Climate explained: how particles ejected from the Sun affect Earth’s climate


Earth’s magnetic field protects us from the solar wind, guiding the solar particles to the polar regions.
SOHO (ESA & NASA)

Annika Seppälä


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz


When the Sun ejects solar particles into space, how does this affect the Earth and climate? Are clouds affected by these particles?

When we consider the Sun’s influence on Earth and our climate, we tend to think about solar radiation. We are acutely aware of the skin-burning dangers of ultraviolet, or UV, radiation.

But the Sun is an active star. It also continuously releases what is known as “solar wind”, made up of charged particles, largely protons and electrons, that travel at speeds of hundreds of kilometres per hour.

Some of these particles that reach Earth are guided into the polar atmosphere by our magnetic field. As a result, we can see the southern lights, aurora australis, in the southern hemisphere, and the northern equivalent, aurora borealis.

Aurora Australis
Aurora australis observed above southern New Zealand.
Shutterstock/Fotos593

This visible manifestation of solar particles entering Earth’s atmosphere is a constant reminder there is more to the Sun than sunlight. But the particles have other effects as well.




Read more:
Why is the sun’s atmosphere so hot? Spacecraft starts to unravel our star’s mysteries


Solar particles and ozone

When solar particles enter the atmosphere, their high energies ionise neutral atmospheric nitrogen and oxygen molecules, which make up 99% of the atmosphere. This “energetic particle precipitation”, named because it’s like a rain of particles from space, is a major source of ionisation in the polar atmosphere above 30km altitude — and it sets off a chain of reactions that produces chemicals that facilitate the destruction of ozone.

The impact of solar particles on atmospheric ozone was first observed in 1969. Since the early 2000s, thanks to new kinds of satellite observations, we have seen growing evidence that solar particles play an important part in influencing polar ozone. During particularly active times, when the Sun releases large amounts of particles into space, up to 60% of ozone at altitudes above 50km can be depleted. The effect can last for weeks.

Lower down in the atmosphere, below 50km, solar particles are important contributors to the year-to-year variability in polar ozone levels, often through indirect pathways. Here, solar particles again contribute to ozone loss, but a recent discovery showed they also help curb some of the depletion in the Antarctic ozone hole.

How ozone affects the climate

Most of the ozone in the atmosphere resides in a thin layer at altitudes of 20-25km — the “ozone layer”.

But ozone is everywhere in the atmosphere, from the Earth’s surface to altitudes above 100km. It is a greenhouse gas and plays a key role in heating and cooling the atmosphere, which makes it critical for climate.

In the southern hemisphere, changes in polar ozone are known to influence regional climate conditions.

Satellite image of Earth's atmosphere
Solar particles ionise nitrogen and oxygen molecules in the atmosphere, which leads to other chemical reactions that contribute to ozone destruction.
Shutterstock/PunyaFamily

Its depletion above Antarctica had a cooling effect, which in turn pulled the westerly wind jet that circles the continent closer. As the Antarctic hole recovers, this wind belt can meander further north and affect rainfall patterns, sea-surface temperatures and ocean currents. The Southern Annular Mode describes this north-south movement of the wind belt that circles the southern polar region.

Ozone is important for future climate predictions, not only in the thin ozone layer, but throughout the atmosphere. It is crucial we understand the factors that influence ozone variability, be it man-made or natural like the Sun.

The Sun’s direct influence

The link between solar particles and ozone is reasonably well established, but what about any direct effects solar particles may have on the climate?

We have observational evidence that solar activity influences regional climate variability at both poles. Climate models also suggest such polar effects link to larger climate patterns (such as the Northern and Southern Annular Modes) and influence conditions in mid-latitudes.

The details are not yet well understood, but for the first time the influence of solar particles on the climate system will be included in climate simulations used for the upcoming Intergovernmental Panel on Climate Change (IPCC) assessment.




Read more:
Solar weather has real, material effects on Earth


Through solar radiation and particles, the Sun provides a key energy input to our climate system. While these do vary with the Sun’s 11-year cycle of magnetic activity, they can not explain the recent rapid increase in global temperatures due to climate change.

We know rising levels of greenhouse gases in the atmosphere are pushing up Earth’s surface temperature (the physics have been known since the 1800s). We also know human activities have greatly increased greenhouse gases in the atmosphere. Together these two factors explain the observed rise in global temperatures.

What about clouds?

