Just how big is the universe we live in? This answer is something we are unable to obtain, given our current technology and measurement of the universe. We can make an educated guess, but we are far from exploring the universe.
We can better estimate the size of our galaxy. All in all, it’s a massive place, and it is teeming with planets. But how many of these worlds are similar to Earth; how many of them are habitable? This is another answer hard to obtain, but we can do the math based on observations throughout the years.
New research using data from the Kepler space telescope estimates that there are as many as 300 million potentially habitable planets in our galaxy. The best part of the new estimates is that they could be relatively close to Earth; any of these potentially habitable exoplanets are located no farther than 30 light-years from Earth.
The findings, which present the new estimates, will be published in The Astronomical Journal.
The new estimates saw researchers from NASA, the SETI Institute, and other organizations around the world collaborate in one massive study which helps us better understand the galaxy we live in.
While 300 million planets may seem like a pretty big number, its far from the total number of planets estimated to exist in the milky Way, according to our best estimates, the Milky Way is home to at least one planet per star, which means there could be anywhere for 100 billion to 400 billion planets in the galaxy we live in.
The observable Universe
The universe (observable), on the other hand, is home to at least 125 billion galaxies.
Co-author Jeff Coughlin, a scientist who studies exoplanets at the SETI Institute, revealed that “This is the first time that all of the pieces have been put together to provide a reliable measurement of the number of potentially habitable planets in the galaxy.”
The best part is that if we understand how many exoplanets are habitable in the galaxy, we can then take a different look at the Drake Equation.
“This is a key term of the Drake Equation, used to estimate the number of communicable civilizations — we’re one step closer on the long road to finding out if we’re alone in the cosmos,” the researcher revealed.
The Drake Equation essentially calculates the probability of how many potentially technological alien civilizations could exist in our galaxy and how many of them we could contact from Earth.
The new–revised–estimate of potentially habitable planets in our galaxy saw researchers look for worlds of similar size to Earth. They also factored into their calculations planets that are most likely rocky in nature.
Scientists then searched for Sun-like stars in the universe, looking for stars that are approximately the same age as our sun and with a similar temperature.
Another important factor to consider is whether exoplanets meet the requirements for liquid water to exist on their surface, as this greatly impacts distant worlds’ habitability. All of this was considered in the new study, which differs from previous studies that only looked for potentially habitable planets in the galaxy, heavily basing their estimate on the planet’s distance from the star.
The new research considers a few more things, like how much light from the star impacts the planet; this is an important factor for estimating the chances of liquid water on the surface.
To make this possible, researchers looked at data gathered by the Kepler Space Telescope and data gathered by the Gaia Mission, lead by the European Space Agency.
The Kepler space telescope, a mission that ceased searching for exoplanets in 2018, identified more than 2,800 exoplanets across the galaxy. Many of these worlds are still awaiting confirmation and could increase the number of worlds in the universe we have discovered to date.
To date, there are 4,296 confirmed exoplanets, 5634 NASA exoplanet candidates, and 3,188 solar systems. You can find out more here.
You can read the press release by SETI here.
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