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To a layman like me, it seems almost impossible that light reflected from a body that lies “much farther from the star than Pluto does from the sun” could be seen from Earth at a distance of 450 light years, when Pluto, only 6 light hours away, reflects so little light to Earth.

Peter Jeming
Seattle, Wash.

The researchers imaged a star with a companion farther away than Pluto’s distance from Sol. The question was whether this is a planet or a brown dwarf star. That we can see an image at all seems to preclude it from being a planet. It must be producing its own light somehow.

Matthew C. Cook
San Francisco, Calif.

Whether planet or brown dwarf, the body is emitting light. Very young planets generate their own infrared light by gravitational contraction of the material that coalesced to make them. Telescopes are now sensitive enough to detect and resolve infrared-bright planets that lie relatively far from their parent stars. —R. Cowen