On June 20th is the Summer Solstice, which officially marks the start of summer in the northern hemisphere, and the start of winter in the southern hemisphere. It is also the longest day of the year in the northern hemisphere, and on this day, at about 22:34 UTC, the Earth’s North Pole will be directly over the Tropic of Cancer at latitude 23.44 degrees North. This position represents the northern-most point of the Sun’s apparent motion across the sky.
Although there are no meteor showers during the month, June offers several opportunities to see the ISS fully illuminated as it orbits Earth. Observers in far northern latitudes will also have several opportunities to observe noctilucent clouds during June. Noctilucent clouds are clouds that “shine” at night, since they are illuminated by the Sun that is never far below the horizon at far northern latitudes at this time of the year.
On June 3rd, the Moon will be at its nearest position to the Earth (perigee), while twelve days later on June 15th it will be at its greatest distance from Earth (apogee). June also offers some good views of earthshine, especially during the waxing crescent Moon from the 6th to the 11th, and then again during the waning crescent Moon during the first and last days of the month. Below are the phases of the Moon for June 2016:
New Moon: 5th
First Quarter: 12th
Full Moon: 20th
Last Quarter: 27th
The teapot shaped constellation of Sagittarius features prominently in the eastern horizon after dark, and can be found lying just below the red star Antares in Scorpius, which together with Mars and Saturn form an impressive celestial triangle. Other notable constellations during June and in the following months include Ophiuchus, Serpens Cauda, and Hercules toward the south around midnight, as well as the head of the Dragon, Draco, which will be almost overhead.
June is not a good time to observe Mercury or Venus, as the inner planets will be setting less than an hour after the Sun, meaning that they will be lost in the Sun’s glare during twilight.
Although Mars will be visible for much, if not most of June, its apparent magnitude will fade from -2.0 at the start of the month to -1.6 at the month’s end, which is slightly brighter than Sirius would be at this time. Look for Mars’ red glow between the constellation of Scorpius and its neighbor Libra, which lies low over the southern horizon from shortly after sunset to about 01:00 UT. On the 17th, the red planet will be about 8 degrees toward the lower right of the Moon.
Mars will continue its retrograde (east-to-west) motion until the 30th of the month, after which it will resume its prograde (west-to-east) motion relative to the background stars. The apparent retrograde motion of Mars is an excellent practical demonstration of the differences in the orbital velocities of the planets. In this case, Mars’ apparent “backward” motion is caused by the Earth overtaking it in the “inside lane” due to earth’s higher orbital velocity around the Sun.
The King of the planets still dominates the western night sky until about midnight, when it sets over the western horizon. Look for Jupiter in the lower reaches of Leo late on the 17th of the month, when it will be about 3 degrees to the upper right of the Moon that will be almost 50% illuminated. Despite Jupiter’s close proximity to the almost half-moon, a small telescope will still reveal the Galilean Moons as they weave their way around the giant planet.
The ringed planet reaches opposition with Earth on the 3rd of the month, and being at its closet point to Earth in a long while, it will shine with an apparent magnitude of 0.0, which although bright for Saturn, is five times dimmer than Mars. However, the color difference between the two planets is so striking that it would be almost impossible to miss Saturn, especially since the two planets will be at about the same elevation (about 16 degrees) above the southern horizon. Look for Saturn about 18 degrees to the west (right) of Mars at the start of the month.
On the 17th, the waxing gibbous Moon will form the apex of a triangle, the base of which will be formed by Mars and Saturn. On the next night, look for the close conjunction between Saturn and the waxing Moon, with Saturn below, and separated from the Moon by less than 3 degrees.
Although Saturn’s rings are still tilted toward Earth and excellent views of the ring system can still be had during June, astute observers will notice a distinct narrowing of the ring system as the planet continues to tilts on its axis in its 29-year-long orbit of the Sun.
Although Uranus will be rising at about midnight at month’s end, it remains a difficult object to observe
Neptune also rises just after midnight during June, and observers with large-aperture telescopes should be able to find it about 26 arc seconds toward the lower left of the +3.7 magnitude star Lambda Aquarii. By comparison, Neptune will be shining with an apparent magnitude of +7.9, which makes it difficult to spot, even with the brighter star as a “guide post”. Note that only large telescopes will be able to resolve the planet into a tiny disc, but don’t expect to see a disc any bigger than 2 arc seconds in any but the most powerful instruments.