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Астронет: Астрономическая картинка дня На краю космоса http://variable-stars.ru/db/msg/1750043/eng |
Credit & Copyright: Ralf Rohner
Explanation:
Where
does space begin?
For purposes of spaceflight some would say at the
Karman line,
currently defined as an altitude of 100 kilometers (60 miles).
Others might place a line 80 kilometers (50 miles) above Earth's mean sea level.
But there is no sharp physical
boundary
that marks the end of
atmosphere and the beginning of space.
In fact, the Karman line itself is near the transition between the
upper mesophere and lower thermosphere.
Night shining or noctilucent clouds
are high-latitude summer apparitions
formed at altitudes near the top of the mesophere,
up to 80 kilometers or so, also known as polar mesopheric clouds.
Auroral bands
of the northern (and southern) lights caused by
energetic particles exciting atoms in the thermosphere can
extend above 80 kilometers to over 600 kilometers altitude.
Taken from a cockpit while flying at an altitude of 10 kilometers
(33,000 feet) in the realm of
stratospheric
aeronautics,
this snapshot captures both
noctilucent clouds and aurora borealis under a starry sky,
looking toward planet Earth's
horizon
and the edge of space.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.