Skylights: October 2024

Sun

Earth moves to within 1.000 au of the Sun on October 5, and will remain closer than 1.000 au until April 3.

The Sun is 1.8° north of Spica on the 16th, and on the 26th it is positioned halfway to solstice by measure of declination (-12° 43’ 09”).

The Sun moves into Libra on the 30th, after having spent the past 44 days traversing Virgo, the longest constellation, during the Sun’s annual trip on the ecliptic.

Moon

The Moon is new on the 2nd, beginning Lunation 1259. Although New England doesn’t experience it, an annular eclipse occurs over the southern Pacific Ocean and South America.

What’s always a stunning sight is the pairing of the crescent Moon with Venus, which occurs on the 5th, when the planet is 3.8° north of the 2.8-day, 8.6% illuminated Moon.

Two nights later, on the 7th, the Moon is 1.6° southwest of Antares, in Scorpius.

When the Moon reaches its first quarter phase at 2:55pm on the 10th, it is near its most southerly declination in Sagittarius.

As it waxes through its gibbous phase, the Moon passes 3.0° east of Saturn on the 14th, and 3.7° east-northeast of Neptune on the 15th.

The Full Hunter’s Moon occurs at 7:26am on the 17th, in Pisces. The Moon sets 20 minutes before it reaches full, and rises 6:00pm in the evening, just one minute after sunset.

On the morning of the 19th, the waning gibbous Moon is 4.8° northwest of Uranus, and 2.0° east of the Pleiades in Taurus.

Just before dawn on the 21st, the Moon is 0.6° southwest of Alnath (beta Tauri).

Just after 11:00pm on the 23rd, Mars and the last quarter Moon can be seen rising together about 5° apart. The Moon reaches its precise last quarter phase just five hours later,.in Cancer. 

On the 26th, the waning crescent Moon lies 3.3° north-northwest of Regulus, in Leo.

Mercury

Mercury passed its superior conjunction on September 30th, and although it returns to the evening sky, it remains too close to the Sun to be visible for much of the month.

Venus

Venus is visible in the evening sky, in Libra. It sets about 75 minutes after sunset. Due to the low angle of the ecliptic on the western horizon, Venus is setting earlier each evening, until October 22, when it begins to set later.

Take out your binoculars or small telescope to Venus on the 5th. Not only is the waxing crescent Moon 3.8° to the south of Venus, but the planet is also just 0.9° south of the wide double star Zubenelgenubi (alpha Librae).

Venus will become more easily visible by mid-month. It moves from Libra into Scorpius on the 17th, and sets about 90 minutes after sunset.

On the 22nd, Venus passes 0.6° northwest of the 28,000 light-year-distant globular cluster M80, in Scorpius. 

Venus moves into Ophiuchus on the 24th, and lies 3.1° north of Antares on the 25th. At the end of October, Venus is visible for over 90 minutes after sunset.

Mars

Mars rises at 11:30pm, in Gemini,  in early October.

From the 12th-14th, Mars lies within 1.5° of the Caldwell 39 (NGC 2392), a magnitude 9.2 planetary nebula that lies 9,000 light years away.

Mars reaches its point of western quadrature on the 14th.

The last quarter Moon is 5.0° to its northeast on the 23rd-24th. 

The waning crescent Moon (just inside of last quarter) is 4.6° north-northwest of Mars on the morning of the 25th.

On the 26th, Mars bisects the line connecting Capella and Procyon. Each night following, it gets closer to being in a line with the twin stars Pollux and Castor, until the 28th-29th, when it is right on the line with them. It then “exits” the Winter Hexagon the following night.

The Red Planet enters Cancer on the 29th, and is visible above the east-northeastern horizon by 10:45pm at the end of the month, and the Red Planet enters Cancer on the 29th.

Jupiter

At the beginning of October, Jupiter rises at 9:30pm in Taurus. It reaches its stationary point on the 9th, and begins its retrograde motion, which will continue through February 4.

It is notable that during the first half of October, Jupiter forms a line with Sirius and Betelgeuse, and 3.1° west of M1, the Crab supernova remnant.

On the 8th, Ganymede and Io trade visibility on the western side of Jupiter. At 10:34pm, Ganymede begins to emerge from eclipse. Just two minutes later, Io begins to go into eclipse. Io is completely in shadow at 10:38pm, and Ganymede completely emerges by 10:46pm. Later, at 1:24am, Ganymede begins to pass behind Jupiter, becoming completely occulted 13 minutes later. At 2:02am, Io begins to emerge from occultation, and at 3:19am, Ganymede begins to emerge from occultation.

Watch Ganymede and Io go into eclipse within minutes of each other on the 16th, beginning at 12:20am.

On the night of the 20th-21st, the waning gibbous Moon, near its more northerly declination, is 5.3° north of Jupiter.

A tight grouping of the moons appears on the 22nd-23rd, with Io, Callisto, and Ganymede to the west, and Europa to the east. Io goes into shadow at 2:25am, followed by Ganymede at 4:19am, leaving Jupiter with only two apparent moons, until Io reappears at 5:40am.

