Sunday, July 26, 2015

Journey to the edge of a forming galaxy

in early july i spent two weeks as "scientist in residence" at the ABC as a result of the Top 5 Under 40 award.  the main project i worked on was producing a science ninja adventure story that went live on the science show on radio national yesterday afternoon!

journey to the edge of a forming galaxy (website)
journey to the edge of a forming galaxy (mp3)

Artwork by Mischa Andrews from photo by Jenny Gabache and galaxy image by David Malin

long time readers may remember the seeds of this story from a blog post in 2010. you never know what direction random inspiration will go!

transforming the written story into something radio-ready was an interesting challenge.  phrases that look lovely on the page do not sound smooth or conversational when spoken out loud.  i wrote many versions of the story (in less than 2 days) before settling into one that i could read out loud comfortably.

Artwork by Glen Nagle

once the story was ready, i had the amazing luck of booking an entire afternoon in the studio with award-winning sound engineer Russell Stapleton.  i had shared an early draft of the story with him and he came prepared with directories of "space and ninja" sounds that he had been working with for the last 20 years!  he really made the story come alive and it was fascinating to watch him work. such a unique experience to work with him to create the depth of sound you hear throughout the story.

the science show producer asked me for some unique artwork to display with the story on the webpage, since a regular galaxy image would be a bit boring.  i was busy at a workshop during the couple days i had to produce the image, so i asked twitter for volunteers to help.  they certainly came through - the images are displayed through this post.  thanks so much to Mischa Andrews and Glen Nagle!

Put together by Glen Nagle from photo by Jenny Gabache and galaxy image by David Malin

Hope you enjoy the adventure!

Sunday, July 19, 2015

2015 David Malin Award Winners

Here is the first batch of winning astrophotos from the annual David Malin Awards contest.  These are absolutely stunning captures from non-professional astronomers around australia!

Overall Winner: "Stellar Riches" by Troy Casswell

Deep sky winner: "The Fighting Dragons of Ara" by Andrew Campbell

Nightscape winner: "Aurora Treescape" by James Garlick

Solar system winner: "Solar Crown" by Peter Ward

Saturday, July 18, 2015

seeing the universe through spectroscopic eyes

I published this article at The Conversation last week, reproduced here for your enjoyment :) Original article link

Seeing the Universe Through Spectroscopic Eyes

When you look up on a clear night and see stars, what are you really looking at? A twinkling pinprick of light with a hint of colour?

Imagine looking at a starry sky with eyes like prisms that separate the light from each star into its full rainbow of colour. Astronomers have built instruments to do just that, and spectroscopy is one of the most powerful tools in the astronomer’s box.

The technique might not produce the well-known pretty pictures sent down by the Hubble Space Telescope, but for astronomers, a spectrum is worth a thousand pictures.

Visible spectra reveal huge amounts of information about objects in the distant cosmos that we can’t learn any other way.

So what is spectroscopy?

Spectroscopy is the process of separating starlight into its constituent wavelengths, like a prism turning sunlight into a rainbow. The familiar colours of the rainbow correspond to different wavelengths of visible light.

The human eye is sensitive to the visible spectrum – a narrow range of frequencies among the entire electromagnetic spectrum. The visible spectrum covers wavelengths of roughly 390 nanometers to 780 nanometers (astronomers often use units of Angstroms (10-10), so visible light spans 3,900 to 7,800 Angstroms).

Once visible starlight reaches the curved primary mirror of a telescope, it is reflected toward the focal point and can then be directed anywhere. If the light is sent directly to a camera, an image of the night sky is seen on a computer screen as a result.

If the light is instead sent through a spectrograph before it hits the camera, then the light from the astronomical object gets separated into its basic parts.

A very simple spectrograph was used by Issac Newton in the 1660s when he dispersed light with a glass prism. Modern spectrographs consist of a series of optics, a dispersing element and a camera at the end. The light is digitised and sent to a computer, which astronomers use to inspect and analyse the resulting spectra.

The video (above) shows the path of distant starlight through the 4-metre Anglo-Australian Telescope (AAT) and a typical spectrograph, revealing real data at the end.

What do spectra teach us?

A spectrum allows astronomers to determine many things about the object being viewed, such as how far away it is, its chemical makeup, age, formation history, temperature and more. While every astronomical object has a unique rainbow fingerprint, some general properties are universal.

Top shows a spiral galaxy spectrum. Bottom shows non-star-forming galaxy spectrum.
Screenshot from Australian Astronomical Observatory video above

Here we examine the galaxy spectra shown in the video. The spectrum of a galaxy is the combined light from its billions of stars and all other radiating matter in the galaxy, such as gas and dust.

