Prominent constellations that can be seen in October include Cetus, Pisces, Aries, Triangulum, and Andromeda. Meanwhile, Cassiopeia and the Milky Way are both nearly directly overhead, with the Milky Way stretching across the sky from east to west. Collectively, these constellations contain a variety of spectacular deep-sky objects, examples of which we will cover later on this guide to October’s night sky.
For recreational astronomers looking for the constellations and celestial objects mentioned in this guide, I highly recommend a neat free stargazing app called Star Tracker, which you can download here.
The Moon in October 2020
The image above shows an instance of Earthshine, which phenomenon can be observed this October during the waning crescent Moon phase from the 11th to the 16th, and again from the 17th to the 22nd during the waxing crescent Moon phase.
Earthshine occurs when sunlight is reflected off the surface of the earth, and onto the part of the surface of the Moon that is not illuminated by direct sunlight. This phenomenon is also variously known as “[the] ashen glow”, “[the] old Moon in the old Moon’s arms”, or [the] “Da Vinci glow”, after Leonardo Da Vinci, who was the first observer in recorded history to explain the science behind the phenomenon. As a further point of interest, this phenomenon also occurs on the moons of other planets in the solar system, in which case it is known as “planet shine”.
|October 1st||October 9th||October 16th||October 23rd|
NOTE: October has a Blue Moon, or second Full Moon, which occurs on the last day of the month.
The Planets in October 2020
– Mercury reaches its point of greatest elongation on the first day of the month, but although it is located 26 degrees east of the Sun on this date, it sets very shortly after the Sun, which makes the planet visible for only a few minutes low on the horizon, at best. Moreover, since the little planet reaches a point of inferior conjunction on the 25th of the month, it will reappear as an early morning object after this date.
– Venus starts the month rising at about 02:00 (BST), but rises progressively later until at month’s end, it will rise at about 04:00 (BST). This will make it visible as an early morning object for about three hours or so before dawn. Note that Venus will remain a bright pre-dawn object for the remainder of 2020. Nonetheless, at about 03:00 (BST) on the morning of the 14th, Venus will be separated from the waning crescent Moon by about 3 degrees, just north of east, which should make for an interesting sight in binoculars.
– Mars will be the brightest it will ever be until September of the year 2035. Note that the Red planet comes into opposition with the Sun on the 13th , and as a result, it will transit the meridian at an elevation of about 43 degrees when it is due south. Look for Mars in the constellation Pisces, about 7 degrees from the fourth-magnitude star Alrisha (alpha Piscium). Note also that due to it approaching opposition, Mars will be visible throughout the night during October, but at about 03:00 (BST) on the 3rd, the planet will be within one degree above the (nearly) Full Moon.
– Jupiter / Saturn will continue their joint progression across the sky during October, until they will reach what is known as their “great conjunction” during the second half of December 2020. However, while the two gas giants remain close, both will remain within about 15 to 16 degrees above the southern horizon as seen from the northern hemisphere. This could make it difficult to obtain clear views of either planet without the aid of an atmospheric dispersion corrector.
– Uranus will come into opposition with the Sun on the last day of October, and should therefore be visible during the hours of darkness for all of October. Medium and large telescopes should reveal the planet in the constellation Aries, about ten or so degrees to the southward of the constellation’s brightest star, Hamal (alpha Arietis). Note though that it may be difficult to discern the planet’s blue-ish tinge, given that it will be no brighter than magnitude +7.8.
Meteor Showers in October 2020
Although October sees the peaks of seven meteor showers, only three are worth staying up for. However, while the three showers listed below are not particularly productive, observers who have access to dark skies might see some bright meteors from the showers listed below, nevertheless-
– The Draconids Meteor Shower peaks on the 7th of the month. Although it differs from all other showers in the sense that it is best viewed during the early evening, it is not expected to produce more than about 10 (or so) meteors per hour during its peak period. This shower is created by debris shed by the comet 21P Giacobini-Zinner.
– The Orionids Meteor Shower is expected to peak on the night of the 21st/22nd, during which up to about 20 meteors per hour may be visible. Although the Oronids is not known for producing large or particularly bright meteors, there will be no moonlight after midnight this year, which should make it possible to observe even faint meteors. This shower is produced by debris left by the comet Halley.
– The Southern Taurids Meteor Shower, which is expected to peak on the night of the 29th/30th, might be better observed from the southern hemisphere than from the northern hemisphere, but some meteors from this shower are always visible in the northern hemisphere. However, while this shower is not expected to produce more than 5 to 10 meteors per hour, this Southern Taurids is known for producing particularly bright meteors, at least some of which should be visible although the Moon will be close to full during the peak period. The shower is produced by debris left by the comet 2P Encke.
NOTE: Other meteor showers during October include-
- The Camelopardalid Meteor Shower that peaks on October 5th
- The δ-Aurigid Meteor Shower that peaks on October 11th
- The ε-Geminid Meteor Shower that peaks on October 18th
- The Leonis Minorid Meteor Shower that peaks on October 24th
Be aware, however, that none of the showers listed above is expected to produce more than between two and five meteors per hour at any time.
Deep Sky Objects to Look For In October 2020
In October, these spectacular deep-sky objects, viewed through a reasonable sized telescope, can be observed in the constellations of Cetus, Pisces, and Andromeda.
Messier 77 (M77, NGC 1068)
Located about 47 million light-years away in the constellation Cetus, this magnitude 9.6 galaxy stretches across 170,000 light-years, which makes it one of the largest galaxies listed in the Messier catalogue. Despite this though, Pierre Méchain, who discovered it, described M77 as a nebula, while William Herschel described it as a star cluster. Look for this galaxy about 0.7 degrees to the east-southeast of the fourth magnitude star Delta Ceti, and decide for yourself if the object resembles a nebula, a star cluster, or a galaxy.
Messier 74 (M74, NGC 628)
Located about 30 million light-years away in the constellation Pisces, this spectacular magnitude 10.0 galaxy, seen directly face-on, is a perfect example of a so-called “grand design” spiral galaxy. However, even though M74 contains an estimated 100 billion stars, it has a very low surface brightness, which makes it one of the most difficult objects in the Messier catalogue to observe with amateur equipment.
Observers that feel up to the challenge of locating and observing M74 should be able to find it 1.5 degrees to the east-northeast of the star Eta Piscium, the brightest star in Pisces.
Andromeda’s Cluster – Mayall II
Located about 130,000 light-years away from the core of the Andromeda Galaxy‘s core, Mayall 11 is the biggest and most massive globular star cluster in the entire Local Group of galaxies. Since it is at least twice as massive as Omega Centauri (the Milky Way‘s most massive globular star cluster) most investigators believe that Mayall II is not a true globular cluster, but rather that it is the remains of a small dwarf galaxy that had been destroyed by the Andromeda Galaxy in the distant past. This is not an altogether unreasonable assumption, since at least 14 satellite dwarf galaxies are currently orbiting the Andromeda Galaxy.