Glossary

Asteroids are another kind of minor planet. Smaller astronomical objects (very similar to large rocks) revolving around the Sun are known asteroids. A large number of asteroids (more than 7.5 lakhs) are revolving between the orbits of Mars and Jupiter, forming a disc. It is known as asteroid belt (Figure 4). They are usually of irregular shape and only four of them are larger than 400 km across (same as distance from Jaipur to Udaipur) and the largest is 1000 km across. So, we cannot see them by naked eyes. The belt is quite wide and the asteroids are small so even if there are so many of them, the belt is thinly populated.
 

Figure 4: Asteroids

Figure 4a: Asteroid 253 Mathilde - measuring about 50 kilometres across (captured in 1997 by the NEAR Shoemaker probe)
(Credit: By NASA - http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/nea_19970627_mos.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1322412)

Figure 4b: Asteroid belt is located between orbits of Mars and Jupiter. Ceres is the only minor planet in the asteroid belt and Vesta is the largest asteroid in the belt.
(Credit: By NASA/McREL https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19380)