Venus in September and October

If you track Venus in the morning sky in September and October, you will see it leave Gemini, pass through Cancer and into Leo. Those constellations are the home of several well-known Messier objects. Near the start of September, Venus is entering Cancer, and makes a quick pass just below the Beehive Cluster in the second week (minimum separation September 13/14 of about 2 degrees). On September 14, a nice thin last crescent moon joins Venus and M44 - photo op! Then on October 2 and 3, Venus slips below Regulus, missing occulting it by a scant 1/12th of a degree 5 minutes of arc! The diagram immediately below (courtesy of Simulation Cirriculum) shows the path of Venus from September 1 to October 30.


September/October: Jupiter and Saturn still good viewing

The two most interesting gas giant planets reached opposition in our sky this past July and they remain in good viewing position well into Autumn. You can't miss Jupiter. Tt is the brightest object in the sky in September, although by then Mars should be making a good showing in the SE sky. Jupiter and Saturn will be near each other in the same constellation, Sagittarius, for most of 2020 and stay near each other for several years, so future oppositions will feature both planets - a nice arrangement for Earthly observers.

Jupiter in September shines at magnitude -2.6 with a surface disk above 44" of arc fading to -2.2 in October. The diagrams of Jupiter and Saturn below show the respective moons at 23:00 on their opposition dates but are not to scale with respect to apparent size. Check your handy Jupiter Moons or Saturn Moons app for the current location. The diagrams below are used with permission of Simulation Curriculum.

Saturn continues for September and October to be a reasonably bright magnitude of 0.3 dropping to 0.6 and a disk diameter of about 18 arc-seconds. The rings are about as wide as Jupiter's disk - 42" of arc across - so Saturn presents a large target for telescopes. The ring plane is nicely tilted our way as well: 21.9°. The diagram below from Starry Night shows the two planets on the meridian around 01:00 July 17.

Finally, the diagram below shows Jupter and Saturn's positions in Sagittarius on October 1/2020.


September 14: Crescent moon, Venus, Beehive Cluster

Venus and the Beehive Cluster (M44) in Cancer, are joined by a thin last crescent moon on September 14 creating an opportunity for a group shot of planetary bodies and a deep sky object. Each is a different distance from us: the Beehive is 610 light-years away, Venus is about 143 million km, and the Moon is closest at 371 000 km. The Moon and planets pass through Cancer regularly since it is on the ecliptic (part of the zodiac) and M44 is only a degree from the ecliptic. The Pleiades are also close - only 4 degrees from the ecliptic - so it is not surprising for Venus and the Moon to pass near or through them periodically.


October 2-3: Venus a whisker from Regulus

Planets very rarely pass in front of stars, and this year we have a very, very close pass of Venus to Regulus, the alpha star of Leo. In the morning sky of October 2 and again on October 3, Venus comes within 5 seconds of arc to Regulus during daylight at about 19:00 when they are still below our horizon. By Venus' rise, at 04:00 on October 2, the separation is still close (about half a degree). The minimum occurs in daylight at about 18:00, but that is just after the pair have gone below our western horizon. By Venus' rise October 3, the two are again about half a degree apart.

The above image is used with the permission of Simulation Curriculum.


October 13: Mars at opposition

This year is a great year for Mars viewers. Not only is it bright (being so near), but it is also well above the turbulent air near the horizon where it was two years ago. Mars will be more than halfway to the zenith at its best in October! Therefore there is no excuse for not seeing surface features on nights of steady seeing. Make a habit of checking Mars every night with a telescope this fall

From July to October, Mars almost doubles in size (13" to 22" across) and goes from magnitude -0.7 to -2.62 (the brightest planet in the sky, even brighter than Jupiter). The diagrams below give the change in brightness and diameter from August last year to opposition this October in 2020. More information about the Mars opposition this year can be found in the September/October issue of SGN.


October 14: Uranus, Mars, Neptune, Saturn and Jupiter

Five planets appear in the sky from SE to SW (110° of the ecliptic) in mid-October. By far the most special one is Mars as described above, but Uranus and Neptune also reach opposition about the same time, although these are not much better viewing than usual because they are so far away from Earth. If you catch Venus in the morning sky, than only Mercury is left in your planet marathon. Mercury, unfortunately is too close to the sun to be seen this fall. The below diagram is used with the permission of Simulation Curriculum.


October 20/21: Orionid meteor shower peaks

Orionid meteors should appear on the evening of October 20/21 and peak at 01:00 October 21. Under the best conditions, 20 per hour are expected and although the Moon sets by 21:30 so the sky will be dark, the radiant in Orion does not rise for another hour or so, so numbers will be reduced. Orionids are the second fastest shooting stars, streaking across the sky at 67 km/s (241,000 km/hour!) - swifter than Perseids at 60 km/s but outdone by Leonids at 71 km/s.

There are an average of 5-6 random shooting stars ("sporadics") on any given night which will add to the Orionid true meteors. The particles (called meteoroids) that produce the streaks of incandescence (called meteors) appear to come from a point in the constellation Orion (the radiant), but only because the Earth in its orbit is moving into the stream of debris trailing behind the comet that shed the particles. This time it is the famous Comet Halley which has been seen on numerous trips around the solar system in its 76-year orbit. Annual meteor showers are produced by sand-grain sized particles with few larger pieces. Do not expect meteorites, the larger solid pieces of debris to drop down into a field near you; no meteor shower has been known to produce meteorites normally. Most meteorites are usually from large random pieces of space debris that encounter Earth.

Observers in a dark location could ideally see from 10-20 meteors per hour, and though the Moon is only a thin 5 day crescent which sets about an hour before that, the radiant stays below on the horizon until 22:30 local time. This will reduce the numbers somewhat. Observers are encouraged to go out Tuesday October 20 and observe after dark. The moon will leave the sky for most of the night and the peak occurs just after midnight.

Meteor observing requires no special equipment. Just relax on a recliner and keep warm with a blanket to ward off the chill and dew at night. Binoculars are also recommended if you want to spot a few Messier objects like the Andromeda Galaxy or the Wild Duck Cluster (my favourite). Meteors appear all over the sky; the longer ones tend to show farther from the radiant. View to the east towards Taurus and then Orion as it rises in our sky. More info is provided here: Sky&Telescope Meteors.

Photography is encouraged! This site provides hints on how: Imaging meteors. Another one from Sky&Telescope is here: S&T meteors imaging.

The diagram below courtesy of Sky&Telescope shows the view to the east with radiant in Orion at about 01:00 October 21.


Content on this page created by John Hlynialuk except where otherwise noted.