Why the stuff between the stars is like a glass of beer

By Nola Wilkinson  

Ever wondered what there is between the stars? Dr Naomi McClure-Griffiths not only wonders about it, she’s on a mission to find out.

Naomi is fascinated with the life of stars, the behaviour of interstellar gas, and how gas and stars interact.  “As an astronomer, I’d like to understand how the galaxy formed and how it’s living its life,” she says.

Naomi has conducted a massive survey of all the hydrogen gas in and around in the Milky Way. In doing so, she has shown that the stuff between the stars is actually foamy.

“The galaxy is much more frothy and bubbly than we ever thought. It looks like the head on a glass of beer.”

Very large stars, 8-20 times the size of our sun, experience dramatic supernova explosions that push gas out of the galaxy via solar winds travelling at up to 1000 kilometres a second.

It is these solar winds that blow bubbles in the gas between the stars, creating a frothy, foamy appearance.

Watch this video to find out more about Naomi and her amazing work:

Naomi’s team undertook the Galactic All Sky Survey using our Parkes telescope and is planning future work using our ASKAP radio telescope.


The first images from ASKAP reveal slices through space

Three of the dishes used by the Australian Square Kilometre Array Pathfinder telescope.

Three of the dishes used by the Australian Square Kilometre Array Pathfinder telescope. Image: CSIRO / Terrace Photographers

By Lisa Harvey-Smith, CSIRO

The first images from Australia’s Square Kilometre Array Pathfinder (ASKAP) telescope have given scientists a sneak peek at the potential images to come from the much larger Square Kilometre Array (SKA) telescope currently being developed.

ASKAP comprises a cluster of 36 large radio dishes that work together with a powerful supercomputer to form (in effect) a single composite radio telescope 6km across.

What makes ASKAP truly special is the wide-angle “radio cameras”, known as phased array feeds, which can take up to 36 images of the sky simultaneously and stitch them together to generate a panoramic image.

Why panoramic vision?

Traditional radio telescope arrays such as the Australia Telescope Compact Array near Narrabri, NSW, are powerful probes of deep-space objects. But their limited field of view (approximately equivalent to the full moon) means that undertaking major research projects such as studying the structure of the Milky Way, or carrying out a census of millions of galaxies, is slow, painstaking work that can take many years to realise.

The special wide-angle radio receivers on ASKAP will increase the telescope’s field of vision 30 times, allowing astronomers to build up an encyclopedic knowledge of the sky.

This technological leap will enable us to study many astrophysical phenomena that are currently out of reach, including the evolution of galaxies and cosmic magnetism over billions of years.

For the past 12 months a team of CSIRO astronomers has been testing these novel radio cameras fitted on a test array of six antennas.

The first task for the team was to test the ability of the cameras to image wide fields-of-view and thus demonstrate ASKAP’s main competitive advantage. The results were impressive!

A wide-field image of the sky taken with the ASKAP test array.

A wide-field image of the sky taken with the ASKAP test array. Image: I. Heywood/ACES team, CSIRO

One of the first test images from the ASKAP test array is seen above. The hundreds of star-like points are actually galaxies, each containing billions of stars, seen in radio waves. Using CSIRO’s new radio cameras, nine overlapping images were taken simultaneously and stitched together.

The resulting image covers an area of sky more than five times greater than is normally visible with a radio telescope. The information contained in such images will help us to rapidly build up a picture of the evolution of galaxies over several billion years.

Where next for ASKAP to look

On the back of this success, the commissioning team turned the telescope to the Sculptor or “silver coin” galaxy to test its ability to study deep-space objects.

Sculptor is a spiral galaxy like our own Milky Way, but appears elongated as it is seen almost edge-on from earth.

The Sculptor galaxy seen rotating edge-on using the ASKAP test array.

The Sculptor galaxy seen rotating edge-on using the ASKAP test array. Image: P. Serra/ACES Team, CSIRO

This image (above) shows the radio waves emitted by hydrogen gas that is swirling in an almost circular motion around the galaxy as it rotates.

The red side of the galaxy is moving away from us and the blue side is moving towards us. The speed of rotation tells us the galaxy’s mass.

The team has also tested the ability of the telescope to “weigh” the gas in very distant galaxies. The image (below) shows a grouping of overlapping galaxies called a gravitational lens.

Gravitational lens image

A cluster of galaxies aligned to form a ‘gravitational lens’ was captured using ASKAP’s test array.

Seven billion years ago, radio waves from a distant galaxy were absorbed by a foreground galaxy in this group. That signal was processed by ASKAP to form the spectrum (top right in the above image).

