The Night Sky This Month: July 2020

Noctilucent clouds
Noctilucent clouds: Image credit Wikipedia Commons

The Summer Triangle is a familiar feature of the northern summer night sky. As such, this famous asterism continues to dominate the celestial heavens throughout July and can be seen rising in the eastern sky before reaching overhead around midnight.

The first half of July also offers some excellent opportunities to view noctilucent clouds during deep twilight. The clouds typically form at altitudes of about 80km, and many researchers have reported increases in both the brightness and frequency of noctilucent clouds. While this type of cloud is not well understood, some researchers have suggested a link between noctilucent clouds and increasing changes in the global climate, however, there is no empirical evidence available to support this view.

Regardless of their origin though, look towards the northwest during deep twilight to see these clouds being illuminated by the Sun from below the horizon.

Moon Phases In July 2020

Full Moon
Third Quarter
New Moon
First Quarter
July 5th July 12th July 20th July 27th

Note that a penumbral lunar eclipse occurs on July 5th. This type of eclipse occurs when the Moon passes through only a part of Earth’s shadow, meaning that while the Moon will darken noticeably, it will not darken as much as it does during a full eclipse.

Sadly, the eclipse will be visible only from extreme Western Europe, and observers in the UK will only observe a partial eclipse. However, observers in most of the eastern United States will be able to observe the entire event.

The Planets in July 2020

Mercury passes behind the Sun on the last day of June, and will, therefore, reappear as a predawn object on June 17th, at which time it will shine at magnitude 1.1. Since the little planet will rise only about 60 or so minutes before the Sun, it will rise close to the Sun. Therefore, extreme care must be taken not to use optical aid to observe the planet after the Sun has risen.

Note also that Mercury reaches its position of furthest western elongation from the Sun on July 22nd, on which date it will be located about 22 degrees west of the Sun, and shine at magnitude 0.2, having an illuminated phase of 37%.

Venus starts July rising in the constellation Taurus approximately 2 hours before sunrise, but rises progressively earlier until, by month’s end, it will rise about 3 hours before the Sun.  Note that Venus will shine at about magnitude -4.7 throughout the month, which should make it particularly easy to spot, especially since it will rapidly rise to an elevation of about 35 degrees. This marks its highest rate of ascent in the current 8-year cycle of apparitions.

Look for Venus about one degree above the bright star Aldebaran in the pre-dawn sky on July 11th in the Hyades cluster as the planet passes through the constellation Taurus. Take note though that binoculars might be required to spot the planet in the brightening sky.

Mars starts the month rising in the southeast about 30 or so minutes after midnight (BST) in the constellation Cetus, shining at magnitude -0.5. The Red planet will spend most of the month in Cetus, but it will reach and enter the constellation Pisces on July 29th, by which time it will rise at about 11:15 PM (BST), shining at magnitude -1.1. At this time the planet will have an angular diameter of 14.5 seconds of arc, which should make it possible to view some major Mars surface details with small to medium telescopes in good seeing conditions.

Jupiter is now approaching a point of opposition, and will, therefore, remain visible throughout the night. Since the planet will reach opposition on July 14th, its brightness will largely remain constant at magnitude -2.7 throughout the month, although it will brighten marginally to magnitude -2.8 for a few days on either side of July 14th.

The King of the planets will not rise above about 16 degrees even when due south at about 1:00 AM, which means that an atmospheric dispersion corrector might be required to view the Great Red Spot, on the following dates and times-

  • July 3rd – 23:25 (UT)
  • July 8th – 22:32 (UT)
  • July 20th – 22:24 (UT)
  • July 27th – 23:04 (UT)

Saturn is like Jupiter, also approaching a point of opposition, which it will reach on July 20th. Also, like Jupiter, Saturn will remain visible throughout the hours of darkness during July, and its brightness will, therefore, remain relatively constant at magnitude -0.1. Sadly, and although Saturn’s angular diameter will increase to 18.5 seconds of arc, it will like Jupiter, not rise above about 16 degrees when it transits the meridianAn atmospheric dispersion corrector might therefore be required to get clear views of the ring system that is now tilted towards our line of sight by about 22 degrees.

Meteor Showers in July 2020

The Delta Aquarids meteor shower is expected to peak on the night of July 28th /29th as Earth passes through the debris trails of comets Marsden and Kracht. However, even though this shower is expected to deliver no more than about 20 or so meteors per hour during the peak, relatively bright moonlight will obtrude during the peak. Consequently, only the very brightest meteors might be observable in the hours directly after midnight on the night of July 29th.

Deep Sky Objects to Look For In July 2020

Visible constellations, although not necessarily prominent, in the south at this time of the year include Boötes, Lyra, Aquila, Cygnus, and parts of Scorpio that may contain the bright star Antares– depending on the observer’s latitude. Of course, Ursa Major, which is north circumpolar, is always visible, and although the Big Bear contains many spectacular deep sky objects, we will only highlight a few here that are visible with modest amateur equipment:

 Interacting Galaxies M81 and M82

M81 and M82
Image credit: NASA

These two galaxies designated Messier 81 and Messier 82 respectively, are visible in the same (low power) field of view in a small telescope. M82, the galaxy on the left in this image, is located between 11 million and 12 million light-years away, and although not much detail is shown here, the galaxy is currently undergoing an intense burst of star formation because of its interaction with M81.

Nonetheless, M82 is of major scientific interest because it contains an unknown object that is emitting radio waves of a type that has never before been observed anywhere in the Universe, especially since it appears to be moving at four times the speed of light. The object seems to be related to relativistic jets emanating from a supermassive black hole, but there is as yet no evidence of the presence of a black hole in the indicated location.

Pinwheel Galaxy (M101)

Pinwheel Galaxy
Image credit: NASA

Located about 24 million light-years away, the Pinwheel Galaxy (M101) belongs to the Sc class of spiral galaxies. These are spiral galaxies with small, compact nuclei and loosely spaced spiral arms, which gives this particular galaxy the appearance of a popular firework. M101 also happens to be one of the largest known spiral galaxies, which with a diameter of 170,000 light-years, makes it about 40,000 light-years bigger than the Milky Way galaxy.

Whirlpool Galaxy (M51)

Pinwheel Galaxy
Image credit: NASA

Although the Whirlpool galaxy does not fall strictly within the boundaries of Ursa Major, it is nevertheless associated with the constellation. Located about 37 million light-years away, close to the bright star Alkaid, M51 is the first galaxy in which spiral structure was observed, which happened in 1845 at Birr Castle in Ireland. The observer was Lord Rosse, who used his 72-inch reflecting telescope that was fitted with a polished metal mirror.

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