THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
<http://www.google.com/url?q=http%3A%2F%2Fwww.usm.maine.edu%2Fplanet&sa=D&sntz=1&usg=AFQjCNHulkHuLP13bOG2PkNrPazsGWFs2A>
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 2458794.16
2019-2020:  XLVII
              ""I'm sure the universe is full of intelligent life. It's
just been too intelligent to come here."   -Arthur C. Clarke


THE DAILY ASTRONOMER
Wednesday, November 6, 2019
Valentine Sun


[image: sun-spin-e1420472903945.jpg]
Valentine's Day

                                          [image:
sun-spin-e1420472903945.jpg]
                                Today

The Universe will never fail to astonish us.   Not only with its copious
starbirth rate (20,000 per second),  unfathomable extent and immense time
spans.   It also offers smaller surprises that still baffle and astound.
For instance, did you know that the Sun's altitude now is lower than the
Sun's altitude on Valentine's Day?     Do you find that statement a bit
difficult to believe?    After all, the weather we experience in early
November is, despite the deepening chill, milder than what we have to
endure in February.     One would think that the Valentine Sun would far
lower than the one in early November.

We'll work through the details:

The sun's altitude in your sky depends on your location and the Sun's
declination: its angular distance north or south of the celestial equator,
the projection of Earth's equator onto the sky.     The declination changes
continually throughout the year as our tilted planet revolves around the
Sun.    When the north pole is aligned as closely to the Sun as possible on
the summer solstice, the Sun attains its maximum altitude of 23.5 degrees
north of the celestial equator.    When the north pole is aligned away from
the Sun to its maximum extent, the Sun's altitude reaches a minimum 23.5
degrees south of the celestial equator.

If we could chart the Sun's position relative to the celestial equator
throughout the year, we would produce an undulating curve that is
alternately "above" and "below" the celestial equator.  The graphic below
shows this path against the starfield.  We refer to this curve as the
"ecliptic," the Sun's annual path through the sky.

[image: zodiac_and_ecliptic1338120626742-thumb400.png]
We can see that except for the two solstice points, the Sun will be at the
same declination twice a year.    For instance, the Sun's declination is
precisely 0 on both the vernal and autumnal equinoxes, the first days of
spring and fall, respectively.     On Valentine's Day, the Sun's
declination is just about -13 degrees, meaning that it will be 13 degrees
south of the celestial equator.     The Sun is also just about 13 degrees
below the celestial equator on October 28th.
The Sun's daily path through the sky in late October is the same as that in
mid February.  Now that we're toward the end of November's first week, the
Sun is even lower in the sky.
The Sun's declination today is -16 degrees!

Why is the average temperature now higher than that of early to mid
February?   Simply because November follows a protracted warm period (in
theory).  February follows  protracted cold period.      Meteorologists
refer to "thermal inertia" to explain the difference between mid winter
cold and mid autumn chill

So, February is colder than November even if the Sun is actually higher in
the sky in early February than it is currently.  Another astronomical
surprise.

To subscribe or unsubscribe from the "Daily Astronomer"
http://lists.maine.edu/cgi/wa?A0=DAILY-ASTRONOMER