The best meteor showers are a spectacular sight but, unfortunately, 2021 starts with a whimper. Moonlight this January will wash out the first of the big three — the Quadrantids (seen above in 2020).
In addition to the year’s other reliable performers we’ve included one wild card: the Aurigids, in late August. Most years, the Aurigids are a very, very minor shower, but they just might put on a show this year.
So here is our pick of the meteoric highlights for 2021.
For each meteor shower, we give you a finder chart showing the radiant (where the meteors appear to come from in the sky) and where best to look in the sky, the full period of activity and the forecast peak. Most meteor showers typically only yield their best rates for about a day around maximum, so the peak night is definitely the best to observe.
The Zenithal Hourly Rate ZHR is the maximum number of meteors you would expect to see under perfect observing conditions. The actual number you will see will likely be lower.
Most meteor showers can only really be observed from either the northern [N] or southern [S] hemisphere, but a few are visible from both [N/S].
The Lyrids are one of the meteor showers with the longest and most storied histories, with recorded observations spanning millenia. In the past, they were one of the year’s most active showers, with a history of producing spectacular meteor storms.
Nowadays, the Lyrids are more sedate, putting on a reliable show without matching the year’s stronger showers. They still throw up occasional surprises such as an outburst in excess of 90 meteors per hour in 1982.
This year’s peak Lyrid rates coincide with the first quarter Moon, which will set around midnight, local time, for most locations. The best time to observe will come in the early hours of the morning, after moonset.
For observers in the northern hemisphere, the Lyrid radiant will already be at a useful altitude by the time the Moon is low in the sky, so some brighter meteors might be visible despite the moonlight in the late evening (after around 10:30pm, local time).
Once the Moon sets the sky will darken and make the shower much easier to observe, yielding markedly higher rates.
For observers in the southern hemisphere, the Lyrid radiant reaches a useful altitude in the early hours of the morning, when the Moon will have set. If you’re a keen meteor observer, it could be worth setting your alarm early to get out and watch the show for a few hours before dawn.
Lyrid meteors are fast and often quite bright so can be rewarding to observe, despite the relatively low rates (one every five or ten minutes, or so). Remember, this shower always has the potential to throw up an unexpected surprise.
The Eta Aquariids are an autumn treat for southern hemisphere observers. While not one of the big three, they stand clear as the best of the rest of the annual showers, yielding a fine display in the two or three hours before dawn.
The Eta Aquariids are fast meteors and are often bright, with smoky trains. They are fragments of the most famous comet, 1P/Halley, which has been laying down debris around its current orbit of the Sun for tens of thousands of years.
Earth passes through that debris twice a year, with the Eta Aquariids the best of the two meteor showers that result. The other is the Orionids, in October.
Where most meteor showers have a relatively short, sharp peak, the Eta Aquariids remain close to their best for a whole week, centred on the maximum. Good rates (ZHR > 30 per hour) should be visible before sunrise on each morning between May 3–10.
The Moon will be a waning crescent when the Eta Aquariids are at their best. Its glare should not interfere badly with the shower, washing out only the faintest members.
Observers who brave the pre-dawn hours to observe the Eta Aquariids will have the chance to lie beneath a spectacular sky. The Milky Way will be high overhead, with Jupiter, Saturn and the Moon high to the east and bright, fast meteors streaking across the sky from an origin near the eastern horizon.
The Perseids are the meteoric highlight of the northern summer and the most observed shower of the year. December’s Geminids offer better rates but the timing of the Perseid peak makes them an ideal holiday treat.
The Perseids are debris shed behind by comet 109P/Swift-Tuttle, which is the largest known object (diameter around 26km) whose orbit currently intersects that of Earth.
Perseid meteors are fast, crashing into Earth at a speed of about 216,000km/h, and often bright. While the shower is active, at low levels, for more than a month, the best rates are typically visible for at the three nights centred on the peak.
For observers at European latitudes, the Perseid radiant rises by mid-evening, so the shower can be easily observed from 10pm local time, and remains high all through the night. The later in the night you look, the higher the radiant will be and the more meteors you’re likely to see.
Where the other showers are reliable and relatively predictable, offering good rates every year, the Aurigids are an entirely different beast.
In most years, the shower is barely visible. Even at its peak, rates rarely exceed just a couple of meteors seen per hour. But occasionally the Aurigids bring a surprise with short and unexpected outbursts of 30-50 meteors an hour seen in 1935, 1986, 1994 and 2019.
The parent comet of the Aurigids, C/1911 N1 Kiess, moves on an orbit with a period far longer than the parent of any other shower on our list.
It is thought the orbit takes between 1,800 and 2,000 years to complete, although our knowledge of it is very limited as it was only observed for a short period of time.
In late August every year, Earth passes through debris shed by the comet at a previous passage thousands of years into the past. In most years, the dust we encounter is very sparse.
