**Update: Since the original announcement, astronomers have obtained more accurate estimates of the planets' orbital periods, including the period of a seventh planet. This post has been updated with the new data.**

In February, 2017, astronomers announced that the nearby star TRAPPIST-1 has seven Earth-like planets. The orbital periods of the planets have nearly integer ratios. When periods are related by integer ratios, then the corresponding frequencies are related by integer ratios, too. The orbital frequencies of the Earth-like planets of TRAPPIST-1 have nearly integer ratios of 4:6:8:12:18:30:48.

Integer ratios remind me of musical chords. For example, the frequencies of a major chord’s notes are related by the ratios 4:5:6. While I know what a major chord sounds like, I didn’t know what a “TRAPPIST-1 chord” sounded like—until now. The button below plays the “TRAPPIST-1 Chord” where the frequency of each musical note in cycles per second is four times the frequency of the corresponding planet’s orbit in orbits per Earth year.