It’s finally here. The month the clocks change! Ignore those who moan about it getting dark early, shun those who bewail leaving work in the dark. Finally, finally, it’s possible to be a hobby astronomer and still keep social hours that allow you to have, you know, a social life. Even better, Autumn is the season for the most beautiful constellation of them all to start to come to life – Orion, the mighty hunter, jewel of the winter skies. A constellation which works on so many levels of beauty – for the astrophysicist, it’s a tour-de-force of the star life cycle; for the layperson, it’s just goddamn there, bright, unmissable, a wonderful introduction to some of the highlights of the galaxy.
Let’s wrap up warm and begin, shall we?
First off, let’s actually find the damn thing. You’ll be able to spot it even on a full moon night in the Autumn and Winter, it’s so big and obvious, and as the winter draws on it will come to dominate the sky. Look to the East once it gets dark; you’re looking for something that looks like this:
Don’t worry about all the little stars, there’s seven big ones that we’re looking for; four in a long almost rectangle shape, three in a belt across the middle, closely backed in an evenly spaced line. Imagine a man standing legs apart, arms above his head – bingo, you’ve got it. For those with good colour perception, there should be a reddish/yellow one top left, and a blueish one bottom right. The blue one is the brightest; this is Rigel, a blue giant, and sixth brightest star in the night sky. It’s very obvious, even to the naked eye casual observer; it’s a blue supergiant some 770 light years away (you’re currently seeing it as it was in 1245 AD) and it’s big – it’s 12 times the mass of the sun, which means that it’s burning some 85,000 times brighter and hotter, glowing a hot bright white/blue colour. As a result, even though it’s bigger, it’ll burn through its fuel far faster, far hotter than our favourite puny little yellow dwarf star. Alike most blue supergiants, it’s very young – only about 10 million years old – and when it runs out of fuel, it’ll make one heck of a mess. You can’t see with the naked eye, but it’s actually a three star binary; it has two smaller siblings orbiting around it.
Second brightest, on the top left of the constellation and on the other end of the cosmic scale to Rigel is Betelgeuse (Pronounced Beetlejuice, but don’t say its name three times in any observing session, or you’ll be visited by the shade of Carl Sagan). Glowing orange-red, Betelgeuse is a gargantuan red giant, the dying stage of a star which was once very similar to our sun. As it burns though its hydrogen fuel it expands, meaning the same amount of energy has to go out of a greater surface area – so its surface cools to a mere 100,000 times the brightness of the sun. This sucker is vast, one of the largest known stars – if it were in the solar system, it would easily swallow the Earth, with the Moon as a chaser.
It’s also dying.
One day relatively soon (on a cosmic scale, that is), its core will stop burning hydrogen, and start burning helium instead. Helium is a by – product of earlier hydrogen burning, but there isn’t as much of it, and pretty soon that’ll be gone too. The star then has to gobble up heavier and heavier atoms in order to keep burning, requiring more and more energy to do so, until nuclear fusion just isn’t generating the energy needed to keep that vast outer shell from collapsing in on itself. Once that happens, the process is extremely quick, as the star collapses in on itself, compressing down before violently exploding outwards in an impossibly bright burst which can outshine most galaxies – a supernova. At a mere 643 light years from Earth, we’ll have front row seats – never mind being able to spot it in the night sky, you’ll be able to see it in broad daylight. You’ll need sunglasses. Alas, we don’t know when that will be in the next million years or so, so we’re unlikely to get treated to the greatest show in the galaxy in our lifetimes.
Next, top right, is Bellatrix. Bellatrix is a hot, luminous blue-white giant star; it is one of the hotter stars visible to the naked eye, emitting about 6,400 times more light than the Sun and has eight or nine solar masses. Within a few million years, Bellatrix will become an orange giant and eventually a massive white dwarf, shedding its outer layers to leave the cooling, dying cinders of its cooling heart behind. It’s also the star Bellatrix Lestrange is named after in Harry Potter; the Black family naming their children after the stars (Sirius, Regulus), reflecting their lofty ambitions; naming your kids after stars is an idea I particularly like. Mrs Astronomer, however, is less taken by the idea for some reason.
