Six in Sync

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Six in Sync

A nearby star has one of the largest families of planets yet seen — an even half-dozen. Only two other known exoplanet families are bigger. But this system is different from the others. All of the planets march in time — their orbits are in perfect sync.

The star is known as HD 110067. It’s about a hundred light-years away, in the constellation Coma Berenices, which is in the east this evening.

The star is a bit smaller and cooler than the Sun. But it’s probably several billion years older. And that’s one reason its planetary system is remarkable.

The planets appear to range from about two to three times the size and mass of Earth. The innermost planet orbits once every nine days, while the outermost world takes about 55 days — much shorter than the orbit of Mercury, the Sun’s closest planet. And all of the orbits are synchronized. Each of the four inner planets completes three orbits for every two orbits of the next one out. And planet number five completes four orbits for every three made by the most-distant planet.

Planetary systems may all be born in sync. But few of them stay that way. Passing stars can nudge some of the planets into different orbits. So can collisions between planets, as well as the presence of especially heavy planets.

So far, then, the HD 110067 system is unique — a family of planets that’s remained in sync for a long, long time.

Script by Damond Benningfield

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