Clouds are much lower in the atmosphere than where most solar particles penetrate. Particles know as galactic cosmic rays (coming from the centre of our galaxy rather than the Sun) may be linked to cloud formation.

It has been suggested cosmic rays could influence the formation of condensation nuclei, which act as “seeds” for clouds. But recent research at the CERN nuclear research facility suggests the effects are insignificant.

This doesn’t rule out some other mechanisms for cosmic rays to affect cloud formation, but thus far there is little supporting evidence.The Conversation

Annika Seppälä, Senior Lecturer in Geophysics

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Mangroves from space: 30 years of satellite images are helping us understand how climate change threatens these valuable forests


Travel Sourced, Pixabay.
Travel Sourced, Pixabay, CC BY-SA

Nicolás Younes Cárdenas, James Cook University; Karen Joyce, James Cook University, and Stefan W Maier, James Cook UniversityAustralia is home to around 2% of the world’s mangrove forests and is the fifth most mangrove-forested country on Earth. Mangroves play a crucial role in the ecosystem thanks to the dizzying array of plants, animals and birds they feed, house and protect.

Mangrove forests help protect coastal communities from cyclones and storms by absorbing the brunt of a storm’s energy. They help our fight against climate change by storing vast amounts of carbon that would otherwise be released as greenhouse gases.

In other words, mangroves are some of our most precious ecosystems. Despite their importance, there is much we don’t know about these complex wetland forests. For example, when does their growing season start? And, how long does it last?

Usually, answering these types of questions requires frequent data collection in the field, but that can be costly and time-consuming. An alternative is to use satellite images. In the future, this will allow us to track the impacts of climate change on mangroves and other forests.

Mangroves flowering and fruiting in Townsville, QLD.
Mangroves play a crucial role in the ecosystem thanks to the dizzying array of plants, animals and birds they feed, house and protect.
Nicolas Younes

What is phenology?

Our research used satellite images to study the life cycles of mangrove forests in the Northern Territory, Queensland, and New South Wales. We compared the satellite images with field data collected in the 1980s, 1990s and 2000s, and found a surprising degree of variation in mangrove life cycles.

We’re using the phrase life cycle, but the scientific term is “phenology”. Phenology is the study of periodic events in the life cycles of plants and animals. For example, some plants flower and fruit during the spring and summer, and some lose their leaves in autumn and winter.

Phenology is important because when plants are growing, they absorb carbon from the atmosphere and store it in their leaves, trunks, roots, and in the soil. As phenology is often affected by environmental conditions, studying phenology helps us understand how climate change is affecting Australian ecosystems such as mangrove forests.

So how can we learn a lot in a short amount of time about mangrove phenology? That’s where satellite imagery comes in.

How we use satellites to study mangrove phenology

Satellites are an excellent tool to study changes in forest health, area, and phenology. Some satellites have been taking images of Earth for decades, giving us the chance to look back at the state of mangrove forests from 30 years ago or more.

You can think of satellite images much like the photo gallery in your smartphone: you can see many of your family members in a single image, and you can see how everyone grows and “blooms” over time. In the case of mangroves, we can see different regions and species in a single satellite image, and we can use past images to study the life cycles of mangrove forests.

For example, satellite images depicted below, which use data from the Australian government’s National Maps website, show how mangroves forests have changed in the Kimberley region of Western Australia between 1990 and 2019. You can see how the mangrove forest has reduced in some areas, but expanded in others. Overall, this mangrove forest seems to be doing pretty well thanks in large part to the fact this area has a reasonably small human population.

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Images: NationalMap/Data61

Our study of satellite images of mangrove forests in the Northern Territory, Queensland, and New South Wales – and how they compared with data collected on the ground – found not all mangroves have the same life cycles.

For instance, many mangrove species grow new leaves only once per year, while other species grow new leaves twice a year. These subtle, but important differences will allow us to track the impacts of climate change on mangroves and other forests.

Mangroves at different growth stages in Bushland Beach, QLD
Satellite images of mangrove forests reveal not all mangroves have the same life cycles. Here we see mangroves at different growth stages.
Nicolas Younes

How climate change affects mangrove phenology

Climate change is changing the phenology of many forests, causing them to flower and fruit earlier than expected.

Science cannot yet tell us exactly how mangrove phenology will be affected by climate change but the results could be catastrophic. If mangroves flower or fruit earlier than expected, pollinators such as bats, bees and birds may starve or move to a different forests. Without pollinators, mangroves may not reproduce and can die.