But occasionally we intersect a denser, narrow stream of debris, material laid down at the comet’s previous passage. That dust has not yet had time to disperse so is more densely packed and hence gives enhanced rates: a meteor outburst.
Several independent research teams studying the past behaviour of the shower have all come to the same conclusion. On August 31, 2021, the Earth will once again intersect that narrow band of debris and an outburst may occur, with predictions it will peak around 21:17 UTC or 21:35 UTC.
Such an outburst would be short-lived. The dense core of the debris stream is so narrow it will take the Earth just ten or 20 minutes to traverse. So you’ll have to be lucky to see it.
The forecast outburst this year is timed such that observers in Eastern Europe and Asia will be the fortunate ones, with the radiant above the horizon. The waning Moon will light the sky when the radiant is above the horizon, washing out the fainter meteors from the shower.
The Aurigids tend to be fast and are often quite bright. Previous outbursts of the shower have featured large numbers of bright meteors. It may just be worth getting up and heading outside at the time of the predicted outburst, just in case the Aurigids give us a show to remember.
The Geminid meteor shower is truly a case of saving the best until last. By far the best of the annual meteor showers, it graces our skies every December, yielding good numbers of spectacular, bright meteors.
The shower is so good it is always worth observing, even in 2021, when the Moon will be almost full.
Over the decades, the Geminids have gradually become stronger and stronger. They took the crown of the year’s best shower from the Perseids in the 1990s, and have continued to improve ever since.
For observers in the northern hemisphere, the Geminids are visible from relatively early in the evening, with their radiant rising shortly after sunset, and remaining above the horizon for all of the hours of darkness.
As the night progresses, the radiant gets very high in the sky and the shower can put on a truly spectacular show.
For those in the southern hemisphere, the situation is not quite as ideal. The further south you live, the later the radiant will rise, and so the later the show will begin.
When the radiant reaches its highest point in the sky (around 2am–3am local time), it sits closer to the horizon the further south you are, so the best meteor rates you observe will be reduced compared to those seen from more northerly locations.
Despite these apparent drawbacks, the Geminids are still by far the best meteor shower of the year for observers in Australia, and are well worth a look, even on the moonlit nights of 2021.
Peak Geminid rates last for around 24 hours, centred on the official peak time, before falling away relatively rapidly thereafter. This means that observers around the globe can enjoy the display.
The best rates come when the radiant is highest in the sky (around 2–3am) but it is well worth looking up at any time after the radiant has risen above the horizon.
So wherever you are on the planet, if skies are clear for the peak of the Geminids, it is well worth going outside and looking up, to revel in the beauty of the greatest of the annual meteor showers.
In September 2019, my colleague Anna Kapinska gave a presentation showing interesting objects she’d found while browsing our new radio astronomical data. She had started noticing very weird shapes she couldn’t fit easily to any known type of object.
Among them, labelled by Anna as WTF?, was a picture of a ghostly circle of radio emission, hanging out in space like a cosmic smoke-ring. None of us had ever seen anything like it before, and we had no idea what it was. A few days later, our colleague Emil Lenc found a second one, even more spooky than Anna’s.
Anna and Emil had been examining the new images from our pilot observations for the Evolutionary Map of the Universe (EMU) project, made with CSIRO’s revolutionary new Australian Square Kilometre Array Pathfinder (ASKAP) telescope.
EMU plans to boldly probe parts of the Universe where no telescope has gone before. It can do so because ASKAP can survey large swathes of the sky very quickly, probing to a depth previously only reached in tiny areas of sky, and being especially sensitive to faint, diffuse objects like these.
I predicted a couple of years ago this exploration of the unknown would probably make unexpected discoveries, which I called WTFs. But none of us expected to discover something so unexpected, so quickly. Because of the enormous data volumes, I expected the discoveries would be made using machine learning. But these discoveries were made with good old-fashioned eyeballing.
Our team searched the rest of the data by eye, and we found a few more of the mysterious round blobs. We dubbed them ORCs, which stands for “odd radio circles”. But the big question, of course, is: “what are they?”
At first we suspected an imaging artefact, perhaps generated by a software error. But we soon confirmed they are real, using other radio telescopes. We still have no idea how big or far away they are. They could be objects in our galaxy, perhaps a few light-years across, or they could be far away in the Universe and maybe millions of light years across.
When we look in images taken with optical telescopes at the position of ORCs, we see nothing. The rings of radio emission are probably caused by clouds of electrons, but why don’t we see anything in visible wavelengths of light? We don’t know, but finding a puzzle like this is the dream of every astronomer.
We have ruled out several possibilities for what ORCs might be.
Could they be supernova remnants, the clouds of debris left behind when a star in our galaxy explodes? No. They are far from most of the stars in the Milky Way and there are too many of them.
Could they be the rings of radio emission sometimes seen in galaxies undergoing intense bursts of star formation? Again, no. We don’t see any underlying galaxy that would be hosting the star formation.
