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Scientists rediscover 'lost planet' more like the ones in our own solar system

A new method could help astronomers find more potentially habitable planets.

The NGTS facility in Chile is working on tracking down exoplanets located in their stars' "Goldilocks" zones.
ESO/G. Lambert

Exoplanets, those mysterious planets that dwell outside of our solar system, are always fascinating, but humanity is particularly interested in those located in their stars' habitable zones where liquid water might exist. A new method for detecting exoplanets could help scientists spot many more of these intriguing, distant worlds.

A planet named NGTS-11b is the poster child for this new technique. A team of researchers led by Samuel Gill of the University of Warwick in the UK rediscovered the planet by starting with data from NASA's planet-hunting TESS telescope. 

This is a cosmic detective story. TESS first located the planet by seeing a subtle dip in brightness when it crossed in front of its star. But TESS only stares at a section of space for a limited period of time, usually 27 days. Scientists like to observe two dips in brightness to confirm an exoplanet's existence, but some of those planets take longer than 27 days to circle back around.

This is where the Next-Generation Transit Survey (NGTS) telescopes in Chile come into play. NGTS conducted a follow-up observation on the star, which is 620 light-years away, but watched it for 79 nights. The researchers were able to log two dips in brightness, effectively rediscovering NGTS-11b, which travels around its star every 35 days.

"These discoveries are rare but important, since they allow us to find longer period planets than other astronomers are finding. Longer period planets are cooler, more like the planets in our own solar system," Gill said in a release from the University of Warwick on Tuesday.

While NGTS-11b has a temperature cooler than Mercury and Venus, Gill said it's still too hot to support life as we know it. The NGTS work, however, could point the way to more planet discoveries in the "Goldilocks zone," a whimsical reference to the habitable zone around stars. Other planets found this way may be more hospitable than NGTS-11b.

Gill is eyeing the hundreds of single transits spotted by TESS that could become targets for NGTS. "Some of these will be small rocky planets in the Goldilocks zone that are cool enough to host liquid water oceans and potentially extraterrestrial life," he said. The search is off to a good start.