The unique planet orbits a sun-like star around 50 light years away from Earth, and has a mild atmospheric temperature.
Cesar Rubio, one of the citizen scientists behind the planets' discovery, said his seven-year-old son also has a passion for the cosmos.
The star system contains at least three planets that supposedly lie in a region known as the habitable zone.
"It's incredible to be able to make these kinds of discoveries," said researcher David Armstrong.
Determining the abundance of Earth-like planets is one of the major goals of planetary science.
"Maybe Kepler-88 d is the new supreme monarch of this planetary empire, the empress," said astronomer Lauren Weiss.
"This is comparable to several musicians beating distinct rhythms, yet who beat at the same time at the beginning of each bar," said researcher Nathan Hara.
"This intriguing, distant world gives us even greater hope that a second Earth lies among the stars, waiting to be found," said an associate administrator at NASA.
Temperatures on the day side of the planet—which perpetually faces its star—are hot enough to vaporize iron.
"There is a reasonable chance that the planet hosts a large ocean underneath the atmosphere at pressures and temperatures similar to those in the Earth's oceans," researcher Nikku Madhusudhan said.
The planet is located around 1,000 light-years from Earth and experiences average temperatures of more than 1,800 degrees Fahrenheit.
Surface temperatures on KELT-9b can reach up to 7,800 degrees Fahrenheit, making it the hottest known exoplanet.
Research could shed light on which distant planets have the potential to host life.
"I was pretty excited. Coming into the internship, it would be hard to say that I expected to find a planet," Wolf Cukier said.
These planets are roughly the size of Jupiter, however, they are around a hundred times lighter.
"'Are we alone?' is one of the biggest unanswered questions," said study first author Howard Chen.
Mayor's co-laureate, Didier Queloz agreed, telling Newsweek, "It's time to stop dreaming and confront reality, and for our human society to carry our effort and act to ensure that a future exists and that maybe, one day, we will be able to journey among the stars."
"I can't believe we are the only living entity in the universe," Didier Queloz said
In 2015, an astrophysicist discovered that the star would undergo irregular dips in brightness over a period of days or weeks.
"In the search for life beyond our solar system, the most promising planets might not be Earth twins," says geochemist Stephanie Olson.
The exoplanet, dubbed WASP-121b, is located around 900 light-years from Earth.
The three planets are among the smallest and closest exoplanets found to date, according to astronomers.
More than 4,000 planets beyond our solar system have been discovered since the first in 1992.
The Teegarden star—a red dwarf with a mass less than a tenth that of the sun—is located just 12.5 light-years away in the constellation Aries.
Build-ups of toxic gases in the atmospheres of many exoplanets in the "habitable zone" could limit the "safe zone" in which life outside our solar system could actually exist.
In 2009, NASA's groundbreaking Kepler mission identified its first potential exoplanet.
Scientists think life might survive on Proxima b, in spite of powerful lashings from its host star.