June 30 is Asteroid Day, being the anniversary of the 1908 Tunguska event.
Something exploded in the atmosphere above Siberia, flattening forests over a vast area and sending shock waves around the world.
There were theories that the object might have been a comet or even a black hole; most likely it was a lump about 50 meters wide that had once been part of Comet 2P Encke. It could count as a small asteroid and a meteor. I have now collected my remarks about the Tunguska event into a new page.
Asteroid Day might better be celebrated on January 1, when the first asteroid, Ceres, was discovered in 1801.
Around this year’s June 30, the most observable asteroid is, as so often, the fourth, Vesta, not discovered till 1807, yet the only one that can reach unaided-eye brightness. Indeed it reached magnitude 5.9 when it was at opposition on March 4, but it is now becoming more distant and has dimmed to magnitude 7.7, so it is for binoculars or telescope.
It is 74° out from the Sun in the evening sky, sliding eastward from Leo into Virgo.
See the end note about enlarging illustrations.
This is a more close-up view, with radius 8.5°. The dots for Vesta, at the beginning of each day by Universal Time, are sized for its magnitude, so that it can be compared with stars of about the same brightness. On June 30 Vesta is at right ascension 11h 42m, declination 9° 31′. Perhaps the best way to find it is to start from 2nd-magnitude Denebola, the tail of the Lion, move 5° southward, and 8 minutes of r.a. westward.
Vesta was the Roman goddess of the hearth, and of the family home of which the hearth was the focus. She was equated with the Greek goddess Hestia, who had similar functions, and was one of the twelve chief gods, a sister of Jupiter. She was symbolized by a fire in her temple in Rome’s forum, kept burning by her priestesses, the Vestales or Vestal virgins.
And her fire was rekindled in 1826 by the invention of Vesta wax friction “strike anywhere” matches, for which were invented Vesta cases, which, also known as just “Vestas,” are sought by collectors.
The match that struck a glancing blow in 1908 was, luckily for us, a dud. It didn’t set forest and atmosphere aflame.
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ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image”, then enlarge. Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers). Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.
Sometimes I make improvements or corrections to a post after publishing it. If you click on the title, rather than on ‘Read more’, I think you are sure to see the latest version.
This weblog maintains its right to be about astronomy or anything under the sun.
That Tunguska region is pretty empty.sadly I’ve not done the Trans Siberian Express but I’ve flown across Siberia from Hong Kong to Paris and it’s just trees,trees,trees.i saw some lights down there but I realized after a bit it was the Moon reflecting off lakes.if it’s that empty these days no wonder there was no one to witness the Tunguska explosion mind had there been they probably would have been killed!I don’t think that any investigation was made until after Lenin’s death when scientists went to take a look.
The link in Guy’s text above provides details about the witnesses who saw it (and didn’t die) and the eventual exploration.of it.
Vesta is my favorite asteroid, since she’s the brightest. I enjoyed watching Vesta make her graceful looping tour of eastern and central Leo from January until earlier this month. I last saw Vesta through 10×42 image-stabilized binoculars on June 17, near Iota Leonis. For the past couple of weeks the weather has been increasingly cloudy and foggy (I haven’t even seen the Moon since June 23!). Now that Vesta is getting lower in the evening sky, and dimmer, I probably won’t see her again until she appears as a morning object near Saturn next Spring.
When I was growing up many kitchens had a metal match holder on the wall by the stove. Everybody had a gas stove with a pilot light, so I guess the matchboxes were leftovers from earlier days. And sometimes the pilot light would go out and need to be relit, so matches came in handy.
I’m not terribly worried about a catastrophic asteroid or comet impact. There are so many anthropogenic threats to our survival that are so much more pressing, and, since we’re causing them, much more easily reduced or eliminated. And the occasional impact is not entirely a bad thing. If the dinosaurs had redirected the Chicxilub asteroid, we mammals would still be tiny insectivorous nocturnal trees dwellers.
I’m not sure whether the Drake equation (for the probable number of civilizations in the galaxy capable of communicating) takes account of asteroid strikes. Instead of the one term for the average duration of civilizations, there should perhaps be two: one, for duration controlled by home-planet factors such as environment and collective sanity; the other, on the probability of asteroid strikes and other cosmic catastrophes such as supernovas.
If the dinosaurs had survived, could their body plan have allowed them to develop technology? Or would that have been as unlikely as Defoe’s talking and writing horses, the Houyhnhms? Though the dinosaurs “ruled the world” in that they were the top predators and the largest land animals, couldn’t a smaller animal, by competing with them and evolving defences against them, have become dominant and technological, exterminating or domesticating them?
If nobody has written that science fiction story, somebody should!