This is an image of an amazing stellar dance, these two stars orbit each other in 2.5 hours and they are gradually moving inwards towards a collision. This type of collision betwixt Neutron stars is the cause of the most powerful explosions in the Universe, a gamma ray burst. A collision between two Red Dwarf stars will not be as spectacular, but still something worth witnessing. The Universe is an amazing place, there are amazing sights to see, but we need the will and the funds to be able to reach the stars and catalogue these scientific discoveries up close. The phenomenon of Vampire Stars that is one star using its gravity to siphon material off an orbiting neighbor. A black hole can also perform this feat, but obviously to greater effect. A black hole moving through space can drag a star along with it, which is obviously bad news if it is heading towards Earth.
But that is a remote possibility, there are so many other natural disasters that could befall the Earth. The La Palma land-slide could happen, this is a giant block of rock that would slip into the ocean, creating a 50 – 100 meter tall Tsunami that would travel outwards at an initial velocity of 720 kilometers an hour. The wave would be between 15 – 25 meters tall when it reaches New York. Since the wave would only take 8 hours to cross the ocean, there would be little warning and not much hope of evacuating all of the cities inhabitants in time to save everyone. The roads would be jammed with cars and no-one would be able to escape. The best policy is to move as far inland as you can, to escape any danger. Of course if the Yellowstone volcano erupts or if an asteroid impacts in the center of the continental US, then there is still danger.
An asteroid equal in size to the one that created the Chixalub crater would be an enormous disaster if it was to happen today. With the nuclear winter effects of the massive amount of dust thrown up into the atmosphere, it would decimate agriculture and cause enormous loss of life. The movie Armageddon showed a truly stupendous asteroid that was threatening the Earth. They blew it up with a bomb even though in reality even a 200 megaton bomb would only vaporise out a giant cavern underground and would not split the asteroid at all. It is the size of Texas and one bomb is supposed to be able to split it in half? You might need a 10,000 megaton warhead. Even the Saturn 5 rocket could only carry a 700 Megaton warhead, nowhere near enough power to destroy such a massive rock. Building a 1 Gigaton warhead is a possibility, such a massive bomb would cause unimaginable destruction if you detonated it at the center of Europe or North America.
There is no theoretical upper limit to the size of a thermonuclear bomb, you could build a 1000 Gigaton bomb conceivably if you had enough material and did not need it to be mobile in any way. That bomb if placed at the core of the Armageddon asteroid would destroy it easily. I wish you could destroy that movie and save humanity from such tripe.