Although not visually pretty, this type of observation has enormous scientific value, allowing astronomers to understand how quickly galaxies use up their star-forming fuel.

The latest demonstration with the ASKAP test array is a movie (below) of layers through a cloud of gas in our Milky Way.

This series of images – similar to an MRI scan imaging slices through the human body – demonstrates the ability of the telescope to measure the intricate motions of the spiral arms of the Milky Way and other galaxies.

Building to the bigger array

These images are just the beginning of a new era in radio astronomy, starting with SKA pathfinders like ASKAP and culminating in the construction of the SKA radio telescope.

Once built, the SKA will comprise a vast army of radio receivers distributed over tens to hundreds of kilometres in remote areas of Western Australia and South Africa.

Just like ASKAP combines signals from several dishes, the SKA will use a supercomputer to build up a composite image of the sky.

Each ensemble of antennas will work together to photograph distant astronomical objects that are so faint, that they can’t be seen at all with current technology.

The SKA will thereby open up vast tracts of unexplored space to scientific study, making it a game-changer in astrophysical and cosmological research.

This article was originally published on The Conversation.
Read the original article.


Our Galaxy takes its food in pills

Vanessa Hill:

Where does our Galaxy get the fuel to keep forming stars? The answer may lie in thousands of gas clouds flying around the outskirts of our Galaxy.

Originally posted on Universe @ CSIRO:

A spiral galaxy seen face-on.

Our Galaxy (an artist’s conception): where does it get the fuel to keep forming stars? Image: Nick Risinger

“Food pills” were a staple of science fiction for decades. For our Galaxy, they may be real.

The Galaxy has been making stars for the last 8 billion years. What’s kept it going all that time?

When old stars die, some of their gas goes back into the galactic “soup” for star making. But in the long run a lot of it gets locked up in long-lived dwarf stars.

So the Galaxy needs fresh supplies of gas.

Astronomer think that gas rains in from intergalactic space, probably in the form of “clouds”, and that this fuels the star-making.

But there’s a problem.

A star-forming region. Credit: NASA, ESA, STScI/AURA

A star-forming region. Credit: NASA, ESA, STScI/AURA

If a regular gas cloud were to hit the warm outer parts of the Galaxy — the halo — the gas would dissipate…

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Cataclysms in the distant Universe

Vanessa Hill:

Some exciting news from ‘The Dish’ today.

Originally posted on Universe @ CSIRO:

The parkes telescope with clouds of red gas in the background.

Found with Parkes: radio ‘bursts’ from the distant Universe. The red background in this visualisation is gas in our galaxy. Credit: Swinburne Astronomy Productions, vr.swin.edu.au

In the journal Science today, astronomers using our Parkes telescope have revealed signs of cataclysms in the distant Universe.

They’ve found four ‘bursts’ or ‘flashes’ of radio waves, the furthest one coming from about 11 billion light-years away. And, they say, if you had ‘radio eyes’ — eyes that could detect radio waves — you’d see one of these ‘bursts’ going off somewhere in the sky every ten seconds. It would be like a continuous show of distant fireworks.

What is a ‘burst’? It’s a spike in the radio energy the telescope receives. Here, from the Science paper, is what the astronomers found. (‘Flux density’ means signal strength.)

radio_bursts_large

‘FRB’ stands for Fast Radio Burst. Because they really are very fast, lasting for only…

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On the road to Wee Waa

Researcher in helmet

NASA Mohawk Guy’s got nothin’ on CSIRO Helmet Guy.

If you thought ISS Commander Chris Hadfield’s micro gravity rendition of Space Oddity was the hit of the week, think again.

The latest album from electro music duo Daft Punk is being launched in Wee Waa this week and we’re ready to get down. It was reported that the French duo chose Wee Waa, in regional NSW, because of its proximity to our Australia Telescope. The global album launch will include a party at the Wee Waa show on Friday night.

The Australia Telescope Compact Array is so ready that it’s been getting down to Daft Punk’s Get Lucky.

Our researchers are getting into the swing of things too, giving a tour of the telescope operating room in signature Daft Punk helmets.

And finally, researchers dancing.


The stars are shining bright for Giovanna

It's certainly not a typical 9 to 5 job for Giovanna!

It’s certainly not a typical 9 to 5 job for Giovanna!

Meet Giovanna Zanardo: a PhD student at the International Centre for Radio Astronomy Research who’s using our telescopes to study the remains of a star that exploded in 1987.

Called Supernova 1987A, the explosion made astronomers super excited, because it was the first naked-eye supernova to occur since optical telescopes were invented four centuries ago.

