Northern Hemisphere
Ian Morison tells us what we can see in the Northern Hemisphere night sky during October 2019.
The Planets
- Jupiter, shining on the 1st at magnitude -2 and falling to -1.9 during the month, can be seen low in the southwest as darkness falls. As the month progresses, its angular size drops from 35.8 to 33.5 arc seconds. Jupiter lies in the southeastern part of Ophiuchus and is heading towards the southernmost part of the ecliptic so, as it appears in the twilight, will only have an elevation of ~10 degrees. With its low elevation, atmospheric dispersion will take its toll and an atmospheric dispersion corrector would greatly help to improve our views of the giant planet.
- Saturn, will be seen in the south as darkness falls at the start of the month. Then, its disk is ~16.8 arc seconds across and its rings - which are still, at 25.2 degrees, nicely tilted from the line of sight - spanning some 41 arc seconds across. During the month its brightness falls from magnitude +0.5 to +0.6 whilst its angular size falls to 16 arc seconds. Sadly, now in Sagittarius and lying on the south-western side of the milky way, it is at the lowest point of the ecliptic and will only reach an elevation of ~14 degrees. As with Jupiter, an atmospheric dispersion corrector will help improve our view.
- Mercury, reaches eastern elongation (at an angular distance of 24.6 degrees) on the 19th of the month but, as the ecliptic is at such a shallow angle at this time of the year, its elevation at sunset (~1.5 degrees) is so low that, lying to the upper left of Venus, it will be very hard to spot. A very low south-western horizon will be needed along with binoculars - but please do not use them until after the Sun has set.
- Mars, which passed behind the Sun (superior conjunction) on September 2nd, returns to the pre-dawn sky at the start of its new apparition. It might just be glimpsed just south of east in the latter part of the month but will only have an elevation of ~11 degrees at sunrise by month's end. Binoculars could well be needed to spot its +1.8th magnitude, 3.7 arc second disk - but please do not use them after the Sun has risen.
- Venus, may be glimpsed in the west south-west some 30 minutes after sunset at the start of the month, but will be very difficult to see due to the fact that the ecliptic is at a shallow angle to the horizon and so Venus will have a very low elevation. By month's end it sets about one hour after the Sun but will still be hard to spot. Its magnitude remains at about -3.9 and its disk, ~10 arc seconds across, is almost fully lit. Binoculars and a very low horizon will be needed, but please do not use them until after the Sun has set.
Highlights
- October - observe Saturn. Saturn is now low (at an elevation of ~13 degrees) just west of south as darkness falls lying above the 'teapot' of Sagittarius. Held steady, binoculars should enable you to see Saturn's brightest moon, Titan, at magnitude 8.2. A small telescope will show the rings with magnifications of x25 or more and one of 6-8 inches aperture with a magnification of ~x200 coupled with a night of good "seeing" (when the atmosphere is calm) will show Saturn and its beautiful ring system in its full glory.
As Saturn rotates quickly with a day of just 10 and a half hours, its equator bulges slightly and so it appears a little "squashed". Like Jupiter, it does show belts but their colours are muted in comparison.
The thing that makes Saturn stand out is, of course, its ring system. The two outermost rings, A and B, are separated by a gap called Cassini's Division which should be visible in a telescope of 4 or more inches aperture if seeing conditions are good. Lying within the B ring, but far less bright and difficult to spot, is the C or Crepe Ring.
Due to the orientation of Saturn's rotation axis of 27 degrees with respect to the plane of the solar system, the orientation of the rings as seen by us changes as it orbits the Sun and twice each orbit they lie edge on to us and so can hardly be seen. This last happened in 2009 and they are currently at an angle of 25 degrees to the line of sight. The rings will continue to narrow until March 2025 when they will appear edge-on again. - October - find the globular cluster in Hercules and spot the "Double-double" in Lyra There are two very nice objects to spot with binoculars high, just west of south, after dark this month. Two thirds of the way up the right hand side of the 4 stars that make up the "keystone" in the constellation Hercules is M13, the best globular cluster visible in the northern sky.
Just to the left of the bright star Vega in Lyra is the multiple star system Epsilon Lyrae often called the double-double. With binoculars a binary star is seen but, when observed with a telescope, each of these two stars is revealed to be a double star - hence the name! - October, late evening: the Double Cluster and the 'Demon Star', Algol. October is a good time to look high in the Southeast towards the constellations of Cassiopea and Perseus. Perseus contains two interesting objects; the Double Cluster between the two constellations and Algol the 'Demon Star'. Algol in an eclipsing binary system. Normally the pair has a steady magnitude of 2.2 but every 2.86 days this briefly drops to magnitude 3.4. Visible times of the eclipse are (in UT): on the 5th at 22:12 and the 28th at 20:42.
