Misconceptions about meteors
Incorrect to call phenomenon ‘shooting stars’
When I was a student and budding astronomer in San Diego, I bought many old astronomy books from a second-hand bookstore in a run-down part of downtown.
Climbing the rickety, steep wooden stairs to the tall, dusty shelves in a dim back corner, I would become engrossed in the old books.
One day I found a treasure, a copy of the bestselling 19th-century astronomy textbook, The Geography of the Heavens.
The author, Elijah H Burritt, was born in 1794 in Connecticut. He published the first edition of his book in 1833, and it was so popular in schools that it went on to sell 300,000 copies over the next 50 years.
My copy of the book is the “greatly enlarged, revised and illustrated” 1856 edition by H Mattison. Poor Burritt had been attracted by an opportunity to obtain a large tract of land as a colonist in the Republic of Texas, which had declared its independence from Mexico in 1836. In 1838, Burritt’s group, including his sister and brother, chartered a ship for the 28-day voyage to Texas. On arrival, they foundered on a sandbar near Galveston, but made it ashore and on to Houston, where they briefly lived in tents. Briefly, because they came down with yellow fever, and most died, including Elijah. There are parallels to the 1820 settlers here in the Eastern Cape.
Texas was only an independent republic from 1836 to 1845 when it became the 28th state of the USA. From 1842 to 1845 there was an embassy in St James, London, in rented accommodation above the famous — and still going — Berry Brothers and Rudd Wine Shop on Pall Mall, not far from the Royal Astronomical Society (of which I am a fellow and past vice-president). There is still a plaque there that reads, “Texas Legation in this building was the legation for the ministers from the Republic of Texas to the Court of St. James 1842-1845.”
When the Texans left, they had an outstanding rent bill of £160. For the 150th anniversary in 1986 of the founding of the Republic of Texas, 26 Texans in full buckskin outfits, visited Berry Brothers and paid the bill!
Chapter XVII, entitled falling or shooting stars, of my edition of The Geography of the Heavens begins with these words: “The phenomenon of shooting stars, as it is called, is common to all parts of the earth.
“The unerring aim, the startling velocity, and vivid brightness with which they seem to dart athwart the sky, and as suddenly expire, excite our admiration; and we often ask, ‘what can they be’?”
Burritt did not know the answer. The word “meteor” has its roots in the ancient Greek word “metéron” meaning something high up, or in the atmosphere. This is why we call the study of weather “meteorology”. Burritt thought meteors were an atmospheric phenomenon related to electricity, which itself was not well-understood at that time.
When I started school our neighbour, Mr Hill was 100, born in 1853 when no-one knew what a meteor is. We know now. Meteors — shooting stars — are not stars at all.
They are small stones orbiting the sun that collide with the earth at a typical speed of 100,000km/h and burn up in the atmosphere, creating the streak of light that we see as the shooting star. The typical meteor is only the size of a grain of sand or a pebble. When it slams into the atmosphere it is heated by friction to about 2,000°C so that it causes the air to glow.
Millions of meteors hit the earth’s atmosphere every day bringing in thousands of tons of material, most of which eventually falls to the ground as dust. Bigger rocks do hit, sometimes making fireballs, and those can hit the ground, leaving remnant rocks called meteorites. The biggest of them can be tens of km across and it is those rare giants that cause mass extinctions.
When you next see a shooting star, you can enjoy the ephemeral beauty, and you can enjoy knowing what they are.
To Burritt they were a mystery, but no longer to us.
Next month, I will tell you about meteor showers and the December Leonid meteor shower, famous for its fireballs.