The next step in our research is to figure out how climate change is affecting the life cycles of mangroves. To do this, we will use satellite images of mangroves across Australia and factor in data on temperature and rainfall.

We think rising temperatures are causing longer periods of leaf growth, a theory we plan to test by studying data from now with satellite images from the 80s and 90s.

A mangrove forest.
The next step in our research is to figure out how climate change is affecting the life cycles of mangroves.
Shutterstock

Satellite monitoring can’t do it all

Satellites can tell us a lot about how a mangrove forest is faring. For example, satellite images captured a dieback event (depicted below, using data from the Australian government’s National Maps website) that happened between 2015 and 2016, when around 7,400 hectares of mangroves died in the Gulf of Carpentaria due to drought and unusually high air and sea temperatures.

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Images: NationalMap/Data61

But satellite monitoring is not enough on its own and cannot capture the detail you can get on the ground. For example, satellites cannot capture the flowering or fruiting of mangroves because flowers are often too small and fruits are often camouflaged. Also, satellites cannot capture what happens under the canopy.

It is also important to recognise the work of researchers on the ground. Ground data allows us to validate or confirm the information we see in satellite images. When we noted some mangrove forests were growing leaves twice per year, we validated this observation with field data, and confirmed with experts in mangrove ecosystems. Field data is crucial to understand the life cycles of ecosystems worldwide and how forests are responding to changes in the climate.The Conversation

A bird in a wetlands.
Wetlands, including mangroves, are some of our most precious ecosystems.
Shutterstock

Nicolás Younes Cárdenas, Postdoctoral research fellow, James Cook University; Karen Joyce, Senior Lecturer – Remote sensing and spatial information, James Cook University, and Stefan W Maier, Adjunct Research Fellow, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Look up! Your guide to some of the best meteor showers for 2021



Flickr/Mike Lewinski , CC BY

Jonti Horner, University of Southern Queensland and Tanya Hill, Museums Victoria

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).

After that, the year just gets better and better, with the Perseids (another of the big three along with the Geminids) a particular highlight for northern hemisphere observers in August.




Read more:
Explainer: why meteors light up the night sky


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].

Lyrids [N/S; N favoured]

Active: April 14–30

Maximum: April 22, 1pm UTC = 11pm AEST (Qld) = 7am CST = 3am Hawaii time

ZHR: 18

Parent: Comet C/1861 G1 Thatcher

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.

Flash of two meteors across a night sky.
A couple of Lyrids.
Flickr/DraconianRain, CC BY-NC

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.

Across the US, the Lyrid radiant is high in the east before sunrise, above the Summer Triangle of Vega, Deneb and Altair. Low to the horizon, Jupiter and Saturn are rising. US around 4am local time.
Museums Victoria/Stellarium

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.

The Boorong from north-western Victoria saw the Lyrids as Neilloan, the Mallee fowl, kicking up shooting stars while preparing her nest. Melbourne, 5am.
Museums Victoria/Stellarium

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.

Eta Aquariids [S]

Active: April 19–May 28

Maximum: May 6, 3am UTC = 1pm AEST (Qld/NSW/ACT/Vic/Tas) = 11am AWST (WA)

ZHR: 50+

Parent: Comet 1P/Halley

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 crescent Moon, the two biggest planets, a couple of bright stars and the Eta Aquariids all in the east before sunrise on May 6. Australia, around 4am local time.
Museums Victoria/Stellarium

Perseids [N]

Active: July 17–August 24

Maximum: August 12, 7pm–10pm UTC = 8pm–11pm BST = August 13, 4am–7am JST

ZHR: 110

Parent: Comet 109P/Swift-Tuttle

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.

An asteroid streak across the sky with a volcano and telescope in the foreground.
A Perseid crosses the sky over the Teide volcano and Teide Observatory on Tenerife.
Flickr/StarryEarth, CC BY-NC

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.

The Perseids radiate from the north-east, with the radiant rising high in the sky during the early hours of the morning. London, 11pm (left) and 4am (right)
Museums Victoria/Stellarium

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.

Aurigids [N favoured]

Active: August 28–September 5

Maximum: Potential Outburst on August 31, peaking between 9:15pm–9:40pm UTC = 10:15pm–10:40pm BST = 11:15pm–11:40pm CEST = September 1, 1:15am–1:40am Gulf Standard Time = September 1, 5:15am–5:40am AWST (WA)

ZHR: 50–100 (?)

Parent: Comet C/1911 N1 Kiess

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.

