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Астронет: Астрономическая картинка дня Натриевый след Меркурия http://variable-stars.ru/db/msg/1675516/eng |
Credit & Copyright: Andrea Alessandrini
Explanation:
What is that fuzzy streak extending from Mercury?
Long exposures of our
Solar System's innermost planet may reveal something unexpected: a tail.
Mercury's thin
atmosphere
contains small amounts of
sodium
that glow when excited by light from the Sun.
Sunlight also liberates these molecules from
Mercury's surface and pushes them away.
The yellow glow from sodium, in particular, is relatively bright.
Pictured, Mercury and its
sodium tail
are visible in a deep image taken in late May from
Italy
through a filter that primarily transmits
yellow light emitted by
sodium.
First
predicted
in the 1980s, Mercury's tail was first
discovered
in 2001.
Many tail details were revealed in
multiple observations
by
NASA's robotic
MESSENGER
spacecraft
that orbited Mercury between 2011 and 2015.
Tails are usually associated with
comets.
The tails of
Comet NEOWISE are currently
visible with the unaided eye in the
morning sky.
Comet NEOWISE from Around the Globe:
Notable Images Submitted to APOD
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.