Those are the three big ticket stars – there’s a lot more ordinary stars in the constellation, but they’re mostly just dull points of light, and we’re only here for the good stuff.
Let me introduce you to Messier-42.
Alright, you’re going to need binoculars for this. Take a look at those three stars in the middle, the belt. Look at the two stars on the left, bisect them, then go down a bit. Imagine a sword hanging from a belt and you won’t go far wrong.
This is where stars are born; a whirling cloud of dust and gas, in places coalescing, other places being blown away, constantly shifting, light years across, backlit by the very stars it gave birth to. With your binoculars, it won’t look like the picture above – that’s taken by the Hubble Space Telescope, and is (to the best of my knowledge) the most detailed picture ever taken of the Orion Nebula. It’s why I love the Orion constellation; there are colossal, mighty stars on the edge of death, and there are fresh new-born stars bursting into life – the whole galaxy in a single patch of sky. It’s a really easy target for even the most hap-handed of beginners, and you need only the most basic equipment to see it. Through your binoculars it won’t have the vivid colouring; it’ll be a lot smaller and greyer. But you will be able to (just!) pick out the faint pin-pricks of light of new-born stars, and that’s not something you see every day now, is it?
Anyway, what’s on for the rest of the month, I hear you cry?
04 Nov – Taurids meteor shower. This isn’t a bad shower, with meteors at a regularity of one about every five minutes or so. These have been produced by dust left over from the catchy-named comet 2P Enke. However, the full moon tonight will make viewing any but the brightest meteors rather difficult. If you do have a clear sky, it’s well worth wrapping up warm with a deck chair, a blanket, and a thermos of something hot and just sitting out watching the stars, waiting for a glimpse of the meteors – and if you don’t see them, then it’ll be a perfect romantic moonlit night. Just don’t plan on any deep field astronomy.
13 Nov – Conjunction of Venus and Jupiter. These two (very bright!) planets will be extremely close together at dawn, about 1/3rd of a degree apart. Look for the bright pairing in the Eastern sky as it starts to get light in the morning.
Annoyingly, There’s some horseshit conspiracy theory doing the rounds that Earth will experience 15 days of darkness due to the conjunction of Jupiter and Venus today. Now, let’s take 30 seconds to examine why this is an utter crock of shit.
First off, in order for the Earth to experience total darkness, something has to get between it and the sun. This occasionally happens in the form of a solar eclipse (as the entire population of the United States can testify). As the entire population of the United States may also testify, totality doesn’t last that long – only a couple of minutes, tops, due to the Moon’s orbital velocity. 15 days is right out.
The conspiracy theory also states that it’s due to the conjunction of Venus and Jupiter. Yes, they will appear near to each other in the sky, but that doesn’t actually mean they are. Jupiter is behind Venus by quite a long way – as in, on the other side of the solar system, on the other side of the asteroid belt where it belongs. It’s just a trick of geometry that makes them look close in the sky.
So, what about putting those planets in front of the sun. That’ll make everything go dark, right? I mean, it worked for the moon? In order to block the sun, Venus has to go in front of it. So far, so obvious.
Do you remember those days in June 2004 and 2012 when the sky went as sackcloth when Venus blocked the sun?
Of course you don’t, it didn’t happen.
Venus transited the Sun, of course. That did happen. However, as it only blocked 0.0074% of the Sun’s rays, you didn’t notice unless you knew about it in advance and were actively looking for it. (The maths is exceedingly simple for that calculation: (R_p/R_*)^2, where R_p is the radius of the planet and R_* is the radius of the star in question, all squared). Yes, it occasionally gets between us and the Sun, but the Moon is so much closer, which is why it makes such a difference. It is literally like this:
A transit of Venus takes about three hours, and the next one isn’t due until Dec 2117, by the way. So we’re still a long way from our 15 days of darkness bullshit scenario. However, just for fun, let’s put Jupiter between us and the Sun, just for giggles. The maths is:
(R_v + R_j/R_*)^2
Where R_v and R_j are the radius of Venus and Jupiter respectively. Here we’re doing a little better, the sun’s brightness would dim by 1.2%, but that’s still not enough. More concerning is the fact that Jupiter is at least 416.4 million miles away from where it’s supposed to be, on the other side of the asteroid belt where is belongs. Go home Jupiter, you’re drunk.
