Venus passes by the Pleiades and the Moon occults the star Alniyat in this week’s stargazing guide. <\/p>
What\u2019s in the night sky in the week of 10 to 16 April, 2023 in our weekly stargazing guide. This week offers the chance to see Venus glide past the Pleiades open cluster, and an occultation of the star Alniyat by the Moon.<\/p>
Chris Bramley <\/strong>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 www.skyatnightmagazine.com or digital edition by visiting on iTunes or Google Play.<\/p>\n Ezzy Pearson <\/strong>Greetings, listeners, and welcome to Star Diary, a weekly guide to the best things to see in the Northern Hemisphere\u2019s night sky. As we are based here in the UK, all times are in BST. In this episode, we\u2019ll be covering the coming week from 10 to 16 April. I\u2019m as he appears in the magazine features editor and I\u2019m here to take you through this week\u2019s stargazing highlights. And actually we start this week with a carry on from last week\u2019s episode. If you go back and listen to that, you\u2019ll remember that we were talking about Venus, the planet Venus passing by the Pleiades<\/a>, which is an open cluster that looks a little bit like a miniature version of the plough, but it\u2019s surrounded by this beautiful nebulosity on 10 April, Venus is going to be making its closest approach to the Pleiades<\/a> when it\u2019s only going to be 2.7 degrees away. It\u2019ll remain fairly close on 11 April as well. So if you don\u2019t manage to get to see it on 10th or the weather, isn\u2019t that great? There is a second opportunity to see it on the 11th. From then on, it will continue moving out across the night sky, away from the Pleiades and towards a different cluster, the Hyades<\/a>. So the Hyades is a V-shaped cluster. It\u2019s not quite as spectacular as the Pleiades. It\u2019s not got as many members to it, but it is still quite an interesting thing to be able to see. There\u2019s also a bright star that appears to be in the Hyades, and that is Aldebaran<\/a> which is a plus 0.9 magnitude star. So fairly bright star, but this isn\u2019t actually associated with the Hyades. So when you get an open cluster like these, these are all stars that are gravitationally bound together, usually because they were formed in the same stellar nursery and they haven\u2019t quite moved away from each other yet. But Aldebaran is 150 lightyears away from this cluster. That\u2019s a very long way. It\u2019s not actually gravitationally associated with them at all. It just happens to be along the same line of sight. And on 13 April, the planet Venus is going to be between the Pleiades and the Hyades open clusters right there in the middle. It will remain in the vicinity of the Pleiades until 14 April, at which point it will start really moving across onto other targets on the night sky. But Venus is very bright at the moment. It is still a -4.0 magnitude planet, so it is still going to be the brightest thing on the sky after the Moon. So keep an eye out for that on 10 and 11 April and then keep an eye on it right the way through to the 14th as well.<\/p>\n Then on 10th April, we have an occultation<\/a>. An occultation occurs when a foreground object, in this case the Moon, appears to pass in front of a more distant background object, which is going to be the star Alniyat otherwise known as Sigma Scorpii. Alniyat a +2.9 magnitude star. So naked eye visible but definitely not one of the brightest in the sky. And in fact, not one of the brightest in Scorpius even. But what you should see, if you look towards the Moon on 10 April at around about 3:30 in the morning. So this is going to be an early one if you want to catch this occultation, as you should see that the Moon and the star are very close together. They\u2019ll be about 11 degrees from the southern horizon is where you want to be looking for this pair. And around about 3:30 \u2013 where we are, it\u2019s exactly 3:33 BST \u2013 the star will disappear behind the Moon. The Moon will carry on its way across the night sky and then at about 4:30, what you should see is the star appears to blink back in. And that time it will appear on the dark limb. So when it disappears, it\u2019s going to be on the lit side of the Moon, which means that it does kind of blur out that that sudden disappearance. But when it reappears, it\u2019s going to be on the dark limb. So it\u2019ll be suddenly from the darkness appears this bright point of light again. If you want to catch this event, do set up with plenty of time. You really want to make sure that you\u2019ve looked up exactly when it\u2019s going to happen in your particular location, because it does vary a little bit. Make sure you\u2019re set up 20 minutes, half an hour beforehand so everything\u2019s good to go when the event does roll around and make sure you\u2019re looking towards it for about 5 minutes before you expect it to happen, to make sure that you don\u2019t miss it. It is very much a blink and you\u2019ll miss it moment, so be sure that you are paying attention.