The Night Sky – 9 to 15 July 2018

This week is still a brilliant time to see the planets and with Mars rapidly approaching opposition the red planet is just getting brighter and bigger with every day that passes. Now that it’s about a month since the Pleiades starting rising in the morning (Matariki in this part of the world and this time of the year) then it’s a great time to see this awesome cluster if you happen to be up before dawn. Another highlight of this week is the favourable position that Mercury will be in, if you time it right and catch it in the early evening just after sunset. Venus is also getting close to Regulus, the bright 1.4 magnitude star in Leo, earlier in the week. It’s a great week for observing deep sky objects as the Moon is nicely tucked away and there’re a few really interesting objects to have a look at. There are actually significant more than a few but we’ll focus in on three that I think are really special objects well worth checking out.

First, the planets. Jupiter is still in a commanding position in the sky but it has been surpassed in brightness by Mars as the red planet approaches the closest it’s been to Earth since 2003 – it’s opposition. This is the point where Earth sits right between Mars and the Sun and it’s due to occur at the end of the Month when it will be just under 58 million kilometres away from us. This week Mars starts off being 63 million kilometres away and by Sunday it will be significantly closer at nearly 60 million kilometres. This is why it has overtaken Jupiter in brightness. By Midnight Mars is getting really high in the sky and well above the worst of the atmosphere so is ripe for viewing. Through a moderate telescope it will be a bright orange/reddish disk and if you’re lucky you might be able to make out some of the surface features such as the Syrtis Major Planum which is a prominent dark feature on the planet. The other objects that observers often spot are the icy regions of the poles, unfortunately the much larger Northern Polar Ice Cap is not visible at the moment so observers will probably not pick out the distinctive white patch than can sometimes be seen at either pole. To make things even worse, there’s a huge dust storm enveloping  the planet which will make spotting any features nearly impossible – maybe you’ll catch a glimpse of Olympus Mons peaking above the dust storm.

Mars dust
Mars might look a bit like this at the moment (Credit: Me and NASA textures)

About ten days ago we went to the top of Mount Victoria in central Wellington to watch Matariki rise (Pleiades) just before dawn. As is typical of Wellington, we had to put up with quite a bit of cloud around the horizon but at least it was clear above us for a while, so those who braved the brisk morning got to have some fantastic views of Mars and Saturn whilst listening to Haritina explain how to find Matariki. Given the amount of cloud around we were very lucky to actually spot the illusive cluster, at least on that morning. I was lucky enough to have my binoculars trained on the right patch of sky as the clouds parted briefly to show the fine group of hot blue stars that make Pleiades so distinctive. This cluster is very young at around 120 million years old and the giant hot blue stars are burning their fuel at such a rate that they will only last a few hundred million more years before treating whoever is around on Earth to a fantastic display of supernovae. The brightest star in the cluster is called Alcyone and it is, a massive, 10 times the diameter of our Sun and nearly six times as heavy. More importantly though, it pumps out enough high energy photons to be over 2000 times as bright as our Sun showing just how quick it is burning through it’s fuel.

Hot young blue star3
Maybe Alcyone looks a bit like this, I don’t how to draw the ejected disk of material though. (Credit: Me and youtube vids on how to use Blender)

Because the Moon is not washing out our chances to view some interesting deep sky objects it’s worth having a look at some of the interesting objects around Capricornus that are starting to get a bit higher in the sky and not too late (so you can look at these and still get plenty of sleep before work, or school or whatever). One my favourites is the very faint Barnard’s Galaxy (NGC6822), which is an irregular galaxy in the local group and about 1.6 million light years away. It has a similar structure to the Small Magellanic Cloud with its a bunch of star forming regions that produce some very hot large stars. From an observational perspective, it’s a large dim patch unless you have a powerful telescope in which you might catch a glimpse of some structure. What makes this object so interesting is that not too far from it, just over 1/2 a degree is the Little Gem Nebula. This is bright planetary nebula that looks like a fuzzy star, maybe with a faint blue greenish hue to it. If you’re into astroimaging then you’re in for a treat with Barnard’s Galaxy as there’re a number of nebulae that can be captured on one end of the galaxy – you won’t visually see much with a telescope unless you own Hubble but it’s certainly worth photographing if you can.

Barnard’s Galaxy, and a satellite and the three little nebulae on the right hand side (Credit: Me)

On the other side of Capricornus is the Saturn Nebula (NGC7009). The first time that you see this bright planetary nebula you’ll see why it is called the Saturn Nebula. Through a moderate telescope you can see a Saturn-type shape, basically what Saturn would like like through a telescope with really bad optics. It’s quite blurry but there’s a definite elongation on one axis and a subtle greenish hue. What really gives it the ringed Saturn shape is the much fainter extensions that are really only visible in a larger telescope. In the same area as the Saturn Nebula are two Messier catalog objects, one is the small and faint globular cluster, M72, and the other is the loose group of stars known as M73. M72 is a great Messier Catalog object to find as it’s quite a challenge and can be difficult to spot – especially if there’s any light pollution. It’s one of the more distant globular clusters and not visually very big. In a small telescope it will just be a faint patch of fuzziness, you’ll need a good sized telescope to be able to resolve any hints of stars around the edge. Next to M72 is the other object, M73, which is basically an asterism that looked a bit like a nebula to Charles Messier, so he stuck it in his catalog of things that should not be confused as comets. Basically it’s just four unrelated stars that visually appear to be grouped together. It’s a great Messier Catalog to view though, in all of it’s unremarkable glory.

Enjoy the night sky this week, and I hope that it’s clear for you!