A peculiar and rapidly changing orientation of the Galilean moons occurs on the 23rd-24th, when, soon after Jupiter rises, all four moons form an irregular quadrilateral to the east of the planet, with Callisto and Io nearest to Jupiter, and Ganymede and Europa farther out. By 10:30pm, they form a slightly irregular trapezoid, and as Io moves into transit at 12:34am, the outer three moons begin to arrange themselves into a triangle, pointing away from the planet. This figure becomes most prominent at around 2:00am.

At the end of October, Jupiter rises before 8:00pm.

Saturn

Saturn is in Aquarius, and well placed for viewing during the evenings. It lies conspicuously on the line from Fomalhaut (alpha Piscis Austrini) through the western edge of the Great Square in Pegasus. 

Its largest moon, Titan, is eclipsed by the planet as the sky darkens on the 24th. Titan begins to emerge from shadow at 7:09pm, and takes over a half-hour to fully come into view.

The waning gibbous Moon is 3.0° to the east on the 14th.

Uranus

In early October, Uranus rises at about 8:30pm in Taurus.

Although the seventh planet is still two months from opposition, it is still in prime position for viewing. Its position near the northernmost section of the ecliptic puts it in optimal position for observers in the northern hemisphere, as it attains a high elevation in our sky, although in October we have to wait until around midnight for this to occur.

At magnitude 5.7, Uranus is well within reach of binoculars, even in a bright moonlit sky, and from a dark sky, may even be visible without optical aid.

Located just 5° southeast of the Pleiades cluster, Uranus is quite easy to locate. From the westernmost bright stars of the Pleiades, move directly south 4.5° to find a pair of 6th magnitude stars, 14 and 13 Tauri, which are separated by 1/3° and lie on an east-west line. The nearest object of similar brightness to this pair of stars, just over 1° to the west-southwest, will be the blue-green glow of Uranus.

By the end of the month, Uranus will be visible above the east-northeast horizon at the end of evening twilight.

Neptune

Neptune shines at magnitude 7.7 in Pisces, about 14° east-northeast of Saturn. 

It can be found by looking for a quadrilateral of 4th and 5th magnitude stars located between the Circlet and magnitude 3.6 iota Ceti, to the southeast. The quadrilateral consists of two parallel lines just under 1.0° apart, 2.5° tall, and aligned in a roughly south-southeast to north-northwest orientation, with the easternmost pair extending slightly longer to the north. Drawing a line diagonally from the southeastern star (33 Psc) through the northwestern star (27 Psc) and extending another 1.5° northwestward will lead to Neptune.

The waxing gibbous Moon is 3.7° east-northeast of Neptune on the 15th.

Minor Planets

Comet C/2023 A3 Tsuchinshan-ATLAS is visible with binoculars in October, and could possibly become bright enough to be visible to the naked eye. In the early days of the month, it is located in the eastern sky before sunrise. 

The comet is at its closest to Earth on October 12, at a distance of 0.472 au, after which it moves westward at about 6° per day, and becomes visible in the early evening sky.

On the 14th, the nucleus of the comet will be 5° west-southwest of the globular cluster M5 in Serpens. If it retains a sufficiently long tail, it may pass directly over the cluster. On the following evening, the 15th, look for the comet just 1.2° south of M5. Coincidentally, if you’re still following Comet 13/P Olbers, it will be just 1.8° to its southwest. 13/P will be about 10th magnitude.

As Earth and C/2023 A3 move away from each other, the comet’s motion across the sky becomes noticeably less as the month progresses. It it moving at a rate of 5° per day on the 15th, 4° per day on the 18th, 3° per day on the 21st, 2° per day on the 25th, and 1° per day on November 2. 

The nucleus of the comet passes through a notable former constellation known as Taurus Poniatovii in northeastern Ophiuchus during the waning days of October, and on the 27th-29th, it lies within 3° south of the open cluster IC 4665, which will make a fine sight in  binoculars.

Ceres is moving eastward through Sagittarius. At magnitude 9.0, it is located just 0.2° north of the globular cluster M54 on the 7th. On the 14th, it is 0.4° southwest of Ascella, the southeasternmost star of the teapot asterism. It then moves outside of the familiar asterism.

In late October, 4 Vesta will become visible in the eastern sky before dawn. The magnitude 8.2 asteroid is in Virgo, where it will reside until early February. On the 15th and 16th, it passes within 0.1° south of nu Virginis, and on the 22nd, it is located about halfway between Zavijava (beta) 9 Virginis.

Pluto can still be found in Capricornus, 1.7° south-southeast of globular cluster M75. The distant dwarf planet is near the meridian at dusk.

The distant dwarf planet Eris reaches opposition on the 21st, in Cetus. At 94.656 au Earth, its magnitude 18.6 light takes 13.1 hours to reach us.

The Draconids, a very short-duration meteor shower originated from comet 21 P/Giacobini-Zinner, peaks on October 8. The radiant point is located near the head of Draco, which is circumpolar from Rhode Island, so there is no time that this shower is hidden from our latitude. This is a low-rate shower, so don’t expect to see a lot of meteors. 

If you miss the peak night of the Draconids, but are still seeing meteors, you’re likely seeing sporadics, or Orionids, which are active throughout October.

The Orionids, consisting of dust left by comet 1P/Halley, and usually one of the year’s better meteor showers, are active throughout October, peaking on the night of the 21st-22nd, when the 83% illuminated waning gibbous Moon will interfere with viewing.