Saturday: If the Sun looks big today, your eyes are not playing tricks on you. The Earth is at perihelion at 9:00 this morning. If you dig out your Greek language textbook, you’ll see that peri- means “in close proximity” and helios means “Sun.” So, perihelion is when an object is closest to the Sun in its orbit, about 1.5 million miles closer than its average distance of 93 million miles. Since it is winter in the Northern Hemisphere now, the seasonal temperature changes must not be caused by the Earth getting farther from and closer to the Sun. Otherwise, we’d have summer when the Earth is closest to the Sun. The seasons are caused by the angle of the sunlight hitting the Earth. In the winter, sunlight hits the Earth at a very low angle, an angle far from perpendicular or straight up and down. This means that a given “bundle” of sunlight is spread out over a large area and does not warm the surface as much as the same bundle in the summer. For the Northern Hemisphere, that very low angle occurs in December, January, and February.
This evening and tomorrow morning’s weather forecast:
showers. Meteor showers, that is. The Quadrantid meteor shower peaks this
evening. Meteor showers are named after the constellation from which the
meteors appear to originate. That makes this shower mysterious because there
isn’t any constellation with this name now. The shower was named after Quadrans
Muralis, an obsolete constellation found in some early 19th century
star atlases. These meteors appear to come from a point in the modern
constellation Draco the dragon. This point is about three fists above the
northeastern horizon at 1:00 a.m. This year, the brightness of the Full Moon
obscures the dimmer meteors.
Meteors are tiny rocks that hit the Earth and burn up in the
atmosphere. Most meteors are associated with the path of a comet. This shower
consists of debris from an asteroid discovered in 2003. Keeping with the
comet-origin paradigm, astronomers think the asteroid is actually an “extinct”
comet, a comet that lost all its ice as it passed by the Sun during its many
orbits. For more information about the Quadrantid meteor shower, go to http://earthsky.org/?p=155137.
Sunday: Has it been tough to wake up this past week? It
should have been because the sunrise has been getting a little later since
summer started. I know. I know. December 21 was the shortest day of the year.
But, because the Earth’s orbit around the Sun is elliptical and not circular,
the Earth does not travel at a constant speed. It moves faster when it is
closer to the Sun and slower when it is farther away. This leads to the latest
sunrise occurring in late December/early January and the earliest sunset
occurring in early December. Neither of these happen on the first day of
winter. On the first day of winter, however, the interval between sunrise and
sunset is the shortest, making it the shortest day of the year. For more
information, go to http://goo.gl/SJC5r.
Monday: At 7:30 p.m., Saturn is three fists above due
southwest and Jupiter is two and a half fists above the eastern horizon.
Tuesday: Let’s review three important sets of three cats.
There’s Josie, Valerie, and Melody of Josie and the Pussycats. Felix, Tom, and
Sylvester from old time cartoons. And, if you want to get away from the
mind-numbing effects of television, there’s Leo the lion, Leo Minor, and Lynx
in the night sky. Leo is by far the most prominent of these three
constellations. Its brightest star called Regulus is two fists above the
eastern horizon at 10:00 p.m. The backwards question mark-shaped head of Leo is
above Regulus and the trapezoid-shaped body is to the left of it. Leo Minor
consists of a few dim stars right above Leo. Pretty wimpy. The long dim
constellation called Lynx spans from just above Leo Minor to close to straight
overhead. You and fellow stargazers won’t need to wear a long tail or ears to
enjoy these stellar cats.
Wednesday: In 1984, American singer Rockwell released the
song “Somebody’s Watching Me”, backed up by Michael Jackson. In 2020, NASA’s
Spitzer Space Telescope released a picture of two bubbles of gas and dust that
look like eyes watching you. Stare back at them by going to https://www.spitzer.caltech.edu/image/ssc2020-17a-something-out-there-is-watching-you.
Thursday: Now that you know meteors are rocks that burn up
in the atmosphere, you will soon start to wonder what would happen if those
rocks hit the surface of the Earth. Well, wonder no more. The browser-based app
called Asteroid Launcher will simulate the collisions. You select the asteroid
type, size, speed, and angle of impact. The most common impactor material is
stone and the typical speed is 40,000 miles per hour, in case you want to
introduce some realism into your simulation. Go to https://neal.fun/asteroid-launcher/,
click on the map where you want the asteroid to land and then launch your
virtual asteroid.
Friday: Draco Malfoy makes an appearance in all seven books
of the Harry Potter series. Perhaps you’ve heard of these. But the
constellation Draco the dragon makes an appearance in the sky every night. It
is a circumpolar constellation as viewed from Ellensburg meaning it never goes
below the horizon. The head of the dragon is one fist above due north at 10:30
p.m. Eltanin, the brightest star in the constellation, is at the lower
left-hand corner of the trapezoid-shaped head of Draco.
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.
All times are Pacific Time unless noted.