- October: find Uranus. This month is a good time to find the planet Uranus in the late evening as it reaches opposition on October 28th. With a magnitude of 5.7, binoculars will easily spot it and, from a really dark site, it might even be visible to the unaided eye. A medium aperture telescope will reveal Uranus's 3.7 arc second wide disk showing its turquoise colour. It lies in Aries, close to the boarders of Pisces and Cetus as shown on the chart on the ‘Night Sky Jodrell’ page.
- October - evening: find the 'Coathanger'. Looking upwards after dark you should spot the three stars making up the 'Summer Triangle'. The lowest is Altair in Aquilla, up to its right is Vega in Lyra and over to its left is Deneb in Cygnus. With binoculars sweep upwards about one third of the way from Altair towards Vega. You should spot a nice asterism, formally 'Brocchi's Cluster' but usually called the Coathanger. It is formed of a straight line of six stars below which is a 'hook' of four stars. A pretty object!
- October 3rd - after sunset: Jupiter near the Moon. After sunset, low in the south-west, Jupiter will be seen down to the lower left of a waxing crescent Moon.
- October 5th - after sunset: Saturn near the Moon. After sunset, low in the south, Saturn will be seen just up to the left of the first quarter Moon.
- October 17th - late evening: The Moon close to the Hyades Cluster. In the late evening, looking southeast, the waning Moon will be seen up to the left of Aldebaran and to the left of the Hyades Cluster. [NB, Aldebaran is not part of the cluster and lies closer to us.]
Southern Hemisphere
Haritina Mogosanu and Samuel Leske tell us what we can see in the southern hemisphere’s night sky during October 2019.
- A bit about October. October, as the name says it, (from the Greek ôctō meaning "eight") is the eighth month in the old calendar of Romulus c. 750 bc. The original calendar consisted of 10 months beginning in spring with March; October retained its name after January and February were inserted into the original Roman calendar.
- What’s the Sun up to? The reality is that the Sun does not spend an equal amount of time passing through the zodiacal constellations, for the simple reason that these constellations are different areas patches in the sky. So technically, this month, the Sun is in Virgo until the 1st of November when it moves into Libra and has been in Virgo since the 17th of September. Virgo is a really long constellation to transit.
- What’s at Zenith? Beautiful Sagittarius is at Zenith just after Sunset and then as the month progresses it’s replaced by other amazing constellations such as Microscopium, which is basically a rectangle, and then one of our favourite constellations, Grus towards the middle of the month - or later on in the evening, whichever you prefer. The cool thing about Grus, the Crane is that it has many double stars, it almost looks like a curved line, which is the imaginary tail that points us towards the Small Magellanic Cloud, which is in the neighbouring constellation, another bird, the Toucan.
In addition to that, another favourite of mine, Fomalhaut, is getting very close to Zenith this time of the year. I love Fomalhaut because when I was in the Northern Hemisphere, before I travelled here, it was the southernmost star that I could see, and it was said to show the passage south. It actually does if you know where to look. Fomalhaut is one of the Royal stars, along with Antares, Regulus and Aldebaran. The Royal stars were the guardians of the sky in approximately 3000 BCE during the time of the Ancient Persians in the area of modern-day Iran. The Persians believed that the sky was divided into four districts with each district being guarded by one of the four Royal Stars. The stars were believed to hold both good and evil power and the Persians looked upon them for guidance in scientific calculations of the sky, such as the calendar and lunar/solar cycles, and for predictions about the future. - What’s on the Ecliptic? The ecliptic is the part of the sky that holds the path of the Sun as we see it from here from Earth, and other than bright planets, it also hosts some bright stars. There’s Zubenelgenubi and Zubeneschamali in Libra getting close to the western horizon and then red giant Antares in Scorpius and a few of the stars in Sagittarius, that make the teapot. Capricornus has also some bright stars and it’s very characteristic shape of a golf flag. Then, this is kind of it with the bright stars, will have to wait until late in the night to see Taurus and Aldebaran, the other of the Royal Stars and last but not least, Regulus, in Leo will rise just before the Sun.
