Night Sky Highlights for April-June 2016
Solar System
Mercury after Sunset
If you have a good view to the west, you should be able to see Mercury shortly after sunset in mid-April. It is at its greatest eastern elongation (farthest from the Sun as we see it) on April 18, so the week around this date is the best time to look for it.
Transit of Mercury
May 9, early morning through mid-afternoon
One of the most interesting sky events this spring will be the transit of Mercury, and in the eastern US we are in a very good position to observe it, weather permitting. As always, it is essential to use proper precautions when observing the Sun! Mercury will be seen as a tiny black dot crossing the solar disk. It will enter the Sun’s disk on the east edge and cross the surface of the Sun over a period of about 7 hours. Here is the schedule (in Eastern Daylight Time):
7:12 am: First contact on the Sun’s eastern limb
10:57 am: Closest to the center of the Sun
2:42 pm: Last contact on the Sun’s southwestern limb
The next transit of Mercury will be in November 2019.
Venus
It will be difficult or impossible to view Venus this spring. It might be just possible to see it low in the east just before sunrise during early April. After that it gets closer and closer to the Sun (though it is actually passing behind it from our viewpoint), so it will not be visible in May or June.
Mars
Mars is in the vicinity of Scorpius, and it will be getting closer to the Earth and therefore larger and more impressive in views through a telescope. It reaches opposition (opposite the Sun, so it rises as the Sun sets) on May 11, and it is closest to Earth on May 21, when it will be 18.6 arcseconds in diameter. It will be nearly as large for many weeks before and after, so this is a good time to use high power and look for surface details.
Jupiter
The giant planet is in Leo, and throughout the spring it will be the brightest object in the evening sky other than the Moon. This is an ideal time to observe Jupiter and its four Galilean moons.
Saturn
Saturn will rise late in the evening during April, and then steadily earlier until it reaches opposition on June 3. Besides observing its beautiful rings, it is always interesting to search for as many of its brighter moons as you can see with your telescope.
Eta Aquarid Meteor Shower
May 5, before dawn
The meteors from this shower are debris from Comet Halley. Because the radiant is in Aquarius, the shower favors the southern hemisphere, but those of us in the north should still be able to see some meteors beginning about 2 am when the radiant rises, and getting better until the light of dawn interferes. The Moon is new so it will not be a problem.
Deep Sky Objects
Many fascinating deep sky objects are visible during the spring. This list includes a few prominent star clusters, but this is the ideal time of year to look for galaxies in Leo, Virgo, Coma Berenices, Ursa Major, and the surrounding areas. The galaxies mentioned here are found it groups of two or more, making it even more worthwhile to make the effort to track them down.
Messier 41
Open cluster in Canis Major
Just about 3 degrees down from Sirius, the brightest star in the sky, this large open cluster is easy to see in binoculars, and it is an impressive sight through a telescope with a low-power eyepiece.
Messier 44, the Beehive Cluster
Open cluster in Cancer
Dimly visible to the naked eye from a dark site, this is good binocular target.
Messier 3
Globular cluster in Canes Venatici
This is one of the brightest globular clusters in the sky. It can be seen any telescope, but the bigger the scope, the more impressive the view.
Messier 65 and 66, and NGC 3628
The Leo Trio
These three bright spiral galaxies in Leo form a triangle about 1/2 degree wide, so they can easily fit in the same field of view with a low-power eyepiece.
Messier 95, 96, and 105
Galaxies in Leo
This is another group of galaxies that can be seen together in a low-power eyepiece. M95 and M96 are oblong spiral galaxies, and M105 is an elliptical galaxy. Other fairly bright galaxies can be seen in the vicinity as well.
Messier 59 and 60, and NGC 4647
Galaxies in Virgo
M59 and M60 are two elliptical galaxies about ½ degree apart, appearing diffuse and fuzzy with brighter centers. Just to the northwest of M60, seeming to almost touch it, is the dimmer spiral galaxy NGC 4647.
Messier 88 and 91
Galaxies in Coma Berenices
These two galaxies are part of the Virgo galaxy cluster, just north of the constellation boundary between Virgo and Coma Berenices. They are about 1 degree apart, with oblong M88 to the west, and the face-on spiral M91 to its east.
Messier 81 and 82
Galaxies in Ursa Major
This is one of the nicest pairs of galaxies visible through amateur telescopes. M81 appears egg-shaped, and M82, the Cigar Galaxy, is long and narrow, but irregular in its appearance.