En un interesante hecho, la ESA(Con ayuda de la NASA -segun ellos-), descartó que el amenazador asteroide Apophis vaya a impactar el planeta Tierrra en un futuro cercano.


“The 20% increase in diameter, from 270 to 325 m, translates into a 75% increase in our estimates of the asteroid’s volume or mass,” says Thomas Müller of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, who is leading the analysis of the new data.

By analysing the heat emitted by Apophis, Herschel also provided a new estimate of the asteroid’s albedo – a measure of its reflectivity – of 0.23. This value means that 23% of the sunlight falling onto the asteroid is reflected; the rest is absorbed and heats up the asteroid. The previous albedo estimate for Apophis was 0.33.

Knowing the thermal properties of an asteroid indicates how its orbit might be altered due to subtle heating by the Sun. Known as the Yarkovsky effect, the heating and cooling cycle of a small body as it rotates and as its distance from the Sun changes can instigate long-term changes to the asteroid’s orbit.

“These numbers are first estimates based on the Herschel measurements alone, and other ongoing ground-based campaigns might produce additional pieces of information which will allow us to improve our results,” adds Müller.