Getting to know the accurate number of planets in the galaxy has become controversial. Schools in the past made students believed that there are nine planets with Pluto being the smallest and the farthest from the Sun while Mercury is the closest and probably the hottest planet in the galaxy. Scientists have however continued to argue that there are more planets in the galaxy than we can imagine.
In 2005, a scientist, Mike Brown discovered an icy object; the size of Pluto called Eris, giving the notion that there may be other planets apart from the known nine. In 2006 the International Astronomical Union classified Pluto and some other newly discovered planets as dwarf planets. The Union said any celestial body that is not in orbit around the sun, and has not cleared the neighborhood around it cannot be described as a planet. They then classified newly discovered Ceres, Haumea, Makemake and Eris as dwarf planets.
But a new study by University of British Columbia (UBC) astronomers revealed that there may be as many as “one Earth-like planet for every five Sun-like stars in the Milky way Galaxy.”
One of the researchers, Michelle Kunimoto, said planets like Earth are more likely to be missed by a planet search than other types since they are small and orbit is far from their stars. “My calculations placed an upper limit of 0.18 Earth-like planets per G-type star. Estimating how common different planets are around different stars can provide important constraints on planet formation and evolution theories and help optimize future missions dedicated to finding exoplanets,” she said.
Another UBC astronomer, Jaymie Matthews said the MilkyWay has as many as 400 billion stars while seven percent of them being G-type star. By implication, over four million stars in the galaxy may be earth-like planets.
Explaining how she came about the estimate, Kunimoto said, “I started by simulating the full population of exoplanets around the stars Kepler space craft searched. I marked each planet as ‘detected’ or ‘missed’ depending on how likely it was my planet search algorithm would have found them. Then, I compared the detected planets to my actual catalogue of planets. If the simulation produced a close match, then the initial population was likely a good representation of the actual population of planets orbiting those stars.”
Kunimoto’s estimate gives credit to what John Johnson, a Professor of Planetary Astronomy said in 2013 that there are at least 100 billion planets in the galaxy. As student continues to grapple with nine planets, scientists may continue to detect other unknown planets in the galaxy.
