Archive for May 14th, 2011

Is there “life” beyond the orbit of Neptune?

Gy. M. Szabo, K. Sarneczky, L. L. Kiss / ESO

Without a doubt, one of the brightest comets of the past century is the well-known comet Hale-Bopp. This gigantic comet, possibly the biggest known, decorated the northern sky for many months! Many of today’s amateur astronomers came into astronomy specifically because of this heavenly guest.

Comet C/1995 O1 (Hale-Bopp) passed perihelion April 1, 1997, but observations still continue! Of course, it is no longer within reach of amateur telescopes, but it remains an attainable goal for the large observatories of the world. The latest observation of the comet was Deceber 4, 2010 with the 2.2 meter telescope of the Southern European Observatory (ESO, LaSilla, Chile). Notable is the fact that for the most “distant” observations of the comet, at the moment of imaging of C/1995 O1 it lay 30.7 a.u. from the Sun. That is, farther than the orbit of Neptune! Of course, we should take into account the practically perpendicular inclination of the comet’s orbit to the plane of the ecliptic.

In the images the comet was found not far from the calculated position, and appeared starlike with a brightness of mag. 23.3. In comparison with images from three years ago, the external appearance of the comet has greatly changed. The reflective surface area has decreased by a factor of nine, to 485 km?. From these and earlier estimates, the diameter of the comet’s nucleus is 60-70 km. One can conclude that the comet nucleus is surrounded by a very diffuse small coma, i.e. Comet Hale-Bopp remains active even at a distance of more than 30 a.u. (4.488 billion km) from the Sun!

Astronomers have also estimated the temperature of its surface – 53.1K. In their opinion, the comet’s activity may stop at a temperature of 50-53K, but that means it is possible that we are seeing signs of “life” in the comet for the last time. Very soon the nucleus of the comet will completely freeze for thousands of years. The Sun will once again melt the comet’s ice in another 2500 years.

From material in arXiv:1104.4351v1 [astro-ph.EP]

May 2011
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