The Scruffy Astronomer

Just a brief one today. Gratulerer med dagen, alle sammen! Idag er det syttende mai - dvs Grunnlovsdag i Norge! Yes, it's Constitution Day in Norway today. Norway adopted its constitution on this day in 1814. On that day the country separated from Denmark. It wasn't a complete victory though, because at the same time Norway was ceded to Sweden. This was part of Denmark's punishment for backing the wrong side in the Napoleonic wars. Norway didn't finally became independent until 1905, when they proudly erased the Swedish flag from their own. Maybe I'm a bit of a Nordophile, but today is also a good opportunity to segue into auroras and the solar cycle. Yes, the Sun is waking up after its mid-cycle nap. Just the other day some weak Auroras appeared and were photographed from Victoria. That's pretty good by Southern Hemisphere standards. Normally they're only seen from the southernmost parts of Tasmania. Auroras are caused by charged par...

Bolides, or fireballs, are brightly burning meteors that have entered the Earth's atmosphere. Most small meteors burn up inside the atmosphere, and occasionally they bounce off the upper atmosphere before moving away from the Earth again. These provide spectacular but harmless light shows. Sometimes, however, they cause havoc on the ground. The Chelyabinsk Event in February 2013 was an explosion caused by a meteor about 20m across entering the atmosphere. The explosion released about the same energy as the Hiroshima bomb. Damage was widespread, and several fragments were recovered. Recovered fragments of meteorites are of significant interest to scientists, of course. But how do you find them? The International Meteor Organisation records meteors and bolides reported by citizen scientists. These include visual records, mostly from all-sky cameras, and the occasional sound recording. Scientists can use these to estimate the meteor's trajectory when it entere...

It's lockdown in Melbourne (still) and I'm looking for something to point a telescope at. I've sworn off deep sky targets for the time being, as the light pollution in the city here makes anything I produce - even narrowband - look blah in comparison to images taken from the dark sky site. I've also been taking photos of planets, but I left the Celestron 8 at work. Besides, (and I might be getting a little controversial now) there's a difference between nebulas and planets. Once you've taken a great image of a planet (not that I have yet) it gets a bit repetitive. There's not that many of them (sorry, Pluto). But wait - there's the sun! I pulled out my trusty solar telescope, a Coronado PST. This type of solar telescope doesn't work in the same way as a solar film filter. A solar film is an example of a neutral density filter, which turns down all the colours (frequencies) of light to more or less the same extent.  A solar telescope cuts out all ...

The other night was the first night in weeks where it wasn't cloudy. Of course, there was a mad scramble when Melbourne-based astrophotographers were all running outside to take photos. Naturally, I was one of them. We couldn't run far though. The Melbourne Coronavirus lockdown prevented anyone from leaving their homes. On the night in question, the Moon was about three quarters full (waxing gibbous, if you're into that sort of thing), and not far from Jupiter and Saturn. Mars was up later. The Helix Nebula was around half way between Saturn. and Mars, and the Sculptor Galaxy followed. But imaging under moonlight is challenging, especially if you're after deep-sky targets like nebulas or galaxies. Moonlight washes out the really faint light from these targets, meaning the signal (nebula light) to noise (moonlight) ratio is really low. You can drag out these details using many subexposures, or use light pollution or narrowband filters, but at best you'll get an image...

Fragile, ethereal and mysterious, they're being seen more in the last couple of decades. Could these wraiths be a portent of doom? Image of Noctilucent clouds over Uppsala, Sweden : Wikipedia Noctilucent clouds are thin, filament-shaped clouds that form in deep twilight. They look very beautiful, light against a deep blue background. But, yes, it looks like they have a dark side. They form in the coldest parts of the atmosphere, at an altitude of about 83,000 metres called the mesopause where the temperature is around -140°C. They're normally restricted to a circular area around the North pole, specifically between 55 and 65 degrees. What's more, they tend to happen only in Summer. They have been seen in the south, but very rarely. They were first reported in the late 1880s. Probably because this was soon after the eruption of Krakatoa, it was initially thought they were associated with volcanic activity, or with dust injected into the upper atmosphere by meteors. But ther...

Do you suffer from pareidolia? Nearly everyone sees objects in clouds. Some people see faces in toast. My wife says that, as a child, she used to see teddy bears' faces in knot patterns in her bedroom's wood panelling. Your brain is very good at making out objects in backgrounds, even when the object isn't actually there. It doesn't have to be images that our brains try to make sense of. Norwegian farmers feared the Fossegrime, a spirit that lived in waterfalls, luring people through sound. In the white noise coming from rushing water, our brains can nearly make out speech. Victims of the Fossegrime, looking for the source, would come nearer and nearer the dangerous waters, eventually to be taken by the malevolent spirit. The Moon is a fertile source of pareidolic images. A while back I wrote a piece on the "Lunar X" , as well as a few other features. Certainly, everyone has heard of the man in the Moon. That image doesn't stand out quite so much here in ...

