I've gathered a few comet facts to publish here on astronomy for beginners. Of course comets are often only visible for a short number of days in a normal year, but when a particularly important comet passes by then it makes for quite an astronomical occasion.
Fact1: A comet is a conglomerate of particles bound together by ice (not necessarily H2O water ice, it could be dry ice (CO2), for example)
Fact2: When a comet approaches the sun the ice melts and releases the particles from the main body.
Fact3: The tail of a comet always points away from the sun.
As the picture below shows, there are in fact two tails, both curved, and they are 30 MILLION kilometres long. That's a lot of fine particles. The theory is that the solar wind is responsible for the blue gas and gravity alone for the larger particles.