The year 2015 begins with three planets in the evening sky. To the naked eye, all three planets look like bright stars. During the first half of January, Venus and Mercury are close together in the southwest shortly after sunset. Venus and Mercury set in the west soon after the sun, and as they do, Jupiter will rise in east. Jupiter will remain up all night. Venus and Mercury will be low in the sky, so you will need a good exposure to the southwest. Venus is far brighter than any star in the sky, and though Mercury is bright too, it is not nearly as bright as Venus. Venus’s brightness will aid in finding Mercury. Mercury will be to the lower right of Venus the first week of January, and then it will be to the right of Venus through the 17th. Between January 8 and 12, Venus and Mercury will be less than a degree apart. Because it orbits so close to the sun, Mercury is difficult to see, so many people have never seen it. There are only a few brief times each year that Mercury is readily visible. Those times are when Mercury is near its greatest elongation from the sun. Each year, Mercury’s greatest elongation from the sun occurs about three times in the evening and three times in the morning. The circumstances are such that the best opportunity to see Mercury is when its greatest elongation from the sun is visible in the evening early in the year. This happens on January 14, so this probably is your best chance to see Mercury in 2015.
After midmonth, Mercury rapidly plunges toward the horizon and departs the evening sky before month’s end. Venus will remain in the evening sky until midsummer, all the while brightening and getting higher in the sky. Venus achieves its greatest evening elongation from the sun on June 6 and its greatest brilliancy about a month later, after which it too will plunge toward the horizon. Though not nearly as bright as Venus, Jupiter is much brighter than any star. It dominates the sky once Venus sets, but throughout late winter and spring, Jupiter moves westward each evening, closing the distance between it and Venus. On June 30, Venus and Jupiter will meet in what we call a conjunction. They will appear only about 1/3 degree apart on that date. In August, Venus and Jupiter depart the evening sky, but shortly thereafter they will reemerge in the eastern sky shortly before sunrise. Venus again will be at greatest brilliancy on the morning of September 21 and greatest elongation from the sun on the morning of October 26. Coincidentally, Venus and Jupiter once again come into conjunction about this time, though not nearly as close together as on June 30.
Saturn reaches opposition on May 22, meaning that Saturn will be up all night on that date, rising at sunset and setting at sunrise. From late April until late July, Venus, Jupiter, and Saturn will be visible in the evening. However, after the departure of Venus and Jupiter from the evening sky in early August, Saturn will have the evening show to itself into November. After that, there will be no planets in the evening sky, except for Mercury right around Christmas, but it will not be easy to spot. However, Venus and Jupiter will continue to dominate the morning sky through the year’s end.
If you have a telescope, you certainly will want to use it to examine the planets. However, you may be disappointed by the appearance of Mercury and Venus early in the year. We call Mercury and Venus inferior planets, because they orbit the sun closer than the earth does. Inferior planets appear to go through phases similar to the moon’s phases. Early in the year, Venus and Earth are on opposite sides of the sun, so Venus will be about as far from us as it can get. Its great distance will make Venus look tiny through a telescope. It will look like a small, almost fully lit ball, similar to a gibbous moon. The gibbous moon is the phase just before and after the full moon, where the moon looks a bit less than full. Mercury will be much closer to us, but it is a smaller planet, so it won’t look any larger than Venus. Mercury will appear half-lit, similar to a lunar quarter phase. If you watch Mercury over several evenings, you probably will notice an increase in its size and a changing shape in its phase. Venus will be much closer to us later in the year, so it will appear much larger then. I suggest that you regularly examine Venus through a telescope starting in late April. From then until late July, you will see Venus grow in angular size as its lit portion shrinks, going from a gibbous phase through a quarter phase to a crescent. If you manage to get up early and look at Venus in the morning starting in late August through the end of the year, you will see Venus reverse the process as it goes from a large crescent to a quarter phase to a smaller gibbous shape.
Jupiter will be fine to look at through a telescope any time that it is up, though you probably ought to do so when Jupiter is high in the sky—the earth’s atmosphere blurs images when you view them low in the sky. Through even a small telescope, you will see the disk of Jupiter and its four largest satellites, or moons. The satellites will look like four stars lined up with Jupiter. The innermost satellite takes less than two days to orbit Jupiter, while the outermost moon takes less than 17 days. From one night to the next, the orbital motion is obvious, but you can see some motion in just an hour or two. If you don’t see all four satellites, it’s probably because one or more of them are behind or in front of the planet. If you wait a while, you will see them reappear. If your telescope is large enough, you may see dark bands in the atmosphere of Jupiter. You are not likely to see Jupiter’s Great Red Spot—it has been muted for much of the past half century. And, of course, we can’t leave out Saturn. Saturn is my favorite thing to look at through a telescope. Even with a very modest telescope, you easily can see Saturn’s rings. I will never forget the first time that I saw Saturn’s rings more than 45 years ago.
There are a few other things of note that will happen in the sky in 2015. The Perseid meteor shower will peak the night of August 12–13. The Perseid meteor shower probably is the most dependable meteor shower, and it has the bonus of being at the height of summer when the weather is warm. In 2014, the Perseids coincided with a full moon. When the moon is bright, not many meteors are visible, so the 2014 Perseid meteor shower was a bust. With a waning crescent moon, the 2015 Perseid meteor shower ought to be great. I’ll probably post a reminder in August.
On September 27, we in North America will have a ringside seat for a total lunar eclipse. As many of you may know, this is the fourth of a so-called tetrad of total lunar eclipses that fall on Hebrew holy days. Some people see fulfilment of Bible prophecy in these, but I have serious problems with this (see here and here). We had hoped to watch the first of these four eclipses here at the Creation Museum on April 15, 2014, but we were clouded out. We managed to see the second one on the morning of October 8. The third one on March 20, 2015 won’t be visible in North America, but the September 28 eclipse will be in the evening here in Northern Kentucky. We plan to have a special event to watch the eclipse that evening here at the Creation Museum, so stay tuned for future announcements.