Where I live in Virginia, March brings the signs of a new season. The days are slowly warming, and the evenings, which were quiet all winter, are now enlivened by the calls of spring peepers and woodcocks. The stars also indicate, more reliably than the weather, that spring is here. Most of the winter constellations are falling toward the western horizon by late evening, while the spring constellations are getting higher in the east. For all these reasons, March is a good time to be out under the stars.
However, March of this year won’t bring many noteworthy astronomical phenomena (conjunctions, meteor showers, eclipses, etc.). Due to quirks of gravity and orbits, many of this spring’s astronomical events are clustered in April.
During April, most of the bright planets will be strung across the southeastern sky before sunrise, resulting in several tight conjunctions before the month is over. The first conjunction will occur on the morning of April 5, when Mars and Saturn will pass about 0.4° from each other as seen from the United States. (For comparison, the apparent diameter of the Moon is about 0.5°.) The planets will be nearly identical in brightness, but you should be able to distinguish them by color: Mars is reddish, while Saturn is white. Although the conjunction will be beautiful when viewed with no optical aid, the planets will be close enough that you should be able to see them both in the same telescopic field of view if you desire a magnified view.
Venus will be moving down toward Jupiter throughout April, and just before sunrise on April 27, the Moon will join these two brilliant planets to form a triangle about 5° across. The closest conjunction on the 27th, though, will be between Venus and Neptune. These planets will pass about 0.3–0.4° from each other as seen from North America. The great distance of Neptune means that it will be too dim to see with the unaided eye, but, at mag. 7.8, it will be well within the grasp of any descent telescope.
Australia and nearby areas are much better placed for the conjunction; from these areas, the planets will pass less than 15 arcseconds from each other. That’s 0.004°, or about the same distance as the apparent diameter of Venus. Since Venus appears about 150,000 times brighter than Neptune, the fainter planet will be lost in the glare of Venus while the planets are closest to each other. (Note: From Australia, the conjunction will occur on the morning of the 28th.)
Venus and Jupiter, the two brightest planets, will have a close encounter on the morning of April 30. From the Americas, the planets will be about 0.5° apart. The timing of the conjunction is more favorable for the opposite side
of the globe, where the planets will appear about twice as close to each other.
On a non-planetary note, the Lyrid meteor shower will peak on the nights of April 21–22 and 22–23. The radiant of the shower will rise in the late evening, leaving several hours of good viewing conditions until the Moon rises in the early morning. The Lyrid shower has a zenith hourly rate of about 18.
A partial solar eclipse will occur on April 30. The southern half of South America is the only inhabited land area where the eclipse will be visible. The greatest eclipse will be visible from the southern tip of the continent, where about half of the Sun will be eclipsed.
