What is "vulcanoid"

a. (context astronomy English) Of or dealing with a vulcanoid n. (context astronomy English) A member of the hypothetical population of small asteroids orbiting in the dynamically stable zone between 0.08 and 0.21 AU from the Sun

The vulcanoids are a hypothetical population of asteroids that orbit the Sun in a dynamically stable zone inside the orbit of the planet Mercury. They are named after the hypothetical planet Vulcan, whose existence was disproven in 1915. So far, no vulcanoids have been discovered, and it is not yet clear if any exist.

If they do exist, the vulcanoids could easily evade detection because they would be very small and near the bright glare of the Sun. Due to their proximity to the Sun, searches from the ground can only be carried out during twilight or solar eclipses. Any vulcanoids must be between about and in diameter and are probably located in nearly circular orbits near the outer edge of the gravitationally stable zone.

The vulcanoids, should they be found, may provide scientists with material from the first period of planet formation, as well as insights into the conditions prevalent in the early Solar System. Although every other gravitationally stable region in the Solar System has been found to contain objects, non-gravitational forces (such as the Yarkovsky effect) or the influence of a migrating planet in the early stages of the Solar System's development may have depleted this area of any asteroids that may have been there.