Washington, February 29 : Mercury has a glowing dragon tail of sodium atoms, which is more than seven times longer than earlier thought, say researchers.
Ann Sprague, a Mercury researcher at the University of Arizona's Lunar and Planetary Laboratory in Tucson, says that new measurements of the planets' yellow-orange tail-which streams in the solar wind like the long tail of a kite-put it at more than 100 times the radius of the planet itself.
The researcher says that the tail also comprises other elements, but it is the sodium which lights up and cane be detected. It scatters photons like crazy, making it a great clue to various processes at work on and around the planet, he adds.
Jeffrey Baumgardner, a researcher at Boston University, says that 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.
"Our forte was wide-angle imaging," Discovery News quoted Baumgardner, the lead author of a report on Mercury's sodium tail in the current issue of Geophysical Research Letters, as saying.
The researcher also revealed that the eight degree-wide image his team had created, with the help of a telescope at McDonald Observatory in Texas, was about 16 full-moons wide. According to him, the actual two degree sodium tail is as long as four full moons.
Baumgardner said that Mercury was blocked out in the image as its brightness outshines the sodium tail. If Mercury were shown to scale in the image, it would be less than a pixel in diameter, he added.
"But even so, you are limited by the sodium in Earth's atmosphere," he said.
The researcher revealed that Earth's own sodium glow is itself created by the steady supply of meteors that burn up in the atmosphere.
With a view to gaining deep knowledge as to how Mercury's tail is created, Baumgardner's team also made close-up sodium-glow images of Mercury, which revealed that the planet has two sodium hot spots, both at high latitudes.
He said that the sodium hot spots 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.
Sprague said that the Messenger spacecraft could reveal that secrets of those hotspots.
Baumgardner said that besides Mercury, neutral sodium is also seen streaming from the moon, and forming a haze around Jupiter from the sodium blasted off of its tiny and hyper-volcanic moon, Io. It's also seen blowing from comets, he added.
Sprague said that because of its association with rocky bodies in the solar system, it seemed that someday such tails could help planet hunters identify rocky worlds orbiting other stars.
"It's a stepping stone to understanding other planets," Sprague said.