Long story short, if anyone wishes to disagree in the comments, this will not happen. And I’m angry people make this shit up. And if you do disagree in the comments, then you are automatically agreeing to a wager with me that it will. I bet you £1,000,000 this will not happen. I’ll collect my winnings in December, thanks.
17-18 Nov – Anyway, back to business. Didn’t catch the Taurids? Stupid full moon wash them out? Don’t worry, the Lost Astronomer has got you covered! In a two for the price of one offer, tonight you get to see the Leonids meteor shower, which peak at a rate of one every three minutes or so. Unlike last time, there’s a new moon, so it’s inky dark skies which will allow even the faintest meteorite to show up. Again, find yourself a lawnchair, a blanket and a thermos, sit back and enjoy the dusty leavings of comet Tempel-Tuttle. What the night sky lacks in stupid romantic full moons it more than makes up for with epic meteorites, so, you know, that’s way cooler.
18 Nov – New Moon . Now is the best time to take advantage of the nights drawing in and commit wanton acts of astronomy.
22 Nov – Mercury at greatest brightness.
24 Nov – Mercury at greatest Eastern Elongation, or, in other words, now is the best time to find the reclusive innermost planet. Because Mercury is so close to the sun, it makes spotting it rather difficult for large periods of its 88 day orbit – for a lot of the time, it’s either in front of, behind, or just to the side of the sun as you look at it.
Alright, I shouldn’t actually have to say this, but don’t actually go and look at the Sun.
It’s going around in an elliptical orbit, which means for certain periods –
Oh, you know what? There’s an easier way for me to describe this. Go find yourself a CD. Once you’ve got one, stick left index fingers through the hole, and hold it up so it’s at eye level, shiny side facing the roof. You should be looking at the edge. Now, imagine the finger going through the hole in the middle is the sun. Next, run your right index finger around the edge. This is Mercury going around its orbit, which it does every 88 days. If your index fingers line up so they’re one in front of the other, Mercury is invisible – either because it’s behind the sun, or because it’s in front of it and your left index finger (the sun) is so bright you can’t see it. Go about quarter way around the CD and nothing should be in line, which is when you can see Mercury because it’s furthest away from being directly behind or in front of the sun, which is what is happening today.
So… Why can’t you see it during the day, even though nothing is lined up?
Same reason you can’t see the stars or any of the other planets – the Sun is just too damn bright. What we need is for the Sun to be hidden, but for Mercury to be visible.
Still got your fingers stuck in that CD? Lie your head on the table on your side, so your point of view is as close to the tabletop as possible. Now hold the CD so it’s still edge on, shiny side facing the wall, and slowly lower it so you can’t see your left index finger, but can still see a bit of CD. This is the sun setting beneath the table horizon. Spin your right index finger around the edge until you can see it – there we go, Mercury is visible, but the Sun is not, and if anybody comes into the room whilst you’re doing this and asks them what you’re doing look them square in the eye and tell them that you’re comprehending the orbital mechanics of the inferior planets before going back to spinning your fingers around a CD with your head lying on a table. Stick your tongue out in concentration for extra effect.
Oh, yeah, I should say that if you want to actually see Mercury for real, go out at dusk and it’ll be the bright point on the Western horizon after the sun sets. A good pair of binoculars ought to bring it right out.
28 Nov – Saturn and Mercury are pretty close, but don’t expect to see anything, as they’ll be really close to the horizon at sunset.
Anyway, that’s all for this month – go out, have fun, and keep looking up!