CUTTING EDGE

Detecting distant moons

Unseen moons may be revealed by their gravitational tug on exoplanets

Astronomy entered the golden age of detecting alien worlds in the early 1990s. In the three decades since, we’ve found almost 4,300. Now, as technology advances, we are able to delve deeper into these systems, including the ability to detect unseen moons orbiting these worlds. In October 2018, using observations from the Hubble Space Telescope, astronomers announced gas giant planet Kepler-1625b could have a smaller companion orbiting it, although this detection is as yet unconfirmed and remains controversial.

Discovering dark planets orbiting dazzlingly bright stars across lightyears of space is itself impressive enough; but detecting the presence of even tinier, unseen moons around these remote worlds