Skywatcher's Guide: October and November 2021

Skywatcher's Guide written by: Lucas Snyder (Flandrau Planetarium Operator)


Stars and Constellations

In October, only a small portion of the spring sky is still visible at the beginning of the night.  The Big Dipper (Ursa Major) is low in the north-northwest.  As always, the last two stars in the bowl point to Polaris, our north star, in the Little Dipper (Ursa Minor).  You can also still follow the arc of the handle of the Big Dipper to Arcturus, the bright star in Boötes, now low in the west-northwest.  The summer constellations are also visible for a good portion of the night, starting the night in the middle of the sky.  The Summer Triangle is almost directly overhead, with Vega closest to the west-northwest, Deneb closest to the northeast, and Altair closest to the south.  The summer Milky Way is still prominently streaking across the sky, cutting from the northeast to the southwest.  Scorpius with the bright star Antares is now getting low in the southwest, and the nearby "teapot" of Sagittarius in the south-southwest.  The fall sky is now very prominent, taking up most of the eastern sky at the beginning of the night.  The "W" of Cassiopeia is easy to spot in the northeast, with Perseus just below.  The Great Square of Pegasus is up in the east, and Andromeda nearby in the east-northeast.  There is also a fairly bright star called Fomalhaut in the southeast, though its constellation Piscis Austrinus is not easy to distinguish.

In November, all but a few of the spring stars are now gone, and the summer constellations are starting to get lower in the west.  Deneb is the highest point of the Summer Triangle, with Vega below to the west, and Altair towards the southwest.  The brightest part of the summer Milky Way is now gone, but a good portion of it is still easy to distinguish.  Scorpius is now gone, but the "teapot" of Sagittarius is still above the horizon in the southwest.  The fall sky is now a little higher, but still in the eastern half of the sky.  We can now begin to see a few winter stars coming up along the eastern horizon, namely the bright Capella in the northeast and Aldebaran in the east-northeast.  Also look for the Pleiades (aka the Seven Sisters or Subaru) star cluster just above Aldebaran.

Interesting Stars Visible in October and November (during observatory hours)

Name / Designation Apparent Magnitude
(lower = brighter)
Arcturus -0.05 36.7  
Vega 0.03 25  
Capella 0.08 42  
Rigel 0.18 770  
Betelgeuse 0.45 427  
Altair 0.76 17  
Aldeberan 0.87 65  
Pollux 1.16 38  
Fomalhaut 1.16 25  
Markab 1.25 140  
Deneb 1.25 3230  
Castor 1.58 52  
Polaris 1.97 431  
Alpheratz or Sirrah 2.07 97  
Mirach 2.07 199  
Algol 2.09 93 variable star
Enif 2.38 670  
Almak 2.1 / 5.0 & 6.3 355  triple star system w/ 64 yr orbit
Albireo 3.2 / 5.8 & 5.1 390 / 380  possibly a triple star system
Eta Cassiopeiae 3.5 / 7.4 19 480 yr orbit

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Solar System

Mercury is passing between us and the Sun in early October and by the end of the month will be visible in the morning sky before sunrise.  It will remain visible for the first part of November, but will then pass behind the Sun towards the end of the month.

Venus is high in the southwest after sunset, reaching its highest point at the end of October.

Mars passes behind the Sun in early October and will be lost in the Sun's glare until at least the end of November, when it will start to reemerge in the morning sky before sunrise.

Jupiter is high in the south-southeast at the beginning of the night in the constellation Capricornus.

Saturn is high in the south at the beginning of the night, also in Capricornus.

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Jupiter Great Red Spot Transits during October and November

Note: The GRS is visible on the disk of Jupiter for 50 minutes before and after meridian transit time.

Date Meridian Transit Time
10/08/21 07:37 PM
10/15/21 08:24 PM
10/22/21 09:12 PM
10/29/21 09:59 PM
11/13/21 07:27 PM
11/20/21 08:16 PM
11/25/21 07:25 PM
11/27/21 09:04 PM

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Calendar of Night Sky Events

Date Event
10/06/21 New Moon.
10/07/21 Mars at conjunction. — Passing behind the Sun.
10/09/21 Mercury at inferior conjunction. — Passing between us and the Sun.
10/09/21 Appulse of Mercury and Mars. — Separated by 2.4°.
10/12/21 First Quarter Moon.
10/20/21 Full Moon.
10/21/21 Peak of Orionids meteor shower.
10/24/21 Mercury at greatest western elongation. — Visible in the morning before sunrise.
10/28/21 Last Quarter Moon.
10/29/21 Venus at greatest eastern elongation. — Visible in the evening after sunset.
11/04/21 New Moon.
11/04/21 Uranus at opposition. — Best time to see this gas giant.
11/05/21 Peak of Southern Taurids meteor shower.
11/10/21 Appulse of Mercury and Mars. — Separated by 1.0°.
11/11/21 First Quarter Moon.
11/17/21 Peak of Leonids meteor shower.
11/19/21 Full Moon and partial lunar eclipse. — Visible from Tucson! Read more here.
11/27/21 Last Quarter Moon.
11/28/21 Mercury at superior conjunction. — Passing behind the Sun.

