What's in the night sky of the week 6 to 12 February 2023 in our weekly stargazing guide.


Chris Bramley Hello and welcome to Star Diary, the podcast from the makers of BBC Sky at Night Magazine. You can subscribe to the print edition of the magazine by visiting skyatnightmagazine.com or digital edition by visiting on iTunes or Google Play.

Ezzy Pearson Greetings listeners, and welcome to Star Diary. A weekly Guide to the best things to see in the Northern Hemisphere as night sky. As we're based here in the UK, all of our times are in GMT. In this episode will be covering the coming week from 6 to 12 February. I'm, Ezzy Pearson, the magazine's features editor, and once again, unfortunately Paul wasn't able to join us this week. So I'm going to be here running you through all of the things so you don't miss anything coming up in this week's night sky. So for those of you who have been listening for a while to the podcast, you will no doubt be familiar with our old friend Comet C/2022, E3 ZTF, which has been paying a nice little visit to the inner solar system over the past couple of weeks. It's currently beginning to fade away. It's gone through its brightest point, but now it's moving away from the Sun and away from us, which means it's going to start fading. Because as it's moving away from us, obviously it's further away, which means it begins to look dimmer because the light has to travel further. But also it's moving away from the Sun and it's the Sun's heat and light which causes the ice on the comet to melt and create that lovely coma and the tails that stream across the night sky for hundreds of kilometres, hundreds of thousands of kilometres even. And though there's actually two tails, there's a dust tail and a gas tail because comets are essentially dirty snowballs. So when you melt the ice, you also kick up a load of dust and it creates two individual tails. But going back to the morning of the 6th of February at about 3 AM, the comet is going to be 1.5 degrees west of Capella, which is the brightest star in the constellation of Auriga. So it's Alpha Aurigae, where Auriga means The Charioteer. At this point is going to pay about +5.2 in magnitude, the comet, So it's beginning to fade away. Then on the morning of 7 February, the comet is going to pass by the kids Asterism formed by Eta and Zeta Aurigae. Constellations are some of the more famous star patterns that we see out there, ones that have, you know, entire stories and legends around them. They also correspond to how astronomers divvy up the night sky. And there's 88 of them across both hemispheres. But an asterism is a smaller part of one of these big constellations. So if you think that Orion, Pegasus and Ursa Major are the constellations, then Orion's belt, the square of Pegasus and the Plough would be the asterisms within them. So smaller parts of bigger constellations. So that's what the Kids formed out of Eta and Zeta Auriga, which is where the comet is going to be passing by this week. Then moving on to the evening of 8 February, Comet E3 is going to pass about two thirds of a degree west of Hassla or Iota Aurigae. It'll carry on its way across the night sky until the 10 to 11 February, where it's going to be north east of Mars. Mars is going to be one of the bigger and brighter things to see in the night sky. So it should be pretty easy to locate. So if you're looking for something to help guide your way towards the comet, Mars is probably a good shout this week. So as I said on the night of 10 to 11 Feb, it's going to be towards the north east of Mars. But then on the next night it should be towards the south east of the planet. So you can see it making its way. It's slow progress across the night sky. And by this point, the comet's probably going to have faded away to about +6.0 in the night sky. So magnitude of about +6.0. Comets are notoriously fickle and unpredictable, so those brightnesses might not quite be accurate, but that's one of the good things about comets. Everything in the universe is so predictable that sometimes it's nice to have something that isn't. We can predict where it's going to be, just not necessarily what it's going to look like.

So looking forward to the end of the week from 9 February forward, we're going to see something unusual that we don't always get to see all of the time, even though it's on the surface of our familiar old companion, the Moon. And that's Mare Oriental, which is a libration feature. Libration is caused by the push and pull of gravity between Earth and the Moon, meaning that the Moon seems to wobble backwards and forwards. If you're looking at it on the night sky. It seems to rotate slightly one way and then rotate slightly the other way back. So actually if you looked at it across the entire year, we actually see about 60% of the moon's surface. Largely speaking, the same surface of the Moon always points towards us, the nearside is always pointing towards us, but we can see a little bit more across those two edges. So around about 60% of that surface is visible over time. And from 9 to 16 February. So moving forward into next week, Mare Oriental is one of those features that's going libration is going to bring into view over on the western side of the Moon. Some of you who are up to date on your Latin, up to date is probably the wrong word. Those of you who are good with Latin probably might recognise the Oriental means Eastern sea. So why it's on the west? I'm not entirely sure. I know that astronomers like to flip things around, so it's probably because if you actually standing on the surface of the Moon, it would be over towards the east. But looking up from the ground is on the western side. If you want to try and see it, you are going to need a telescope to really be able to view it in any great detail, because it is quite difficult thing to see. It is very we are looking at it very much edge on. It will appear, just as a dark patch over on that western side of the Moon. However, if you could look at it from above and we have various orbiters that have managed to look at Mare Orientale from above, you would actually see that it looks like a giant bull's eye. And that's because it is several concentric rings of mountain ranges with dark lava lakes in between them, most likely caused by a huge collision with a meteor crashing into the surface, kicking up these mountain ranges, which then filled in with with lava after them. So it's a brilliant thing to see on the night sky. So those are our highlights for the week. We've got Comet E3 making its way through the night sky. Plus Mari Orientale will be making a rare appearance over on the western side of the Moon. Thank you very much for joining us. If you like that podcast, please be sure to subscribe so that you don't miss the podcast next week and we will hopefully see you all then.

Ezzy Pearson If you want to find out even more spectacular sites that will be gracing the night sky throughout the month, be sure to pick up a copy of BBC Sky at Night magazine, where we have a 16 page pull out Sky guide with a full overview of everything worth looking out for. Whether you like to look at the moon, the planets, or the deep sky, whether you use binoculars, telescopes or neither, our sky guide has got you covered with the detailed star charts to help you track your way across the night sky. From all of us here at BBC Sky and Night Magazine. Goodbye.


Chris Bramley Thank you for listening to this episode of the Star Diary podcast from the makers of BBC Sky at Night magazine. For more of our podcasts, visit our website at www.skyatnightmagazine.com or head to Acast, iTunes or Spotify.


Elizabeth Pearson
Ezzy PearsonScience journalist

Ezzy Pearson is the Features Editor of BBC Sky at Night Magazine. Her first book about the history of robotic planetary landers is out now from The History Press.