elements are formed around the star. Eventually, gravity can't hold on to these shells and they are ejected into space, forming rings around the now dead (small) star (referred to as a "white dwarf"). The star is "dead" because no fusion is taking place, although it continues to emit light. The white dwarf emits radiation for about a million years, which ionizes the gas between the star and the rings that were ejected, sending light photons to Earth that I can capture with my telescope!
The photo I took has a white dwarf in the center, and you can see the rings that exploded outward (and are still expanding outward). Scientists call these types of objects "planetary nebulae" even though they have nothing to do with planets. This could be what our Sun looks like in many billions of years.
Additional Thoughts: Hydrogen is the lightest element on Earth. We fill balloons with helium instead of hydrogen because hydrogen is flammable, and helium is not.
Full size photo here: https://astrob.in/full/c0dwi2/0/
