Washington, Feb 29 : Astronomers have discovered that Mercury has a 1.6-million-mile long glowing tail of sodium atoms, which is more than 100 times the radius of the planet itself.
"Mercury's tail had been spotted before, but its great length was missed because previous attempts were looking at too small a piece of the sky," researcher Jeffrey Baumgardner of Boston University told Discovery News.
Using an eight degree-wide image created by a telescope at McDonald Observatory in Texas, researchers discovered that Mercury's tail is 1.6-million-miles-long, which is more than seven times longer than ever suspected. he neutral sodium atoms that make up the long streamer are thought to be blasted off the surface by the sun and micro-meteor impacts. These impart enough energy to launch the atoms into space.
Other elements are also in the tail, but it's the sodium which lights up and can be detected.
To better understand how Mercury's tail is created, Baumgardner's team also made close-up sodium-glow images of Mercury. This revealed that the planet has two sodium hot spots, both at high latitudes.
These could be the product of the planet's mineralogy, topography or have something to do with how the planet's magnetic field channels in particles from the sun - similar to how Earth does the same thing and creates aurora light shows near the poles.
"The secrets of these hotspots are likely to be revealed by the Messenger spacecraft," said Mercury researcher Ann Sprague of the Lunar and Planetary Laboratory at the University of Arizona in Tucson.
It was also observed that Mercury's tail scatters photons, making it a great clue to various processes at work on and around the planet.
"Because of its association with rocky bodies in our solar system, it's conceivable that someday such tails could help planet hunters identify rocky worlds orbiting other stars," said Sprague.
"It's a stepping stone to understanding other planets," he added.