Astronomy

The Whirlpool Galaxy (M51)

/ Stephen Mackintosh / 1 Comment

They say good things come to those who wait.  Never  was this more exemplified than this evening after several hours in bitterly cold conditions on Culloden moor with my video telescope.  The cold made setup and targeting much more fraught than usual, and the small gas stove I’d balanced pecariously beside the monitor did little to help.

However, near the end of my session I hit the jackpot when this stunning image of the Whirlpool galaxy, over 23 million light years away,  materialised from the video screen.

Whirlpool galaxy

This image is a true testament to the power of video astronomy and the huge increase in aperture it lends to amature telescopes.  Dust lanes and connective spiral arms are clearly in evidence here.  The best naked eye views of the Whirlpool I’ve seen have only really resolved the two central cores of the interacting galaxies.  You generally need a scope of 16 inches or more to reveal dust tendrils in this much detail.

This is how the Earl of Rosse sketched the galaxy back in 1845 with his monstrous 72 inch dobsonian from the grounds of Birr Castle in Ireland.

M51Sketch

Of course back then these structures were given the loose classification of ‘nebulae’ and were assumed part of our local galaxy.  It wasn’t until the 1920s when Edwin Hubble observed cepheid variable stars within each bright core of the Whirlpool that this image was understood to be two distinct but interacting galaxies, the larger of which has been estimated to be 35% the size of our own Milky Way galaxy.

M51 is still a hot target for professional astronomers, not least because of the black hole that exists within the heart of the larger galaxy.  This central region is undergoing rapid stellar changes and star formation.

Venus

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Venus has been a constant jewel in the evening sky recently, popping into view during twilight in the south west and burning with an astonishing intensity in the western skies after darkness.

I’ve been taking my telescope out a few evenings in a row to view the planet from kerb side and marvelled at how well resolved it is at high power.  It’s a half crescent right now, revealing a lovely hazy terminator where Venusian day meets night.  Eager to record its majesty,  I trained my video setup on it this evening, using leg stabilisers and a barrow to maximise the surface area per pixel captured on my Samsung’s CCD chip.  Here’s what I captured.

The visual scale of Venus is impressive here compared to general viewing with eyepiece observation.  This is one of the advantages of having a smaller CCD sensor.  Whilst more limited for large deep sky objects (without focal reduction) it permits big and bold presentations of the planets with just a modest x2 barlow lens.

Notice the pronounced atmospheric haze and refraction of light at the terminator between day and night.  Venus has a thick cloud covered atmosphere which is highly reflective – giving the planet its bright white appearance.  There’s also the slightest hint of mottling or streaking on the surface.  These fine streaks are large cloud structures that ebb and flow slowly within the Venusian atmosphere.

Not so long ago Venus was the target for many pulpy science fiction stories.  These authors imagined the planet full of swamps with dinosaurs and primitive tribes battling across vast continents.  These fantasies were shot down after robotic probe and satellite recognisance of the planet was undertaken, first by the Soviets and later NASA.

Our current understanding of Venus is that it’s a planetary embodiment of hell.  An atmosphere of nearly 96% carbon dioxide traps heat from the sun, raising the pressure to 92 times that of earth, with surface temperatures approaching those inside the finest Italian pizza ovens.  This pizza analogy would apply to any human making it all the way down to the surface of Venus!