Saturday: Today: “Excuse me, do you have the time?”
“No, but the
Big Dipper does.”
You can use
the orientation of the Big Dipper to tell time with a precision of about 15-30
minutes. First, find the two stars at the far end of the Big Dipper cup, the
stars that do not touch the handle. Draw an imaginary line segment starting at
the North Star and passing through the two Big Dipper cup stars. Now, draw a
big circle around the North Star. Your circle is a 24-hour clock. Number the
circle from 0 hours at the top, counterclockwise to 12 hours at the bottom of
the circle, and back up to 24 hours at the top. (O hours and 24 hours are the
same on this clock because the day is 24 hours long.) The hour number on the
big circle closest to where your imaginary line intersects this circle is
called your raw time. Due to the location of the Big Dipper compared to the
rest of the stars, the time nearest the intersection (the raw time) is correct
for March 6. For any other night, subtract two times the number of months the
current date is after March 6 from the raw time. For example, let’s say the
imaginary line between the North Star and the Dipper stars is pointed to the
right. That means the raw time is 18 hours or 6 p.m. If you made this
observation on October 6, which is seven months after March 6, you would
subtract two times seven or 14 hours from the raw time. Thus, the time for November 6 is 18
hours minus 14 hours or 4 hours. In other words, 4 a.m. Don’t forget to convert
for daylight savings time if needed. For a more complete explanation on how to
do the Big Dipper clock math, go to http://goo.gl/02HmA. If you prefer a more
visual tool, and a fun project to do with your kids, there is a simple “star
clock” template and instructions at http://goo.gl/SFKrE. Use this paper star
clock whenever you watch is broken.
Sunday: The
calendar says summer is nearing an end. School starting says summer is nearing
an end. The summer triangle in the sky begs to differ, as it is still high in
the sky. Vega, the brightest star in the triangle, is a little bit west of
straight overhead at sunset. Deneb is a little bit east of straight overhead
and Altair is five fists above the south horizon.
Monday: Venus
is about five degrees above the west horizon at 7:45 p.m.
Tuesday: Fomalhaut,
the southernmost bright star visible from the northern USA, is one fist above
the south-southeast horizon at 11 p.m.
Wednesday: In most parts of the country, a mixture of tasty carbon-based
material and healthy minerals is called a casserole. In Minnesota, it is called
a hot dish. (Uffdah, you betcha!) In space, it is called a supergiant. Antares,
a supergiant in the constellation Scorpius, is forging lighter elements into
carbon, oxygen, silicon, and iron in its core. This stellar casserole is about
one fist above the south-southwest horizon at 9 p.m. Mars, the brighter and
tastier side dish, is about a fist to the upper left of Antares. Saturn, the
ringed dessert, is less than a fist above Antares.
Thursday: Stuart Sutcliffe was the fifth Beatle. d’Artagnan was the fourth
Musketeer. Ophiuchus is the thirteenth constellation in the Zodiac. The Zodiac
consists of all the constellations that the Sun appears to line up with as the
Earth’s celestial perspective changes throughout its annual orbit. You know
twelve constellations in the Zodiac because they are the 12 horoscope signs.
But the Sun also lines up with Ophiuchus for about two weeks every year. You
can spend some time with Ophiuchus tonight. The center of the coffin shaped
group of stars is three fists above due southwest at 9 p.m., right above the
Mars-Saturn-Antares triangle.
Friday: Shine
on, shine on harvest moon, up in the sky. It’s just like a full moon in
January, February, June and July. The only difference is that near the Autumnal
Equinox (also known as the first day of fall), the full moon rises close to
sunset resulting in a full night of light for the harvest. The harvest moon
looks more orange than usual when it is near the horizon because of the dust
kicked up from the harvest. The dust scatters the white light reflecting off of
the Moon resulting in slightly more of the red and orange components of the
white light reaching your eyes. Although the Moon has a dull yellow color
whenever it is near the horizon owing to light scattering off of dust and
atmospheric particles, the effect is more noticeable for the harvest Moon.
Tonight’s full moon is also nearly a Super Moon, meaning it is near its closest
point to Earth for the month. For more information about the harvest moon, go
to http://earthsky.org/?p=4162.
Tonight the Moon passes through the partial shadow of the Earth, leading to a
barely noticeable penumbral lunar eclipse.
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 http://nightsky.jpl.nasa.gov/planner.cfm.
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