Could they be the giant lobes of radio emission we see in radio galaxies, caused by jets of electrons squirting out from the environs of a supermassive black hole? Not likely, because the ORCs are very distinctly circular, unlike the tangled clouds we see in radio galaxies.
Could they be Einstein rings, in which radio waves from a distant galaxy are being bent into a circle by the gravitational field of a cluster of galaxies? Still no. ORCs are too symmetrical, and we don’t see a cluster at their centre.
In our paper about ORCs, which is forthcoming in the Publications of the Astronomical Society of Australia, we run through all the possibilities and conclude these enigmatic blobs don’t look like anything we already know about.
So we need to explore things that might exist but haven’t yet been observed, such as a vast shockwave from some explosion in a distant galaxy. Such explosions may have something to do with fast radio bursts, or the neutron star and black hole collisions that generate gravitational waves.
Or perhaps they are something else entirely. Two Russian scientists have even suggested ORCs might be the “throats” of wormholes in spacetime.
From the handful we’ve found so far, we estimate there are about 1,000 ORCs in the sky. My colleague Bärbel Koribalski notes the search is now on, with telescopes around the world, to find more ORCs and understand their cause.
It’s a tricky job, because ORCS are very faint and difficult to find. Our team is brainstorming all these ideas and more, hoping for the eureka moment when one of us, or perhaps someone else, suddenly has the flash of inspiration that solves the puzzle.
It’s an exciting time for us. Most astronomical research is aimed at refining our knowledge of the Universe, or testing theories. Very rarely do we get the challenge of stumbling across a new type of object which nobody has seen before, and trying to figure out what it is.
Is it a completely new phenomenon, or something we already know about but viewed in a weird way? And if it really is completely new, how does that change our understanding of the Universe? Watch this space!
Astronomers have mapped about a million previously undiscovered galaxies beyond the Milky Way, in the most detailed survey of the southern sky ever carried out using radio waves.
While past surveys have taken years to complete, ASKAP’s RACS survey was conducted in less than two weeks — smashing previous records for speed. Data gathered have produced images five times more sensitive and twice as detailed as previous ones.
Modern astronomy is a multi-wavelength enterprise. What do we mean by this?
Well, most objects in the universe (including humans) emit radiation over a broad spectrum, called the electromagnetic spectrum. This includes both visible and invisible light such as X-rays, ultraviolet light, infrared light and radio waves.
To understand the universe, we need to observe the entire electromagnetic spectrum as each wavelength carries different information.
Radio waves have the longest wavelength of all forms of light. They allow us to study some of the most extreme environments in the universe, from cold clouds of gas to supermassive black holes.
Long wavelengths pass through clouds, dust and the atmosphere with ease, but need to be received with large antennas. Australia’s wide open (but relatively low-altitude) spaces are the perfect place to build large radio telescopes.
We have some of the most spectacular views of the centre of the Milky Way from our position in the Southern Hemisphere. Indigenous astronomers have appreciated this benefit for millennia.
Radio astronomy is a relatively new field of research, dating back to the 1930s.
The first detailed 30cm radio map of the southern sky — which includes everything a telescope can see from its location in the Southern Hemisphere — was Sydney University’s Molonglo Sky Survey. Completed in 2006, this survey took almost a decade to observe 25% of the entire sky and produce final data products.
Our team at CSIRO’s Astronomy and Space Science division has smashed this record by surveying 83% of the sky in just ten days.
With the RACS survey we produced 903 images, each requiring 15 minutes of exposure time. We then combined these into one map covering the entire area.
The resulting panorama of the radio sky will look surprisingly familiar to anyone who has looked up at the night sky themselves. In our photos, however, nearly all the bright points are entire galaxies, rather than individual stars.
Take our virtual tour below.
Astronomers working on the catalogue have identified about three million galaxies — considerably more than the 260,000 galaxies identified during the Molonglo Sky Survey.
We know how important maps are on Earth. They provide crucial navigational assistance and offer information about terrain which is useful for land management.
Similarly, maps of the sky provide astronomers with important context for research and statistical power. They can tell us how certain galaxies behave, such as whether they exist in clusters of companions or drift through space on their own.
Being able to conduct an all-sky survey in less than two weeks opens numerous opportunities for research.
For example, little is known about how the radio sky changes over timescales of days to months. We can now regularly revisit each of the three million galaxies identified in the RACS catalogue to track any differences.
Also, some of the largest unanswered questions in astronomy relate to how galaxies became the elliptical, spiral, or irregular shapes we see. A popular theory suggests large galaxies grow via the merger of many smaller ones.
But the details of this process are elusive and difficult to reconcile with simulations. Understanding the 13 billion or so years of our universe’s cosmic history requires a telescope that can see across vast distances and accurately map everything it finds.
The CSIRO’s RACS survey is an amazing advance made possible by huge leaps in space tech. The ASKAP radio telescope, which became fully operational in February last year, was designed for speed.