Dimming update? Back at the end of December, I posted that the red supergiant Betelgeuse, in the constellation of Orion, was dimming visibly . It used to be one of the brightest stars in the sky, and now it’s not even in the top 20. Yes, it’s less than half as bright as it was just over a year ago. Red supergiant stars such as Betelgeuse normally end their lives in supernovas, which would be seriously cool to see. We’d be quite safe here, at a good enough distance, but we’d be able to see the explosion as it happened during the day, and it’d be months before it dimmed. There are other possible explanations for what we’re seeing. One theory that might be quite feasible is that a large and dense gas cloud has passed in front of the star. This sort of thing does happen, and would explain the phenomenon quite well. Since the star’s dimming has been in the news, more and more people have been watching it. Most recent reports suggest that the rate at which it’s dimming...

In January last year I wrote about Fast Radio Bursts, or FRBs. Now, there's an intriguing update. An FRB is a sudden flash of radio energy from … somewhere way, way out there, beyond our galaxy. They’re a little like a tame version of a Gamma Ray Burst, which is a slightly scary thing I wrote about a little more recently. FRBs are rare, and when I last wrote about them, they seemed random, with only two locations known to have produced more than one. Also, last time I wrote, I mentioned the new CHIME radio telescope in Canada, which was able to search large swaths of sky for these phenomena. Awesome image: CHIME   Well, the update is that CHIME (Canadian Hydrogen Intensity Mapping Experiment if you’re interested) is operational, and has been discovering FRBs hand over fist, including something really weird. One of the places we've detected FRBs, a galaxy about 500 million light years away, seems to be on a repeating cycle, of a bit over 16 days. For four days, the ...

But is it an existential threat? If you’re the anxious type, maybe you’re best not reading this… Image: NASA One of my favourite podcasters is John Green, who is known for his anxieties. He’s able to list and discuss the top 10 existential threats for humans. The other day he talked about one I hadn’t heard of before. A Gamma Ray Burst is (we think) the biggest bang in the universe. It takes the form of a focused blast of gamma rays, which are especially high energy particles. Humans only discovered GRBs when the US launched a satellite in the 1960s to monitor for Soviet nuclear tests. There are two types of GRB, neither one of which you’d like to be near, and both of which result in the creation of a black hole. The collapse of a huge star during a supernova can cause a “long” burst, of “up to a minute”. In this minute, the energy blasted into space is – get this – roughly the same as the energy our sun gives off in its entire lifetime . In January last year, NASA detected a ...

Here in Oz, especially at this time of year, seeing conditions can really be degraded by the atmosphere. Heat haze can play havoc with your images, especially if you’re using an autoguider. Most recently, bushfire smoke has been awful, and the effect has been similar to very severe light pollution, with an orange or brown cast over colour photos. But Ian lives in Saskatchewan, which is in the Western part of Canada. It’s cold there. According to Ian, it was -16°C at the time. Yikes. Low temperatures can bring about beautiful viewing conditions, but they can have other unexpected side effects. This photo shows one of them.   Ian uses an ASI 1600 attached to a William Optics Z71 on a Sky-Watcher AZ-EQ6 (stop drooling, Bill!). While he was imaging the Jellyfish nebula, some approaching snow clouds caused changes in temperature and humidity, and these beauties appeared. They’re called light pillars. Ice crystals form in a large range of shapes. In the right conditions, they form in ...

This was originally five separate Facebook posts. It's been republished by the Astronomical Society of Victoria and in a couple of other places as well. Although I think it was originally a pile of notes that got saved after my university course in History and Philosophy of Science from the mid 1980s. 1: Introduction 4 October 2019 What happens when objective observation comes up against hubris? Hubris wins. At first. I'm going to spin out a yarn. It's quite a good one, about how humans figured out how the planets move through the sky. It also shows a lot about how humans began asking the big questions: of "what?" and more importantly "why?" That humans ask themselves these questions about pretty much everything is, I think, the thing that sets us apart. That these questions are unanswerable doesn't matter - it's a goal that drives our understanding, not only of astronomy, but in fields as diverse as psychology and economics. But it...

A couple of years ago, a mate and I went out on a birding trip. We were after Bustards (we probably dipped - long story) and Red-lored Whistlers (we didn't dip). For an overnight stop, we camped at Broken Bucket Tank. This is on the Murrayville Track, about an hour out of Nhill, getting into the Big Desert. Getting up in the morning, we noticed this fog bow.  A fog bow happens when light from the sun (behind us) encounters fog, which is, of course, tiny water droplets hanging in the atmosphere. The effect is nearly - but not quite - the same as a rainbow. Like for the rainbow, light hitting the spherical water droplets gets refracted on entry to the water, reflected at the back of the droplet, and then refracted again on the way out of the droplet. (See a diagram here .) The angle the light gets reflected back at determines the apparent size of the bow. Where it's different is that fog droplets are way smaller than raindrops. At this size, diffraction starts to become i...

