No, there is no asteroid that is 300,000 miles long. That's simply too large.

Here's why:

* The Largest Asteroid: The largest asteroid in our solar system is Ceres, which is about 590 miles in diameter.

* Scale: 300,000 miles is roughly the distance between the Earth and the Moon. An asteroid that size would be a dwarf planet, not an asteroid.

* Formation: Asteroids are remnants from the early solar system, and they don't have the gravitational pull to grow to such massive sizes.

It's possible you might have gotten confused with the size of a planet or a moon. For example, the diameter of Jupiter is about 86,881 miles.