Northern Lights over the UK — 27 February 2014

Last night, following a coronal mass ejection impact, the auroral oval shifted south enough for the Northern Lights to be visible from southern England. Having watched the POES plot get angrier and angrier during the course of the early evening and with the IMF stubbornly south, I decided to jump in my car and drive out of Bristol.

I headed a little way east, to avoid an oncoming cloud front, and found a place to park just northeast of the Bath junction of the M4. As I got out of the car it was clear there was a diffuse glow hugging the northern horizon and every now and then I saw a faint ray appear above it and then dissolve away. No colour was visible to the naked eye though. Thinking (and hoping!) this might be an aurora, and not a trick of the distant light pollution, I set up my DSLR camera and opened the shutter for 20 seconds.

The following images are what I recorded over about ten minutes, after which the sky hazed up considerably and I decided to go home.

Please note that all the images are copyrighted. Clicking on the image will take you to a larger version.






The asteroid with a surprising tale

With the Geminid meteor shower reaching its peak this weekend – as the Earth passes through the debris trail left by the asteroid Phaethon – here’s an interview I did at EPSC 2013 with Professor David Jewitt about his discovery of the rocky body’s unusual behaviour.

(3200) Phaethon is responsible for the Geminid meteor shower (illustration). Credit: Will Gater

What prompted you to study Phaethon?

We were interested in the Geminid meteoroid stream and where the Geminid meteors come from. When the parent of the Geminid meteors, (3200) Phaethon, was discovered and found to be an asteroid it was interesting to ask why would an asteroid produce dust particles. Phaethon was identified in 1983, but until recently it showed no evidence of any strange behaviour. It just looked like an asteroid, which it is, but it didn’t seem to produce any material or show any obvious mechanism for producing dust. The breakthrough was to use a solar telescope [STEREO] to look at it when it’s near the Sun, when it’s very very hot, instead of using a big night-time telescope when you tend to look away from the Sun. And apparently Phaethon is active when it’s near to the Sun but not far away from it.

Artist’s impression of one of the STEREO spacecraft. Credit: NASA/Goddard Space Flight Center Conceptual Image Lab

So these were relatively recent observations?

Yeah, they were taken with a couple of spacecraft [STEREO A and B] that look at the Sun all the time. Phaethon just happens to pass through their fields of view. It’s been doing that for some years, but we just started to look at the data recently and we found this kind of interesting result. We took the individual images from STEREO and we shifted them and added them together, basically to build up the signal to noise and to make a kind of super image with all of the motion removed. Then we could see the elongation [of the tail] pretty clearly.

And that tail only emerges around the time when Phaethon is close to the Sun?

Yeah, when Phaethon is at its closest to the Sun – 0.14AU, so it’s really close.

Phaethon’s elongated tail appears in the processed STEREO images. Credit: Jewitt, Li, Agarwal/NASA/STEREO

Is the tail material that you’ve detected around Phaethon responsible for the Geminid meteors?

The particles that we see are small and we can tell that because they are pushed very strongly by radiation pressure from the Sun. Radiation pressure is very weak but it can accelerate these dust particles strongly. That’s only possible if they are really tiny, like a thousandth of a millimetre. But the rocks that make the meteors that you can see at night time are more like a millimetre in size so they are individually much bigger than the ones that we see. But on the other hand it’s quite possible, in fact likely, that they are there [in Phaethon’s tail]. You have a distribution of particles sizes – lots and lots of little tiny ones and not so many big ones. The big ones cause the meteors but if you’re just looking at reflected light it comes mostly from the small ones. So we naturally detect the small ones.

So in amongst the small particles you’ve seen there must be bigger ones?

Right, and so the issue is can we go the next step which is to find those bigger guys and prove that those are the Geminid meteoroids being produced now. That would answer the question “is Phaethon still producing the Geminid meteoroids?” Or was there some historical event that was like an impulsive explosion of stuff that came out and that made this ring of debris that the Earth goes through every year. Or is it an active process and this body is continuing to decay.

How can we see those larger particles?

We can’t see them with the solar observing spacecraft, we’ll have to use night time telescopes. We have to see Phaethon in a dark sky and try to see these comparatively rare big particles just by looking very carefully at night time with some big telescope somewhere.

What’s the mechanism releasing the small particles?

We think they’re just being fractured off the surface because the surface is so hot. If you take a rock and heat it up it’s going to expand; a typical rock is made of little grains of different minerals and they’ll all expand at slightly different rates. So if you just heat up a rock it will tend to fracture itself because one part is going to expand more than the other. And when it fractures some of the energy of the expansion goes into the kinetic energy of the fragments. So we think they’re almost like popcorn, bursting on the surface of the object and popping off. And as soon as they leap off the surface then this weak pressure from sunlight can blow them away into a tail.

How long is the tail?

The piece that we see is 350,000km long and it appears in one day. So it goes from nothing to 350,000km in one day. To get up to that speed in such a short time you need a big acceleration. And that’s how we infer the particle size – they have to be small and light to be accelerated quickly to go into the tail.