CSIRO’s engineers developed innovative radio receivers called “phased array feeds” and high-speed digital signal processors specifically for ASKAP. It’s these technologies that provide ASKAP’s wide field of view and rapid surveying capability.
Over the next few years, ASKAP is expected to conduct even more sensitive surveys in different wavelength bands.
In the meantime, the RACS survey catalogue is greatly improving our knowledge of the radio sky. It’ll continue to be a key resource for researchers around the world.
Full resolution images can be downloaded from the ASKAP data archive.
Astronomers know all too well how precious and unique the environment of our planet is. Yet the size of our carbon footprint might surprise you.
Our study, released today in Nature Astronomy, estimated the field produces 25,000 tonnes of carbon dioxide-equivalent emissions per year in Australia. With fewer than 700 active researchers nationwide (including PhD students), this translates to 37 tonnes per astronomer per year.
As a point of reference, the average Australian adult was responsible for 26 tonnes of emissions in 2019, total. That means the job of being an astronomer is 40% more carbon-intensive than the average Australian’s job and home life combined.
While we often defer to governments for climate policy, our global carbon footprint can be dramatically reduced if every industry promotes strategies to reduce their own footprint. For individual industries to make progress, they must first recognise just how much they contribute to the climate emergency.
We found 60% of astronomy’s carbon footprint comes from supercomputing. Astronomers rely on supercomputers to not only process the many terabytes of data they collect from observatories everyday, but also test their theories of how the Universe formed with simulations.
Frequent flying has historically been par for the course for astronomers too, be it for conference attendance or on-site observatory visits all around the world. Prior to COVID-19, six tonnes of annual emissions from flights were attributed to the average astronomer.
An estimated five tonnes of additional emissions per astronomer are produced in powering observatories every year. Astronomical facilities tend to be remote, to escape the bright lights and radio signals from populous areas.
Others, like the Murchison Radio-astronomy Observatory in Western Australia, need to be powered by generators on site. Solar panels currently provide around 15% of the energy needs at the Murchison Radio-astronomy Observatory, but diesel is still used for the bulk of the energy demands.
Finally, the powering of office spaces accounts for three tonnes of emissions per person per year. This contribution is relatively small, but still non-negligible.
Australia has an embarrassing record of per-capita emissions. At almost four times the global average, Australia ranks in the top three OECD countries for the highest per-capita emissions. The problem at large is Australia’s archaic reliance on fossil fuels.
A study at the Max Planck Institute for Astronomy in Germany found the emissions of the average astronomer there to be less than half that in Australia.
The difference lies in the amount of renewable energy available in Germany versus Australia. The carbon emissions produced for each kilowatt-hour of electricity consumed at the German institute is less than a third pulled from the grid in Australia, on average.
The challenge astronomers in Australia face in reducing their carbon footprint is the same challenge all Australian residents face. For the country to claim any semblance of environmental sustainability, a swift and decisive transition to renewable energy is needed.
A lack of coordinated action at a national level means organisations, individuals, and professions need to take emissions reduction into their own hands.
For astronomers, private arrangements for supercomputing centres, observatories, and universities to purchase dedicated wind and/or solar energy must be a top priority. Astronomers do not control the organisations that make these decisions, but we are not powerless to effect influence.
CSIRO expects the increasing fraction of on-site renewables at the Murchison Radio-astronomy Observatory has the potential to save 2,000 tonnes of emissions per year from diesel combustion. And most major universities in Australia have released plans to become carbon-neutral this decade.
As COVID-19 halted travel worldwide, meetings have transitioned to virtual platforms. Virtual conferences have a relatively minute carbon footprint, are cheaper, and have the potential to be more inclusive for those who lack the means to travel. Despite its challenges, COVID-19 has taught us we can dramatically reduce our flying. We must commit this lesson to memory.
And it’s encouraging to see the global community banding together. Last year, 11,000 scientists from 153 countries signed a scientific paper, warning of a global climate emergency.
As astronomers, we have now identified the significant size of our footprint, and where it comes from. Positive change is possible; the challenge simply needs to be tackled head-on.
Humans have long been inspired and transfixed by the Moon, and as we’re discovering, moonlight can also change the behaviour of Australian wildlife.
A collection of recently published research has illuminated how certain behaviours of animals – including potoroos, wallabies and quolls – change with variation in ambient light, phases of the Moon and cloud cover.
How big is the Moon? Let me compare …
One study found small mammals were more active on cloudy nights. Another found variation in moonlight led to differing amounts of species captured in non-lethal traps. And a study on willie wagtails found males just love singing on a full moon.
These findings are interesting from a natural history perspective. But they’ll also help ecologists and conservation scientists better locate and study nocturnal animals, and learn how artificial light pollution is likely changing where animals can live and how they behave.
Most of Australia’s mammals are nocturnal, and some smaller species are thought to use the cover of darkness to avoid the attention of hungry predators. However, there’s much we don’t know about such relationships, especially because it can be difficult to study these interactions in the wild.
