MERCURY AND MAYBE PLUTO ALSO HAVE COMET-LIKE TAILS
Mercury's Tail Makes it a 'Comet-Planet'
Analysis by Ray Villard
As if the debate over what is and what is not a planet hasn't gotten confusing enough, we are beginning to see a class of object that could be called “Comet-Planets.”
The innermost planet Mercury has been photographed spouting a faint comet-like tail. Unlike a comet, which is a sublimating ball of dusty ices, Mercury is bone dry. This tail is created by a gusher of solar radiation accelerating sodium atoms off Mercury's surface. They absorb enough energy to escape the planet's gravitational pull and zoom off into space. The pressure of the solar wind sweeps back the expanding cloud into a windsock-like tail.
BIG PIC: MESSENGER Approaches Mercury
Pluto May Have Comet-Like Tail
The latest measurements of Pluto's tenuous atmosphere indicate that it may be shaped into a comet-like tail, say astronomers
Pluto's has a highly elliptical orbit that takes it inside the orbit of Neptune and then out into the distant icy reaches of the Solar System.
Astronomers have long believed that this would have important effects on the dwarf planet's atmosphere. Their models indicate that Pluto's atmosphere is likely to swell as it moves closer to the Sun and the poles sublimate. Later, the atmosphere should condense as it cools down.
Today, Jan Greaves at the University of St Andrews in Scotland and a couple of buddies reveal the details of their own study of Pluto's atmosphere using the 15 meter James Clerk Maxwell Telescope in Hawaii.
These guys find clear evidence of gaseous carbon dioxide at altitudes of up to four times Pluto's radius. And they say there is significantly more of the stuff than the last time CO was detected in 2000.
Their tentative explanation is exciting: "The marginal CO line red-shift, if real, could indicate a ﬂow forming into a comet-like tail directed away from the Sun," they say.
The thinking is that the expanding atmosphere is interacting with the solar wind and being shaped into a tail.
That could throw the cat among the pigeons next time Pluto's status as a planet comes up for discussion. It gives ammunition to the naysayers who can now claim that far from being a planet or even a dwarf planet, Pluto is merely a giant comet.
There is a river moving very fast now... This could be a good time.
- Hopi prophecy
- NEWFOUND EXOPLANET MAY TURN TO DUST PLANET - Theresa, 2012-05-19, 03:56
- MERCURY AND MAYBE PLUTO ALSO HAVE COMET-LIKE TAILS - Mourann, 2012-05-19, 18:44