There are an estimated 100 billion galaxies in the observable universe. Each galaxy contains an average of 100 billion stars. That means there are approximately 10,000,000,000,000,000,000,000 (10 sextillion) stars in the observable universe.
In 2013, astronomers estimated that there are 700 sextillion planets in the universe. That’s 7 followed by 23 zeroes. And because of the way stars and planets form, there could be even more.
The universe is huge and it’s always expanding. The most recent measurement put the diameter of the observable universe at 93 billion light-years. That’s the distance light can travel in a vacuum in 93 billion years. And because the universe is expanding, that number is only getting bigger.
The universe is also incredibly old. The most recent estimates put the age of the universe at around 13.8 billion years. That means there are some stars that are almost as old as the universe itself.
Most of the universe is empty space. If you took all of the matter in the universe and spread it out evenly, it would barely cover the surface of a penny. That’s because most of the universe is empty space. In fact, it’s estimated that the average density of the universe is less than 1 atom per cubic meter.
Even though the universe is mostly empty space, it’s still incredibly full of energy. In fact, the total amount of energy in the universe is thought to be around 10^114 joules. That’s a 1 followed by 114 zeroes. Most of that energy is in the form of dark energy, which is a type of energy that is associated with the vacuum of empty space.