Posted on by Steve Nerlich

Astronomy Without A Telescope – Let’s Go Around The Room

My dog keeps me in touch with the universe. There are important reasons why he has to go out into the backyard about 9pm and then again around 5.00am – and at both times there are stars out. He has this very particular sound, the canine equivalent of ahem, to let me know it’s time.

Around February is great because on the night shift you see Orion and on the morning shift you see Scorpio. These are two of three constellations, I can easily identify without a book – the other one being the Southern Cross. And this is the only time of the year when I get to see all three, since by the time Scorpio is up in the evenings around August, Orion is already lost to the glare of daytime.

This reminds me of a plan I have to once and for all explain to people how the night sky works. You wallpaper a room with your equatorial and/or ecliptic constellations and on the roof put your circumpolar constellations, which would include the Southern Cross down here or Ursa Minor for your northern folk. Then in the middle of the room you put a big and glaringly bright light.

So around February, you are in that part of the room where when you face away from the light you can see Orion. Then spinning on the spot, you’ll be able to spy Scorpio just before you come around to face the bright light, which prevents you from seeing what’s on the other side of the room. Keep spinning and you come back to night time and admire Orion again – and so on.

Cool wallpaper - the Pleiades, Hyades and Orion as seen from the southern hemisphere

To progress through the year you have to start walking around the room, that is orbiting the bright light – and you can keep spinning on the spot for the day night effect if you like. Once you are around on the other side of the room – you get a much better night-long view of Scorpio, while Orion is lost behind the bright light. Your circumpolar constellations are still visible on the ceiling – but kind of upside down now.

It’s taken a few nights out with the dog to figure out which way you are supposed to spin – not to mention which way to put the wallpaper since if your at my latitude in the north, you’ll need to hang it upside down. For me, if I’m standing in front of Orion, Scorpio is going to be around to my right (but left for you) – and I’m going to orbit to my right (but left for you) – and I’m going to spin clockwise (but anti-clockwise for you).

I almost have it all visualized when there’s certain ahem as dog realizes master is staring vacantly at the sky again. Oh yeah sorry, good dog – and we go back inside.

Posted on by Steve Nerlich

The View from Down Under

Something that baffled me throughout my childhood, growing up in Australia, was the frequent references to the Man in the Moon, in children’s books and other popular media. I just couldn’t see it.

Only in my adult years have I put two and two together and realized that all those references were made by people from the Northern Hemisphere.

South of the equator we really are down under, even in astronomical terms. All the stuff you can see in the night sky around the celestial equator and the ecliptic we can see too, but it’s all upside down (or from our point of view, right side up).

So the lunar maria you see on the Moon’s surface, we can see too, but upside down none of it looks anything like a human face.

And Orion’s Belt? Nope, don’t get that either. obeltconstWhat we see is an asterism we like to call ‘the Saucepan’ because what you see as a dagger hanging off a belt, we see as a handle rising from a pot.

We’ve also got our own down under Aurora Australis, although you’d have to105412main_High_res_jan05 climb a mountain in Tasmania, or even better catch an icebreaker to Antarctica, to see it.

But look, I’m envious. You’ve got a pole star, Polaris, which we never get to see. And you get a good view of the Andromeda Galaxy, which just barely peeks over our northern horizon around summer.

Down under, we have to use the Southern Cross to find the southern celestial pole. The Cross contains some of the southern sky’s brightest stars. During the winter months when it’s high in the sky, it’s generally the first group of stars to become visible after sunset, along with the nearby Pointer stars – which are actually Alpha and Beta Centauri.

The Southern Cross is kite-shaped and if you draw a line out from the kite’s long axis and another line out from between the Pointers, those two lines meet at the southern celestial pole. From there, just drop your hand straight down to the horizon and you are pointing due South. Cheaper than a compass.south

We also have a couple of dwarf galaxies to look at, being the Large and Small Magellanic Clouds. OK, they are much smaller than Andromeda, but they are also a lot closer and hence appear much bigger. To the naked eye, they really do look like a couple of faint, wispy clouds.

For most southern sky observers, the Magellanic Clouds and the Southern Cross are circumpolar, slowly spinning around the southern celestial pole each night without ever setting.

You probably know that the story about how water spirals down the plug hole in opposite directions on either side of the equator is just urban myth. But it is the case that while stars in the Northern Hemisphere appear to spin slowly around Polaris in an anti-clockwise direction, all our stars spin around the southern celestial pole in a clockwise direction.

It’s true – fair dinkum.