NASA announced a major discovery Tuesday—two planets within the universe the size of Earth.

The Kepler Space Telescope team announced the discovery of Kepler 20-E and 20-F. It was the first ever confirmation that there are more worlds in outer space, the same size as ours.

One astronomer called the discovery a watershed moment in human history. They are still looking for planets similar to Earth that might contain life, but this is one big step closer.

The two planets are orbiting a star 950 light years away, and at least size-wise they look very similar to Earth. Kepler 20-F has nearly the exact same surface area as Earth; Kepler 20-E is a fraction smaller than that.

Until now, astronomers had identified more than 700 planets outside our solar system, but these new discoveries are by far, the smallest.

Scientists are crediting the Kepler spacecraft, which launched from Cape Canaveral nearly three years ago. The $600 million telescope has one primary mission—finding new planets similar to Earth that might contain life.

Although the latest finds resemble Earth in size, there is likely no water there, as one of the planets has a temperature of about 800 degrees; the other is a scorching 1,400 degrees.

Nevertheless, astronomers said the discovery proves the telescope can detect the type of planets they are looking for. Eventually they think they may find one with all the conditions necessary for life.

The telescope has found about 2,300 other objects that appear to be planets. But before scientists can declare them to be planets, they have to consider other measurements and calculations.