"I'm Your Venus"
Riddle, Bob, DeVore, Edna, Science Scope
Now that the song "Venus" is dancing around in your head, think about the real Venus, one of the two inner planets in our solar system. It is also one of the two brightest objects, other than the Moon, in the evening skies this spring. Look toward the west around sunset; unless it is overcast, it would be hard not to notice Venus high above the southwestern horizon appearing as a very bright star. During most of April, the largest planet, Jupiter, may still be visible, but low, above the western horizon. However, Jupiter will be setting earlier each day and will gradually move into superior conjunction on the opposite side of the Sun from the Earth during May. It will reappear in the morning skies during August, rising ahead of the Sun.
Venus will be heading toward inferior conjunction and a rare transit of the Sun on June 5. Inferior conjunction with an inner planet is sort of like our new Moon phase--with the Sun and Earth on either side of the Moon (or the inner planet). Since Venus orbits the Sun regularly, an inferior conjunction also occurs at regular intervals of about 19 months. Like our new Moon phase, most of the time the Moon and Venus are above or below the Sun as a result of their orbit being tilted from the Earth's orbit. However, there are times when the new Moon or Venus is in line with the Sun. When this happens at new Moon, we have a solar eclipse; with Venus (or Mercury) at inferior conjunction, we have a transit of the Sun. A solar eclipse happens in part due to the Sun and Moon having the same apparent size. Venus is larger than the Moon; however, it is much farther away, so its apparent size is considerably smaller than the Moon and the Sun's apparent diameter. During a transit, Venus appears as a small dot moving across the Sun's disk.
Transits of the Sun by Venus are rare; they occur in pairs eight years apart, following a much longer cycle of more than a century before another pair of transits. The current pair comprises the transit of June 8, 2004, and June 5, 2012. The next pair is not until the month of December in 2117 and 2125. The June 5 transit will be visible at around sunset from the entire continental United States (see Resources for transit times in selected cities across the United States).
Part of the transit pattern is seen by noting that despite a separation of eight years, transits occur almost on the same day. How this happens is a result of the respective orbital periods of the two planets, Earth and Venus. Venus returns to inferior conjunction at about 19-month intervals, and after five inferior conjunctions, Venus is nearly in the same place relative to the Earth and the Sun. Five inferior conjunctions of Venus are about the same as eight revolutions around the Sun for the Earth. If there is a transit of the Sun by Venus, as was the case in 2004, then Venus will be in roughly the same position eight years later. However, after another eight years, Venus and Earth will again be lined up for inferior conjunction, but by that time Venus will not be lined up for a transit. It will take another 105 years before there will be a transit during inferior conjunction.
For viewing from the continental United States, the transit occurs late in the day on June 5 as the Sun and Venus are setting. The local viewing opportunities vary considerably, with more of the transit event being visible before the Sun and Venus set the farther west one observes. A transit in some ways is like a solar eclipse in that there are several key times during the event marking positions of Venus and the Sun. The leading edge of Venus will make first (exterior) contact with the Sun at approximately 6:09 p.m. EDT on June 5, and about 18 minutes later Venus will make interior contact--Venus is now in front of the Sun moving west or to the right toward the other side of the Sun's disk. Mid-transit will occur about three and a half hours later at about 9:29 p.m. EDT, and the transit will end with the trailing edge of Venus leaving the Sun's disk (exterior contact) at 12:49 a. …