Saturday: Red is a popular Christmas color. It is also a popular star color. And R Leporis, also known as Hind’s Crimson Star, is one of the reddest stars in the sky. It is a star near the end of its life that has burned its helium nuclei into carbon. Convective currents, like those in a pot of boiling water, bring this carbon to the surface. There it forms a layer of soot that scatters away the light from the blue end of the visible spectrum leaving the light from the red end of the spectrum to reach our eyes. For more information about Hind’s Crimson Star and a list of other deep red stars, go to http://goo.gl/EnhRe4. Hind’s Crimson star is one fist to the lower right of Rigel, the brightest star in Orion. You’ll need binoculars or a small telescope to see Hind's Crimson star. But you can easily spot Rigel two and a half fists held upright and at arm’s length above the south-southeastern horizon at 10:00 p.m.
Sunday: At 5:00 p.m., three bright planets and one dim one
line up in the southwestern sky. Very bright Venus is one fist above the
southwestern horizon. Saturn is one and a half fists to the upper left of
Venus. Bright Jupiter is two fists to the upper left of Saturn. Now it gets
more difficult. Neptune is about two and a half fists to the upper left of
Jupiter. But you’ll need binoculars and a darker sky to see it. At 7:00 p.m.,
find the bright star Fomalhaut one fist above the south-southwestern horizon.
Move your binoculars up until you see a bent vertical line of three medium
bright stars, looking like a skinny arrow pointing to the right. Then move your
binoculars up about twice as much until you see a smaller upward-pointing arrow
of three stars of similar brightness. With that arrow at the bottom of your
field of view, Neptune will be near the top of your field of view. Overall,
Neptune is three and a half fists above the south-southwestern horizon.
Monday: With the Sun as low as it gets in the Northern
Hemisphere winter sky, you may wish it was a little more prominent. This past
April, NASA’s Parker Solar Probe got that wish. It passed through the boundary
between outer space and the region where the Sun’s magnetic field has a tight
hold on the plasma that makes up the outer layer of the Sun. Since the Sun does
not have a solid surface, this is as close to touching the Sun as an object can
get. It is analogous to “touching” a cloud. The cloud does not have a defined
surface but there is a definite boundary between “cloud” and “not cloud”. The
Parker Solar Probe pierced the boundary between “Sun” and “not Sun”. For more
about the mission plus short videos, go to https://skyandtelescope.org/astronomy-news/humanity-has-touched-the-sun/.
Tuesday: At 7:57 a.m., Pacific Standard Time, this morning, the Sun reaches its lowest point in the sky with respect
to the background stars. This point is called the Winter Solstice. During the
day that the Sun reaches this point, your noontime shadow is longer than any
other day of the year. Also, the Sun spends less time in the sky on the day of
the Winter Solstice than any other making this the shortest day of the year.
Even though it is the shortest day of the year, it is not the day with the
latest sunrise or the earliest sunset. The latest sunrise is during the first
week in January and the earliest sunset is during the second week in December.
The Sun is at its southernmost point with respect to the background stars on
the day of the winter solstice. This means the Sun spends the least amount of
time above the horizon on that day. But, the Sun rise and set times depend on
more than its apparent vertical motion. It also depends on where the Sun is on
the analemma, that skinny figure-8 you see on globes and world maps. During the
second week in December, the Sun is not quite to the bottom of the
analemma. But, it is on the first part of the analemma to go below the
horizon. During the first week in January, it is on the last part of the
analemma to rise above the horizon.
Wednesday: Are you disappointed because you are not going anywhere
for Christmas? Why not take a (virtual) trip to outer space using Google’s new
visualization tool called 100,000 Stars. It shows the stars in our neighborhood
in a very good 3-D simulation. The Sun is initially at the center. If you zoom
in, you can click on neighboring stars and learn more about them. Go to http://stars.chromeexperiments.com/
for the simulation. It works best on a Chrome browser.
Thursday: Mars is nearly one fist above due southeast at
7:00 a.m. Its “rival”, the bright reddish star Antares, is midway between Mars
and the horizon.
Friday: Just before Christmas, you look for junk to clean
out of your closets so you can re-gift it. I mean, so you can throw it out or
recycle it. NASA’s Meter Class Autonomous Telescope on Ascension Island is a
key tool in a program tracking about 22,000 pieces of space junk. Some of this
junk is dangerous. The International Space Station occasionally performs debris
avoidance maneuvers to keep its panels and sensitive instruments safe. For more
information about the project, go to http://goo.gl/Kxgihd.
The positional information in this column about stars and
planets is typically accurate for the entire week. For up to date information
about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.
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