Science: Sky Centaur

What, after all, is Object-Kowal?

When Hale Observatories Astronomer Charles Kowal announced in November that he had spotted a small object circling the sun beyond the orbit of Saturn, some scientists thought that he might have discovered the solar system's tenth planet. Now, Object-Kowal—as it is temporarily called—has been downgraded. The body, which is at least 160 km. (100 miles) in diameter, could be an errant asteroid or an inactive comet.

Re-examining old sky photographs, astronomers have found Qbject-Kowal on plates taken by Harvard astronomers as far back as 1895. In fact, Kowal himself...

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