1Interstellar Objects
The first known interstellar object detected passing through our Solar System is an asteroid called ʻOumuamua’, which was observed in 2017. It was a rocky, cigar-shaped object tumbling through space. Another interstellar object our solar system may have had a close encounter with happened around 70,000 years ago. A Red Dwarf star named Scholz's Star passed through the Solar System’s Oort cloud (~52,000 AU). It was so close in fact, that it nudged some Comets out of their orbits. It may have been visible to early Humans and Neanderthals.
2. 16 Psyche is a large asteroid that is supposed to be worth $10,000 quadrillion. Orbiting between Mars and Jupiter, it is over 200 km (120 mi) in diameter. It could contain enough iron and nickel to sustain the world’s metal needs for millions of years. 16 Psyche is scheduled for space exploration, with a spacecraft launch planned in 2022, arrival in 2026, and orbital exploration in 2026–2027
3. Our sun will get hotter over time and in about 600 million to 700 million years the conditions on earth won’t allow for photosynthesis. All the oceans will boil away a little while later. The earth will be a dead rock by the time the sun gets within a few billion years of turning into a red giant, at which point the sun will enlarge enough to engulf our planet. Europa might be nice, sunny, and perhaps habitable by then. Given the lead time that humanity has (more than 500 million years) humanity could perhaps engineer the Earth away from the heat (if humanity even survives by that time) or maybe mine the sun to prevent it from becoming a red giant in the first place, followed by moving the sun itself to a more friendly long-term location.
4. One strange way to reach the nearest stars was proposed by astronomer Fritz Zwicky, who was the first person to theorize dark matter, supernovas, and neutron stars. He proposed accelerating the sun via a nuclear fusion-powered stellar engine and having it drag all the planets along. He warned that if the US didn't pursue this, the Russians would. According to a recently published paper, a Caplan thruster could use the sun’s own energy to transport our solar system to any desired location.
5. A 2015 study concluded that the Universe will form over 10 times more planets than what currently exists. Scientists assume that there are currently 40 billion earth-like planets in the habitable zone of their stars in the Milky Way Galaxy alone and a lot more such planets will form throughout the life of our universe. This would imply that there is at least a 92 percent chance that we are not the only civilization the universe will ever have.
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6The Great Nothing
The Boötes void, a.k.a the Great Nothing, is an enormous spherical region of space that has a very small number of galaxies. At nearly 330 million light-years in diameter, it is one of the largest known voids in the Universe. The scale of the void is such that if the Milky Way had been in the center of the Boötes void, we wouldn’t have known there were other galaxies until the 1960s. This void has opened space for many discussions of its origin, including the hypothesis of a Type III civilization in the Kardashev scale. It would be a galactic civilization that can control energy at the scale of its entire host galaxy.
7. Dark Energy is calculated to make up 67% of the known universe, while Dark Matter makes up a further 27%, while what we can actually see and measure, i.e., conventional matter, makes up less than 5% of our universe. Therefore our current model of physics only works for 5% of the matter/energy in the universe. Dark energy should explain the expansion of the universe which is accelerating faster and faster and doesn’t match up with the expected gravity, ergo some kind of energy must be fuelling it. If it doesn’t slow down, one-day inflation of space will be exponentially faster than the speed of light.
8. For more than 200 years, astronomers thought that most of the stars in our galaxy were binary stars and that our sun was a unique exception. Recent discoveries however have revealed that most stars are not binary after all, although most (80%) of sun-sized stars are in pairs. Most stars in the galaxy (85%) are red dwarfs which generally form alone. Scientists also believe a few percent of stellar systems are trinary stars. Since 3-body systems are generally unstable, they only last for significant times if two of the stars are close together, with one far away (think Earth-Moon-Sun).
