SWEEPS-10

Lore & Background

SWEEPS-10 was identified as a candidate extrasolar planet during the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). It orbits its star in just 10 hours, placing it only 1.2 million kilometers from the stellar surface—roughly three times the distance between Earth and the Moon. This extreme proximity makes it among the hottest planets ever detected, with an estimated temperature of about 1,650 degrees Celsius.

The planet's survival so close to its star is attributed to the star's nature: a small, cool red dwarf. Team leader Kailash Sahu noted that the planet must be at least 1.6 times the mass of Jupiter; otherwise, the star's gravitational pull would tear it apart. Such ultra-short period planets appear to occur preferentially around dwarf stars that are smaller and cooler than the Sun.

From June 2007 to August 2011, SWEEPS-10 held the record for the shortest orbital period among known planet candidates, until PSR J1719-1438 b was discovered with an even shorter orbit. The planet remains a candidate, not a confirmed exoplanet.

Reader's Guide

SWEEPS-10's significance lies in its demonstration of the extreme environments in which planets can exist. As an ultra-short period planet (USPP) with a 10-hour orbit, it pushed the boundaries of known orbital mechanics and planetary survival. Its existence around a red dwarf star—smaller and cooler than the Sun—supports the idea that USPPs preferentially form or survive around such stars. The planet's minimum mass of 1.6 Jupiters highlights the gravitational constraints that prevent lower-mass planets from persisting so close to their host stars. Although only a candidate, SWEEPS-10 served as a benchmark for the shortest orbital period from 2007 until 2011, when PSR J1719-1438 b surpassed it. Its detection via the SWEEPS survey, focused on the Galactic bulge, underscores the potential for finding planets in distant regions of the Milky Way. The planet's estimated temperature of 1,650 degrees Celsius places it among the hottest known, illustrating the intense stellar irradiation such close-in planets endure. SWEEPS-10 remains a key example in the study of USPPs and the limits of planetary system architecture.

Did You Know?

• It is located approximately 22,000 light years from Earth.
• The planet's estimated temperature is about 1,650 degrees Celsius.
• It must be at least 1.6 times the mass of Jupiter to avoid being torn apart by the star's gravity.