In 1904, Edward Emerson Barnard was the first person to see a Trojan asteroid. Barnard thought it was a moon of the planet Saturn. In February 1906 a German astronomer named Max Wolf saw a Trojan asteroid and named it 588 Achilles. Wolf was the first person to see a Trojan asteroid and know what it was. Since that time, more than 2000 Trojan asteroids have been seen. The biggest Trojan asteroid is named 624 Hektor. 624 Hektor is 370 km across. Astronomers think that Trojan asteroids are made of ice and dust.