Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid. Mars can be seen from Earth with the naked eye. Its apparent magnitude reaches −2.9,[4] a brightness surpassed only by Venus, the Moon, and the Sun, though most of the time Jupiter will appear brighter to the naked eye than Mars.