In a milestone hailed by scientists as a key step toward finding another Earth-like world, astronomers Tuesday announced the discovery of two blazingly hot planets roughly the size of Earth some 950 light years distant.

The discovery “demonstrates for the first time that Earth-size planets exist around other stars, and that we can detect them,” said Francois Fressin, an astronomer at the Harvard-Smithsonian Center for Astrophysics who led the discovery team.

The two planets orbit a star much like our sun, but they whiz around it so fast and so close that their surfaces sizzle like frying pans.

“They’re way too hot to be anything like our own Earth,” said Sara Seager, a planet hunter at the Massachusetts Institute of Technology and a member of the discovery team.

Still, finding these hot, Earth-size planets is “seriously cool,” said Lisa Kaltenegger, who studies “exoplanets” at the Max Planck Institute in Heidelberg, Germany, and was not involved in the research. “These discoveries are a great technological step forward.”

The planets were announced Tuesday in the journal Nature and in a NASA teleconference.

Detected by NASA’s Kepler space telescope, the two planets, dubbed “Kepler 20e” and “Kepler 20f,” are almost certainly rocky like Earth and not gaseous like Jupiter, Kaltenegger said.

The smaller planet, Kepler 20e, is about the size of Venus but much closer to its star, zooming around it every six days. An Earth year, by contrast, is 365 days.

The larger planet, Kepler 20f, is just 3 percent larger than Earth. “It’s the first Earth-sized planet” ever detected orbiting another star, Seager said. “It is a big milestone.”

Kepler 20f is a bit farther out from its star, completing an orbit about every 20 days. Its surface temperature is hotter than a pizza oven, about 800 degrees Fahrenheit.

The two planets are nestled among three larger planets tightly circling the star Kepler 20.

“It’s a beautiful planetary system,” said Dimitar Sasselov, a planet hunter at the Harvard-Smithsonian center and a member of the discovery team.