Comet Shoemaker–Levy 9
The comet torn apart by Jupiter, whose pieces crashed into the planet in July 1994 while the world watched.
Key facts
- Designation
- D/1993 F2 (Shoemaker–Levy)
- Type
- Comet captured by Jupiter (destroyed)
- Orbital period
- it orbited Jupiter, about once every two years, rather than the Sun
- Closest to the Sun
- it passed within about 40,000 km of Jupiter's cloud tops in July 1992
- Farthest from the Sun
- about 50 million km from Jupiter
- Tilt of orbit
- not meaningful: its orbit was around Jupiter
- Nucleus
- perhaps 2 km before it broke up; more than 20 fragments
- Discovered
- by Carolyn and Eugene Shoemaker and David Levy at Palomar Observatory in March 1993
- Returns
- destroyed in July 1994
Orbit
Shoemaker–Levy 9 was unusual: it orbited Jupiter, not the Sun. It had probably been captured by the planet decades earlier. On 7 July 1992 it passed so close that Jupiter's gravity, stronger on the near side than the far side, pulled it apart. The next pass would be a direct hit.
Size and nature
Before it broke up, the nucleus was probably about 2 km across, though estimates range more widely. After break-up it became a line of more than 20 fragments, nicknamed the string of pearls, each with its own small coma.
History
Carolyn and Eugene Shoemaker and David Levy found the comet on photographs taken in March 1993 at Palomar Observatory in California, during their regular search for comets and asteroids. It was their ninth periodic comet. Its orbit soon showed that the fragments would strike Jupiter in July 1994.
From 16 to 22 July 1994 the fragments hit one after another, each at about 60 km/s. The impacts took place just round the edge of the planet as seen from Earth, but the plumes rose high enough to be seen, and within minutes the impact sites rotated into view. They left dark scars bigger than Earth that lasted for months. The largest, fragment G, released energy estimated at millions of megatons.
Missions
The Galileo spacecraft, on its way to Jupiter, had a direct view of the impact sites and recorded the flashes. The Hubble Space Telescope watched the scars spread.
Space missions
- Galileo The first close look at an asteroid, and the discovery that asteroids can have moons.
Key dates
| Date | What happened |
|---|---|
| 7 July 1992 | Comet Shoemaker–Levy 9 passed close to Jupiter and broke into more than 20 pieces. |
| 16 July 1994 | The first fragment of Comet Shoemaker–Levy 9 struck Jupiter. |
| 22 July 1994 | The last fragment of Comet Shoemaker–Levy 9 struck Jupiter. |
Did you know?
It was the first collision between two Solar System bodies ever watched directly.
The impacts persuaded many governments to take the search for dangerous asteroids seriously.
Chains of craters on Jupiter's moons Ganymede and Callisto show that broken comets have struck before.