In the top spectrum you can see a few strong spikes. These are called “emission lines” and occur at discrete wavelengths due to the atomic structure of atoms as electrons jump between energy levels.

The hydrogen spectrum is particularly important because 90% of the normal matter in the universe is hydrogen. Because of the details of hydrogen’s atomic structure, we recognise the strong hydrogen-alpha emission line at roughly 7,500 Angstroms in the top spectrum image.

In a galaxy, only the youngest, biggest stars are hot enough to excite surrounding hydrogen gas enough that the electrons populate the third energy level, before falling to the second lowest, thus emitting a hydrogen-alpha photon.

Because of this, we know the strength of the hydrogen-alpha line in a galaxy’s spectrum indicates how many very young stars there are in the galaxy. Since the bottom spectrum shows no hydrogen-alpha emission, we can conclude that the bottom galaxy is not sparking new life in the form of shining stars, while the top galaxy harbours several hard working stellar nurseries.

In the bottom spectrum you can see a number dips. These are called “absorption lines” because they appear in the spectrum if there is anything between the light’s source and the observer on Earth absorbing the light. Absorbing material could be the extended layers of a star or interstellar clouds of gas or dust.

The absorption lines close to each other below 5,000 Angstroms in the bottom spectrum are the calcium H and K lines and can be used to determine how quickly stars are zooming around the galaxy.

In a galaxy how far away?

A basic piece of information derived from a spectrum is the distance to the galaxy, or specifically, how much the light has stretched during its journey to Earth. Because the universe is expanding, the light emitted by the galaxy is stretched toward redder wavelengths as it innocently moves across space. We measure this as redshift.

To determine the exact distance of a galaxy, astronomers measure the well-studied pattern of absorption and emission lines in the observed spectrum and compare it to the laboratory wavelengths of these features on Earth. The difference tells how much the light was stretched, and therefore how long the light was travelling through space, and consequently how far away the galaxy is.

The absorption lines ‘shift’ the farther away an object is, giving us an indication of its distance from us.
Georg Wiora (Dr. Schorsch)

In the top galaxy spectrum mentioned earlier, we measure the strong red emission line of hydrogen-alpha to be at a wavelength of roughly 7,450 Angstroms. Since we know that line has a rest wavelength of 6,563 Angstroms, we calculate a redshift of 0.13, which means the light was travelling for 1.7 billion years before it reached our lucky telescope. The galaxy emitted that light when the universe was roughly 11.8 billion years old.

Australia’s strength in spectroscopy

Australia has led the way internationally for spectroscopic technology development for the last 20 years, largely due to the use of fibre optics to direct galaxy light from the telescope structure to the spectrograph.

A huge advantage of using optical fibres is that more than one spectrum can be obtained simultaneously, drastically improving the efficiency of the telescope observing time.

Australian astronomers have also led the world in building robotic technologies to position the individual optical fibres. With these, the AAT and the UK Schmidt Telescopes (both located at Siding Spring Observatory in New South Wales) have collected spectra for a third of all the 2.5 million galaxy spectra that humans have ever observed.

While my own research uses hundreds of thousands of galaxy spectra for individual projects, it still amazes me think that each one of these spectra are composite collections of light created by hundreds of billions of stars gravitationally bound together in a single swirling galaxy, many similar to our own Milky Way home.

Tuesday, July 14, 2015

discovering pluto

later today, the new horizons space craft will fly by pluto at a distance of only 12,500 km - its closest approach is about 1 earth away.   that's incredible!

this mission has already given us way better views of the dwarf planet than we've ever achieved (even with hubble).  what will the new data tell us?  what does the surface looks like? (are there craters? ice? cracks? plumes? mountains?)  what is the atmosphere is made of? (methane, nitrogen, and what else?) does its surface ice turn to gas during different seasons and then does it get released to space?

ultimately, we want to understand what the objects way out in the kuiper belt are made of because they can tell us how all the other planets and the entire solar system was formed.

Created by Alex Parker with NEW images of pluto!
new horizons cannot send data back at the same time it is taking images, so it is following an automatic program, written by the engineers and astronomers, to maximize its data collection during the flyby.  we will receive the first message and prelim images tomorrow (july 15th, 2015 - it takes 4.5 hours for the data to reach earth).  cant wait!

then new horizons will start sending data back to us over the next ~16 months as it flies away out into the depths of the kuiper belt at the outskirts of our solar system.

i'm excited.

i talked (enthusiastically) to Patricia Karvelas on radio national's drive program last friday about pluto and what to expect from this flyby. you can LISTEN HERE.

it also seems like the perfect time to break out this old number: pluto, the previous planet :)

Pluto, the previous planet from carolune on Vimeo.