<\/p>\n Then moving on to 11 April. Mercury<\/a> is going to reach its greatest Eastern elongation<\/a> when it has its furthest separation on the sky from the Sun. And on the 11th of April, it will be 19.5 degrees away from our Sun in the evening sky after sunset. Mercury itself is about +0.2 in magnitude at the moment, and it sets about 2 hours after sunset. So for Mercury, that\u2019s quite a long time that that\u2019s going to be up in the sky. And with a separation of 19.5 degrees when the Sun goes down, it is going to be fairly high in the sky. So you\u2019ve got lots of time to observe the planet, which you don\u2019t normally get. Because it is an inner planet, it tends to be quite close to the Sun most of the time, and that means you don\u2019t get a lot of time when the Sun isn\u2019t in the sky and Mercury is. But on 11th April, you\u2019ll have 2 hours to be able to get to see the pair. Mercury is getting dimmer at the moment and it will continue to get dimmer throughout the month. So if you do want to take a look at it, now is a very good time to be able to see that if you\u2019re looking with a pair of binoculars, you might also be able to see the phases of Mercury. The inner planets, both Venus and Mercury, they go through phases like the moon because we are seeing them at an angle to the Sun. Whereas all the other planets we tend to see fairly straight on because we\u2019re looking back at them rather than in at them. So that might be something to look out for If you are taking the time to look for Mercury on 11 April.<\/p>\n Then on the 12th of April lunar libration is going to bring the Moon\u2019s northern limb better into view. So this region, particularly around the northern pole has a big jumble of all sorts of craters. And when it\u2019s tipped towards you, that means that the lighting conditions are slightly different to what you would normally get. And also, it just gives you a bit of a better view to be able to view this region. The Moon is going to be about 61% gibbous on 12 April, meaning that the terminator is going to be passing through that big craterous region. And that means that there\u2019ll be lots of nice shadows. When you are looking for things on the surface of the Moon around the terminator, when that\u2019s passing over is usually a good time because you get much longer shadows, much more contrast when you are looking at it from Earth. It\u2019s also a great opportunity to get started in some lunar photography<\/a>. If you\u2019ve never done that or even some sketching, lunar sketching<\/a> of a nice crater region up on the Northern hemisphere. If you want to find out how to do either of those things. We, of course, as always, have guides over on www.skyatnightmagazine.com<\/a>. And I will put a link to those below in the show notes as well.<\/p>\n On 14 April, Mars is going to be sitting just 9.5 arc minutes away from the star Mebsuta, Epsilon Geminorum. Mars is about +1.2 in magnitude at the moment. So nice and easy to see that one. Mebsuta is a plus three magnitude star and it\u2019s Epsilon Geminorum. It\u2019s in the constellation of Gemini<\/a>. It\u2019s in fact the hips of the right hand twin Castor, If you\u2019re trying to work out where it is. If you\u2019re trying to find Gemini at all, it\u2019s over the left shoulder of Orion<\/a>, which is probably a better known constellation. Most people can recognise Orion in the sky. If you want to find Mebsuta then you can do that by looking at Betelgeuse, which is Orion\u2019s left shoulder. It\u2019s a slightly red star. You should hopefully be able to see that colouration. And then if you also look for Rigel, which is the right foot of Orion. So you go from Rigel, the right foot draw an imaginary line up to Betelgeuse and then carry on that line about the same distance again. And you should find that it\u2019s pointing at the star Mebsuta. So that\u2019s how you can find that. Should be pretty obvious on 14th, because it will be next to Mars. So if you see what looks like a fairly bright, slightly reddish \u2018star\u2019 in that region, that\u2019s Mars. And the slightly dimmer object next to it is Mebsuta. Mars isn\u2019t going to set until around about 3:00AM, so there\u2019s lots of time to be able to catch those two in the night sky. It\u2019s also a great opportunity if you\u2019re not very comfortable still finding your way around the night sky, you\u2019ve got Mars helping you go from one constellation to another and then maybe look up some nice star hopping guides to try and help you find your way around the other constellations in the region as well. Again, we have all of those guides over on our website www.skyatnightmagazine.com<\/a>.<\/p>\n