9. The moon does rotate, but the time it takes to rotate around its axis is exactly equal to the time it takes to orbit the Earth and as a consequence, we always see the same side of the Moon. This isn’t a coincidence but this happens due to “tidal locking”, which causes the rotation of an object to sync up with its orbit. The tidal force from the Moon isn’t just making the seas and oceans move around, it also pulls at the solid bits of the Earth, ever so slightly slowing down the rotation of the Earth. If the Sun wouldn’t gobble up the Earth when it expands in 4-5 billion years, then some 50 billion years from now the Earth would be tidally locked to the Moon at which point the same side of the Earth would always be facing the Moon and the length of a day would be much longer than the 24 hours it is now.
10. TON 618 is a hyperluminous quasar that possesses an ultramassive black hole which is the largest black hole ever found. It has been observed to be consuming galaxies' worth of matter and is shining with the brightness of a hundred trillion stars, visible from 18 billion light-years away. The back hole is 66 billion times the mass of our sun, greater than the mass of all the stars in the Milky Way galaxy combined.
11White Dwarfs
After medium-sized stars like our Sun die and explode into a spectacular planetary nebula, what remains of its core will become a white dwarf. After our sun dies and becomes a white dwarf, it will only be about the size of our earth, but with a surface gravity over 100,000 times higher than Earth's. Eventually, these white dwarf stars will cool into black dwarfs, but this process is theorized to take 100 billion billion years. That’s so far into the future that no regular stars will shine anymore, galaxies will have evaporated, and only then will the first white dwarf turn into the first black dwarf. Planets around white dwarfs could be humanity's last home right before the death of the universe.
12. All stars fuse hydrogen into helium. Medium stars, like our Sun will eventually fuse helium into carbon and oxygen before eventually turning into white dwarfs. It will take stars many times the mass of our Sun to fuse heavier elements. After exhausting helium they’ll burn carbon to neon in centuries, neon to oxygen in a year, oxygen to silicon in months, and silicon to iron in a day, before imploding. This implosion bounces off the iron core and causes a supernova explosion. Above iron, heavier elements are mainly created in supernovae, where there is lots of energy to spare; however, because these are short-lived and (relatively) rare events, elements above iron are rarer than those below.
13. If we were to surround a rotating black hole with a mirror and shoot a laser beam inside it, the beam would get exponentially more and more powerful by stealing energy from the hole via superradiant scattering. It could eventually overpower the mirror and result in a powerful explosion on par with a supernova. We could prevent these black hole bombs from going off by harvesting some of this energy. Using this type of energy we can theoretically power civilization for millions if not billions of years. In fact, these black hole civilizations may be the last home for any species in a dying universe.
14. In 2015, scientists detected, for the first time, the merger of 2 black holes in a galaxy 17 billion lightyears away by measuring the gravitational waves emitted by the collision. As they spun around each other violently, they released more energy in the form of gravitational waves than the combined light from all the stars in the Milky Way in 4400 years.
15. The classic movie portrayal of a crowded asteroid belt in our solar system where the asteroids are only meters apart is inaccurate. In reality, the average distance between asteroids is around 965,000 km (600,000 miles) and if you were to fly through it, a collision would be unlikely. Ceres, which is supposed to be the largest object (with a 473 km radius) in the asteroid belt, alone is estimated to hold about a third of the asteroid belt's mass. In fact, the asteroid belt is so not-dense that when sending probes through it, mission control doesn’t even bother calculating a clear path. The chances of hitting something are so low that it’s a waste of time to worry about it. NASA estimates that the odds of hitting an asteroid if you just randomly shoot a probe at the asteroid belt are 1/1,000,000,000.
16Galactic Orbit
Our solar system revolves around a giant black hole in the middle of the galaxy in the constellation Sagittarius. This galactic orbit takes about 250 million years, so the last time the earth was on the other side of the galaxy, the dinosaurs were around. Dust clouds at the center of our galaxy however obscure this black hole from ever being visible from earth. If we could however remove those dust clouds, then we would be able to see a fireball rise every night rivaling the moon in brightness with a raging black hole in the center.
