Night Sky Highlights for April-June 2018

Solar System

There will be a good opportunity to observe Mercury during the last week of June and continuing into the first half of July, when it will be low in the west right after sunset.  You will need a clear view of the western horizon.

Venus will be easy to see in the west after sunset throughout the spring and summer this year.  At about magnitude -4, it is the brightest object in the sky besides the Sun and the Moon.

Mars will rise after midnight in April and around midnight by June, and it will be getting steadily brighter and larger in apparent size as it approaches the Earth.  By mid-June, it will be magnitude -1.7 and a respectable 18″ in diameter (about half the apparent size of Jupiter), as it heads toward a fairly close opposition to Earth in late July.

The giant planet will rise in mid-evening during April, and by June it will be high in the eastern sky after sunset.  This will be a good time to observe its cloud bands, the red spot, and its four brightest moons.

Saturn is in Sagittarius, rising after midnight in April but shortly after sunset by the end of June. Its rings continue to be tilted at a good angle for viewing them from our vantage point.

Uranus and Neptune
Uranus is in Pisces, and Neptune is in Aquarius.  They will not rise until the early morning hours during April and May, and Uranus will be close to the Sun.  By June, Neptune will rise around midnight, and Uranus will follow a few hours later. This is not a convenient time to spot them, but if you try, you will need a finder chart such as the one in this article from the Sky & Telescope website:


Deep Sky Objects

Here are some good targets for backyard astronomers to seek out during the spring months. For each object, click on the star-hop chart to get instructions and printable maps showing how to find the object in the evening sky.

Porrima (Gamma Virginis)
Double star in Virgo
Porrima is a bright naked-eye star at magnitude 2.7. Its two components are less than 3 arcseconds apart, so a telescope at high power is required to split them. The components are about equally bright, one yellow and one blue, making a beautiful color contrast. The two stars are about 38 light years away and about 34 astronomical units apart. Star-hop chart

Messier 49
Galaxy in Virgo
M49 is a large elliptical galaxy, one of the brightest in the Coma-Virgo galaxy cluster and one of the brightest in our sky at magnitude 8.4. It can be seen through any telescope as a round, featureless glow with a very bright center. The galaxy is about 54 million light years away.  Star-hop chart

Messier 51, the Whirlpool Galaxy
Galaxy in Canes Venatici
The Whirlpool Galaxy is one of the brightest examples of a face-on spiral galaxy visible in our skies. It is about 23 million light years away. The irregular companion galaxy that appears to be connected to one of the spiral arms is NGC 5195. The companion is actually slightly farther away.  Star-hop chart

Messier 53
Globular Cluster in Coma Berenices
At an estimated 58,000 miles away, Messier 53 is a fairly distant globular cluster, but it is bright and easy to see. Through large amateur scopes, its stars are well resolved. The cluster is about 220 light years in diameter.  Star-hop chart

Messier 61, Oriani’s Galaxy
Galaxy in Virgo
This beautiful face-on barred spiral galaxy was discovered in 1779 by Barnabas Oriani, a Catholic priest and accomplished astronomer. It is on the southern outskirts of the Virgo galaxy cluster. Through small scopes, it appears as a circular glow with a brighter center. Large scopes will show its two large spiral arms.  Star-hop chart

Messier 63, the Sunflower Galaxy
Galaxy in Canes Venatici
M63 is a bright galaxy, magnitude 8.6, and its diffuse oblong shape and stellar nucleus can be seen in even small telescopes. The many bright knots in its arms, surrounding a small and bright nucleus, give the Sunflower Galaxy its name. These tiny knots are difficult to see visually through a telescope, but the galaxy has a mottled appearance in large scopes.  Star-hop chart

Messier 67
Open cluster in Cancer
Messier 67 is a fairly bright open cluster of some 200 stars. It is estimated to be about 4 billion years old, making it one of the oldest known open clusters. It is not as well known as the nearby Beehive Cluster (Messier 44), but it is quite an attractive object when viewed with a small telescope at low power.  Star-hop chart

Messier 88 and 91
Galaxies in Coma Berenices
M88 is a nice spiral galaxy with a bright nucleus surrounded by tightly wound arms. Through large telescopes, some detail in the structure of these arms can be seen. Less than 1 degree to the east is M91, a barred spiral. At magnitude 10.2, it is the dimmest of the galaxies on Messier’s list, but it is still easily within the reach of amateur telescopes. It appears as a faint oval with a brighter center. Star-hop chart

Cor Caroli
Double star in Canes Venatici
Cor Caroli is a wide double star, with a bright white primary star (magnitude 2.9) and a dimmer companion (magnitude 5.5). The brighter star is called a “magnetic star” because it has an intense magnetic field. The distance between these two stars is about 680 astronomical units, and they are about 115 light years away.  Star-hop chart

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