Giovanna has been using the Australia Telescope Compact Array – a set of six dishes near Narrabri, NSW – to study the aftermath of the exploded star. And this month she’s going to be using our iconic Parkes telescope to look at it again.

While at Parkes, Giovanna and fellow scientists will be looking to see if a pulsar – a compact spinning star packed with neutrons – has been created after the collapse of the star’s core, which drove the stellar explosion.

“My PhD in astronomy has been a fantastic journey. I’ve got a front row seat to watch the evolution of a truly amazing object and the chance to use all of Australia’s radio telescopes.”

Part-time astronomer, part-time bridge builder. Giovanna finishing off a bridge on the Great Northern Highway.

Part-time astronomer, part-time bridge builder. Giovanna finishes off a bridge on the Great Northern Highway.

Giovanna began her career as a structural engineer in Western Australia, but after hearing plans to build the Square Kilometre Array (SKA), she saw this as an opportunity to get into radio astronomy.

From the moment she had a glimpse at the early radio images of Supernova 1987A, Giovanna was hooked. And she’s never looked back.

“I became an engineer because I love structures – but I’ve always loved physics and astronomy. My work allows me to combine the two by investigating large structures in space and seeing how they impact and interact with the surrounding environment,” says Giovanna.

To learn more about careers with us, head to our LinkedIn page.


A new day, a new dawn

the sun rising over a hill

Sunrise over Bodrum, Turkey. Photo: Nevit Dilmen. Source: Wikimedia Commons

Tomorrow is ANZAC Day, and some of you will be getting up to go to dawn services.

What is the dawn, anyway? Sure, it’s when the Sun comes up, but did you know there’s a difference between dawn and sunrise?

Sunrise: not what it seems

Sunrise is the moment when the edge of the Sun seems to peep over the horizon. “Seems”, because the Sun hasn’t actually reached the horizon yet: in fact, its image is refracted — the light rays are bent — by the Earth’s atmosphere.  The average amount of refraction is 34 arcminutes (an arcminute is a sixtieth of a degree); however, it varies, depending on atmospheric conditions.  (Thirty-four arcminutes is quite a lot: if you stand 100 m away from a target, 34 arcminutes is the angular distance between the bullseye and a point one metre off to the side of it.)

On top of that, the Sun isn’t just a point of light, but an extended source, a disk about 16 arcminutes in radius.

The combination of these two factors means that sunrise actually occurs when the Sun’s centre is 50 arcminutes, or almost one degree, below the horizon.

Diagram showing that the sun is below the horizon at dawn and dusk.

Sunrise and sunset, dawn and dusk, all occur when the Sun is below the horizon. Source: Wikimedia Commons

Dawn

Dawn, on the other hand, is the beginning of morning twilight — the time when the sky begins to lighten, well before the Sun shows its face.

Astronomers, sailors and ordinary folk have different kinds of dawn.

Astronomers — optical astronomers, anyway — like things to be really dark. For them, dawn occurs when the middle of the Sun’s disk lies 18 degrees below the horizon in the morning.

Nautical dawn takes place when the Sun is 12 degrees below the horizon, while civil dawn occurs when it is just six degrees below the horizon.

Astronomical, nautical and civil twilight. Source: Wikimedia Commons

Astronomical, nautical and civil twilight. Source: Wikimedia Commons

The Earth’s shadow

Shortly before sunrise, if you look in the opposite direction to the Sun (i.e. to the west), you may see a dark blue or greyish-blue band in the sky. This is the shadow that the Earth itself casts on its lower atmosphere. The pink band that appears above it is called the Belt of Venus: it is the Earth’s upper atmosphere, illuminated by the Sun’s rays. Both the shadow and the Belt can be seen at sunrise or sunset.

A blue band in the sky near the horizon with a pink band above it.

The Earth’s shadow (blue) and above it, the Belt of Venus (pink). Source: Wikimedia Commons

“And tomorrow the sun will shine again”*

Dawn is synonymous with hope. For Christians, Easter morning marks the resurrection of Christ. At the Neolithic tomb of Newgrange in Ireland, when the Sun rises on the winter solstice its rays pass straight into the heart of the mound: we cannot know exactly what this meant to the tomb’s builders, but they went to a great deal of trouble to make it happen.

If you’re never up early enough to see the dawn, don’t despair: here’s a nice video of sunrises in South Australia to remind you of what it’s all about.


Source: YouTube . Posted by VK5SW.

* The English translation of the first line of a beautiful song, “Morgen”, by German composer Richard Strauss.


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