Mercury (mag. -0.1) is making its best evening appearance of the year. Look for this small but bright planet low in the western sky about 45 to 60 minutes after sunset. Use binoculars to scan the sky above the sunset point, looking for a starlike point of light deep in the darkening twilight. Mercury fades quickly to mag. 1.6 over the next week, and disappears from the evening sky by mid-month.
As the darkness deepens in the west, look for Mars (a dim, reddish point of light) to the upper left of Mercury. It sets around 10 p.m. The Red Planet (mag. 1.5) will disappear into the twilight glare of the setting sun in the coming months. On April 27, look for an extremely thin, crescent moon sitting to the lower left of Mars in the western sky about one hour after sunset, with the Pleiades ("The Seven Sisters") star cluster to the lower right of Mars.
You can’t miss Jupiter in early April. This majestic planet reaches opposition (opposite the sun in our sky) on April 7 and is at its closest to Earth. Reaching mag. -2.5, Jupiter shines at its brightest for the year. It rises in the south-east as darkness falls, and is visible all night long. Look for the near-full moon close to Jupiter centred on or near April 10, just a few days after Jupiter’s opposition date.
Saturn (mag. 0.3) is approaching its June 15 opposition and is slowly growing brighter in the evening sky. By the way, Saturn is the farthest world that can be viewed with the eye alone. It rises in the east around 1:30 a.m. at the beginning of April and about 30 minutes earlier with each passing week. The best views of Saturn and its magnificent ring system in a telescope come when the planet is high in the southern sky at the start of morning twilight.
Having moved from the night sky to the morning sky in March, Venus, our solar system’s most brilliant planet, now rises in the east about 1 hour before the sun. By the end of the month, it rises about two and a half hours before sunrise. Venus will actually brighten throughout April, increasing from mag. -4.2 as the month opens, to mag. -4.7 on April 30. For a few days, centred on April 23, Venus will be paired with the waning crescent moon.
Comet 41P/Tuttle-Giacobini-Kresak (TGK) passes through the constellation of Draco - the Dragon in April. Draco sits between the constellations of Ursa Major - the Big Bear and Ursa Minor - the Little Bear. These three constellations are part of a number of northern constellations which are known as circumpolar constellations, which all revolve around Polaris - the North Star. As such, they do not dip below the horizon and are visible all night long. Weather permitting, and with the moon out of the night sky, Comet TGK can be viewed from dusk til dawn. After the moon moves into the morning sky in the second week of April, the best views will be in the evening sky.
Currently at mag. 8, it is predicted the comet could increase in brightness to mag. 5, well within naked-eye visibility from a dark site. During its visit to our solar system in 1973, the surface of Comet TGK broke open, and the comet increased in brightness by 10 magnitudes. As the comet makes its closest approach (perihelion) to the sun on April 13, it is possible that the comet will, again, brighten significantly and become a spectacular sight during the second half of the month.
The Lyrid meteor shower (radiant in Lyre - the Harp) peaks during the pre-dawn hours of April. 22. The waning crescent moon won't rise until around 4 a.m. It is thought that this will be the best viewing conditions of any spring or summer meteor shower this year. The Lyra constellation rises in the east in late evening and is at its highest point in the sky as morning twilight begins to brighten the eastern horizon. Expect to see about 18-plus meteors per hour under a dark-sky site away from city lights.
Until next month, clear skies.
At a glance
April 7 - Jupiter at opposition; peak brightness for 2017
April 11 - Full moon; 3:08 a.m.
April 15 - Moon at apogee (farthest from Earth); 7:05 a.m.
April 19 - Last quarter moon; 6:57 a.m.
April 22 - Lyrid meteor shower peaks (pre-dawn sky)
April 26 - New moon; 9:16 a.m.
April 27 - Moon at perigee (closest to Earth); 1:15 p.m.
Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid amateur astronomer since he was a small child. His column appears in The Guardian on the first Wednesday of each month. He welcomes comments from readers, and anyone who would like to do so is encouraged to email him at firstname.lastname@example.org.