Kepler-1708b

Lore & Background

Kepler-1708b was initially detected in 2011 by the Kepler space telescope, but its status as a candidate planet was not established until 2019. The planet is a gas giant slightly smaller than Jupiter, with a radius of 0.89 Jupiter radii. Its mass remains unmeasured, though transit timing analysis places a 2-sigma upper limit on its mass. In 2021, astronomer David Kipping and colleagues reported a candidate Neptune-sized exomoon orbiting Kepler-1708b, based on analysis of Kepler transit data. Subsequent research has raised discrepancies about the exomoon's existence, similar to the case of Kepler-1625b, though more recent studies still find the exomoon's existence likely.

Reader's Guide

Kepler-1708b is significant primarily for the candidate exomoon reported around it, which would represent only the second such candidate (after Kepler-1625b) and the first of Neptune size. The planet itself, discovered by the Kepler mission, contributes to the census of Jupiter-sized exoplanets orbiting Sun-like stars. The ongoing debate over the exomoon's existence highlights the challenges of confirming small, distant companions via transit data. The planet's location in Cygnus, 5,600 light years away, places it well beyond the immediate solar neighborhood, yet within the reach of Kepler's long-term photometric monitoring. The unresolved status of the exomoon—with some studies raising doubts and others supporting its likelihood—underscores the iterative nature of exoplanetary science, where candidate detections require careful scrutiny over years. The planet's mass remains unconstrained, leaving its internal composition and formation history open to further investigation.

Did You Know?

• Kepler-1708b was first detected in 2011 but not identified as a candidate planet until 2019.
• A candidate Neptune-sized exomoon was proposed to orbit Kepler-1708b in 2021 by David Kipping and colleagues.
• The planet has a radius of 0.89 Jupiter radii, making it slightly smaller than Jupiter.
• The existence of the candidate exomoon remains disputed, with some research raising discrepancies and other studies finding it likely.