Still, one aspect that could put our calculus on a different perspective is this: We only know how life adapts and evolves based on the species that live and lived on our planet. There is no telling on what life is limited to in Outer Space, and thus, many planets that we might consider inhospitable to us might actually be hospitable to other unknown species. What we do know is that life exists, adapts, and evolves.
You might think our Solar System is unique, but there are over 5, solar systems that have been discovered already and are closely analyzed. Every year, scientists learn more and more solar systems, which are either different, similar, or unlike ours. They also discover new solar systems every year. With that being said, scientists have estimated that there could be tens of billions of solar systems in our Milky Way galaxy alone.
Many believe that there might be as many as billion. Whatever the case, not only planetary systems exist within our galaxy. There are also stellar systems, which are stars that orbit amongst themselves. Others estimated that the Milky Way galaxy might have anywhere between to billion planets. Currently, over 4, exoplanets have been discovered, and every day, more and more follow. These planets are either part of a planetary system, or they are rogue planets. Take our Solar System, for example; there are eight planets and at least five dwarf planets which orbit our star, the Sun, a single star.
There might as well be a ninth planet, or what some call Planet X, but we are still on the hunt for it. If only one star, our Sun, could host as many as eight or nine planets, then surely, our Milky Way galaxy, which contains billions upon billions of stars, should also have billions upon billions of planets as well.
Older studies only considered the distance of a planet from its host star to calculate habitability — a gross measure, the new study suggests. Instead, this research also takes into account how much light a planet would receive from its star based on more than mere distance alone.
NASA's Kepler mission zoomed in on stars to see if there are planets orbiting within their habitable zone. Meanwhile, the European Space Agency's Gaia mission measured the positions, distances, and motions of stars to get a more definitive estimate of how much light — and thus, heat — they bestow on their planets.
The study found that there could be million habitable planets in the Milky Way. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. For many years scientists have studied our own solar system and modern technology allows them to look deeper and deeper into space.
Knowing the Sun is only one of a few billion stars in the Milky Way galaxy, I can imagine scientists also started studying other planetary systems… at least enough to know how many planetary systems like our solar system reside in our galaxy.
Is there any information available that would be able to at least "indicate" how many planetary systems reside in our galaxy? A good, but hard question to answer - as you stated, only an indication could be provided. But, there is some information available from the number of exoplanetary systems found 'locally', according to the NASA web page How many solar systems are in our galaxy?
So far, astronomers have found more than solar systems and are discovering new ones every year. Given how many they have found in our own neighborhood of the Milky Way galaxy, scientists estimate that there may be tens of billions of solar systems in our galaxy, perhaps even as many as billion.
An important caveat from the NASA site is that exoplanetary observations are still in its infancy - so over time, this estimate is likely to improve.
All in all it is said that on average, 1. So almost all stars form a kind of solar system with planets. However, there is still a lot of uncertainty regarding the numbers, since small planets are very, very hard to detect. Only four of the worlds are far enough from their stars to potentially host liquid water, but those planets are probably too big to be rocky worlds like Earth.
However, it was easier for Kepler to see planets that are close to their stars, and that is the case for all the newly verified worlds. For example, the outermost planet in one system, known as Kepler, is about the same distance from the star as Earth is from the sun.
But Kepler lives on.
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