Toutatis Safely Passes the Earth
Click on images for larger picture.
Summary - (Sep
29, 2004) As predicted, Asteroid Toutatis made its closest approach to
the Earth today, passing a mere 1.5 million km (930,000 miles) away from our
planet - 4 times the distance from the Earth to the Moon. The 4.6 km (2.9 mile)
long asteroid hasn't made an approach this close since 1353. Since it was first
discovered in 1989, Toutatis has been closely studied by astronomers because it
has an orbit that brings it close to the Earth every 4 years. Unfortunately,
it's still too dim to see with the unaided eye, but skilled amateur astronomers
with telescopes watching the southern skies have spotted it. Toutatis won't get
this close again until 2562.
Full Story - Today, September 29, 2004, is undisputedly the Day
of Toutatis, the famous "doomsday" asteroid.
Not since the year 1353 did this impressive "space rock" pass so close
by the Earth as it does today. Visible as a fast-moving faint point of light in
the southern skies, it approaches the Earth to within 1,550,000 km, or just four
times the distance of the Moon.
Closely watched by astronomers since its discovery in January 1989, this
asteroid has been found to move in an orbit that brings it close to the Earth at
regular intervals, about once every four years. This happened in 1992, 1996,
2000 and now again in 2004.
Radar observations during these passages have shown that Toutatis has an
elongated shape, measuring about 4.6 x 2.4 x 1.9 km. It tumbles slowly through
space, with a rotation period of 5.4 days.
The above images of Toutatis were taken with the ESO Very Large Telescope
(during a technical test) in the evening of September 28. They were obtained
just over 12 hours before the closest approach that happens today at about 15:40
hrs Central European Summer Time (CEST), or 13:40 hrs Universal Time (UT). At
the time of these observations, Toutatis was about 1,640,000 km from the Earth,
moving with a speed of about 11 km/sec relative to our planet.
They show the asteroid as a fast-moving object of magnitude 10, about 40 times
fainter than what can be perceived with the unaided, dark-adapted eye. They also
prove that Toutatis is right on track, following exactly the predicted
trajectory in space and passing the Earth at a safe distance, as foreseen.
Detailed calculations, taking into account all available observations of this
celestial body, have shown that although Toutatis passes regularly near the
Earth, today's passage is the closest one for quite some time, at least until
the year 2562. The ESO observations, obtained at a moment when Toutatis was very
close to the Earth, will help to further refine the orbital calculations.
The "parallax effect" demonstrated!
Simultaneous images obtained with telescopes at ESO's two observatories at La
Silla and Paranal demonstrate the closeness of Toutatis to the Earth. As can be
seen on the unique ESO PR Photo 28e/04 that combines two of the exposures from
the two observatories, the sighting angle to Toutatis from the two
observatories, 513 km km apart, is quite different. Astronomers refer to this
effect as the "parallax". The closer the object is, the larger is the
effect, i.e., the larger will be the shift of the line-of-sight.
Interestingly, the measured angular distance in the sky of the beginnings (or
the ends) of the two trails (about 40 arcsec), together with the known distance
between the two observatories and the position of Toutatis in the sky at the
moment of the exposures fully define the triangle "Paranal-Toutatis-La
Silla" and thus allow to calculate the exact distance to the asteroid.
It is found to be very close to that predicted from the asteroid's position in
its orbit and that of the Earth at the moment of this unique observation,
1,607,900 km. This exceptional, simultaneous set of observations thus provides
an independent measurement of Toutatis' distance in space and, like the measured
positions, a confirmation of its computed orbit.
SOURCE: Universe Today