Taking a census of brown dwarfs

Using the Hubble Space Telescope, two teams have been in hot pursuit of some of the coolest objects in the universe.

Infrared image of brown dwarfs and stars in the Trapezium cluster. NASA, Luhman, et al.

Those objects, known as brown dwarfs, straddle a heavenly boundary: They’re too massive to be planets yet too scrawny to be stars.