[ad_1]
The outermost part of our planet's atmosphere extends well beyond the lunar orbit, almost twice the distance of the moon.
A recent discovery based on observations from the ESA / NASA solar and heliospheric observatory, SOHO, shows that the gaseous layer that envelops the Earth extends up to 630 000 km, or 50 times the diameter of our planet.
"The Moon is flying in the atmosphere of the Earth," said Igor Baliukin of the Russian Space Research Institute, lead author of the paper presenting the results.
"We did not know it before dusting off observations made by the SOHO satellite more than two decades ago."
Where our atmosphere merges with space, there is a cloud of hydrogen atoms called geocorona. SWAN, one of the spacecraft's instruments, has used its sensitive sensors to trace the signature of hydrogen and accurately detect the distance that separates the very periphery of the geocorone.
These observations could only be made at certain times of the year, when the Earth and its geocorone would be visible for SWAN.
For planets containing hydrogen in their exospheres, the water vapor often appears closer to their surface. This is the case for the Earth, Mars and Venus.
"This is particularly interesting when we are looking for planets with potential water reservoirs beyond our solar system," says Jean-Loup Bertaux, co-author and former senior scientist at SWAN.
The first telescope on the Moon, placed by the Apollo 16 astronauts in 1972, captured an evocative image of the geocorone surrounding the Earth and shone with ultraviolet light.
"At that time, astronauts on the lunar surface did not know that they were actually embedded in the suburbs of the geocorone," says Jean-Loup.
Hydrogen cloud
The Sun interacts with hydrogen atoms through a particular wavelength of ultraviolet light called Lyman-alpha, which atoms can both absorb and emit. As this type of light is absorbed by the Earth's atmosphere, it can only be observed from space.
Thanks to its hydrogen absorption cell, the SWAN instrument could selectively measure the Lyman-alpha light of the geocorone and reject the hydrogen atoms further into the interplanetary space.
The new study found that sunlight squeezes hydrogen atoms into the geocorn on the land side, and also produces a region of increased density on the night side. The densest region of hydrogen at the level of the day is still rather rare, with only 70 atoms per cubic centimeter at 60,000 kilometers from the surface of the Earth and about 0.2 atoms at the distance from the Moon.
"On Earth, we call it empty, so this extra source of hydrogen is not important enough to facilitate space exploration," said Igor.
The good news is that these particles pose no threat to space travelers during future crew missions orbiting the moon.
"There is also ultraviolet radiation associated with geocorone, since hydrogen atoms scatter sunlight in all directions, but the impact on astronauts in lunar orbit would be negligible compared to the main source of radiation – the Sun, "said Jean-Loup Bertaux.
On the other hand, the terrestrial geocorone could hinder future astronomical observations made near the Moon.
"Spatial telescopes observing the sky in ultraviolet wavelengths to study the chemical composition of stars and galaxies should take this into account," adds Jean-Loup.
The power of archives
Launched in December 1995, the SOHO space observatory has been studying the Sun for more than two decades, from its deep core to the outer ring, to the solar wind. The satellite is in orbit around the first point of Lagrange (L1), about 1.5 million kilometers from the Earth towards the Sun.
This location is a good point of view to observe the geocorone from the outside. The SOHO SWAN instrument imaged the Earth and its atmosphere extended three times between 1996 and 1998.
The research team of Jean-Loup and Igor in Russia decided to extract this dataset from the archives for further analysis. These unique geocorone views from SOHO bring a new light to the Earth's atmosphere.
"Data archived many years ago can often be used for new science," says Bernhard Fleck, scientist for ESA's SOHO project. "This discovery highlights the value of the data collected over 20 years ago and the outstanding performance of SOHO."
"SWAN mapping / SOHO Lyman-alpha: Hydrogen Geocorona extends well beyond the Moon" by I. Baliukin et al is accepted in Journal of Research Report: Geophysical Research: Space Physics.
Related Links
Solar and heliospheric observatory
Earth Observation News – Suppiliers, Technology and Applications
|
We need your help. The SpaceDaily information network continues to grow, but revenues have never been more difficult to maintain. With the rise of ad blockers and Facebook, our traditional revenue streams via quality advertising on the network continue to decline. And unlike many other news sites, we do not have a paywall – with these usernames and boring passwords. Our press coverage takes time and effort to publish 365 days a year. If you feel that our news sites are useful and useful, then consider becoming a regular supporter or, for the moment, make a one-time contribution. |
||
|
SpaceDaily Contributor $ 5 billed once credit card or paypal |
 |
SpaceDaily Monthly Supporter $ 5 billed per month paypal only |
Russian satellite records unknown physical phenomena in the Earth's atmosphere
Moscow (Sputnik) February 12, 2019
An ultraviolet telescope installed on the Russian Lomonosov satellite has recorded slight "explosions" in the atmosphere of the planet, whose physical nature has not yet been explained, said the director of the Research Institute in Nuclear Physics of the State University of Russia in an interview with Sputnik.
"With the help of the telescope, we have achieved even greater results than expected.It seems that we have encountered new physical phenomena … We do not yet know their n … read more
[ad_2]
Source link