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Comet Halley is parent of 2 meteor showers

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Comet Halley visited last in 1986

The famous comet 1P/Halley – aka Comet Halley – swings into the inner solar system about every 76 years. At such times, the sun’s heat causes the comet to lose its icy grip over its mountain-sized conglomeration of ice, dust, and gas. And so, at each pass, the crumbly comet sheds a fresh trail of debris into its orbital stream. It lost about 1/1,000 of its mass during its last flyby, in 1986.

And it so happens we intersect Comet Halley’s orbit not once, but twice each year. That’s why – although the comet itself is nowhere near – Comet Halley is the parent of not just one, but two well-known annual meteor showers, one in May and one in October.

In early May, we see bits of this comet as the annual Eta Aquariid meteor shower.

Then, some six months later, in October, Earth in its orbit again intersects the orbital path of Comet Halley. This time around, these broken-up chunks from the comet burn up in Earth’s atmosphere as the annual Orionid meteor shower.

And, by the way, Halley is pronounced like valley. According to Ian Ridpath:

Many people nowadays say “Hailey,” a legacy of the 1950s rock group Bill Haley and the Comets.

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Compare this image to the one above. Here’s how observers saw Comet Halley on May 29, 1910. Image via Wikimedia Commons.

The famous Halley’s Comet is the parent of 2 annual meteor showers: the Eta Aquariids in May and the Orionids in October. We witness these showers when we cross the comet’s orbit. But if we cross the orbit of Comet Halley twice each year, does that means there’s a chance that Earth and the comet will collide?

Comet debris litters Comet Halley’s orbit

Because Halley’s comet has circled the sun innumerable times over countless millennia, cometary fragments litter its orbit. That’s why the comet doesn’t need to be anywhere near the Earth or the sun in order to produce a meteor shower.

Instead, whenever our Earth in its orbit intersects Comet Halley’s orbit, cometary bits and pieces – often no larger than grains of sand or granules of gravel – smash into Earth’s upper atmosphere, to vaporize as fiery streaks across our sky: meteors.

The diagrams below can help you visualize Earth’s orbit with respect to the path of Halley’s comet.

Diagram: Round orbit of Earth with parabolic orbit of comet crossing it twice. — The path of Halley’s comet intersects Earth’s orbit twice each year. In early May it produces the Eta Aquariid meteor shower (left) as the particles leave the inner solar system. Diagram via JPL Horizons Program.

Diagram: Comet's parabolic orbit intersecting round Earth orbit at 2 places. — In mid-October, Halley’s comet produces the Orionid meteor shower (right) as the particles enter the inner solar system. Diagram via JPL Horizons Program.

Another view of Comet Halley’s orbit intersecting Earth’s

Oblique view of orbit of Earth with long curved orbit of comet crossing it 2 places. — Will Comet Halley someday strike Earth? After all, we cross its orbit twice every year. This illustration is from master astronomy chart-maker Guy Ottewell. Watch a 2-minute video with EarthSky’s Deborah Byrd for more. Image via Guy Ottewell. Used with permission.

Their radiant points

You don’t need to know the radiant point to enjoy a meteor shower, because the meteors will appear anywhere in the sky, but if you trace back their direction, you’ll see that they seem to fly outward from one area. Meteor showers get their names from the location of the radiant point.

The Orionids radiate from a point near the upraised club of the constellation Orion the Hunter. And the Eta Aquariids appear to originate from the middle of Aquarius the Water Bearer.

Lines marking constellation with radial arrows near middle of it. — The radiant point of the Eta Aquariid meteor shower is near the star Eta Aquarii in the constellation Aquarius the Water Bearer. The radiant rises in the wee hours after midnight and is still climbing toward its highest point — in the south as seen from the Northern Hemisphere — at dawn. It’s because we’re in a different part of our orbit — and have a unique perspective of the comet’s orbit — that the two meteor showers appear in different parts of the sky. See the illustration below. Chart via EarthSky.

Chart with dots for constellation Orion and a circle of arrows showing the radient of the Orionid meteor shower. — The Orionids radiate from a point near the upraised club of the constellation Orion the Hunter. The bright star near the radiant point is ruddy, somber Betelgeuse. You might catch an Orionid meteor any time between about September 26 and November 22. Chart via EarthSky.

Where is Comet Halley now?

Often, astronomers like to give distances of solar system objects in terms of astronomical units (AU). An AU is the sun-Earth distance. Halley’s comet lodges 0.587 AU from the sun at its closest point to the sun (perihelion) and 35.3 AU at its farthest point (aphelion).

