Levy: “It was something that we felt was causing the world to pause for a moment”
Shoemaker-Levy 9’s co-discoverer David Levy relives the comet’s crash with Jupiter twenty years on
Could you explain how you found Comet Shoemaker-Levy 9?
Well, I’ll try to do it briefly. We [Levy, Gene and Carolyn Shoemaker] have been observing together for a number of years as part of a program to discover comets and asteroids that could pose a threat to the Earth at some time. We never expected to find this guy.
On the night of 23 March 1993 we were observing and actually taking photographs through patchy clouds – it was just before a major weather disturbance. We got our work very much done and taken care of, when Carolyn was scanning the images that we took that night and she found what she felt was a squashed comet. It was on two of the photographs that Gene and I had taken and it was named, as is customary for the discoverers, Shoemaker- Levy 9. That is the short version of how we discovered the comet.
When you discovered that the comet would collide with Jupiter, did you realise it would be such a historic event?
The answer is yes. We knew as soon as we found out that there was going to be a collision (we found that out on 22 May 1993) that this would be a historic comet. But right away everybody started squealing and yelling that we wouldn’t see anything, you know, it would be a dud because things hit [Jupiter] all of the time and we never see anything.
What we didn’t realise was that apparently nothing that size had collided with Jupiter within the memory of humanity. The spots that were formed were clearly the darkest and most obvious formations to ever be seen on the gas giant. We started seeing them immediately after the first impact and when the other pieces collided, they left spots that were even bigger.
The largest [impact] was left by the fragment known as G and this turned out to be the most obvious feature ever to be seen on the planet Jupiter since the invention of the telescope.
You said that some were sceptical of whether we’d see the impact – would you be able to explain a bit more about that?
[Astronomers] knew it would make an impact, but what they weren’t certain about was whether even the Hubble Space Telescope would notice anything. So, we had everybody looking just in case we saw something and boy, did we ever see something!
Once the impact was eventually over, did it exceed your expectations?
It exceeded them by a huge amount. I remember that – a few days into the collisions – the Naval Observatory was open to the public on the grounds of the vice president’s residence in Washington. I remember standing in a long line and people were encouraging me to go forward, I didn’t want to, but I did. I finally got in to look through the telescope after about an hour and I was just amazed at what I was seeing – really dark black spots across the entire face of Jupiter. They were so easy to see and so clear and obvious, I could even see them through the telescope’s finder.
How did you cope with the media reaction surrounding the impact?
It was so interesting to be on the front pages of all of the newspapers for a whole week… and all of the TV stations. I remember sitting at NASA headquarters the day before the impacts, being interviewed by maybe 15 to 20 different television stations, one after the other. Then, in the middle of the impacts, I was interviewed again by television stations one after the other. That was really quite an experience. It was something that we felt was causing the world to pause for a moment. To pause from its preoccupation, the normal buzz of the nightly newscast, and [kind of] look up into space for a moment and contemplate the vastness of the universe, as well as the role of humanity in that universe.
You know, we thought that there were more stars in our galaxy than there are grains of sand on a beach, as well as more galaxies in the universe than there are grains of sand on all of the beaches of the world. Despite that, there is only one of you and only one of me in the entire universe.
You can read the entire interview with David Levy in issue 28 of All About Space, on sale 24 July 2014