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Aphelion
Day
Aphelion
Day is
the day that the Earth and Sun are at their furthest distance from
each other. Every July the Earth is at aphelion, the furthest
from the Sun for the year and in January it is at perihelion, the closest
to
the Sun for the year.
Earth
in Orbit
*
Printable Image *
Earth's
orbit shown from above the Sun's North Pole; seasonal references
are for Earth's Northern Hemisphere, and would be opposite for
the Southern Hemisphere. Each year during the first
week of July the
Earth is at the point in its orbit called aphelion, which
is its farthest distance from the Sun, 94.5 million miles / 152
million kilometers.
In
2019 the exact time of aphelion is July
4 at 3:11am
PDT (22:11 UT). On July
4 we
are 94.5 million miles away from the Sun, which is 3 million miles
further
away than when our Earth was at perihelion on January
2, 2019 at
9:20pm
PST (05:20 UT Jan.
3).
We are so far away from the Sun in July that its light is 7% less intense
than it was in January!
BTW: If
you have trouble remembering the difference between perihelion and
aphelion, an old astronomer's trick is to recall that the words "away" and "aphelion" both
begin with the letter "A".
Sun
~ Perihelion and Aphelion
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Printable Image *
The above image is a composite of two pictures that Luis
Carreira * took
from opposite
ends of Earth's orbit: perihelion and aphelion.
When the Earth is at aphelion, the Sun looks a little smaller than
usual.
Sun's
Size in January and July
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Printable Image *
Hmmm
... Why
is it colder in January for the Northern Hemisphere when the Sun
is closer? Why is it hotter in July for the Northern Hemisphere when
the Sun is farther away? What's the weather like in the southern
hemisphere for July? The tilt of the Earth plays a big role in answering
these questions.
Here's a fun
and simple explanation about the winter and summer Sun ... with
the following disclaimer!
Does
one hemisphere have a hotter summer
and colder winter than the other?
You might
expect northern summer to be cooler because it occurs when Earth
is farther from the Sun. Not so, explains Roy Spencer of the Global
Hydrology and Climate Center [Now
known as the Earth
Science Office]. "The
oceans and land on Earth are not evenly distributed around the globe.
The northern hemisphere
has more land; the southern hemisphere has more water. This tends
to moderate the impact of differences in sunlight between perihelion
and aphelion."
At aphelion
the land-crowded northern half of our planet is tilted toward the
Sun. For a given amount of sunlight, land warms up more than water
(in other words, land has a lower heat capacity). Sunlight is therefore
more effective at raising the temperature
of the northern hemisphere. This results in the surprising fact
that northern summer is a little warmer than southern summer even
though Earth is farther from the Sun in July. From: NASA's
Aphelion Day 2000
Earth
at Aphelion ~ A Global View
Here
are a few more Earth/Sun
facts as well as a review of perihelion and aphelion. View
the following links to see a
2001-2100 year chart for Solstices
and Equinoxes and Earth
at Perihelion and Aphelion. Enjoy!
Fourth
of July
Holiday and Holy Day
Our physical Sun conjuncts our spiritual Sun,
and we are free to travel the Milky Way!
I'd like to know your thoughts about The Night Sky ...
send me an email.
May your Night Sky traveling always be filled
with Celestial Delights and Treats!
Susan Sun
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