Halley’s Comet. Even the name of this giant ball of dust and gas is enough to make anyone over the age of 40 wistfully recall what happened 35 years ago this week when the oldest and most famous observed comet paid us a predicted visit.
If you did see Halley’s Comet in 1986 as a child then you have a fighting chance of seeing it again in your lifetime—and you can’t say that about any other naked-eye comet.
On February 9, 1986, Halley’s Comet reached its perihelion—the closest it got to the Sun during its short trip into the inner Solar System and between the orbits of Mercury and Venus—before disappearing into the depths of the outer Solar System.
So where is it now? And when it is coming back?
What is Halley’s Comet?
Officially called 1P/Halley, it’s an intermediate-period comet that’s been seen every 75 years since at least 240 BC, though only in 1705 did anyone work out that the same bright object that kept returning to the night sky. It’s about 9 miles by 5 miles/15 km by 8 km; Halley’s Comet is a big deal.
When is Halley’s Comet coming back?
Halley’s Comet has a highly elliptical orbit of the Sun and will return to the inner Solar System in 40 years, reaching its perihelion on July 28, 2061. It’s set to be much brighter than in 1986 because Earth will be closer to the comet.
We know this because it returns to the inner Solar System every 75.3 years on average, though it can change to between 74 to 79 years because Jupiter and Saturn’s gravity can alter its orbit.
However, some calculate that its close approaches to Jupiter and Venus in future will mean that Halley’s Comet will eventually be ejected from the Solar System altogether … perhaps to become an interstellar interloper like ‘Oumuamua. Others think it could evaporate within 25,000 years, or collide with something.
Why was its 1986 apparition so important?
Largely because we were able to get a close look. Or, at least, the science community was. Although millions of school projects, hundreds of TV documentaries and miles of press coverage was afforded the return of Halley’s Comet, it wasn’t actually that easy to see. Many people alive at the time think they saw it, but it was only slightly brighter than Polaris, the North Star.
Far more significant that any fleeting visual observations in 1986 was the incredible close-ups obtained by the European Space Agency (ESA)’s Giotto spacecraft, one of several to study Halley’s Comet in 1986.
On March 13-14, 1986 it got to within 373 miles/600 km of Comet Halley and spotted the comet’s nucleus and jets of gas and dust as its flew through its tail, detecting complex organics in its coma—the gas around its nucleus.
For space fans it had been a dramatic few months; on January 24, 1986—just as Halley’s Comet was closest to the Sun—NASA’s Voyager 2 spacecraft conducted a flyby of Uranus for humanity’s first and only glimpse of the “Bull’s Eye” planet. However, that was forgotten just four days later when NASA’s Space Shuttle Challenger exploded just after launch.
Where is Halley’s Comet right now?
Go outside tonight just after dark and find Orion’s Belt in the southeastern night sky. Now look down towards the horizon to find the very bright star Sirius. Halley’s Comet is currently slightly further east close to bright star Procyon.
That’s where it is in the night sky, but of course Halley’s Comet is not as far as any star. It’s in what’s called the Kuiper Belt, the outer Solar System beyond the orbit of Neptune and Pluto. Right now it’s 35 astronomical units (AU) from the Sun, which is about as far as its gets—its aphelion—and about the same distance from the Sun as Pluto.
An AU is 35 times the Earth-Sun distance, about 93 million miles/150 million km, which astronomers use to describe the scale of the Solar System.
Why is Halley’s Comet so famous?
Because of what English astronomer Edmond Halley deduced about it. He calculated that the “great comet” that kept on being seen every 75 years was, in fact, the same object. He knew of “great comet” sightings in 1531 and 1607, saw the comet that would later bear his name in 1682, worked that its orbit in 1705, and predicted that it would return in 1758. It duly did, though he was dead by then and it was actually the last few days of 1758 before it was observed.
Astronomy got a new class of object that orbited the Sun and historians had away to assign precise dates to historical sightings of a “great comet.”
Halley’s Comet therefore must have been the “broom star” recorded by Chinese astronomers in the Shiji on May 25, 240 BC—now regarded as the first recorded sighting of Halley’s Comet.
How to see bits of Halley’s Comet later this year
In early May and late October each year Earth moves through streams of particles left in the inner Solar System by Halley’s Comet from that last pass in 1986.
The Eta Aquariids is a meteor shower that last from April 19 to about May 28 and peaks on May 5/6 each year and produces about 55 “shooting stars” each hour.
Running from October 2 through November 7 is the Orionids meteor shower, though its peaks on October 21/22 when onlookers can expect to see about 20 “shooting stars” per hour after midnight.
Wishing you clear skies and wide eyes.
This article is auto-generated by Algorithm Source: www.forbes.com