April, 2018 – Monthly Skywatching by Chris Vaughan, Starry Night Education
The night sky tonight and on any clear night offers an ever-changing display of fascinating objects you can see, from stars and constellations to bright planets, often the moon, and sometimes special events like meteor showers. Observing the night sky can be done with no special equipment, although a sky map can be very useful, and a good beginner telescope or binoculars will enhance some experiences and bring some otherwise invisible objects into view. You can also use astronomy accessories to make your observing easier, and use our Satellite Tracker page powered by N2YO.com to find out when to see the International Space Station and other satellites. Below, find out what’s up in the night sky tonight (Planets Visible Now, Moon Phases, Observing Highlights This Month) plus other resources (Skywatching Terms, Night Sky Observing Tips and Further Reading).
Monthly skywatching information is provided to Space.com by Chris Vaughan of Starry Night Education, the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu and Chris at @Astrogeoguy.
Editor’s note: If you have an amazing skywatching photo you’d like to share for a possible story or image gallery, please contact managing editor Tariq Malik at firstname.lastname@example.org.
Hamilton RASC would also like to thank club member Troy McCoy for providing us with this article.
Calendar of Observing Highlights
Monday, April 2 pre-dawn – Mars meets Saturn
In the southern sky between 3:30 a.m. and dawn on the morning of Monday, April 2, the eastward orbital motion of the red planet Mars will bring it close to yellowish Saturn. With Mars slightly more than 1 degree below Saturn, the two planets will appear equal in brightness and fit together in the field of view of binoculars (orange circle) or a backyard telescope at low magnification. The teapot-shape constellation of Sagittarius will sit directly below the two planets.
Tuesday, April 3 midnight to dawn – Moon near Jupiter
When the waning gibbous moon rises just before 11 p.m. local time on Monday evening, it will be positioned 4 degrees to the upper right of Jupiter in the constellation of Libra. The pair of naked eye objects will cross the sky together for the rest of the night, eventually moving to a point low in the southwestern pre-dawn sky on Tuesday morning.
Saturday, April 7 pre-dawn – Mars, Saturn and the Moon Line up
In the southeastern pre-dawn sky on Saturday, April 7, the last quarter moon will form a picturesque linear grouping with Mars and Saturn. Reddish Mars will sit about 5 degrees to the lower left of the moon, with yellowish Saturn roughly midway between them. The trio will appear low over the horizon after 3 a.m. local time. By dawn, they will be higher, and the moon will have shifted closer to Saturn. The trio will fit nicely into the field of view of binoculars, and make a nice
Sunday, April 8 at 3:18 a.m. EDT – Last Quarter Moon
At its last quarter phase, the moon rises around midnight and remains visible in the southern sky all morning. At this phase, the moon is illuminated on its western side, towards the pre-dawn sun. Last quarter moons are positioned ahead of the Earth in our trip around the sun. About 3½ hours later, Earth will occupy that same location in space. After this phase, the waning moon traverses the last quarter of its orbit around the earth, on the way to new moon.
Saturday, April 14 at dawn – Mercury above the Moon
In the eastern pre-dawn sky of Saturday, April 14, the old crescent moon will be situated 4 degrees to the lower right of Mercury. Due to the shallow morning ecliptic, this will be a difficult observation for northern latitude observers. This image is for Jacksonville, Florida. The farther south your observation location is, the higher the pair of objects will be.
Sunday, April 15 at 9:57 p.m. EDT – New Moon
At its new phase, the moon is travelling between Earth and the sun. Since sunlight is only reaching the far side of the moon, and the moon is in the same region of the sky as the sun, the moon is completely hidden from view. A day or two after new moon, look for the slender sliver of the young crescent moon just above the western horizon after sunset.
Tuesday, April 17 after sunset – Moon meets Venus
Low in the western sky for about 90 minutes after sunset on Tuesday, April 17, the very young crescent moon will be visible sitting six degrees to the lower left of bright Venus. The pair will fit within the field of view of binoculars (orange circle) and make a lovely photo opportunity.
Wednesday, April 18 evening – Moon in the Hyades
On the evening of Wednesday, April 18 in the western evening sky, the crescent moon will traverse the constellation Taurus. The V-shaped face of the bull is formed by a large open star cluster known as the Hyades, one of the closest clusters to Earth. The moon will enter the “V” at about 8:30 p.m. local time and reach the midway point by the time it sets around 10:30 p.m. local time. A few hours later, observers in most of Uzbekistan and Kazakhstan, Central and Northern Russia, Northern and Eastern Scandinavia, Northern Greenland, and Northern Canada will witness the moon occult the bright, orange star Aldebaran, which sits at the southeastern corner of the bull’s face.
Sunday, April 22 pre-dawn – Lyrid meteors peak
The annual Lyrids meteor shower, derived from particles dropped by comet C/1861 G1 (Thatcher), runs from April 16 to 25 and peaks before dawn on Sunday, April 22. This shower can produce up to 18 meteors per hour, with occasional fireballs. The first quarter moon, which sets shortly after midnight, should not spoil the show too much.
Sunday, April 22 at 5:46 p.m. EDT – First Quarter Moon
After the moon has completed the first quarter of its orbit around Earth, the relative positions of the Earth, sun, and moon cause us to see it half illuminated – on its eastern side. The first quarter moon always rises around noon and sets around midnight, so it also appears in the afternoon daytime sky. The evenings around first quarter are the best times to see the lunar terrain while it is dramatically lit by low-angled sunlight.