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Deep Sky

There are many deep sky objects we can see since the summer Milky Way is high in the sky.  There are many open star clusters that can be seen with only binoculars scanning this part of the sky.  For example we have the Butterfly Cluster (M6) and Ptolemy's Cluster (M7) near the tail of Scorpius.  Further north there is the Wild Duck Cluster (M11) in the faint constellation of Scutum between Sagittarius and Aquila.  There is also the asterism of the Coathanger between Aquila and Cygnus in the fainter constellation of Vulpecula.  Next, heading towards the west we can see the Coma Star Cluster in the constellation of Coma Berenices, which is even visible naked-eye.  The Pleiades (M45) will be visible later in the night, after midnight.

There are a several globular clusters we can see as well, as the center of our galaxy is the highest it gets for the year.  Near the bright star Antares in Scorpius lies the globular cluster M4.  In Sagittarius we also have the Teapot Cluster (M22).  Of course we have the famous Hercules globular (M13) high in the east.  Also, M15 is visible in the east near the head of Pegasus.

For nebulae, we have several in the plane of the galaxy, one of which is the Swan Nebula (M17) in Sagittarius, also known as the Omega Nebula.  There is also the Lagoon Nebula (M8) nearby and the North America Nebula (C20) further north in Cygnus.  For planetary nebulae we have the Ring Nebula (M57) in Lyra, the Dumbell Nebula (M27) in Vulpecula, and the Blue Snowball (C22) in Andromeda.

And now the galaxies:  Although the Big Dipper is getting lower in the sky, you may still be able to find some of the galaxies in this part of the sky.  We have the Whirlpool Galaxy (M51) and the Pinwheel Galaxy (M101) near the handle, and the Cigar Galaxy (M82) and Bode's Galaxy (M81) near the bowl.  The spectacular Andromeda Galaxy (M31) is now coming up in the northeast, along with the nearby Triangulum Galaxy (M33).

Interesting Deep Sky Objects to Observe during October and November (during observatory hours)

Designation Name Apparent Magnitude Apparent Size Distance
Messier 45 Pleiades 1.6 110' 440 open cluster
Messier 31 Andromeda Galaxy 3.4 3° x 1° 2,900,000 spiral galaxy
Messier 42 Orion Nebula 4 85' x 60' 1400-1600 diffuse nebula
Messier 33 Triangulum Galaxy 5.7 67' x 42' 3,000,000 spiral galaxy
Messier 3 (in Canes Venatici) 6.2 18' 34,000 globular cluster
NGC 7293 Helix Nebula 7.3 16' 450 planetary nebula
Messier 27 Dumbbell Nebula 7.4 8' × 6' 1,250 planetary nebula
NGC 7009 Saturn Nebula 8 36" 2,400 planetary nebula
Messier 81 Bode's Galaxy 8.5 21' 1,200,000 spiral galaxy
Messier 57 Ring Nebula 8.8 1' 2,300 planetary nebula
Messier 82 Cigar Galaxy 9.5 14' 1,200,000 galaxy

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Frequently Asked Questions

What gives nebulae their shapes?

Nebulae come in all different shapes and sizes.  Some look like perfect circles, some look like hourglasses, some look like ghosts, some look like animals.  These shapes depend on the type of nebula and how it forms.

As far as the shapes go, there are two main categories: stellar remnants and diffuse nebulae.  Stellar remnants come from dying stars, either from slowly dying stars (planetary nebulae) or exploding stars (supernovae).  Both of these types of star death can form nearly perfectly circular nebulae if the material ejected from the star spreads out evenly in all directions.  This means the star did not have anything nearby to block or redirect the flow.  A couple examples of this are the Ring Nebula and the Bubble Nebula.

If a dying star does have something nearby, it can change the shape of the resulting nebula.  For example, if the star has a disk of debris around it, that will cause the nebula to take on an hourglass or butterfly shape as it expands.  Or if the star is part of a binary system, you might end up with complicated spiral patterns.  Usually these phenomena result in symmetrical shapes, but at times they may be asymmetrical as well.  A couple examples of this are the Dumbbell Nebula and the Cat's Eye Nebula.

Finally we have diffuse nebulae.  These are typically not symmetrical, and can take on nearly any shape, just like a cloud.  Diffuse nebulae are often shaped only by gravity slowly pulling material together across vast distances.  This may result in wispy or feathery shapes, such as the Swan Nebula or the Lagoon Nebula.  If there are stars forming within the nebula, they can push material around due to their stellar winds.  This will often create sharp boundaries and irregular clumps.  A couple examples of this are the Horsehead Nebula and the Pillars of Creation.

Because each process results in different types of shapes, you can often tell just by looking at a nebula how it might have formed.  So the next time you're looking through a telescope or browsing cool space images online, see if you can figure it out!

If you have any questions you'd like me to answer in the next issue of SWG, please let me know.  I'm also happy to take suggestions or comments, and also pictures if you'd like to send them.  Happy viewing!

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