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Wednesday, 12 July 2017

Sound in Space: The drumbeats of pulsars

The Allen Antenna array.

The stars are beautiful, or at least very sparkly. But most people will tell you they're not much to listen to - after all, in space no-one can here you scream, so how would you hear the stars? But there are signals out there - radio wavelength signals - that we can listen to with the right equipment.

So, if you wore radio dishes on your ears, what would you hear?*

Not a peaceful sky, or even a snatch of Beethoven. No, you'd hear a Milky Way echoing to the buzzing, humming, and drumming sounds of pulsars. These are incredibly dense objects, forged from the collapsing cores of supernova - and spun up to incredible speeds by them. Never more than twenty kilometres across, a new born pulsar can spin hundreds times a second. They give out intense beams of radiation, including radio waves, so as they spin radio antenna on Earth hear the click of the beam briefly sweeping over us.

There are old, slow ones that drum like a runners footsteps...

... and there are fast young ones that swarm in star clusters like 47 Tucanae, filling the sky with a whine like the universe's most terrifying cloud of mosquitoes...

But a universe full of strange knocking and humming sounds isn't the odd bit. The odd bit is that you can buy an album of music made using them.

*Given my knowledge of fashion this could actually be a thing for all I know

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Friday, 7 July 2017

The Universe in 101 words: Why should we return to Enceladus?

Above: The dwarf planet Ceres, which is suspected of having once held an underground ocean. Um. It doesn't really turn back and forth in that way
Our solar system is, well, awash with ocean worlds. And, thanks to the Cassini mission, we've gotten to know one really well: Enceladus, 500km wide moon of Saturn.

So what's it like?

Dark - the ocean's covered in 20Km of ice - but maybe not totally black: There's volcanic activity on the ocean floor, like the white smoker vents of earth, so there'd be the dim  glow of volcanism. More importantly the salty, alkaline, water contains organic chemicals and hydrogen - food for possible micro-life.

Cassini's mission is nearly over - but it's now hard to imagine us not returning to Enceladus....

Tuesday, 4 July 2017

Sound in Space: The noise of interstellar space

It may be true that in space no-one can hear you scream, but you can hear some far stranger things out there.

The recording above was taken by the Voyager 1space probe, as it left our solar system - it's of waves with the same frequency as sound, but it's not sound as we know it. Where regular sound is a vibration in a gas, solid or liquid, these sounds are vibrations in the ultra thin soup of ions, called plasma, that fills space. Far too faint for any human sense to detect, Voyager had been listening to vibrations like these for decades. But this set was different - their pitch was suddenly a lot higher. That meant the density of the plasma they travelled through had changed dramatically in a short space of time - one of the markers for the boundary with interstellar space.

So the weird little vibrations are literally the sound of Voyager going where no-one had been before...

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