4179 TOUTATIS, THE POTENTIALLY HAZARDOUS ASTEROID

Today, The Grandma has received the visit of one of her closest friends, Joseph de Ca'th Lon. 

Joseph loves Astronomy and they have been talking about 4179 Toutatis, the asteroid that passes within four lunar distances of Earth, on a day like today in 2004.

4179 Toutatis (provisional designation 1989 AC) is an elongated, stony asteroid and slow rotator, classified as a near-Earth object and potentially hazardous asteroid of the Apollo asteroid group, approximately 2.5 kilometers in diameter. Discovered by French astronomer Christian Pollas at Caussols in 1989, the asteroid was named after Toutatis from Celtic mythology.

Toutatis is also a Mars-crosser asteroid with a chaotic orbit produced by a 3:1 resonance with the planet Jupiter, a 1:4 resonance with the planet Earth, and frequent close approaches to the terrestrial planets, including Earth.

In December 2012, Toutatis passed within about 18 lunar distances of Earth. The Chinese lunar probe Chang'e 2 flew by the asteroid at a distance of 3.2 kilometers and a relative velocity of 10.73 km/s.

Toutatis approached Earth again in 2016, but will not make another notably close approach until 2069.

Toutatis was first sighted on 10 February 1934, as object 1934 CT, but lost soon afterwards. It remained a lost asteroid for several decades until it was rediscovered on 4 January 1989 by French astronomer Christian Pollas, and was named after the Celtic god of tribal protection Toutatis (Teutates). The name of this god is very familiar in France due to the catchphrase Par Toutatis! by the Gauls in the comics Asterix.

The spectral properties suggest that this is an S-type, or stony asteroid, consisting primarily of silicates. It has a moderate Bond albedo of 0.13. Radar imagery shows that Toutatis is a highly irregular body consisting of two distinct lobes, with maximum widths of about 4.6 km and 2.4 km, respectively. It is hypothesized that Toutatis formed from two originally separate bodies which coalesced at some point (a contact binary), with the resultant asteroid being compared to a rubble pile.

Its rotation combines two separate periodic motions into a non-periodic result; to someone on the surface of Toutatis, the Sun would seem to rise and set in apparently random locations and at random times at the asteroid's horizon. It has a rotation period around its long axis (Pψ) of 5.38 days. This long axis is precessing with a period (Pφ) of 7.38 days. The asteroid may have lost most of its original angular momentum and entered into this tumbling motion as a result of the YORP effect.

Large amounts of data of Toutatis were obtained during Chang'e 2's flyby. Toutatis is not a monolith, but most likely a coalescence of shattered fragments. This bifurcated asteroid is shown to be mainly consisting of a head (small lobe) and a body (large lobe). The two major parts are not round in shape, and their surfaces have a number of large facets. In comparison with radar models, the proximate observations from Chang'e 2's flyby have revealed several remarkable discoveries concerning Toutatis, among which the presence of the giant basin at the big end appears to be one of the most compelling geological features, and the sharply perpendicular silhouette in the neck region that connects the head and body is also quite novel. A large number of boulders and several short linear structures are also apparent on the surface.

Toutatis has been observed with radar imaging from the Arecibo Observatory and the Goldstone Solar System Radar during the asteroid's prior Earth flybys in 1992, 1996, 2000, 2004, and 2008. It was also observed with radar during the December 2012 flyby and observed more distant flyby with radar in December 2016.

After 2016, Toutatis will not pass close to Earth again until 2069.

Resolution of the radar images is as fine as 3.75 m per pixel, providing data to model Toutatis's shape and spin state.

The Chinese lunar probe Chang'e 2 departed from the Sun–Earth L2 point in April 2012 and made a flyby of Toutatis on 13 December 2012, with closest approach being 3.2 kilometers and a relative velocity of 10.73 km/s, when Toutatis was near its closest approach to Earth. It took several pictures of the asteroid, revealing it to be a dusty red/orange color.

More information: NASA

Asteroids have us in our sight.
The dinosaurs didn't have a space program,
so they're not here to talk about this problem.
We are, and we have the power
to do something about it.
I don't want to be the embarrassment of the galaxy,
to have had the power to deflect an asteroid,
and then not, and end up going extinct.

Neil deGrasse Tyson