Researchers have made an incredible
discovery. The Earth’s outer atmosphere extends much further than expected,
stretching to 630,000 kilometers (391 000 miles), which is roughly 50 times the
diameter of our planet. Obviously, you cannot breath there as the
atmosphere becomes more tenuous the further from Earth's surface you are, but
this finding has important implications for space travel and space observatories.
The findings, reported in the Journal of Geophysical Research: Space Physics, were possible thanks to decades of observation from the
ESA/NASA Solar and Heliospheric Observatory (SOHO). The observations were
actually made decades ago, and can only be done at certain times of the year.
"The Moon flies through Earth's
atmosphere," lead author Igor Baliukin, from Russia's Space Research
Institute, said in a statement.
"We were not aware of it until we dusted off observations made over two
decades ago by the SOHO spacecraft."
The data showed that the Earth’s
exosphere is slightly denser than interplanetary space for a significant
distance. At the Moon distance, on average 384,000 kilometers (239,000 miles)
away, there are only 0.2 atoms per cubic centimeter. At 60,000 kilometers
(37,000 miles) from Earth, there are still 70 hydrogen atoms per cubic centimeter
and the density only drops down to less than 1 atom per cubic centimeters at
over four times that distance. Despite the low density, the hydrogen interacts
with sunlight, ultraviolet rays in particular. This emission is what allowed
researchers to study the so-called geocorona.
Learn more here.