The icy, dusty and gassy volatiles that envelop it and gradually left behind as trail, are lightened by the sun!
Comets are visible because they reflect sunlight. As a comet travels closer to the Sun, the sunlight heats up the comet's surface, causing it to release gas and dust that form a glowing coma and tail. This reflected sunlight is what makes comets visible from Earth.
From Earth it would be the Sun, which, however not a planet, but a star
Halley's comet is visible approximately every 76 years.
Halley's comet
It is a comet
It is a comet
No, Halley's comet was not visible in 1834. Halley's comet has an orbital period of about 76 years, so it was last visible from Earth in 1986 and will next be visible in 2061.
The next visible comet that is expected to be visible to the naked eye is Comet Leonard in late 2021.
Halley's comet is visible every 76 to 79 years. the last appearance was during the 1980's
Never.
Comet C/2006 P1 McNaught
The next comet will be Comet Ison which will pass by the earth in 2013. It will be visible with lenses during late summer and will be visible to the naked eye by approximately November.