An artist’s concept of an Earth-like planet orbiting an evolved star that has formed a "planetary nebula." Earlier in its life, this planet may have been like one of the eight newly discovered worlds orbiting in the habitable zones of their stars. (David A. Aguilar/CfA)

The hunt for more just hit pay dirt. Astronomers have discovered eight more planets in the “Goldilocks” zone of their stars, meaning they orbit close enough that their surfaces could hold water and they get just the right amount of sunlight such that the water neither evaporates nor freezes. Scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) made the announcement Tuesday at the American Astronomical Society meeting in Seattle, Washington.

“Most of these planets have a good chance of being rocky, like Earth,” lead author Guillermo Torres of CfA said in a news release.

This find doubles the total of such known planets, and two in this grouping — Kepler-438b and Kepler-442b — appear more similar to Earth than any previously discovered exoplanets, the news release states. They each orbit their stars, at 35- and 112-day intervals, and have a 60 to 70 percent chance of sharing Earth’s rocky terrain.

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That fact led Courtney Dressing, another CfA scientist, and fellow astronomers to have a little fun, offering up the “” for making other Earths, including 1 cup each magnesium and silicon, 2 cups each iron and oxygen, a bit of aluminum, nickel, calcium and sulfur, plus a dash of water.

“Blend well in a large bowl, shape into a round ball with your hands and place it neatly in a habitable zone area around a young star,” the recipe continues. “Do not over mix. Heat until the mixture becomes a white hot glowing ball. Bake for a few million years.”

As it turns out, often consist of the same base as Earth, Dressing said in a news release, adding, “Our solar system is not as unique as we might have thought.”

Despite that, the scientists can’t say with certainty that life could exist on these exoplanets, noted David Kipping, also of the CfA. “All we can say is that they’re promising candidates.”

As with much in science, further conclusions requires further study — a fact made all the more challenging by the distance of the most promising planets. Kepler-438b and Kepler-442b are respectively 470 and 1,000 light-years away from Earth.

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April 24 marks the 25th anniversary of the Hubble Telescope. To celebrate, NASA and the European Space Agency, which jointly run the telecope, released this image of the star cluster Westerlund 2. (NASA/ESA/Hubble Heritage Team/A. Nota/Westerlund 2 Science Team)