Three planets that go around the Sun in orbits larger than ours, Jupiter, Saturn, and Mars, are easily visible to us even without any optical aid. These three planets are called Superior Planets, because they have these bigger orbits. At various times, due to the combined motions of these planets and the motion of Earth itself, each of the three planets come into positions where they appear at their brightest to us on Earth. This month, on February 6th, it is Jupiter’s turn.
We call this position OPPOSITION, because the planet is seen “opposite” the Sun in the sky. In other words, if we would be able to look down on our solar system from above, we could draw a line from the Sun to the Earth and continue it on the Jupiter, on February 6th, and Jupiter would appear to rise above the eastern horizon as the Sun would be seen setting in the west. Jupiter, which takes 12 years to orbit the Sun, reaches opposition in every calendar year, some 39 days later than the previous year, and appears to spend one year in each zodiac constellation.
This year Jupiter’s opposition will appear among the very faint stars of Cancer the Crab, while last year when Jupiter reached opposition in very early January, it was “in” Gemini. Jupiter will be well up above the eastern horizon by 8 pm, and will dominate the night sky all night throughout winter and even into the spring at magnitude –2.6. Three days before opposition, Jupiter will be seen about 5 degrees above February’s Full Moon (the night of February 3/4).
Jupiter’s only rival in brightness, other than the Moon, this month will be Venus, which at magnitude –3.9 is six times brighter. Venus is visible as soon as twilight starts low in the southwestern sky where it remains visible until it sets around 8 pm. A neat conjunction of sky objects occurs on the night of February 20th. Looking toward Venus in the southwest, one hour after sunset, look for Mars just 0.7 degrees above and right of Mars, with the very thin crescent Moon just to the right of the planet pair!
Though we pass the exact mid-point of winter on February 2nd, there is still lots of cold weather to come before spring and summer arrive. The main winter constellations of Orion, Canis Major and Canis Minor, Gemini, Auriga, and Taurus are all in full glory due south as we reach full darkness each February night. However skywatchers can get a glimpse of summer by looking south-southeast from 4 am to dawn and finding Scorpius the scorpion rising there. Saturn, the famous ringed planet, appears to cross the northern(upper) portion of Scorpius, only about 9 degrees above and slightly left of Antares, the brightest star of Scorpius. A nice color contrast can be seen between the red-orange glow of Antares, and the creamy white of Saturn. Saturn is the brighter, at +0.5; while Antares is +1.0.
Moon phases this month: Full (Feb. 3); Last Qrtr. (Feb. 11); New (Feb. 18); and 1st Qrtr. (Feb. 25).