Monday, April 23 wee hours – Moon buzzes the Beehive
Between late evening on Sunday, April 22 and 2:30 a.m. local time on Monday morning, the waxing gibbous moon will visible as it passes below the large open star cluster in Cancer known as the Beehive, Praesepe, and Messier 44. The moon will reach a position less than 2 degrees below the cluster just before it sets in the northwestern sky at 2:35 a.m. local time. Binoculars will show both the moon and the cluster in the same field of view (orange circle).
Tuesday, April 24 evening – Moon passes Regulus
After darkness falls on the evening of Tuesday, April 24, look for the bright white star Regulus sitting 3 degrees to the right of the waxing gibbous moon. Several hours earlier, near 19:00 UT, observers in Central Russia and the northeastern tip of Kazakhstan can see the moon occult Regulus.
Sunday, April 29 pre-dawn – Mercury at Greatest Western Elongation
On Sunday, April 29, Mercury (orbit shown as a red curve) will reach its widest separation west of the Sun. Due to the shallow morning ecliptic (green line), this will be a very poor pre-dawn apparition for Northern Hemisphere skywatchers, but a very good one for those in the Southern Hemisphere.
Sunday, April 29 at 8:58 p.m. EDT – Full Pink Moon
The April full moon, known as the Pink Moon, Sprouting Grass Moon, Egg Moon, or Fish Moon, always shines in or near the stars of Virgo. Full moons always rise in the east as the sun sets, and set in the west at sunrise. Since no shadows appear on a full moon, all of the brightness differences are generated by the reflectivity, or albedo, of the surface rocks.
Monday, April 30 at 17 – Full Moon near Jupiter
Just before they set in the west on the morning of Monday, April 30, the full moon and Jupiter will be separated by only 6 degrees. The objects will appear together all night long, but will reach minimum separation of a binocular field apart (orange circle) near dawn.
Mercury begins April in inferior conjunction with the sun. For the remainder of the month, the elusive planet slowly climbs away from the sun the eastern pre-dawn sky. Due to the shallow morning ecliptic, this will be a very poor pre-dawn apparition for Northern Hemisphere skywatchers, but a very good one for those viewing the planet from the Southern Hemisphere. During the month, Mercury will also shrink in apparent diameter while waxing to a half-illuminated phase. At month end, Mercury will reach its widest separation, 27 degrees west of the Sun.
During April, Venus settles into a long and very good apparition that lasts into early autumn. Each evening through the month, our bright sister planet will climb the western early evening sky – moving farther from the sunset and becoming easier to see. During the month, both its apparent disk size and percentage of illuminated drop slightly. After sunset on April 17, a very young crescent moon will be visible sitting six degrees to the lower left of the planet. The pair will fit within the field of view of binoculars and make a lovely photo opportunity. For most of the month, the planet traverses Aries. On April 19, Venus crosses into Taurus, and passes within 5 degrees of the Pleiades star cluster from April 22-18, with closest separation of 3.5 degrees on April 25.
Mars will spend April in the southeastern pre-dawn sky among the stars of Sagittarius. For the early days of the month, Mars will be close to Saturn, and the two planets will appear nearly equal in brightness. Meanwhile, on April 2, Mars will pass only half a degree to the northeast of the globular star cluster Messier 22. On April 7, the last quarter moon will form a linear grouping with Mars and Saturn – close enough that all three objects will appear within a binocular field of view. During the course of April, Earth’s orbital motion will continue to reduce our distance from the Red Planet. As a result, Mars will brighten from visual magnitude 0.27 to -0.38 and its apparent disk diameter will increase in size from 8.5 to 11 arc-seconds.
During April, very bright Jupiter (visual magnitude -2.4) will be in central Libra, slowly moving westward in a retrograde loop that will last until July. When the waning gibbous moon rises just before 11 p.m. local time on the evening of April 3, it will be positioned 4 degrees to the upper right of Jupiter. On April 30, one lunar orbit later, the nearly full moon will again pass Jupiter in almost the same position. Throughout the month, the planet will grow slightly brighter and larger in telescopes as Earth slowly draws closer to it ahead of next month’s opposition.
Saturn will be easily observable in the southeastern pre-dawn sky during April, appearing as a yellowish, visual magnitude 0.5 object located above the Teapot asterism of Sagittarius and sitting with 4 degrees of the Messier objects 22, 25, and 28. During the first week of the month, dimmer Mars will remain within a handful of degrees of Saturn, but the red planet’s eastward orbital motion will steadily draw them apart. On April 7, the last quarter moon will form a linear grouping with Mars and Saturn – close enough that all three objects will appear within a binocular field of view. Over the course of the month Saturn will rise steadily earlier in preparation for becoming an evening object next month.
During April, blue-green Uranus will not be observable. It reaches conjunction with the sun on April 18 and enters the morning pre-dawn sky toward month end, when it will cross from Pisces into Aries.
Blue-tinted Neptune spends April in the eastern pre-dawn sky among the stars of Aquarius. The shallow morning ecliptic will keep the dim planet too close to the twilit horizon to be observable in telescopes until the latter part of the month, when it will rise in a dark sky about 4:30 a.m. local time.