In other words, at its farthest, Halley’s comet resides about 60 times farther from the sun than it does at its closest.

It was last at perihelion in 1986, and will again return to perihelion in 2061.

In December of 2023, the comet reached its farthest point from the sun that binds it in orbit. Then — pulled inexorably by the sun’s gravity — it curved around and is heading back toward the inner solar system again. Comet Halley will be back in 2061.

So the comet is far away. Even so, meteoroids — bits of debris left behind in the comet’s orbit — swim throughout Halley’s comet’s orbital stream. So each time Earth crosses the orbit of the comet, in May and October, these meteoroids turn into incandescent meteors once they plunge into the Earth’s upper atmosphere.

Multiple concentric planet orbits and elongated blue oval line crossing them. — A diagram of Halley’s comet seen from above the solar system plane. The comet’s orbit reaches from near the sun to beyond the orbit of Neptune. Image via Ian Ridpath. Used with permission.

Oblique view of solar system showing comet orbit at angle to orbits of planets. — The orbit of Comet Halley. The comet does not stay in the same plane as the planets but is tilted 18 degrees and it revolves around the sun in the opposite direction as the planets. Diagram produced by JPL Horizons Program.

Meteor showers and comets

Of course, Halley’s comet isn’t the only comet that produces a major meteor shower.

Three of the comets in the table below are each responsible for two meteor showers. We’ve already discussed Halley’s comet. The asteroid 2004 TG10, responsible for the Northern Taurids, is part of the Taurid Complex, which includes Comet Encke, itself producing the Southern Taurids. And, asteroid 2003 EH1, responsible for the Quadrantids, appears to be part of the Machholz Complex, which also includes Comet 96P/Machholz, itself producing the Delta Aquariids.

Meteor Shower	Parent Comet	Peak Date	Orbital Period	Perihelion	Aphelion

Quadrantids	2003 EH1 (asteroid	Jan 4	5.52 yrs	1.19 AU	5.06 AU
Lyrids	Comet Thatcher (1861 G1)	Apr 22	413 yrs	0.92 AU	110 AU
Eta Aquariids	Comet 1P/Halley	May 5	75.3 yrs	0.59 AU	35.3 AU
Delta Aquariids	Comet 96P/Machholz	July 30	5.28 yrs	0.12 AU	5.94 AU
Perseids	Comete 109P/Swift-Tuttle	Aug 13	133 yrs	0.96 AU	51.2 AU
Draconids	Comet 21P/Giacobini-Zinner	Oct 8	6.62 yrs	1.04 AU	6.01 AU
Orionids	Comet 1P/Halley	Oct 21	75.3 yrs	0.59 AU	35.3 AU
S Taurids	Comet 2P/Encke	Nov 5	3.30 yrs	0.33 AU	4.11 AU
N Taurids	2004 TG10 (asteroid)	Nov 12	3.34 AU	0.31 AU	4.16 AU
Leonids	Comet 55P/Tempel-Tuttle	Nov 17	33.2 yrs	0.98 AU	19.69 AU
Geminids	3200 Phaethon (asteroid)	Dec 14	1.43 yrs	0.14 AU	2.40 AU
Ursids	Comet 8P/Tuttle	Dec 22	13.6 yrs	1.03 AU	10.38 AU

What are those asteroids doing here?

Until recently a comet was a comet, and an asteroid was an asteroid. But the more we have learned about them the more the lines between them became blurred. The long-held belief that meteor showers can come only from active comets has been challenged by the discovery of asteroids being the parent objects of meteor showers. Most notably are the asteroids 2003 EH1 generating the Quadrantids and 3200 Phaethon behind the Geminids.

One of three things is going on here, or a combination of them. Perhaps the asteroid was once a comet and at that time expelled material that causes the meteor shower. The comet then became exhausted and all we have left is a small rocky nucleus.

Another possibility is that the asteroid was once part of a comet that at one time expelled material to cause the meteor shower, then the asteroid broke off and the comet was perturbed into a different orbit.

Or maybe the asteroid is still emitting material. A recent example of this is the asteroid Bennu, seen here ejecting material from its surface.

Dark space rock against black space, with particles coming off it. — Asteroid Bennu, as imaged by the OSIRIS-REx spacecraft. Bennu ejected 11 plumes of dust into space from January 6 to February 18 as captured in this composite image. Image via NASA/ Goddard/ University of Arizona/ Lockheed Martin.

Bottom line: The famous Halley’s comet spawns the Orionid meteors in October and the Eta Aquariids in early May. It’ll return to the inner solar system in 2061. Other comets, and even some asteroids, produce meteor showers.