In the relatively diverse mammal community at Mt Rothwell, Victoria, we examined how variation in ambient light affected species’ activity, and how this might influence species interactions. Mt Rothwell is a fenced conservation reserve free of feral cats and foxes, and with minimal light pollution.
Over two years, we surveyed the responses of predator and prey species to different light levels from full, half and new moon phases.
Potential prey species in our study included eastern barred and southern brown bandicoots, long-nosed potoroos, brushtailed rock-wallabies, and brushtail and common ringtail possums. Eastern and spotted-tailed quolls are their potential predators.
Just as we predicted, we found that while there does appear to be relationships between cloud cover, Moon phase and mammal activity, these interactions depend on the sizes and types of mammals involved.
Both predators and prey generally increased their activity in darker conditions.
Smaller, prey species increased their activity when cloud cover was higher, and predators increased their activity during the half and new moon phases.
This suggests their deadly game of hide and seek might intensify on darker nights. And prey might have to trade off foraging time to reduce their chances of becoming the evening meal.
It’s important to acknowledge that studies in sanctuaries such as Mt Rothwell might not always reflect well what goes on in the wild, including in areas where introduced predators, such as feral cats and red foxes, are found.
Another recent study, this time of small mammals in the wilds of Victoria’s Mallee region, sheds further light on the situation. The authors tested if variation in weather and Moon phase affected the numbers of five small mammal species – Bolam’s mouse, common dunnart, house mouse, southern ningaui, and western pygmy possum – captured in pitfall traps.
Pitfall traps are long fences small animals can’t climb over or through, so follow along the side until they fall into a bucket dug in the ground. Ecologists typically use these traps to capture and measure animals and then return them to the wild, unharmed.
At more than 260 sites and over more than 50,000 trap nights, they found wind speed, temperature and moonlight influenced which species were caught and in what numbers.
For example, captures of a small native rodent, Bolam’s mouse, and carnivorous marsupial, southern ningaui, decreased with more moonlight, whereas captures of pygmy possums were higher with more moonlight.
Research from last month has shown even species normally active by day may change their behaviour and activity by night.
It’s not uncommon to hear bird song by night, including the quintessentially Aussie warbling of magpies. Using bioacoustic recorders and song detection software, these researchers show the willie wagtail – another of Australia’s most recogisable and loved birds – is also a nighttime singer, particularly during the breeding season.
While both male and female wagtails sing by day, it is the males that are most vocal by night. And it seems the males aren’t afraid of a little stage-lighting either, singing more with increasing moonlight, with performances peaking during full moons.
This work provides insight into the importance and potential role of nocturnal song for birds, such as mate attraction or territory defence, and helps us to better understand these behaviours more generally.
These studies, and others, can help inform wildlife conservation, as practically speaking, ecological surveys must consider the relative brightness of nights during which work occurred.
Depending on when and where we venture out to collect information about species, and what methods we use (camera traps, spotlighting, and non-lethal trapping) we might have higher or lower chances of detecting certain species. And this might affect our insights into species and ecosystems, and how we manage them.
As dark skies become rarer in many places around the world, it also begs a big question. To what extent is all the artificial light pollution in our cities and peri-urban areas affecting wildlife and ecosystems?
Pipistrelle bats, for example, will be roughly half as active around well-lit bridges than unlit bridges. They’ll also keep further away from well-lit bridges, and fly faster when near them.
This means artificial light might reduce the amount and connectivity of habitat available to some bat species in urban areas. This, in turn could affect their populations.
Research is underway around the world, examining the conservation significance of such issues in more detail, but it’s another timely reminder of the profound ways in which we influence the environments we share with other species.
We would like to acknowledge Yvette Pauligk, who contributed to our published work at Mt Rothwell, and that the traditional custodians of this land are the Wathaurong people of the Kulin nation.
Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University; Courtney Marneweck, Postdoctoral Researcher in Carnivore Ecology, Clemson University , and Grant Linley, PhD Candidate, Charles Sturt University
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Are we headed for a period with lower Solar activity, i.e. sunspots? How long will it last? What happens to our world when global warming and the end of this period converge?
When climate change comes up in conversation, the question of a possible link with the Sun is often raised.
The Sun is a highly active and complicated body. Its behaviour does change over time and this can affect our climate. But these impacts are much smaller than those caused by our burning of fossil fuels and, crucially, they do not build up over time.
The main change in the Sun is an 11-year Solar cycle of high and low activity, which initially revealed itself in a count of sunspots.
Sunspots have been observed continuously since 1609, although their cyclical variation was not noticed until much later. At the peak of the cycle, about 0.1% more Solar energy reaches the Earth, which can increase global average temperatures by 0.05-0.1℃.
It’s smaller than other known sources of temperature variation, such as volcanoes (for example, the large eruption of Mt Pinatubo, in the Philippines in 1991, cooled Earth by up to 0.4℃ for several years) and the El Niño Southern Oscillation, which causes variations of up to 0.4℃.
