NASA's TESS Uses Gravitational Microlensing to Discover Distant Exoplanet

• NASA's TESS spacecraft has identified a new exoplanet, Gaia23bra b, using gravitational microlensing, a method previously considered outside its capabilities.
• Gaia23bra b is a "super-Jupiter" orbiting its star at a distance similar to Jupiter's distance from the Sun.
• The star system is located 40,000 light-years from Earth, significantly further than the typical 150-light-year range of TESS.

Scientific Context

• The discovery, published July 1, 2026, in the Astrophysical Journal Letters, relied on Einstein's theory of general relativity.
• Gravitational microlensing occurs when a foreground star (with or without planets) passes in front of a more distant star, bending spacetime and magnifying the distant star's light.
• Gaia23bra b was detected through a "double lens" effect, where both the host star and the planet amplified the background star's brightness.

Implications for Planet Hunting

• While TESS typically uses the "transit method" (observing light dips as planets cross stars), this discovery proves it can identify planets in wider orbits and deeper space using archival data.
• Microlensing events are one-off, non-repeating phenomena, meaning the specific planet is unlikely to be observed again.
• The discovery was made possible by combining TESS's high-precision instruments with the wide-field mapping data provided by the ESA’s Gaia spacecraft.