By Andy Veh, for the Redoubt Reporter
The starry sky is at its best with the most prominent stars being well placed high in the south — blue Rigel and red Betelgeuse in Orion, Sirius beneath it, Procyon to its left, Pollux and Castor higher up, Capella almost in the zenith and Aldebaran and the Pleiades completing the splendor.
The Big Dipper starts out close on the northern horizon, but Cassiopeia, Perseus and Andromeda are close to the zenith. In the west Cygnus and Pegasus are about to set while bright Vega, being circumpolar in Alaska, stays close to the horizon.
Leo’s Regulus rises in the evening, trailing Gemini and Cancer low in the east.
Planet in the evening and all night:
- You can’t miss bright Jupiter as it rises in the northeast in the early evening, moving through the south and setting in the northwest when school starts in the morning. This winter it appears in between the constellations of Cancer and Leo, connecting Gemini’s Pollux and Castor with Leo’s Regulus, all of them bright stars but appearing dim when compared with the giant planet reflecting our sun’s light. Jupiter is in retrograde motion (an optical illusion caused by Earth’s orbit) this month, seemingly moving away from Regulus back into Cancer. That motion continues through January and February. In March and April we will have passed Jupiter enough that we can see its regular motion, back toward Regulus. Look for the almost-full moon beneath the giant planet on Jan. 8.
Planets in the evening:
- Venus should be visible in the southwest shortly after sunset, somewhat below Mars.
- Between Jan. 8 and 20 look for a much fainter light next to Venus — that’s Mercury. Due to its tight orbit around the sun, it is rarely visible, so give it a try. The crescent moon appears above Venus on Jan. 20.
- Mars is low in the southwest during the early evening, moving through Aquarius. It passes bluish Neptune around Jan. 19. Binoculars are advised for viewing. The crescent moon appears above Mars on Jan. 22.
- Uranus and Neptune can still be seen in the evening but they require finder charts (I recommend Googling them).
Possible planet in the morning:
- Saturn rises around 5 a.m. in the southeast. It is to the left of Virgo’s Spica and close to Scorpius’ Antares. But it might be too close to the southern horizon for it to be seen in Alaska. The waning crescent moon joins Saturn on Jan. 16.
Earth is at perihelion, on its closest approach to the sun on Jan. 4 (91.4 million miles), but only by 3 percent closer compared to its aphelion — its farthest distance from the sun on July 5 (94.5 million miles), which means that about 6 percent more of the sun’s energy reaches Earth.
That in itself is not the reason for the seasons. After all, perihelion and aphelion occur during the wrong seasons on the northern hemisphere, the maximum difference of 6 percent in solar radiation is way too small to account for the large temperature fluctuations between the seasons, and the varying distance doesn’t explain why and is not connected to how the lengths of the days and the altitudes of the sun above the horizon vary.
Due to the 23-degree tilt of the Earth’s axis to its orbital plane, the length of day (which at its extreme is 70 percent shorter in winter than in summer — 5.7 hours compared to 19 hours) as well as the angle of the sun above the horizon are much more important.
On the Kenai Peninsula, the noon sun is only at 7 degrees above the southern horizon in January, versus 53 degrees in July, and these angles are important for how much energy is actually absorbed. Due to that large difference, any given ground surface area receives 85 percent less energy.
Andy Veh is an associate professor of physics, math and astronomy at Kenai Peninsula College.