Wonders of the universe
One of the first things that filled the imagination of early humans was the sky, they would look up at night and see countless flickering light and watch in amazement asking what they were and why they were up there. We have come a long way from those days but the universe still fills us with wonders and a lot of unanswered questions. Any of those flickering lights viewed up close is a source of wonder but there are few among them that are better than others. This list is by no means a comprehensive one but it’s certainly a great starting point. So let’s begin with object that are small and close to home:
1) Comets. They are composed mainly of rocks and ice, they normally orbit around our solar system in what’s called the Oort cloud and only a small fraction of them enters the inner solar system and it’s placed in a perennial orbit around the sun. Those orbits are usually highly elliptical, passing very close behind the sun and then stretching back to the Kuiper belt and beyond. Being composed of ice when they get close to the sun the ice will leave the comet’s core and form a plume usually millions of miles long. Every time they circle the sun they will lose a big chunk of mass and once they lose all the ice they will continue orbiting the sun in the form of asteroids. For millennia they were considered a sign of great misfortune, luckily they reputation has improved over time.
2) Planets. We live in one of those. So far the one we live on is the only one we know of that’s capable of supporting life but with discovery of many more planets in the last decade or so ( we know of at least 400+ planets so far) the chances of discovering one that can actually support life cannot be too far away.Even by just looking only at our solar system we can get an idea about how different they can get. variations in size can go from few hundreds miles like mercury to the size of a small protostar like Jupiter. Some of them are big enough to be able to hold on to an atmosphere, however the composition of that atmosphere can be very different from planet to planet. Our atmosphere is just right for life to flourishbut just a short distance from us we find Venus with a very heavy,poisonous, acidic and hot atmosphere on one side while on the opposite side we find Mars with it’s very tenuous and cold one. Life as we know it cannot exists on either one of those planets. Some of them have a rocky core and some of them are composed only of gas, some have a small scale system of moons orbiting around them while others have none, some have majestic rings, some possess powerful magnetic fields while others are at the complete mercy of the solar winds. Some of them moves around the sun in the same direction of the sun while few of them are moving backwards. Outside the solar system they go to even bigger extremes. Some are way hotter than Venus,some have atmosphere where instead of raining water it rains molten lead, some of them are gravitationally locked to their stars so that on one side there’s perennial hot lava flowing around while on the opposite side everything is frozen solid. It’s any wonder so many kids want to be an astronaut?
3) Stars. Immense balls of fire, mainly composed of hydrogen and helium, they come in as many sizes as the planets comes in flavours. From immensely hot to relatively cold, from yellow to blue, with sizes ranging from just bigger than Jupiter to 100.000 the mass of our sun, they can last for longer than the present age of the universe to few millions of years. They can die quietly or offer the best fireworks show in the universe with explosions so big they can outshine entire galaxies. They have magnetic fields ranging from very weak to tremendously strong, so strong as to periodically ripped apart the surface of the star. While a lot of them are solitary bodies a small fraction of them can come in pairs or more going around each other in semi permanents orbits. As far as we know thought systems of more than 3 stars won’t allow for stable planetary orbits.they are classified according to their age into population I, very old, and population II, much younger stars.
4) Supernovae and planetary nebulae. Supernovae are a class of stars that ends they lives with big explosions after they runs out of fuel. They comes in 2 flavours. Type I are solitary stars at the end of their lives, they will explode leaving behind only the core of the star (see numb. 5) surrounded by a planetary nebula. Planetary nebulae are the outer layers of the star that’s been thrown into outer space at fantastic speed. Some of the best pictures from the Hubble telescope show the fantastic shapes and colors they can form while travelling for millions of years before finally dispersing into space. Type II are basically type I with a companion star that orbits very close to them. So close in fact that the remain core will draw matter from the companion star until they reach critical mass and then blow up again. Because of their cyclic nature they are used as a standard candle to gauge distances between galaxies.
5) Pulsars. They are the remnant of big stars, they rotates very fast around it’s own axis while releasing powerful blast of energy from it’s poles. heir cycle is so finely tuned that they have been thought to be a sign of an intergalactic civilisation which of course they are not. No planet in orbit around that star would be able to survive intact the supernova explosion or the x-ray bath of the pulsar.
6) Galaxies. Big islands of luminous matter in the darkness of the universe galaxies are big clusters of stars glued together by gravity. they can be small to huge, containing few millions to few billions stars. They also tend to form big galaxy clusters where a number of galaxies will rotate around the center of gravity. Occasionally two or more of them will collide with each other forming a variety of oddly shaped galaxies. They are classified according to their shape into
6.1) Elliptical. Spherical with no easily visible core, usually filled with population I stars, they can either be the result of galaxy collisions or the older version odd spirals.
6.2) Spirals. Our galaxy is one of them. Usually they have very easily recognisable central cores with 2 or 4 spiral arms rotating around the core of the galaxy. Usually filled with both populations of stars they are thought to be the youngest type of galaxy.
6.3) Barred. Usually spirals with 2 arms linked by a visible bar that runs through the core of the galaxy. Thought to be the results of galaxy collisions.
6.4) Irregular. All other shapes that don’t fit into any of the above classes.
7) Black holes. They are the result of a the death of the most massive stars and one of the most loved celestial body in science fiction. They are at the same time the ultimate destroyers and the ultimate creators. The unbelievable force of gravity this monster possess can pull in and destroy a star in a matter of minutes leaving nothing behind. However they have recently been linked with the formation of galaxies so ultimately we would not be able to exists if they were not here. As far as we know every galaxy possess a gigantic black hole at their center that can either be active or not. Their main feature is the singularity that is at the center of any black hole. We still don’t really know what a singularity looks like and we certainly won’t be able to take a look at them anytime soon mainly because in nature every singularity comes with an event horizon and nothing from one side of the horizon can peek into the other side.