17. Turbulence in stellar nurseries will cause groups of stars from the same cloud to be scattered relatively quickly. There’s no reason to think that the current nearest stars to the sun are our siblings, though we probably do have sibling stars out there somewhere. Scientists have probably found a star (HD 162826) that formed from the same molecular cloud as our sun about 110 light-years away. This star might have shared the stellar nursery the sun was born in about 4.6 billion years ago. This star is 15 percent more massive than the sun, so it can’t be called a solar twin, just a solar sibling.
18. Due to angular momentum, when really massive spinning stars collapse to form black holes, they start spinning faster and faster. In fact, some black holes spin millions of times a second. This spinning creates a volume of dragged space-time called the ergosphere, which is escapable. Theoretically, any injected matter could capture some of the spinning black hole's angular momentum. British mathematician Roger Penrose hypothesized a way to steal some energy from a rotating black hole by injecting matter into the ergosphere and capturing some of the spinning black hole's angular momentum.
19. When a star goes supernova, the rapidly expanding bubble of hot, metal-rich gas from it hits the edge of the galactic disk where it suddenly encounters much less resistance from a much lower density of the interstellar medium, allowing it to form a chimney perpendicular to the disk. After arcing well outside the disk, this material then cools and rains down over a large portion of the galaxy, seeding stellar nurseries with metals that will later become planets.
20. Our solar system is surrounded by an 89,000 degree Fahrenheit orb of plasma created by the interaction between the sun and interstellar winds. This creates a 100 million miles wide sausage-shaped bubble known as the heliosphere and it protects the solar system from harmful cosmic rays. Outside the heliosphere begins the interstellar space, beyond which Oort cloud is theorized to exist. The solar system’s boundary is theorized to include Oort cloud from where long-period comets are thought to originate. Traveling at the speed of the fastest man-made object it would take 'Voyager 1' 300 years to reach it and it would take another 30,000 years to pass through it. Outside this, our solar system is currently in an area with only 5% of the average density of the galaxy. It was likely blasted clear by a supernova 20 million years ago.
21Quasi Star
A Quasi-star is a type of (extremely) massive star that may have existed early in the universe. The matter in the early universe was so dense that quasi stars could grow to thousands of times the mass of our sun. The cores of these stars might have been crushed by their own weight so much to actually collapse into black holes while the star was still forming. Its energy would come from material falling into a central black hole, as opposed to nuclear fusion. These stars might explain the supermassive black holes that exist today as the universe is simply not old enough for these supermassive black holes to exist.
22. It is believed that one star goes supernova somewhere in the universe on average every single second and for the Milky Way galaxy this number is 3 stars every century. Humanity has only recently developed instruments like neutrino detectors that are sensitive enough to detect new supernovas. Neutrinos are emitted directly when the core collapses, so they arrive here earlier than the light. So if a neutrino detector picks up a supernova signal, they automatically send a message to various telescopes to watch that spot for the upcoming supernova. In fact, anyone can sign up to their early warning mailing list so you will get notified if they detect one. It's not reserved for just astronomers.
23. White holes are the hypothetical opposite of black holes. It is supposed to be a region of space-time that cannot be entered from the outside, although matter and light can escape from it. Some scientists suggest that 'The Big Bang' might have been produced by a supermassive white hole explosion. It theoretically exists as a result of Einstein’s field equations, but there is no physically known process for one to be made.
24. Hypervelocity stars travel the galaxy at 1000 km/sec. They’re made when one star in a binary system gets sucked into the supermassive black hole in the middle of a galaxy, and its partner is flung out 100x faster than other stars, sometimes faster than the galactic escape velocity. One neutron star in particular (RX J0822-4300) was measured to be moving at a record speed of over 1,500 km/s (0.5% of the speed of light) in 2007 by the Chandra X-ray Observatory.
25. On an interstellar scale, humanity is practically invisible. The radio signals that we transmit into outer space may extend over an impressive 200 light-years, but this is only a tiny fraction of the Milky Way (105,700 light-years in diameter). Even if someone were listening, after a few light-years our signals will decay into noise, impossible to identify as the source of an intelligent species.
