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We confirm the existence of TOI-2407鈥塨, a warm Neptune-sized planet that has a radius similar to Neptune鈥檚 and orbits a small, cool star known as an early M-type star. This planet completes an orbit every 2.7 days and has an estimated temperature that suggests it is relatively warm. TOI-2407鈥塨 was first spotted by NASA鈥檚 Transiting Exoplanet Survey Satellite (TESS), which detects planets by observing small dips in a star鈥檚 brightness when a planet passes in front of it. We confirmed the planet鈥檚 existence using additional observations from ground-based telescopes at different wavelengths of light.
One of these observations came from a new infrared instrument called SPIRIT, which uses advanced CMOS-based detectors and is part of the SPECULOOS Southern Observatory. These detectors are especially useful for studying M-dwarf stars, like the one TOI-2407鈥塨 orbits, because they collect high-quality data in infrared light鈥攚here these stars shine the brightest.
TOI-2407鈥塨 is particularly interesting because it falls within the 鈥淣eptune desert,鈥� a region where we see very few Neptune-sized planets orbiting close to their stars. Future studies, such as measuring the planet鈥檚 mass through its gravitational effects, will help us better understand where this planet fits among known types of planets. TOI-2407鈥塨 is also similar in size, orbit, and host star type to Gliese 436鈥塨, a well-known Neptune-sized planet. Comparing these two planets could help scientists learn more about how Neptune-like planets form and evolve around small stars.
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Figure 1.
TESS听light curves of TOI-2407 (TIC 15307857). Long-cadence sectors 3 and 4 are shown in the top panel and short-cadence sectors 30 and 31 in the bottom panel. Planetary transits are highlighted with vertical lines. The binning showed corresponds to 1.5听h bins.