From Europe, the expected peak of the Aurigids occurs just before Moonrise. Be sure to look for the Pleiades whilst watching for any Aurigids – they’re a spectacular cluster of bright stars, commonly known as the Seven Sisters. Vienna, 11:30pm.
Museums Victoria/Stellarium
The crescent Moon has risen in Asia at the time the Aurigids peak. Dubai, 1:30am.
Museums Victoria/Stellarium

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.

While waiting for the Aurigids, the morning sky in Perth is also packed with many famous constellations and bright stars. Perth, 5:30am.
Museums Victoria/Stellarium

Geminids [N/S]

Active: December 4–17

Maximum: December 14, 7am UTC = 6pm AEDT (NSW/ACT/Vic/Tas) = 3pm AWST (WA) = 2am EST

ZHR: 150

Parent: Asteroid 3200 Phaethon

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.

At its highest point, the Geminids radiant sits higher from Brisbane (left) than from Hobart (right), which is why northern observers have a better chance of seeing more meteors.
Museums Victoria/Stellarium

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.


The Geminid radiant rises at about the following times across Australia., Author provided

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.The Conversation

Jonti Horner, Professor (Astrophysics), University of Southern Queensland and Tanya Hill, Honorary Fellow of the University of Melbourne and Senior Curator (Astronomy), Museums Victoria

This article is republished from The Conversation under a Creative Commons license. Read the original article.

‘WTF?’: newly discovered ghostly circles in the sky can’t be explained by current theories, and astronomers are excited



Bärbel Koribalski / ASKAP, Author provided

Ray Norris, Western Sydney University

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.

The ghostly ORC1 (blue/green fuzz), on a backdrop of the galaxies at optical wavelengths. There’s an orange galaxy at the centre of the ORC, but we don’t know whether it’s part of the ORC, or just a chance coincidence.
Image by Bärbel Koribalski, based on ASKAP data, with the optical image from the [Dark Energy Survey](https://www.darkenergysurvey.org), Author provided

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.




Read more:
Expect the unexpected from the big-data boom in radio astronomy


Hunting ORCs

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.




Read more:
The Australian Square Kilometre Array Pathfinder finally hits the big-data highway


We know what they’re not

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.

A genuine mystery

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.




Read more:
How we closed in on the location of a fast radio burst in a galaxy far, far away


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!The Conversation

Ray Norris, Professor, School of Science, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

We’ve mapped a million previously undiscovered galaxies beyond the Milky Way. Take the virtual tour here.



CSIRO, Author provided

Aidan Hotan, CSIRO

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.

The Rapid ASKAP Continuum Survey (or RACS) has placed the CSIRO’s Australian SKA Pathfinder radio telescope (ASKAP) firmly on the international astronomy map.

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.

What is radio astronomy?

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.




Read more:
From 7809 Marcialangton to 7630 Yidumduma: 5 asteroids named after Aboriginal and Torres Strait Islander people


A stellar breakthrough

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.

Why do we need to map the universe?

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.




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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.

Image of the Centaurus A galaxy.
The giant Centaurus A galaxy was one elliptical galaxy captured in the RACS survey. Although more than ten million light years away, it’s one of the closest radio galaxies to Earth. You can see its ‘intensity’ represented by different colours.
CSIRO, Author provided

High technology putting new goals within reach

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.The Conversation

Aidan Hotan, ASKAP lead scientist, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Astronomers create 40% more carbon emissions than the average Australian. Here’s how they can be more environmentally friendly



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Adam Stevens, University of Western Australia and Sabine Bellstedt, University of Western Australia

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.




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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.

Where do all the emissions come from?

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.

Antennas and a satellite dish in the foreground, with others in the background, in the WA desert.
Antennas of CSIRO’s ASKAP telescope at the Murchison Radio-astronomy Observatory in Western Australia.
CSIRO Science Image

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.

Some, like the Parkes radio telescope and the Anglo-Australian Telescope near Coonabarabran, are connected to the electricity grid, which is predominately powered by fossil fuels.

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.

They’re doing it better in Germany

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.

Taking emissions reduction into our own hands

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.




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The good news is this is already happening. A recent deal made by Swinburne University to procure 100% renewable energy means the OzSTAR supercomputer is now a “green machine”.

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.




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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.The Conversation

Adam Stevens, Research Fellow in Astrophysics, University of Western Australia and Sabine Bellstedt, Research Associate in Astronomy, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.