halley's comet formation

Halley's comet was made when a nebula was formed by a supernova. That gas and dust from the nebula collects, and later it freezes in cold outer system. That gas forms into icy objects and those objects accrete(objects come together). Those icy objects formed Halley's comet making it a rocky and an icy object. Later the sun's gravity pulls Halley's comet to orbit it. While coming to the inner layer of the solar system, some gases of the comet warm up and that is why scientists found hot and cold gases on Halley's comet.

PLUTO not a planet?

Scientists have found that Pluto is not a planet. How is this? Well they discovered another object bigger than Pluto which name is Eris. For an object to be a planet it has to govern all the objects around it and Pluto is smaller than Eris, so it does not govern the planet.

Halley's comet is not a planet because it is not spherical, it doesn't orbit any star and it doesn't have any gravitational pull to control the objects around it. Halley's comet is a rock who orbits its on orbit.

Halley's commet compared to the sun

The size in diameter of Halley's commet is 1024 km and the sun has a diameter of 1,400,000 km
The sun is much bigger than Halley's commet therefore Halley's commet fits 1367 times into the sun.

The sun is bigger than Halley's commet even though Halley's commet tail extended to 30 million km.

1024 diameter