Tag Archives: astronomy

My new adventure – astro-photography

Southern CrossI’ve always been fascinated by the stars. All those suns out there, all those galaxies, all that distance. When I was a young person growing up in Perth the street lights were turned off at 1am. Frugal city fathers. Besides, who’d need street lights at that hour? In fact, they famously left the lights ON one night, so John Glenn could see the city as he whizzed over in his space craft in 1962. Read all about it here.

But that was just one night. Normally blackness would descend and the Milky Way would sparkle overhead, a veritable river of stars. Apart from street lights after 1am, it was also true that few of us had air conditioners. So when the temperatures soared in summer, and you couldn’t sleep from the heat, people ventured outside to enjoy the cool of the night. Relatively speaking, you understand. My sister and I indulged in star gazing using binoculars. To keep them steady we tied them to a cake rack, which we tied to a step ladder. And with that contraption we saw the Pleiades – many more than 7 sisters. Gazed at the Orion nebula and its trapezium of stars, marvelled at the Jewel Box in the Southern Cross. And so on. I started learning what I could about astronomy – not the hard stuff with equations, just the things I could understand, like the life cycle of stars, the different types of stars and their properties, the Doppler effect, galaxies… And I bought a telescope, a three inch refractor.

That was a long time ago. But I still love the stars and now I’ve ventured into the world of astro-photography. I want to take magnificent pictures of the Milky Way sprawled across the sky above the Outback or the sea. And maybe some of the horse head nebula in Orion. Or the Jewel Box. Or a galaxy or two. Yes, I have a new telescope.

But for now, that one at top left is the Southern Cross from my front yard. And this one is the sky facing north from my house. Orion is in the middle. You can see Rigel, Betelgeuse, Sirius, Taurus with its principle star Aldebaran, and beneath that the open cluster of the Pleiades. It’s a bit over exposed, but it’s early days. Watch this space. They were taken with my Canon 5D with a Rokinon 14mm lens at 2.8

Oh, by the way, my latest Dryden Universe story, The Eye of the Mother, is coming along. There’s stars in that, too.

Orion etc

Wishing and hoping doesn’t make it real

Credits: NASA/JPL-Caltech/T. Pyle

Credits: NASA/JPL-Caltech/T. Pyle

Look, I’m a space nut. It says so on the header up there. So when NASA announced the discovery of “Earth 2.0” I was as excited as the next space nut.

But let’s put this into context, people. What do we really KNOW about this planet, as FACT?

  • It’s in the constellation of Cygnus, 1,400 light years from Earth.
  • It orbits a star slightly larger than our sun, but of the same solar type.
  • The planet has an orbit of 385 Earth days.
  • It’s slightly larger than Earth.

And that’s it.

Let’s face it folks, astronomers have done a LOT of conjecturing on what amounts to a slight dip in the brightness of the star as the planet passes across its face. Science Alert has a rather good article about the discovery, with a little less hype.

We don’t know how long its day is. We don’t know the composition of its atmosphere. We might think it’s rocky but we can’t be certain. We certainly can’t suggest for a moment that its surface looks like the wonderful artist’s impression at top left. We should remember that Mars and Venus are in our sun’s habitable zone. Venus, in particular, could be seen as Earth’s twin – from a distance.

That said, (and to quote Captain Piett) it’s the best lead we’ve had. He was promoted to Admiral not long after that. Maybe we should send a star fleet to check Kepler 452b out. Maybe we’ll meet some Klingons.

 

 

A little bit of moonshine in the night

A lunar eclipse happened in my part of the world on 28th November, hard on the cosmic heels of a solar eclipse earlier in the month. As it turned out, the penumbral eclipse was a huge disappointment. No shadow across the moon’s disc, not even a reddening of the light. So the cirrus cloud partially obscuring the view didn’t matter much. We had moonshine as we always do and the photos were a fizz.

However, it got me to wondering about moons; ours, and other moons in general. To start with, let’s mention the eclipse – the truly spectacular solar eclipse that happened earlier this month. It was a partial eclipse in my part of the world, but even so it is a special event. But why is it so? The moon is tiny compared to the sun.

An extraordinary cosmic coincidence

The sun is about 400 times the moon’s diameter and about 400 times as far way from the Earth and that ratio means that when the moon comes between the sun and the Earth, that shadow is just about a perfect fit.  That relationship is a coincidence. Evidence indicates that the Moon was once closer to the Earth and is gradually moving away, so enjoy your cosmic moment, knowing that in the distant future, there will be no total solar eclipse.

That factoid is not the only extraordinary thing about our moon. Not at all.

It’s not the largest moon in the solar system. In fact, going by this list it comes a creditable fifth after Ganymede (Jupiter iii), Titan (Saturn vi), Callisto (Jupiter iv) and IO (Jupiter i). Indeed, Ganymede and Titan are both larger than Mercury and let’s not talk about poor Pluto. Really, when you think about it, it makes perfect sense that the largest planets have collected the largest moons.

Except ours.

Why is this so?

I have in my possession a tattered little paperback, a collection of essays on astronomy by Isaac Asimov (Asimov on Astronomy, Coronet, 1974). One of the things I loved about Asimov, who had a PhD in chemistry and an interest in everything scientific, was that he could explain complex physics in a way that an interested amateur with absolutely zippo mathematical ability could understand. He wrote papers regularly for magazines and the like and subsequently, they were published in book form. This little volume is a treasure trove of scientific fact and some intriguing speculations. True, some of it is now dated, since it was published before the epic discoveries of Voyagers I and II. Pluto had not yet been demoted. And yet before it could be proved he predicted that many planets other than Saturn would have rings.

To get back to the point, one of these essays is entitled “Just Mooning Around” in which Asimov talks about the gravitational effects of the sun, the planets and the moons in the solar system have on each other. Without going into all the details of the paper, he talks about the ‘tug of war’  ratio, which argues that in most cases, the gravitational attraction of a planet on its moons is vastly greater than the pull of the sun on those same moons. There is also a kind of ‘goldilocks’ zone around a planet in which a true moon would exist (as opposed to loosely captured satellites like Neptune’s Nereid). A moon must be between a minimum Roche limit and a maximum ‘tug of war’ distance. For the mind-bending number-crunching, go read it yourself – I told you I can’t do maths. However, I can appreciate logic. And you will see it is so.

According to his theory, of the four innermost rocky planets, Mercury could not have a moon because it has no ‘goldilocks’ zone. The other three are highly unlikely to have moons because of the narrowness of the ‘goldilocks’ zone. And indeed, Mercury and Venus do not have satellites, and Mars’s Phobos and Demos are overlarge potatoes which are expected to disintegrate.

I see you jumping up and down. What about us? Earth and that thing up there?

Ah, Asimov argues that the Earth/Moon pair is not a true planet/moon relationship because the Moon is so much larger in comparison with its primary than any other such relationship in the solar system. By a long way. He suggests that the Earth/Moon combo is really a binary planet, waltzing its way around the sun. Of course, all planets with moons have a wobble in their orbit but the Earth/Moon shimmy must be quite pronounced. Certainly I don’t think there’s much disagreement these days that our Moon was derived from the same stuff as the Earth. This article suggests accepted theory is that a Mars-sized object collided with the Earth, aggregating the material and spewing off a portion which later formed the Moon.

The next thing you have to wonder is – how important is that massive moon to life on Earth? But that’s another topic, isn’t it?

Isn’t science wonderful?