How hot does Phaethon get when it’s close to the Sun?

At midday on the surface of Phaethon with the Sun directly overhead you have the peak temperature, which is about 1000K [over 700°C]. We know that if you take rocks that we find on the Earth and heat them up to those same temperatures they do crack. Some rocks contain water and they dry out, shrink and crack at temperatures even lower than that.

And that’s hot enough to rule out water-ice helping form the tail?

Yeah. There’s no way to keep water ice at the surface – it sublimates so quickly.

Finally, you’ve also ruled out the tail being a sodium tail. Why’s that?

Well if you look at comets, there are some that go close to the Sun. Some of those comets show a sodium tail. The sodium seems to come from rocks; it is boiled out and gets blown away, making a distinct sodium tail. So I thought maybe that could be the case also for Phaethon. But, in fact, it can’t be because we have a filter on the camera that excludes light from sodium so we couldn’t, even if it were there, see it.

You can read the paper announcing the discovery of Phaethon’s tail here:

The Perseids pack a punch thanks to clear skies

The skies were mostly clear in southern England for the peak of the Perseid meteor shower last night. Here are a few pictures that I captured of the display from the countryside to the east of Bristol.

Perseid fireball_12-13 08 2013webA brilliant Perseid fireball streaks across the sky. Credit: Will Gater

fireball_animation_smallThe same fireball image as above animated together with the previous and following frame to show the presence of a ‘persistent train’. Credit: Will Gater

Perseid 12-13 08 2013webA faint Perseid (top right), the Andromeda Galaxy and Double Cluster. Credit: Will Gater

Perseid fireball_dew_12-13 08 2013webA spectacular Perseid fireball captured with a lens covered in dew! Credit: Will Gater

Perseid_12-13 08 2013_croppedA Perseid meteor falls through the constellations of Pegasus & Aquarius. Credit: Will Gater

Sporadic meteor 13082013Not a Perseid! A short sporadic meteor points the way (sort of) to M31. Credit: Will Gater

Summer stargazing on Dartmoor

Despite the short nights, and often poor weather, the summer night skies offer some spectacular celestial sights. My favourite areas to observe at this time of year are the rich swathes of the Milky Way in Cygnus, Sagittarius and Scutum. These regions are packed with dense starfields, glowing emission nebulae and some of the night sky’s finest star clusters.

On Saturday I spent the evening on Dartmoor imaging these wonderful parts of the sky. I wanted to capture a large portion of them in each frame, so I used a 50mm prime lens on my unmodified Canon 550D DSLR, which itself was mounted on an HEQ5 Pro mount.

The first image below shows part of the Sagittarius, Scutum & Serpens region. Several Messier objects are visible in the frame, including: M8 (the Lagoon Nebula), M20 (the Trifid Nebula), M22, M17, M16 (The Eagle Nebula) and M24. The second shot shows a region of the Milky Way in the constellation of Cygnus. The red glow of the North America Nebula (NGC 7000) and the nebulosity around the star Sadr (right of centre) are apparent. You can also, just, make out the two main fragments of the Veil Nebula right on the very bottom edge of the frame. The shot with the silhouetted tree is a single 15-second exposure, at ISO 1600, with the lens wide open at f/1.8.

Dust lanes weave through the Sagittarius, Scutum & Serpens region. Credit: Will Gater

The Milky Way near the bright star Deneb (top) in Cygnus. Credit: Will Gater

A lone Dartmoor tree stands silhouetted against the summer Milky Way. Credit: Will Gater

Envisioning the Universe at the National Maritime Museum

I’ll be speaking at the National Maritime Museum, in London, this coming Sunday as part of an event called ‘Envisioning the Universe’. The day will consist of talks, debates and discussions about the science and art of astrophotography. My fellow panellists include 2012 Turner Prize winner Elizabeth Price, author Elizabeth Kessler and Guardian art writer Jonathan Jones.

For more information and to book tickets visit the National Maritime Museum website here.

Image credit: NASA, ESA and the Hubble SM4 ERO Team

The Story of a Shooting Star – filming begins!

Over the last 12 months I’ve been working, in my spare time, on a short film about meteors. Called The Story of a Shooting Star it “follows the journey of a tiny grain of space dust, tracing its origins all the way back to the birth of the Solar System before exploring its final fleeting moments blazing across the night sky as a meteor”. Having spent a while scriptwriting and researching I recently started filming for the project.

In May I spent a fascinating day at the Norman Lockyer Observatory, in Devon, with the Solar, Planetary & Meteor group there learning about radio meteor detection. And this past weekend I filmed in the stunning surroundings of Dartmoor National Park. I’ll be posting occasional updates on the film (and hopefully some short clips too) here, but for now here are some pictures from the first few days of location shooting.

