11.7 billion years
Halley's comet appears as a bright ball of light with a long, glowing tail. It is typically visible to the naked eye and has been observed by astronomers for centuries. The length and brightness of its tail can vary depending on its position in its orbit around the sun.
Halley's Comet was a periodic comet; it returns to the inner system every 76 years. Hale-Bopp is a very long-period comet; it may have been last seen in 2215 BC. That may have been Hale-Bopp's first approach to the Sun; its orbit was likely altered by close brushes with Jupiter then, and again during its last pass in 1997. Hale-Bopp's next appearance may be in or around the year 4530 AD.
Halley's Comet has a nucleus (solid center) estimated to be about 9 miles (15 kilometers) wide. The most recently verified sighting of Halley's Comet was in 1986.
Halley's comet is in orbit round the sun. Its orbit time is about 75 years, but as the orbital path is long and narrow, most of that is spent far out where we cannot see it. We see it for a few months when it is near the sun.
As long as cows have been in existence, or the whole Bos primigenius species and subspecies have been in existence.
Halley's Comet is a periodic comet that is visible from Earth roughly every 75-76 years. When it passes close to the sun, it develops a bright coma and a visible tail. Halley's Comet is known for its long, elliptical orbit that takes it from the outer solar system to the inner solar system.
they have been in existence for 110 years since 1901.
Helium is has been in existence since the beginning of the universe.
No it won't. It will be seen from Earth, but it will be a long way from Earth, so it poses no danger to us. You can see many things in the sky at night that are a very long way away. Right now Halley's Comet is too far away to see, but when it is close enough to see, it will still be a very long way from Earth in 2061, just like it was when it was seen in 1986 and in 1910 and other previous occasions that it has been seen from Earth.
long time
There are no data with which to answer that question, because no comet has ever yet been observed in orbit around a moon.
since 1992