Taichi Uyama

In the dark clouds of gas and dust where new stars are just igniting, the Keck Telescope in Hawaii picked out two faint points of light next to young stellar objects. These aren't stars but their companions — too light to shine on their own.

The companion of the star HIP 53005 has stumped astronomers. Its color and brightness and spectrum point to a mass of about 80 Jupiters — right at the hydrogen-burning limit, where an object is no longer a planet but not yet a star. Yet its orbital motion demands nearly twice that mass: 185 Jupiters.