6 May 2019 Because I'm both a birder (who likes to take photos) and an astrophotographer, I'm always keeping an eye on the clouds. The other day I was walking the dog in the local park. It was humid and threatening to rain, and the clouds were fairly dramatic, as the picture shows. There was a thin band of dark, mid-level cloud starting to form ahead of a rain band, but above that was a large gap, with much higher cloud behind it. But there was a stripe across the sky, which was dark in the middle with light edges. What was it, and what caused it? It was an aeroplane approaching Tullamarine. It had been flying in the clear area between the two cloud layers and was just descending into the thin lower layer. My guess is that the plane's wings were pushing the air immediately below it downwards into the clear air below, while vortices at the end of the plane's wings were pushing the air there upwards into the layer above. The band of cloud must have been pretty thi...

24 April 2019 Occultation of Propus ( η Geminorum), 11 April 2019, 21:32 (ACST)   This was a totally unexpected happening. Dean and I had made camp at Acraman Bore (with the permission of the station manager, of course). We were relaxing after dinner, and watching The Emu come out to our south. I was using my binoculars to wander around the sky when I noticed the Moon was especially close to a reasonably bright star. Were we were going to see an occultation? An occultation is when the Moon moves in front of a star. It actually happens all the time, but it's hard to see unless it's a bright star, as the Moon blots out everything around it. But usefully, when the Moon is a crescent, it has dimly lit side. This dim light is reflected off the Earth, and you can see stars right up to this side. Interestingly, this means that occultations normally only happen in the week or more prior to the full moon, as during this time the Moon appears to move towards its dim side. After t...

1 February 2019 The Earth's poles are shifting! Are we all doomed? Probably not. One of the things the Earth has always had is a magnetic field. It's mostly caused by the molten core inside the Earth and how it swirls about deep underground. It protects us from solar radiation, produces the most awesome auroras, and it might help migratory birds know what direction to go. It also helps us navigate using magnetic compasses. This includes using a compass to align an equatorial mount (see my blog ). The magnetic field generated by the Earth isn't fixed, but wanders around slowly as the swirls in the Earth's core change their behaviour from year to year. However, in the last few years, there's been a noticeable increase in its rate of change. So what's going to happen? It's hard to say. Because the poles are wandering randomly about, rather than going in a consistent direction, it's difficult to predict what's going to happen. But, becaus...

30 January 2019 A planet-sized game of pool? It reminds me of Red Dwarf episode, but that's how Earth got a lot of its elements. I was talking with a customer the other day about water on Earth. We both found it mind-boggling that most of our water came from space in the form of harmless comet collisions. The majority of comets are cricket-ball sized "dirty snowballs". When they hit our atmosphere they turn to steam, and fall as rain. But what about the other stuff? Over 4 billion years back, our newly-formed Sun was creating a giant disc of dust and garbage gathered from previous supernovas in the area. Astronomers call this a proto-planetary disc. They've seen it happening around other new stars as well well - this photo is from a system called HL Tauri. In this disc, elements were gathering in bands at different distances from the centre. It's really an astronomical-sized centrifuge. As planets formed in the disc, they started off with just the elemen...

28 January 2019 FRBs... WTF? A fast radio burst (FRB) is just that - a single huge blast of radio energy that lasts only a few milliseconds and then stops. It's the radio version of a cosmic camera flash. What's more, there are only two sources that are known to have flashed twice. All other recorded events seem to be random. The amount of energy contained in a single FRB would power our sun for about 80 years. That'd expose a lot of film. The one thing we are really sure about is that they come from well outside our galaxy. But as to what causes them, we really only have theories. Astronomers have speculated that they might be caused by collisions of black holes or neutron stars, or that they might be linked with gamma ray bursts (look these up - these nasties are an actual existential threat to the Earth!). Of course, astronomers haven't been able to rule out artificial sources either. Alien selfies? Canada has just finished building a new type of ra...

24 December 2019 Rainbows happen when the white light from the Sun is refracted by raindrops in the air, a bit like the triangular prism on the front of the Dark Side of the Moon album. But what happens if the sun is very close to setting, and the dust and atmosphere has blocked out all the blue end of the spectrum, giving the red colour of a sunset? Well, this happens. The light that does hit the raindrops gets refracted, but there's no green or blue in the rainbow.   In telescopes and binoculars, this refraction is undesirable, and called chromatic aberration. Doublet and triplet refractor telescopes have specially designed lenses that counter this.