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Comet Thatcher has not visited your neck of the solar system since the American Civil War. 2276. But every April, some of its debris puts on a nighttime light show enjoyed by millions of stargazers: the Lyrid Meteor Shower.
The intensity of this exhibition is one of the most important, with some showers being more spectacular than others. If conditions are favorable – and you know where to look – you can usually expect 10 to 15 minutes per hour when the Lyrid shower peaks. Yet every few decades or so, they'll arrive in far greater numbers, giving us a springtime storm of celestial activity. Usually, the show lasts from April 16 to April 25, give or take a few days. This year is no different. Stargazers can watch the Lyrid for about 10 days, but it is expected to peak on April 22.
An Infrequent Guest
Meteor showers mostly unfold in the pathways of comets. Made of ice, dust, rock and frozen gases, comets are celestial bodies that revolve around our sun and other stars in the universe. So far, astronomers have discovered more than 6,400 individual comets. The Lyrid showers are a byproduct of one particular specimen known as "C / 1861 G1 (Thatcher)." Admittedly, that's a mouthful, so-and-so, thatcher's comet.
Amateur astronomer A.E. Thatcher is credited with its discovery. On April 5, 1861, he was watching the heavens from his New York City home. That evening, he noticed a strange, luminous body in the Draco constellation. It did not stay put. Just over a million, flying just 31.1 million miles (50.1 million kilometers) overhead. Then there are more and more people in the world, every area of the planet from the Mercury to Mars – plus the asteroid belt.
You will never get the chance to see Thatcher's comet up close. Like our beloved planet, it orbits the sun, but we now know that it takes Comet Thatcher approximately 415.5 Earth years to a full rotation around the life-giving ball of plasma.
Because of its orbital path, Comet Thatcher spends most of its time far beyond the recesses of our inner solar system. A. E. Thatcher was lucky; he got to watch his comet during one of its rare forays into the area. Astronomers think that it will occur in 2276 or so, ending in centuries-long hiatus.
Crossing Paths
Though Comet Thatcher seldom comes our way, Earth predictably crosses its orbital path once a year. In the process, our atmosphere gets pelted by rubbish.
Whenever comet approaches the sun, the heat melts some of its ice, freeing little pieces of dust and rock. So, passing comets leave debris trails behind. And those tiny chunks occupy the same orbit as the comet that shed them. Eventually, the comet itself may disintegrate entirely. However, even after it, it will be necessary to use it in its place, filling the orbital route that the object used to take over the sun.
That's why Earth gets annual meteor showers. On its own sun-centered journey, the planet reliably crosses paths with the debris-clogged orbits of many different comets – including A.E. Thatcher's.
The detritus starts to burn up the earth. Fear not; most chunks will never reach the ground. The ones that hit our planet's surface are called meteorites. They're far less than meteoroids, those chunks that completely vaporize in our atmosphere. Both meteorites and meteoroids produce flashes of light known as meteors.
Every April, our planet makes its annual passage through Comet Thatcher's orbit. Stargazers are treated to a meteor shower while Earth intersects the debris trail.
Heroes and Lyres
Now if you're standing on the ground, the meteors in whatever shower you're going to appear to emanate from the same general point in the sky. (Even though they do not that that's just an illusion.)
This spot is called the radiant shower. Most of the yearly showers are named after constellations that sit by their radiant points. For example, meteors in the Perseid Shower, which thrills us every August, seems to fly out of the Perseus constellation.
By the same token The Coming Thatcher is called the Lyrid Shower because of its radiant is next to Lyra, a constellation representing the lyre played by the Greek hero Orpheus. Vega – one of the brightest stars in the sky – helps the instrument's crossbar.
Knowing where the radiant is can enhance your shower-watching experience, but veteran stargazers will tell you not to look at the constellation directly. Meteors will show up all over the sky, and the longest-looking ones are going to appear far away from the radiant.
An Illuminated History
The number of meteors you can expect during the Lyrid shower varies from year to year. At the peak of a Lyrid shower, it's typical to see 10 to 20 per hour. Usually, the Perseid showers are a whole lot denser.
But every so often, an exceptional Lyrid shower occurs. During the peak of the 1982 Lyrids, for instance, viewers in the Eastern United States reported around 100 meteors per hour. Comets do not shed their dust particles at a constant rate, so one year may be more intense than the next one.
To try and predict the intensity of a coming shower, the astronomers make computer models that take things like comet trajectories and atmospheric changes in account. This year, you can help scientists gather Lyrid data. Simply register with the International Meteor Organization and report your observations after you go Lyrid-gazing.
Lyrids is an ancient pastime. You see, a Chinese document dating back to 687 B.C.E. refers to "stars [that] Lyrid meteor shower – or indeed, fell like a rain Any meteor shower – in recorded history.
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