And it’s small compared to human-induced global warming, which has been accumulating at 0.2℃ per decade since 1980.
Although each 11-year Solar cycle is different, and the processes underlying them are not fully understood, overall the cycle has been stable for hundreds of millions of years.
But the fall in Solar activity was too small to account for the temperature drop, which has since been attributed to volcanic eruptions.
Solar activity picked up during the 20th century, reaching a peak in the cycle that ran from 1954 to 1964, before falling away to a very weak cycle in 2009-19.
Bear in mind, though, that the climatic difference between a strong and a weak cycle is small.
Because changes in Solar activity are important to spacecraft and to radio communications, there is a Solar Cycle Prediction Panel who meet to pool the available evidence.
Experts there are currently predicting the next cycle, which will run to 2030, will be similar to the last one. Beyond that, they’re not saying.
If activity picks up again, and its peak happened to coincide with a strong El Niño, we could see a boost in temperatures of 0.3℃ for a year or two. That would be similar to what happened during the El Niño of 2016, which featured record air and sea temperatures, wildfires, rainfall events and bleaching of the Great Barrier Reef.
The extreme weather events of that year provided a glimpse into the future. They gave examples of what even average years will look like after another decade of steadily worsening global warming.
Solar physics is an active area of research. Apart from its importance to us, the Sun is a playground for the high-energy physics of plasmas governed by powerful magnetic, nuclear and fluid-dynamical forces.
The Solar cycle is driven by a dynamo coupling kinetic, magnetic and electrical energy.
Explainer: how does our sun shine?
That’s pretty hard to study in the lab, so research proceeds by a combination of observation, mathematical analysis and computer simulation.
Two spacecraft are currently directly observing the Sun: NASA’s Parker Solar Probe (which will eventually approach to just 5% of the Earth-Sun distance), and ESA’s Solar Orbiter, which is en route to observe the Sun’s poles.
Hopefully one day we will have a better picture of the processes involved in sunspots and the Solar cycle.
Is the sky blue on other planets, like on Earth? What is an atmosphere, and do other planets have one? – Charlie, age 10
G’day Charlie, and thank you so much for your incredibly curious question.
Before I get too excited talking about the atmospheres of other planets, first we have to talk about what an atmosphere actually is.
The atmosphere is normally the outermost layer of a planet. On rocky worlds like Earth it is usually the lightest and thinnest layer.
The thing that makes an atmosphere an atmosphere is what it’s made of. It’s not made up of big lumps of rocks or huge swirling oceans; it is made up of gases.
Atmospheres can contain a wide variety of gases. Most of Earth’s atmosphere is a gas called nitrogen that doesn’t really react with anything. There’s also a fair bit of oxygen, which is what we need to breathe. There are also two other important gases called argon and carbon dioxide, and tiny amounts of lots of other ones.
The mix of gases is what gives a planet’s atmosphere its colour.
Earth’s atmosphere is made up of gases that tend to bounce blue light in all directions (known as “scattering”) but let most other colours of light straight through. This scattered light is what gives Earth’s atmosphere its blue colour.
Do other planets have blue atmospheres? Some of them sure do!
The atmospheres of the two ice giants in our solar system, Neptune and Uranus, are both beautiful shades of blue.
However, these atmospheres are a different blue than ours. It’s caused by the huge amounts of a gas called methane swirling around.
(Side note: methane is also the main component of farts. That’s right, there’s a layer of farts on Uranus.)
Jupiter and Saturn, however, have completely different-coloured atmospheres.
Ice crystals made of a chemical called ammonia in Saturn’s upper atmosphere make it a pale shade of yellow.
Uranus’ atmosphere also contains some ammonia, which makes the planet a slightly greener shade than the deep blue we see on Neptune.
Jupiter’s atmosphere has distinctive brown and orange bands, thanks to gases that may contain the elements phosphorus and sulfur, and possibly even more complicated chemicals called hydrocarbons.**
In some extreme cases, the entire planet might just be a huge atmosphere with no rocky surface at all. Astronomers and planetary scientists like myself are still trying to work out whether Jupiter and Saturn have rocky surfaces, deep down in their atmosphere, or whether they’re both simply huge balls of gas.
However, there are some planets that have no atmosphere at all! The Sun’s closest and smallest neighbour, Mercury, is one example. Its surface is exposed to the vastness of space.
So far I’ve been talking about the atmospheres of planets in our Solar system. But what about planets in other planetary systems, orbiting other stars?
Well, astronomers have been detecting the atmospheres of these planets (which we call “exoplanets”) for the past 20 years! It wasn’t until last year, however, that astronomers managed to detect the atmosphere of a rocky exoplanet. The planet is called LHS 3844b and it’s so far away that the light takes almost 50 years to reach us!
LHS 3844b weighs twice as much as Earth, and we astronomers thought it would have a pretty thick atmosphere. But, to our surprise, it has little to no atmosphere at all! So it might be more like Mercury than Earth.
