Comet predictions are hard as much depends on exactly how much water vapour boils off, and this is hard to predict. Comets can have sudden changes in activity. Moreover, Halley's comet isn't the only comet. There are others that can be as visible as Halley will be in There are also long period comets that are undiscovered until they come close to the sun. These can be very bright. Comet Hale-Bopp was a "great" comet in and was visible for many months.
Another great comet could come along any time but we can't predict when. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Learn more. Ask Question. Asked 3 years, 9 months ago. Active 2 years ago. At one time, it was thought that Halley could have delivered water to Earth in the distant past — based on the ratio of deuterium to hydrogen found in the comet's water that showed it to be chemically similar to the Earth's oceans.
However, subsequent observations have indicated that this is unlikely. The ESA's Giotto and Russia's Vega missions gave planetary scientists their first view of Halley's surface and structure. As already noted, Halley's Comet has a long and rich history when it comes to being observed by humans. Including its most recent visits, Halley's Comet has been visible from Earth on 30 separate occasions.
While it is believed that Babylonian scribes recorded the appearance of Halley's Comet when it returned in and 87 BCE, it's most famous appearance occurred shortly before the invasion of England by William the Conqueror. Whereas King Harold of England saw the comet as a bad omen, William and his forces interpreted it as a sign of their impending victory at least according to legend.
Throughout the Middle Ages, the appearances of comets in the night sky were seen as heralds of bad news, indicating that either a person of royal standing had died, or that dark days lay ahead. This is perhaps owing to what was seen as the erratic and unpredictable behavior of comets, when compared to the Sun, the Moon and the stars. With the development of modern astronomy, this view of comets has been largely dispelled.
However, there are many who still hold to the "doom and gloom" view of Halley's Comet, believing that it will strike the Earth at some point and trigger an Extinction Level Event, the likes of which has not been seen since the Dinosaurs. Halley's overall lifespan is difficult to predict, and opinions do vary.
In , Russian astronomers Boris Chirikov and Vitaly Vecheslavov performed an analysis of 46 apparitions of Halley's Comet taken from historical records and computer simulations. Their study showed that the comet's dynamics were chaotic and unpredictable over long timescales, and indicated that its lifetime could be as long as 10 million years.
In , David C. Jewitt conducted a study that indicated that Halley will likely evaporate, or split in two, within the next few tens of thousands of years. Alternately, Jewitt predicted that it could survive long enough to be ejected from the Solar System entirely within a few hundred thousand years.
Meanwhile, observations conducted by D. Hughes et al. By their estimations, it would not be surprising at all if the comet evaporated entirely within the next revolutions or so approx. The last time Halley's Comet was seen was in , which means it will not reappear until As always, some are choosing to prepare for the worst — believing its next pass will signal the end of life as we know it — while others are contemplating if they will live long enough to witness it.
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When Halley's Comet came by Earth in , it was the first time we could send spacecraft up to look at it. That was a fortunate occurrence, as the comet ended up being underwhelming in observations from Earth. When the comet made its closest approach to the sun, it was on the opposite side of that star from the Earth — making it a faint and distant object, some 39 million miles away from Earth.
Several spacecraft successfully made the journey to the comet. This fleet of spaceships is sometimes dubbed the "Halley Armada. The European Space Agency's Giotto got even closer to the nucleus, beaming back spectacular images to Earth. Japan sent two probes of its own Sakigake and Suisei that also obtained information on Halley.
Sadly, the astronauts aboard Challenger's STSL mission were also scheduled to look at the comet, but they never got the chance. The shuttle exploded about two minutes after launch on Jan. It will be many decades until Halley's gets close to Earth again, but in the meantime you can see its remnants every year. The Orionid meteor shower, which is spawned by Halley's fragments , occurs annually in October.
Halley's also produced a shower in May, called the Eta Aquarids. When Halley's sweeps by Earth in , the comet will be on the same side of the sun as Earth and will be much brighter than in At least one study has pointed out that it is difficult to predict Halley's orbit on a scale of more than years, and that the comet could collide with another object or be ejected from the solar system in as little as 10, years, although not all scientists agree with the hypothesis.
When Halley next returns to Earth's vicinity, one astronomer predicted it could be as bright as apparent magnitude It is featured in the famous Bayeux tapestry, which chronicles the Battle of Hastings in In , an international fleet spacecraft met the comet for an unprecedented study from a variety of vantage points. A panel from the Bayeux tapestry showing people looking at what would later be known as Halley's comet.
Each time Halley returns to the inner solar system its nucleus sprays ice and rock into space. This debris stream results in two weak meteor showers each year: the Eta Aquarids in May and the Orionids in October.
Halley's dimensions are about 9. It is one of the darkest, or least reflective, objects in the solar system. It has an albedo of 0. Comet Halley moves backward opposite to Earth's motion around the Sun in a plane tilted 18 degrees to that of the Earth's orbit.
Halley's backward, or retrograde, motion is unusual among short-period comets, as is its greatest distance from the Sun aphelion is beyond the orbit of Neptune. Halley's orbit period is, on average, 76 Earth years. This corresponds to an orbital circumference around the Sun of about 7. The period varies from appearance to appearance because of the gravitational effects of the planets. Measured from one perihelion passage to the next, Halley's period has been as short as
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