by Haritina Mogosanu, @milkywaykiwi
Senior Science Communicator, Space Place

At a glance:

In the evening sky, around 8 pm, Venus is a very thin crescent still very bright in Virgo, spending the last days as the ‘evening star’, joined by Mercury this week (you will see it just below Venus). Jupiter is Libra, hanging over the western horizon. To the northwest, right on the back of the Milky Way Kiwi is Saturn, visited by the crescent Moon this week on Monday. Te Matau a Maui, the fish-hook of Maui, or Scorpius, keeps dragging the Milky Way (Te Ikaroa, the big fish, in Māori) down from the sky this time of the year all night long. Mars is at the meridian, the imaginary line that goes from North to South via zenith (the point overhead). Hidden to the human eye but not our telescopes lie Neptune in Aquarius and Uranus in Pisces. Pluto is hiding in Sagittarius. This week the Sun sets around 7:40 PM and rises near 6:30 AM.  

Visible planets

Where to find the planets in the sky: if you know where to find the path of the Sun or the Moon in the sky, then look for the planets in the same direction. They would be following an imaginary arc that stretches from East and to West stretching through the northern part of the sky in the Southern Hemisphere. They might be anywhere on that arc so look carefully for brightest lights along that way.

The planets visible in the night sky are all aligned in front of the Zodiacal Band: starting from west: Mercury, Venus, Jupiter, Saturn, and Mars. Neptune makes an appearance early in the evening but you’ll have to hang around until after 10 PM to spot the planet Uranus.

Venus is a very thin crescent but even with such low illumination still dominates the early evening horizon. Not for long as it’s getting closer and closer to the setting Sun. It’s a fascinating planet to view and at the moment it’s really worth having look with only around 5% of the disk illuminated it is still a -4.3 magnitude and only 43.9 million kilometres away (just under half the distance that Mars is at the moment). Unfortunately there’s not a lot to see on Venus while it’s so thin as it’s thick atmosphere hides details, even when the full disk is visible. There’s probably only another week or so of Venus being in the evening sky before its brightness is overwhelmed by the setting Sun and then we’ll have to wait until about mid November to catch it in the morning sky.

This week is great to look at Mercury as it will be very close to Venus and about 90% illuminated with a visual magnitude of -0.3, so nothing like as bright as Venus but certainly brighter than Saturn so it shouldn’t be too hard to spot, just look about four finger widths (on your outstretched hand) to the right of Venus over the next couple of nights and you you’ll see the hot little planet. Mercury stays visible for rest of the week as it heads up the sky towards Jupiter. Unfortunately the Sun almost appears to be chasing it indicating that the favourable viewing conditions of Jupiter are also coming to an end. It’s been an amazing season for looking at the planets with the star of the show being Mars. In some ways it’s quite fitting that Saturn starts to get a look in now that the bright planets of Venus and Jupiter are on their way out. Mars is still an impressive site though nothing like it has been as now it is just over 100 million km away and down to a visual magnitude of -1. Notwithstanding the diminishing apparent size of the planet it is still a great view and considerably closer than it spends most of its time.

Brightest stars

The brightest star in the sky is, of course, our very own Sun which is a relatively common main sequence G2 star, meaning it’s an average star in it’s hydrogen burning phase of its life. It’s definitely not average in our Solar System though where it contains about 99.86% of the entire mass of the Solar System.

Another G2 main sequence star is our closest neighbour (that we can see in visible light) Alpha Centauri. The closest star to Earth is Proxima Centauri, which is a red giant and very dim so we cannot see it with the naked eye.  On the other side of the horizon and of the Milky Way is Altair which is a yellow-white star a little under twice the diameter of our own Sun. It has a high apparent motion and moves about 1 degree every 5000 years (no need to print a new star chart just yet).

In the middle of Scorpius is Antares, which is easy to spot by is reddish colour. It’s this colour because it’s a red supergiant. It’s so huge that if it was in our Solar System Antares’ diffuse surface would reach beyond the orbit of Mars. Antares doesn’t have long left and is likely filling up it’s core with inert iron which eventually will let gravity win the eternal tussle, which goes on inside stars between gravity and radiative pressure, resulting in a supernova. In the southern part of the sky, following the trail of the Milky Way we can see Alpha and Beta Centauri and low on the horizon, Canopus, the second brightest star in the night sky and the brightest star always visible in our night sky. Canopus is a circumpolar star. Canopus is no longer burning hydrogen in its core and the bright supergiant is probably entering the last phases of it life, don’t panic though, it’ll outlive all of us.

Deep Sky stargazing

The western part of the sky is dominated by the Milky Way and this is an extraordinary opportunity to observe all those deep sky objects there. Since that is the thickest part of our galaxy you will find plenty, just by swapping the area with a pair of binoculars. The Moon is crossing the Milky Way this week so moving away from the Moon towards Capricornus you should be able to get some good views of the globular clusters in that part of the sky. My favourites from the Northern Hemisphere are M2 and M15 which should be fairly easy to spot. Both of them are between 6 and 6.5 magnitude so should be visible with binoculars or a small scope. With a large telescope M15 shows off it’s rich centre. One more really awesome object to have a look at this week, but you will have to be quick to see it before the moon washes it out, is the Helix Nebula (NGC7293). Through a telescope is quite hard to see and is quite large – about half the size of the Moon. At a dark sky location you might be able to see a faint blob so don’t expect the dazzling details that Hubble can generate. It’s a great object to photograph and if you’re able to do narrowband imaging you in for a treat and the Moon won’t be such a problem.

The Moon

The Moon gets brighter and brighter this week as it starts to dominate the sky. We had fantastic views of our huge satellite on Saturday and had the chance to get a close look at Mare Crisium while it was still close enough to the terminator to see the effects of the shadows on the mountains around this huge area. The Moon is quite close to Saturn on Monday night so it’s worth having a break and just go and see Mare Tranquillitatis and the site of the Apollo 11 landing and then train your telescope on the beautiful ringed planet. With a reasonable size telescope you might even be able to view Titan, the intriguing moon of Saturn with the liquid methane lakes and the thick atmosphere. It’s the brightest point within a few planet widths of Saturn so should not be too hard to see though you’ll need to look at it on Monday night before the Moon gets too bright.

In average, the Moon rises or, if it’s already in the sky, sets about 50 minutes later than the previous day, every day.

Next New Moon: Thursday 8 November

Next First Quarter: Wednesday 17 October

Next Full Moon: Thursday 25 October

Next Last Quarter: Thursday 1 November

Next Lunar Eclipse: 17 July 2019

What’s hot:

Check here for our telescope viewing schedule at Space Place if the weather is good and definitely come see all these jewels in our planetarium and make sure to let us know how it went either on Facebook, twitter or Instagram or by sending me an email haritinam@experiencewellington.org.nz

Clear skies for the week ahead,

Haritina