There are a total of 10 to the power 23 stars in the observable universe. Most stars have planets and thus qualify as solar systems. But the Universe itself is much larger, containing at least 500 billion times as much matter as our own Solar System, and it is also quite possible that it is infinite. Here’s a brief explanation of how solar systems form. In short, each star system is composed of planets and/or moons.
A young solar system starts off as a protoplanetary disk composed of dust and gas. At some point, the central stellar embryo feeds on the collapsing material. The debris can eventually combine to form planets. The Sun has seven billion suns, so there are many more than that. So the question, “How many solar systems are there in the universe?” becomes a fundamental question for astronomers.
Astronomers predict that there should be as many solar systems as there are stars. With a billion trillion stars in the universe, there should be a lot of Earth-like worlds in our galaxy. The number 720 was calculated by Erik Zackrisson, an astrophysicist at the University of Uppsala in Sweden, according to his calculations. Then he figured out that if each star in the universe had as many planets as the solar system itself, there would be more than seventy billion planets in the universe.
Another interesting type of planetary system is the rogue system. These are planets that are not gravitationally bound to their star and orbit the galaxy directly. These objects may have formed in the same way as stars. The IAU has proposed naming such objects sub-brown dwarfs. Some ejected objects, like the planet Cha 110913–773444, still have a system of satellites.
Observations have shown that the rocky planets of the planetary system in L 98–59 orbit their host star. Interestingly, it has four confirmed rocky planets and a fifth could be in the system. Despite being so distant from the star, their orbital periods and masses are similar to those of our own Solar System. In fact, the planets of L 98–59b and L 98–59c are similar to our own.
Giordano Bruno, an Italian Renaissance man, wrote a doctoral thesis on the subject and concluded that less than forty-five percent of stars have planets similar to the Solar System. In December 2009, he was reviewing a newly discovered planet that had been identified as an extrasolar planet. This discovery is significant in several ways. In addition to the fact that there are more than a few solar systems in the universe, it is important to understand the underlying science behind extrasolar planets.
Astronomers estimate that there are more than one trillion galaxies. Our galaxy is part of a spiral galaxy, and the Milky Way is one of them. Other galaxies are irregular and elliptical. The number of solar systems in the universe can be estimated by counting the number of stars in a small portion of the sky. Astronomers estimate that there are at least one hundred thousand million galaxies in the Milky Way galaxy alone.