- The Milky Way, Scorpius and Orion The bulk of the Milky Way is on the Western horizon. The Galactic centre slowly going down sinking behind the Sun. The Southern Cross, which is also visually in the Milky Way, is doing its big descent as it dives towards the horizon, getting lower and lower each evening throughout the month, as seen after sunset. It is circumpolar so it never disappears from the Southern Sky but it means the lovely clusters and nebulae that you would have enjoyed in Spring and Winter have long gone from being in a favourable viewing position — they now compete with the horizon.
The other patch of the Milky Way that remains in a very good position for viewing is the area around Sagittarius and Scorpius with many globular clusters and nebulae (distant, celestial clouds) to look at. The highlights, for me, are the bright nebulae such M16 (the Eagle Nebula), Lagoon Nebula and the very photogenic Trifid Nebula. Ptolemy’s Cluster is a great naked eye object that is visible between the two constellations. - South Circumpolar Zone Just after sunset, the Large Magellanic Cloud and the Southern Cross are close to the horizon where the Small Magellanic Cloud is in a good position to observe.
- Comets If you want to go hunting for comets in the Southern Sky you might be able to spot 289P/Blanpain. It starts the month at 10.2 magnitude so not very bright, but by the end of the month it will be 8.8, and quite close to the Helix nebula. Another one worth having a look for is C/2018 W2 Africano which starts the month at its brightest, at the Aquarius end of Pisces. On Friday the 4 October this comet will get about degree from Neptune so a great opportunity to get a photo of both of these icy cold objects. The comet will be at magnitude 10 and Neptune at 7.8. Another interesting comet that we might catch a glimpse of is P/2008 Y12 Soho. This one will be approaching closer and closer to the sun and can be found not far from Venus, so you’ll need a fantastic horizon and great conditions, it will brighten significantly as it gets near to the Sun, but that will also make it impossible to see.
The best time to see it will be tomorrow night when it is magnitude 4.4 about 4 degrees to the right of Mercury, and 21 degrees from the Sun so it should be high enough above the horizon and dark enough. - The Moon is full on the 14th October and the New Moon is on 28 October. At 11pm on the 17th October the Moon gets very close to Pluto, though at magnitude 14.4 it will be well and truly overshadowed by the -10 magnitude Moon, kind of an almost occultation that you wouldn’t be able to see easily anyway.
On the 5th October it is international observe the Moon night, so get out there with your telescopes, binoculars, or just your eyes and take a moment to appreciate the celestial body that gives our planet a handy tilt, tides and a day that’s 24 hours long, without the Moon we may not have been able to climb out of the primordial soup at all. - Mercury It’s a good time to see Mercury at the start of the month with it being a good 20 degrees from the Sun. Mercury should be easy to spot if you have a good Western horizon, just look for Venus, after sunset, almost on the horizon and then the next brightest, slightly orange thing above it is Mercury.
- Jupiter is always amazing to view, though it’s starting to get a bit further away from us, as compared to a month ago. At the start of the month the gas giant will take up 36 arcseconds of your eyepiece but by the end of the month this will have reduced to just a bit more than 33 arcseconds. Jupiter sets about 1:23am at the start of the month and by the end it is setting at 11:48pm.
You will be able to see Europa cross the planet’s disk on the 3rd in the early evening as soon as the Sun goes down, followed by Io again at around 9pm. The next good one to watch is on the 10th at 7:15pm when Europa and then shortly thereafter Io pass in front of Jupiter. Another one of these paired moons crossing starts at 10pm on the evening of the 18th as well. So there are plenty of opportunities to catch an eclipse on Jupiter this month. - Saturn Over the course of the month Saturn gets about 100 million kilometres further away but starts in a good position for viewing. Saturn is almost a month behind Jupiter with it setting at 1:20am at the end of the month, and setting at the start of the month at 3:10am.
- Neptune Another planet that is worth taking a look at, though don’t expect to see much, is Neptune. This cold gas giant is over 4.3 billion kilometers away. It is so far away that it takes light from Neptune 4 hours to get to the Earth. You might be able to make out the hint of a disk, but at an apparent size of 2.4 arcseconds you may need to use a bit of imagination, though you will see the bluish hue of Neptune. You can find it by looking for the bright star Phi Aquarii in Aquarius and it’s about 40 arcminutes from that star.
- Uranus is also worth looking at if you happen to be up quite late as it doesn’t rise until about 10pm at the start of the month and 7:35pm by the end of the month. This planet is a bit closer at 2.8 billion kilometres and its apparent size is 3.7 arcseconds, so you shouldn’t need to use too much imagination to see the greenish hue of its disk.
- Happy Observe the Moon Night on the 5th October.