The asteroid's path takes it inside the orbit of Venus and across that of Mercury, placing it among an extremely rare class of so-called "twilight" asteroids. The only known object with a shorter orbital period, discovered by Sheppard and his team in 2021, completes a lap around the Sun in 113 days.
Sheppard, who studies moons, dwarf planets, and asteroids across the Solar System, leads a survey designed to spot elusive inner-orbit objects that could threaten Earth. His work, partially funded by NASA, employs the Dark Energy Camera on the National Science Foundation's Blanco 4-meter telescope to locate "planet killer" asteroids hidden in sunlight.
Confirmation of 2025 SC79 came from follow-up observations using the NSF's Gemini telescope and Carnegie's Magellan telescopes in Chile. Measuring roughly 700 meters in diameter, the asteroid is currently traveling behind the Sun and will remain unobservable for several months.
"The most dangerous asteroids are the most difficult to detect," Sheppard explained. "Most asteroid research finds these objects in the dark of night, where they are easiest to spot. But asteroids that lurk near the Sun can only be observed during twilight-when the Sun is just about to rise or set. If these 'twilight' asteroids approach Earth, they could pose serious impact hazards."
Further studies of 2025 SC79 will examine its composition, resilience to extreme solar heat, and potential origins.
"Many of the Solar System's asteroids inhabit one of two belts of space rocks, but perturbations can send objects careening into closer orbits where they can be more challenging to spot," Sheppard noted. "Understanding how they arrived at these locations can help us protect our planet and also help us learn more about Solar System history."
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