Last quarter Moon (Chris Vaughan, Starry Night Education)

This Week’s Sky: July 6 to 12, 2020

This week was set to be relatively quiet, but Comet NEOWISE had other plans. Also look for some close astronomical passes over the weekend.

Monday, July 6 pre-dawn – Venus crosses the Hyades

Venus crosses the Hyades (Chris Vaughan, Starry Night Education)

In the eastern pre-dawn sky between July 3 and 12, Venus’ orbital motion (red path with dates:times) will carry it directly through the Hyades star cluster, the large, triangular grouping of stars that forms the face of Taurus, the bull. Its traverse offers an opportunity to easily see the daily motion of a planet. Look with unaided eyes while the sky is still somewhat dark, around 4:30 a.m. local time — or use binoculars (red circle), which will nicely frame the planet and the cluster’s stars surrounding it.

Tuesday, July 7 pre-dawn – Comet NEOWISE below Capella

Comet NEOWISE below Capella (Chris Vaughan, Starry Night Education)

In the eastern pre-dawn sky during early July, a newly discovered comet named C/2020 F3 (NEOWISE) should be visible with unaided eyes, and through binoculars and backyard telescopes. The comet is still relatively close to the Sun, so it’s only visible for 30 to 45 minutes each morning after it rises — until it fades in to the brightening sky. Comets move across the sky — more rapidly when they are near perihelion. This one is climbing daily and shifting to the left compared to the stars around it. On Tuesday morning, the comet will rise at about 3:30 a.m. local time (it varies depending on your latitude). It will be located about 1.5 fist diameters below (or 15 degrees to the celestial southeast of) the very bright star Capella in Auriga. By Sunday, July 12, the comet will be rising about an hour earlier. It will have moved to sit nearly two fist diameters to the lower left (or 19 degrees to the celestial southeast) of Capella. The earlier rise time will place the comet higher in a darker sky, making it easier to see — but it will also be diminishing in brightness every morning as it pulls away from the Sun’s warmth. Look for a small, bright, fuzzy spot, possibly with an orange hue, and a fainter tail that extends upwards away from the Sun. 

Friday, July 10 pre-dawn – Venus at greatest illuminated extent

Venus at greatest illuminated extent (Chris Vaughan, Starry Night Education)

In the early hours of Friday, July 10, Venus will reach its greatest illuminated extent for the current morning apparition. In a telescope, the planet will show a 27-per-cent illuminated waxing crescent phase and an apparent disk size of 37 arc-seconds. Even with a less than fully-illuminated disk (inset), Venus’ nearness to Earth of only 0.4502 Astronomical Units (41.85 million miles or 67.35 million kilometres) will boost its brightness to a brilliant magnitude -4.47. After rising at about 3 a.m. local time, the extremely bright planet will be visible in the eastern pre-dawn sky, just above the bright orange star Aldebaran in Taurus.

Saturday, July 11 after 1 a.m. – Moon hops past Mars

Moon hops past Mars (Chris Vaughan, Starry Night Education)

In the southeastern sky during the hours before dawn on Saturday, July 11, the Moon will shine near Mars. Look for the waning gibbous Moon positioned a generous palm’s width (or 7 degrees to the celestial west) of the bright, red-tinted planet. As the pair crosses the sky together, the Moon’s orbital motion will carry it noticeably closer to Mars by dawn. The same movement will cause the Moon to hop to the left-hand (eastern side) of Mars on Sunday morning, July 12.

Sunday, July 12 pre-dawn – Venus meets Aldebaran

Venus meets Aldebaran (Chris Vaughan, Starry Night Education)

Venus’ trip through the triangular face of Taurus, the Bull will be concluding on Sunday, July 12 when the bright planet passes less than a finger’s width to the upper left (or 57 arc-minutes to the celestial north) of Taurus’ brightest star, Aldebaran. Look for the star and planet sitting above the eastern horizon together for about two hours before dawn. For several mornings centred on July 12, the duo will appear together in the field of view of backyard telescopes at medium magnification (red circle), with Venus displaying a crescent phase.

Sunday, July 12 at 23:29 GMT – Last Quarter Moon

Last quarter Moon (Chris Vaughan, Starry Night Education)

The Moon will reach its last quarter phase at 7:29 p.m. EDT, or 23:29 GMT, on Sunday, July 12. At last quarter, the Moon always rises around midnight and remains visible in the southern sky during morning daylight. The relative positions of the Earth, Sun and Moon cause us to see the Moon half-illuminated on its western (left-hand) side. The last quarter Moon is also positioned ahead of the Earth in our trip around the Sun. About 3.5 hours later, Earth will occupy that same location in space. After this phase, the waning Moon will traverse the final quarter of its orbit around the Earth, on the way to new Moon.

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.