The Norman Lockyer Observatory on day one of filming. Credit: Will Gater

It might not look like much, but this antenna can detect meteors. Credit: Will Gater

Ping! A meteor is detected vaporizing high up in our atmosphere. Credit: Will Gater

Twilight on Dartmoor, a truly stunning sight. Credit: Will Gater

Some serious peering going on in this shot. Credit: Will Gater

New article – “Light Revolution” – in Sky at Night Magazine

lightrevolutionopenerOpener image for my latest piece in Sky at Night Magazine. Credit: Sky at Night Magazine

I have a new feature in the latest issue of Sky at Night Magazine all about light pollution and what the future might hold for our view of the night sky. Specifically, the piece explores recent changes in lighting practices and the rise of LED street lighting technology. You’ll find the article, called ‘Light revolution’, on pages 40-46 of the April issue, which is on sale now.

Comet C/2011 L4 (PANSTARRS) & the dark skies of Galloway Forest Park

IMG_2757edited_blogThe night skies over the rural cottage where we stayed. Credit: Will Gater

I’ve just spent the last week staying very near to Galloway Forest Park, along with my wife and a few of our friends. I’ve been meaning to visit the forest ever since it was declared the UK’s first International Dark Sky Park back in 2009. The night skies were truly incredible and we were lucky enough to have 4.5 clear nights out of seven. I’ve put together a series of photographs below that show the astronomical highlights of our trip, including several sightings of Comet C/2011 L4 (PANSTARRS). If you’d like to find out more about Galloway Forest Park’s dark skies check out this page.

KirroughtreesignThe Kirroughtree Visitor Centre is the site of a dark sky viewing area. Credit: Will Gater

M42_10032012_flatThe Orion & Running Man Nebulae, imaged from just outside the forest. Credit: Will Gater

CometPANSTARRS_11032013_settingOur first glimpse of C/2011 L4 (PANSTARRS) on 11/03/13. Can you spot it? Credit: Will Gater

Orion Trees Galloway ForestOn Monday night we ventured into the forest to see the dark skies there. Credit: Will Gater

ZodiacalLight ClatteringshawsLoch_March2013The zodiacal light was clear to see from near Clatteringshaws Loch. Credit: Will Gater

Leo_Trees_GallowayForestThe trees in the forest appear to stretch toward the constellation of Leo. Credit: Will Gater

Orion et al ClatteringshawsLoch_March2013Orion, Jupiter & the Hyades and Pleiades over Clatteringshaws Loch. Credit: Will Gater

MilkyWay_Trees_GallowayForestThe Milky Way peeking through the trees was an unforgettable sight. Credit: Will Gater

CometPANSTARRS_13032013_sunsetComet C/2011 L4 (PANSTARRS) was much easier to spot on 13/03/13. Credit: Will Gater

CometPANSTARRS_13032013_croppedMuch of the time watching the comet was spent waiting for cloud gaps. Credit: Will Gater

CometPANSTARRS_13032013_setting_croppedComet C/2011 L4 (PANSTARRS) over the hills of Galloway Forest Park. Credit: Will Gater

Earthshine_13032013The Earthshine-lit Moon, taken shortly after Comet PANSTARRS had set. Credit: Will Gater

Earthshine_13032013_wideClouds move past the Earthshine-lit Moon later on in the evening. Credit: Will Gater

LEDstreetlightA modern LED streetlight in the town of New Galloway. Credit: Will Gater

NewGallowayStreetlightingVery little light shines out the sides of the lights (great for astronomy). Credit: Will Gater

CometPANSTARRS_15032013_croppedOn our last night (15/03/2013) we spotted C/2011 L4 again… Credit: Will Gater

CometPANSTARRS_15032013_setting…but it soon set behind the distant hills. Credit: Will Gater

Live astrophotography from the Brecon Beacons

One Show presenter Lucy Siegle talks to Will live from the Brecon Beacons. Credit: BBC

I had great fun on Wednesday night in the Brecon Beacons filming a series of live segments about astrophotography for the BBC’s The One Show. The idea behind the evening was that I would help a group of twenty amateur photographers take their first images of the night sky before judging which was the best shot. When we arrived at the filming location the sky was filled with clouds, but as the Sun set the clouds thankfully dissipated and the photographers managed to capture their pictures (even despite some quite substantial haze).

If you missed the programme, and are in the UK, you’ve got a few days left to catch it on the BBC’s iPlayer; the astrophotography bits can be found here, here and here. And if you’ve captured an astro image lately that you’re particularly pleased with, don’t forget to send it into the 2013 Astronomy Photographer of the Year competition, which is now open for entries.

Marvelling at the mountains on the Moon

Over the last few nights we’ve had some clear skies and good seeing conditions here in the southwest of the UK. On Monday night I spent 3 hours capturing a 50 pane mosaic of the whole of the visible portion of the Moon while last night I decided to focus on the wonderfully rugged region around the lunar Alps and the crater Plato.

Both images are shown below – do click on them to see the full size versions, especially the whole-phase mosaic. They were captured with a Meade 8-inch LX200R Schmidt-Cassegrain telescope and an Imaging Source DMK21AU618.AS CCD camera; the Plato/lunar Alps image is a mosaic of 17 panes made using an additional 2x Barlow lens.

50 pane mosaic of the Moon on 18 February 2013. Credit: Will Gater

Crater Plato and the lunar Alps on 19 February 2013. Credit: Will Gater