Halley’s Comet last appeared in 1986, and it won’t return again until 2061. But according to Space.com, early in May, the Eta Aquarid meteor shower offered a Halley’s Comet reminder — its celestial calling card, if you will.
Messengers From the Dawn
Although comets are usually invisible from Earth, something magical happens when they near the sun’s surface. Comprised of mostly dust and ice, the nuclei of comets are described as sooty snowballs of primordial matter. But as a comet passes near the sun, it is surrounded by a temporary atmosphere of vapor and dust, highly reflective in the bright sunlight. For a few weeks or months, the comet may be one of the brightest objects in Earth’s sky, Space.com explained.
A Repeat Visitor
Most bright comets are one-time visitors. They will not return for thousands or even millions of years. But occasionally a comet’s orbit is deflected a second time, and, per Space.com, it becomes a “periodic” comet, making regular return visits to the inner solar system.
During the 1600s, astronomer Edmund Halley studied observations of famous historical comets and realized that several of them were repeat visits by the same comet. Halley predicted that this comet would make its next pass in 1758. And it did, right on schedule. Halley did not live to see it, but we still call the comet by his name.
Its next visit will not be for 43 years, but earlier this month, we got a preview — the Eta Aquarid meteor shower.
A Twice-Yearly Show
Earth’s orbit intersects the track of Halley’s orbit twice every year, in May and October. Space.com noted that the early May encounter causes the Eta Aquarid meteor shower, while October brings the Orionid shower.
If you’ve never seen a meteor shower before, you may be surprised when you see colorful, bright streaks shoot across the night sky. When a comet’s dust trail collides with the Earth’s atmosphere, the dust particles disintegrate as they burn, which produces this colorful phenomenon, according to NASA.
Meteor showers are named for stars, such as Eta Aquarii, or star groups, such as Orion, not because they have any direct connection to these stars but purely as visual guideposts. NASA reported that Eta Aquarii marks the radiant of the Eta Aquarid meteor shower, or the portion of the sky that meteors in the shower seem to be hurling away from.
This is purely a perspective effect: When we look toward Eta Aquarii we are looking back along the “flight path” of Halley’s fragments as they hurl toward Earth.
Preview of a Comet
A meteor shower is usually not like a celestial fireworks show, though a few have been. This year’s Eta Aquarid meteor shower was expected to produce about 10 meteors an hour for observers in the Northern Hemisphere. Mark your calendar for October 21 and 22, predicted to be the peak days to observe the Orionid shower. To observe it, just find a spot where you have a good view, make yourself warm and comfortable in the predawn hours — and wait.