Be sure to view the moon and the brightest planet, Venus, in the western twilight sky on Wednesday, November 6, 2013. They are the brightest and second-brightest heavenly bodies of nighttime, and they’ll be a wonderful attraction gracing the evening sky. Just be sure to catch the twosome at early evening because the moon and Venus will follow the sun beneath the horizon an hour or so after nightfall.
The moon is in a waxing crescent phase.
If you look at Venus with a telescope at dusk, you’ll see that Venus’ disk is a little less than half (50%) illuminated by sunlight. However, when Venus reaches its greatest brilliancy in the evening sky a month from now, Venus will only be about one-quarter (25%) illuminated by sunlight. It hardly seems to make sense that Venus would shine more brightly at a thinner than a fuller phase.
But there is an explanation. Venus’ distance is constantly changing, and Venus is actually closer to Earth at a thinner phase than a fuller phase. For instance, Venus lodges about 93 million kilometers (58 million miles) from Earth today, on November 6. Contrast that with Venus’ distance one month later, when Venus will come to within 61 million kilometers (38 million miles) of Earth on December 6. That’s a whopping 20 million miles closer!
The angular diameter of Venus’ disk – pole-to-pole apparent diameter – will be a solid one and one-half times larger on December 6 than it is on November 6. The increased size of Venus’ disk will more than make up for Venus’ shrinking phase. On December 6, 2013, the illuminated portion of Venus will cover over the maximum amount of our sky for this present apparition of Venus in the evening sky. Astronomers will say that Venus is at its greatest illuminated extent or greatest brilliancy at this juncture.
So watch Venus through a telescope, starting this evening and over the coming month, as its phase shrinks but its apparent disk size increases.
Venus will stage its greatest illuminated extent – or greatest brilliancy – on December 6, 2013.
Bottom line: Watch for a bright planet near the moon on Wednesday, November 6, 2013. The planet is the brightest one in our skies: Venus.