2013 JX28
is an Atira asteroid, a type of Aten asteroid, that orbits entirely within Earth's orbit. It orbits very close to the Sun, having the eighth smallest semi-major axis of any minor planet in the Solar System. At its closest, it is only from the Sun, but more than 100 minor planets have a smaller perihelion distance.
Despite being officially classified as a near-Earth object, has a MOID with Earth of ~0.067 AU, making it highly unlikely to ever hit Earth. For comparison, the Moon orbits Earth at about 1/26th this distance.
Physical characteristics
has an absolute magnitude (H) of 20.1, which means it is rather small, with the size being approximately 300 meters based on an assumed albedo of 0.15. Its albedo is not known, so a size estimate is not certain. Assuming the albedo is between 0.05 and 0.25, it is somewhere between 260–580 meters in diameter.163693 Atira, an asteroid with an orbit similar to, for comparison, has an absolute magnitude of 16.28 and is notably larger.