This week is all about Earth’s close neighbours — Mars meets Saturn, Venus crosses the Pleiades, the Moon buzzes by the Beehive Cluster and the major main belt asteroid Juno will reach opposition.
Tuesday, March 31 pre-dawn – Mars meets Saturn
Mars will pass close to a second bright planet this month – when it meets Saturn in the southeastern pre-dawn sky of Tuesday, March 31. The pair will be visible until almost sunrise after rising at about 4:15 a.m. in your local time zone. The two planets will have almost the same apparent brightness, but different colors. From Monday to Wednesday, Mars’ faster orbital motion (red line with dates and hours) will bring it within a finger’s width below (or one degree to the celestial south of) Saturn. On Tuesday morning, the two planets will be separated by only 55 arc-minutes (the Moon’s apparent diameter is 30 arc-minutes). Throughout the encounter, Mars and Saturn, with its rings, will appear together in the field of view of a backyard telescope at high magnification (red circle).
Wednesday, April 1 at 10:21 GMT – First Quarter Moon
The Moon will reach its first quarter phase on Wednesday, April 1 at 10:21 GMT. At that time, the relative positions of the Earth, Sun, and Moon will cause us to see the Moon half illuminated – on the western (right-hand) side. Sunlight striking the Moon at a shallow angle produces spectacularly illuminated landscapes along the pole-to-pole terminator that separates the lit and dark hemispheres. First quarter moons rise at noon and set at midnight, so they are visible starting in the afternoon hours. The term “first quarter” refers not to the Moon’s appearance, but the fact that our natural satellite has now completed the one quarter of its orbit around Earth, counting from the last New Moon.
Thursday, April 2 all night – Juno at opposition
On Thursday, April 2, the major main belt asteroid Juno will reach opposition. At that time, Earth will be passing between the asteroid and the Sun, minimizing our distance from Juno and causing it to appear at its brightest and largest for this year. The magnitude 9.5 object will be visible in backyard telescopes all night long. On opposition night, Juno will be positioned below the star Delta Virginis, aka Auva, which marks the northwestern corner of Virgo’s body. One week later, Juno’s motion northward across the foreground stars (red path with labeled date:time) will bring it within 0.5 degrees of that star, allowing both objects to appear together in telescopes for several nights.
Friday, April 3 between midnight and dawn – Moon buzzes the Beehive Cluster
In the western sky between midnight and dawn on Friday, April 3, the waxing gibbous Moon will be positioned less than three finger widths to the lower right (or 2.5 degrees to the celestial west) of the large open star cluster known as the Beehive or Messier 44 in the constellation of Cancer, the Crab. Observers in western North America will see the Moon pass just north of the centre of the cluster. The Moon passes through, or close to, this cluster frequently because the Beehive is located only 1 degree north of the ecliptic (green line). To better see the cluster’s stars, try placing the bright Moon just outside the field of view of your binoculars (red circle).
Friday, April 3 evening – Venus crosses the Pleiades
In the western sky on the evening of Friday, April 3, Venus’ orbital motion (red path with date:time labels) will carry it through the bright Pleiades Star Cluster, otherwise known as Messier 45, the Seven Sisters, the Hole in the Sky, and Subaru. Venus passes that cluster every year – but the orbital mechanics of Earth and Venus only produce traverses of the cluster in a dark sky every eight years, making this event a celestial highlight for 2020. Venus and the cluster will fit together in the field of view of binoculars for several nights surrounding the 3rd, and within the narrower field of backyard telescopes (red circle) from April 2 to 4.
Saturday, April 4 evening – Sirius sparkles in the southwest
After dusk in early April annually, the night sky’s brightest star, Sirius, or Alpha Canis Majoris, sparkles in the lower part of the southwestern sky. Sirius is a hot, white, A-class star located only 8.6 light-years from Earth – part of the reason for its bright appearance. For mid-northern latitude observers, Sirius is always seen in the lower third of the sky, through a thicker blanket of Earth’s refracting atmosphere. This produces the strong twinkling and flashes of colour the Dog Star is known for.
Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the universe together.