Fly-by
of the Near Earth Asteroid 1998 WT24
Students Marcel Bruinstroop, Ikbal Çolak and Andries Wijnands (and their teacher Robert Wielinga) of the St. Gregorius College in Utrecht, the Netherlands captured the Asteroid 1998 WT24 in the night of December 13, 2001, when this 1 km piece of rock passed the Earth at a distance of 2.5 million km (it came even closer on December 16: 1.9 million km, about 5 times the distance earth-moon).
1998 WT24 is a so called NEO, a Near Earth Object. During it's revolution around the sun it crosses the orbits of Mercury, Venus and Earth. Although a collision with the Earth is not foreseen in the near future WT24 is considered a Potentially Hazardous Asteroid (PHA). It's orbit will change a little bit every time it comes close to one of the inner planets. A collision of the asteroid (whose size is between 0.7 and 2.0 km) with Earth would be catastrophic.
The observations of WT24 were made with a 4 inch refractor (f=660mm) and a Starlight Xpress MX916 CCD-camera of the Public Observatory Sonnenborgh in Utrecht, the Netherlands.
First the asteroid had to be identified. In the evening hours of December 13, 2001 the asteroid was in the constellation of Gemini, not far from the bright shining planet Jupiter.
First the the telescope was pointed at Jupiter and then moved according to the difference in coordinates between Jupiter and the asteroid.
Then a 60 second exposure was made. It was difficult to identify the stars that were in this picture. After about 5 minutes a second picture was made. With help of the blinking technique it was easy to identify the asteroid (see picture).
the asteroid was identified using the 'blinking'-technique
From 20.49 to 21.58 UT a series of 60 1-minute exposures was made. From the exposures an animation was compiled, showing the asteroid moving among the stars. Even on the 1 minute exposures the image of the asteroid is elongated because it's fast movement!
During the exposures a satelite or a meteor (one of the Geminids? this meteor shower was active during this night!) was captured.
1998 WT24 moving among the stars of Gemini
LINKS:
Potentially Hazardous Asteroids
Asteroid
and Comet Impact Hazards
St Gregorius College, Utrecht, Netherlands
Museum Sterrenwacht Sonnenborgh