We still have a lot to learn about far-off planets and discovering one with an Earth-like atmosphere that’s ripe for life is still many years away.
Maybe, Charlie, you could be the first astronomer to detect an Earth-like atmosphere on another world!
Where 2019 was a disappointing year for meteor showers, with two of the big three (the Quadrantids, Perseids and Geminids) lost mainly to moonlight, 2020 promises to be much better.
The year starts with a bang with the Quadrantids providing a treat for northern hemisphere viewers. The Perseids, in August, provide another highlight for those in the northern hemisphere, while the December Geminids round the year off for observers all around the world.
But the big three aren’t the only meteor showers that will put on a show this year. So when should you look up to see the meteoric highlights of the coming year?
Here’s our pick of the showers to watch. We have the time each shower is forecast to peak, finder charts showing you where best to look, and the theoretical peak rates you could see under ideal observing conditions. This is a number known as the Zenithal Hourly Rate (ZHR).
Because the ZHR is the theoretical maximum rate you could see per hour, it is likely that the rates you observe will be lower.
For any meteor shower, if you want to give yourself the best chance to see a good display, it is worth trying to find a good dark site, as far from light polluted skies as possible. Once you’re outside give yourself plenty of time to adapt to the darkness, at least half an hour. Then just sit back, relax, and enjoy the show.
Showers that can only really be seen from either the northern or southern hemisphere are denoted by [N] or [S], whilst those that can be seen from both are marked by [N/S].
You can download a ICS file of this guide to add to your favourite calender.
The Quadrantids are the first of the big three meteor showers of the year – the three showers that give fabulous displays with ZHRs in excess of 100, year in, year out.
For most of the fortnight over which the Quadrantids are active, rates are low – just a few meteors per hour. In the hours approaching their peak, rates climb rapidly, before falling away just as rapidly once the peak is past. In total, rates exceed a quarter of their maximum value for just eight hours, centred on the peak.
The Quadrantid radiant is circumpolar (never sets) for locations north of 40 degrees north. As a result, the shower can be observed throughout the hours of darkness for most locations in Europe and many in North America.
The radiant rises highest in the sky in the early hours of the morning, so this is when the best rates can be seen. In 2020, the shower’s peak favours observers in the east of North America, though those in northern Europe should see a good display in the hours before dawn on the morning of January 4.
If skies are clear it is definitely worth wrapping up warm and heading out to observe the most elusive of the year’s big three.
The Lyrids are a shower with a long and storied history – with records reporting their activity tracing back for millennia. Researchers have even suggested the Lyrids may have been active on Earth for more than a million years.
In the distant past, there are reports the Lyrids produced some spectacular displays – meteor storms, with thousands of meteors visible per hour.
The modern Lyrids are usually more sedate, with peak rates rarely exceeding ~18 meteors per hour. But they do sometimes throw up the odd surprise. An outburst of the Lyrids in 1982 yielded rates of ~90 meteors per hour for a short period.
While no such outburst is forecast this year, the peak of the shower will occur just a day before a new Moon, so skies will be dark and viewing conditions ideal.
Although the Lyrids are best seen from the northern hemisphere, their radiant can reach a useful altitude for observers in the northern half of Australia. Keen observers might be tempted to head out in the early hours of the morning to watch.
The radiant rises during the night so the best rates are seen in the early hours of the morning, before dawn. From northern hemisphere sites, reasonable rates can be seen after about 10:30pm, local time -– but for those at southern hemisphere latitudes, the radiant fails to reach a reasonable altitude until well after midnight.
Lyrid meteors tend to be relatively fast and are often bright. Despite the relatively low rates (at least, compared to the big three) they are well worth a watch, especially as conditions this year will be as close to perfect as possible.
While not counted as one of the big three, in many ways the Eta Aquariids stand clear of the pack as the best of the rest.
Only really visible to observers in the tropics and the southern hemisphere, the Eta Aquariids are fragments of the most famous of comets –- Halley’s comet. They mark the first (and best) of two passages made by the Earth through the debris laid down by that comet over thousands of years –- with the other being the Orionids, in October.
The radiant only rises a few hours before dawn, even at southern altitudes, and the further north you go, the closer to sunrise the radiant appears. This is what prevents northern hemisphere observers from taking advantage of the Eta Aquariids –- the Sun has risen by the time the radiant is high enough for the shower to put on a decent show.
The meteors are fast and often bright, and the brighter ones have a reputation for leaving behind noticeable smoky trains. The maximum of the shower is broad, with rates remaining above ~30 meteors per hour for the week around the date of the maximum.
It is well worth getting out to observe the Eta Aquariids at around the time their radiant rises. This gives the maximum amount of time to observe the shower before dawn, but in addition, those few meteors you observe when the radiant is sitting just above the horizon can be spectacular.
