by The space is surprisingly large. Our galaxy alone contains about 100 billion stars, and there may be billions of galaxies in the universe. (And a trillion almost it’s definitely bigger than you think it is!) But do we know how many planets are out there?
Astronomers have gone 5,502 planets were discovered about other stars (known as exoplanets) in the Milky Way. Add to our eight solar system (not nine, sorry Pluto), and that gives us a total of 5,510 known planets, all in our galaxy. Counting planets is a difficult task, however, and astronomers are sure there are many more we have yet to discover.
“Although we only know about 5,000 planets now, we can estimate that there is at least one planet for every star,” Mark Popinchalk, an astronomer at the American Museum of Natural History in New York City, told Live Science. “Our galaxy has 100 billion stars, and probably many more planets. We can’t give an exact number.”
Popinchalk described determining exoplanet totals as trying to figure out how many people live in your city without searching the internet. For the correct number, you can try to meet individuals and count them, but this is not possible at all. It is very easy to get estimates using data such as the number of people living in one household, and the number of households in a city.
Astronomers estimate that each star has at least one planet based on observations. To find out what a typical star house looks like, astronomers look to our neighbors. Scientists have used A couple of different ways to search for exoplanetsincluding i way to go used by Kepler telescope and the radial velocity method that led to Nobel Prize for discovery of 51 Pegasi b. With both motions and velocities of radiation, astronomers look at a star instead of a planet, looking for tiny signs of a planet’s presence—a dip in the star’s brightness when a planet orbits in front of it or moves away from the star’s gravitational pull. planet, respectively.
All the planets discovered so far are well within the Milky Way, however; no one has yet found a planet outside the galaxy (sometimes called an exoplanet), because it is so far away and difficult to see. Another method, called microlensing, has revealed a few possible exoplanets.
“In our galaxy, microlensing planets are found when the stars that host them bend the light of distant stars behind them, and the mass from the planet adds a small blip to the lensing light,” Yoni Brande, an astronomer at the University of Kansas, told Live Science. “Lensing has long been the subject of studies of distant galaxies, so it makes sense that we should be able to detect faint planetary lensing signals in other galaxies, which we haven’t confirmed yet.”
Continuing Popinchalk’s city analogy, looking across the Milky Way we ask how many people live in all the cities on Earth. “If our galaxy has 100 billion planets, and there are another one trillion, and each of them has multiple planets, we can multiply that together to get 100 sextillion planets in the universe,” Popinchalk said. (It’s a 1 followed by 23 zeros.)
Because of these many planets, people often argue that there must be at least one planet with life elsewhere in the universe. Astronomers still don’t know, however, how rare life – and the conditions needed for it to appear – really are. “We’ll have to wait a few decades for the next generation of large exoplanet-focused telescopes (like the Habitable Worlds Observatory) to really start looking for life elsewhere in the galaxy,” Brande said.
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