24 March: The Shoemaker Levy comet

The Shoemaker Levy comet was discovered on this date in 1993. 10 things you might not know about it:

1. The comet’s official name is Shoemaker-Levy 9, because it was discovered by Carolyn and Gene Shoemaker and David Levy. It was the ninth comet of its type, ie a periodic comet, that they’d discovered, hence the number 9. They’d also discovered two more comets of a different type but they use a different naming system.
2. The comet was first spotted in a photograph taken with the 0.4-meter Schmidt Telescope at Mt. Palomar.
3. Since Shoemaker-Levy 9 had already broken up into 20 fragments (labelled A to W) when it was discovered, we don’t know the size of the original comet. Estimates range from 2 to 10 km in diameter. The largest fragments are thought to have been 1 to 3 km in diameter.
4. When discovered, it was already orbiting Jupiter. It had most likely been captured by Jupiter’s gravity, possibly as long as 20-30 years earlier and had been orbiting the planet ever since.
5. In 1992, it made a close approach to the planet and was torn apart by tidal forces.
6. Astronomers got very excited about this because it was very rare to observe a comet which had broken into pieces and it was even more unusual to find one orbiting a planet. They got even more excited when it became clear that the fragments were going to collide with Jupiter, and not only that, but the Galileo space probe, launched in 1989 and due to enter Jupiter’s orbit in 1995, was in a perfect position to observe and beam pictures back to Earth.
7. The impacts started on July 16, 1994, and ended on July 22, 1994.
8. The fragments smashed into Jupiter with the force of 300 million atomic bombs. The fragments created huge plumes 1,200 to 1,900 miles (2,000 to 3,000 kilometres) high and heated the atmosphere to temperatures as hot as 53,000 to 71,000 degrees Fahrenheit (30,000 to 40,000 degrees Celsius). The collisions generated enormous waves which swept across Jupiter at speeds of 450 m/s (1,476 ft/s) and were observed for over two hours after the largest impacts.
9. Afterwards, the scars from the impacts were visible for almost a year, and were even easier to see than Jupiter’s great red spot.
10. What we learned from this is that it is all to possible for a comet to collide with a planet, and had shoemaker-Levy 9 collided with Earth the results would have been catastrophic. It meant astronomers began to take that threat more seriously and start actively looking for objects in space that could pose a threat. That said, it also confirmed the idea that massive Jupiter’s gravitational field protects the inner planets by hoovering up many of the objects that could collide with us.

Character birthday

Medoc, doctor and member of Combat Team Alpha. He is a medical genius but was passed over for jobs and promotions. He blamed his short stature for his failure to advance and harbours some bitterness about that; however, the more likely reason that his bedside manner was somewhat lacking. He was taken on as Team Alpha’s healer and is their expert on all things to do with disease and medicine. He’s also known for being blunt to the extent of rudeness at times.