Known as Earthgrazers, such meteors enter the atmosphere at a very shallow angle, with the result that they can streak all the way across the sky, from horizon to horizon.
The Eta Aquariids reach their peak in 2020 a couple of days before the full Moon. That the radiant does not rise until a few hours before sunrise works to our advantage this year –- the shower’s radiant will rise at around the same time the Moon sets, so the shower can be observed in Moon-free skies, despite the proximity of the Full Moon.
For northern hemisphere observers, the Perseids are perhaps the famous and reliable shower of the year.
While the Geminids offer higher rates, the Perseids fall during the middle of the northern summer, when families are often holidaying and the weather is warm and pleasant. As a result, the Perseids are the most widely observed of all meteor showers, and never fail to put on a spectacular show.
The parent comet of the Perseid meteor shower, 109P/Swift-Tuttle, was last at perihelion (closest to the Sun) in 1991. As a result, during the 1990s, the Perseids offered enhanced rates –- often displaying multiple peaks through the two or three days around their traditional maximum.
Those individual peaks were the result of the Earth passing through individual trails of material, laid down at past perihelion passages of the comet, which have not yet had time to fully disperse into the background of the shower as a whole.
It is now three decades since the comet’s last perihelion passage, but astronomers predict the Earth could well pass through one of those debris trails this year, at around 10am UTC (midnight Hawaii time, 3am Vancouver time), three hours before the normal forecast maximum for the shower.
As a result, peak rates should last for longer, and potentially reach higher values than would normally be expected from a typical Perseid return.
The radiant rises in the mid-evening from northern latitudes, which means the shower can be observed from around 10pm or 11pm, local time. The later in the night you look, the higher the radiant will be, and so the more meteors will be visible.
Unfortunately, the peak of the Perseids in 2020 falls two days after the last quarter Moon, which means moonlight will begin to interfere with the display in the early hours of the morning. The best views of the shower will likely be seen between ~10pm or 11pm local time and ~2am the following morning.
If you can only observe in the hours before dawn, all is not lost. The Perseids are famed for producing plenty of bright meteors. They are worth observing even when the Moon is above the horizon, particularly on the nights around the forecast peak.
The Orionid meteor shower marks the second occasion the Earth encounters the stream of debris left behind by Halley’s comet each year.
In October, Earth passes farther from the centre of Halley’s debris stream than in May, with the result the observed rates for the Orionids are lower than for the Eta Aquariids. Despite this, the Orionids remain a treat for meteor enthusiasts in the northern autumn and southern spring.
The Orionids peak on October 21 but that maximum is often quite broad with activity hovering close to the peak rates for as much as a week around the maximum.
There is some evidence the peak rates vary over time, with a roughly 12 year periodicity, as a result of perturbations by the giant planet Jupiter (which orbits the Sun once every 12 years).
In the final years of the first decade of the 21st Century, the Orionids were markedly more active than expected, with maximum rates in the range 40-70. If the periodicity is real, then 12 years on from the peak of activity it is possible the Orionids will again put on a better than expected show.
So 2020 might well be an ideal year to look up and watch for fragments of Halley’s Comet vapourising high overhead.
The radiant rises just before local midnight, meaning the meteors are best observed in the early hours of the morning. The radiant reaches its highest altitude in the hours before dawn. The Moon will not interfere this year, setting in the early evening, long before the radiant rises.
Observers watching the Orionids are in for an extra treat. While the Orionids are active, so too are the Northern and Southern Taurid meteor showers. Where the Orionids are fast meteors, Taurids are slow, and often bright and spectacular.
Although the rates of both the Northern and Southern Taurids are lower than those of the Orionids (typically just ~5 per hour), their activity makes observations of the Orionids even more productive and exciting.
The Geminids, which peak in mid-December, are truly a case of saving the best until last. The biggest of the year’s big three, the Geminids have, over the past few decades, been growing ever more active and spectacular, with recent years seeing rates in excess of 150 per hour.
For observers in northern Europe, the radiant is above the horizon relatively soon after sunset, meaning that the Geminids can readily be observed from around 8pm onwards.
The further south you travel, the later in the evening the radiant rises. For observers in Australia, the times at which the radiant appears above the horizon can be seen below.
As with all showers, the higher the radiant in the sky, the better the observed rates from the Geminids will be. The longer you watch, the better things will get.
Geminid meteors are of medium speed and often bright so they put on a spectacular show even in those years when moonlight interferes.
In 2020 the Moon will be new around this time so it will be possible to spend the entire night watching the Geminids without any interference from our nearest celestial neighbour.
The radiant reaches its highest at around 2am local time making the hours just after midnight the ideal time to catch the Geminids at their best.
The Geminid peak is relatively broad -– with rates remaining high for at least 24 hours around the forecast maximum. Observers across the globe will be treated to a spectacular display from the shower in 2020.
So find a dark site, wrap up warm, and treat yourself to a night spent watching the year’s most spectacular display of natural fireworks.