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Астронет: Астрономическая картинка дня Перигелий и афелий http://variable-stars.ru/db/msg/1235387/eng |
Credit & Copyright: Enrique Luque Cervigón
Explanation:
This year Aphelion, the point in Earth's
elliptical orbit
when it is farthest from the Sun, occurs tomorrow, July 4th.
Of course, that doesn't
affect the seasons on
our fair planet.
Those are determined by the tilt of Earth's axis of rotation and not
Earth's distance from the Sun, so July is still winter in the south
and summer in northern hemisphere.
But it does mean that on July 4th the Sun will be at its smallest
apparent size.
This composite neatly compares two pictures of the Sun taken with the
same telescope and camera
on the
dates of Perihelion (closest approach) and Aphelion in 2008.
The image labels include Earth's distance in kilometers
from the Sun on the two dates.
Otherwise difficult
to notice, the change in the Sun's
apparent diameter between
Perihelion
and Aphelion is clear.
The difference amounts to a little over 3 percent.
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.