157 asteroids have orbits that lie entirely within Earth’s aphelion distance from the Sun (1.016710 AU). That number reduces to 54 inside Earth’s semimajor axis distance (1.000001 AU). That number further reduces to 28 inside Earth’s perihelion distance (0.983292 AU). Those 28 asteroids are listed below.
Only one asteroid lies entirely within Venus’s orbit, 594913 ‘Ayló’chaxnim (2020 AV2)1, and none are known inside Mercury’s orbit…so far. Asteroids inside of the Earth’s orbit are extremely difficult to detect since their angular distance from the Sun is never very large, and the glare of the Sun interferes. This is especially true for any asteroids that might exist inside of Mercury’s orbit.
An asteroid is given a provisional designation when it is discovered that begins with the year of discovery. After the orbit of the asteroid has been sufficiently well-determined, it is given a number. Then, eventually, the numbered asteroid is given a name.
Interestingly, half of these 28 asteroids have been discovered since 2017, including 1 so far this year. The first was discovered in 1998.
In the table below, i is the orbital inclination relative to the ecliptic plane, e is the orbital eccentricity, q is the perihelion distance, a is the semimajor axis distance, Q is the aphelion distance, and P is the orbital period. The table is listed in order of aphelion distance, smallest to largest.