Whether or not you believe in life beyond Earth, there are actually a minimum of 100 billion planets in our universe, according to a NASA study.
But how many planets make up our solar system?
How many planets are there in our solar system?
There are eight planets in our solar system, which is part of the Milky Way.
Pluto was once called the ninth planet in our solar system, but the International Astronomical Union made some category changes in 2006 and Pluto became a minor or dwarf planet.
The main reason for this decision is that the generic orbit of Pluto intersects the orbit of Neptune.
The idea of a ninth planet has persisted, and astronomers are now looking for Planet X, or Planet Nine, after mathematical evidence from 2016.
Planet Nine is thought to be five thousand times the mass of Pluto and 10 times the mass of Earth, and orbiting beyond Neptune.
What is the order of the planets in our solar system?
The planets in our solar system are generally classified according to their distance from the Sun, Mercury being the closest.
Half of the eight planets are known as terrestrial or interior planets – Mercury being closest to the Sun, followed by Venus, Earth, then Mars.
The other half is made up of Jovian or Jupiter-type planets. In order of distance from the Sun, these are Jupiter, Saturn, Uranus and Neptune.
These last four are massive compared to the four inner planets and are made up of gases like hydrogen, helium and nitrogen.
Jupiter and Saturn are often called the gas giants, while Uranus and Neptune are called the ice giants.
It is believed that they probably all have solid cores.
There are many mnemonics for learning the order of the planets, one of the most popular of which is: My highly educated mother just served us noodles.
How many planets have been discovered?
It is believed that there are 4,108 identified exoplanets in and beyond our solar system.
NASA tweeted in January 2021: “So far we have discovered 4,108 exoplanets – planets beyond our solar system.
“Most of these worlds orbit other stars, but not all of them. ‘Rogue planets’ are not linked to any star as they move through space in darkness.”
Very few of these planets have been considered as potentials to support life forms.
For a variety of reasons, astronomers assume that there is one planet for every star, although in reality some stars do not have planets orbiting and others have several.
There are at least 400 billion stars in our own galaxy, so billions in the entire universe.
Stars are all different from each other, as are galaxies, and even planets, so we can’t just multiply information about our own galaxy or solar system.
Planets can be gaseous or rocky, hot or frozen, and can orbit near their star or billions of miles away.
There are two main methods used to try to identify planets orbiting other stars.
The first is the Stella-wobble method, which uses gravity studies over long periods of time to try to establish the mass and radius of potential planets.
The second is the Transit method, which examines how planets can partially block light from their star.