ICRAR WORK EXPERIENCE 29/09/20 – 2/10/20
The ICRAR work experience is ideal for anyone considering a career in physics, astronomy or astrophysics. This year the program ran over 4 days, but unfortunately, due to renovations we could not visit the ICRAR centre at Curtin. Despite this, my experience at UWA was still rewarding. Each day was filled conversing with brilliant astrophysicists and PhD candidates who gave us insight into their research and were delighted to answer our questions. We learned so many new things over different aspects of astronomy including cosmic dust, galaxies, blackholes and dark matter.
Upon arriving at ICRAR our supervisor named Greg showed us around the building and discussed ICRAR’s major upcoming project, the square kilometre array. The SKA will be the largest ever radio telescope that will monitor the sky intricately and map hundreds of times faster than any other facility in the world. In fact, the data collected by the SKA in one day would take about 2 million years to playback on an iPod. After our orientation, we were introduced to Kevin Vinsen, a long-time member of ICRAR since its opening in 2010. Using an insightful and interesting presentation, he gave as an overview of the fundamentals of astrophysics. In the presentation, I particularly enjoyed the quest to find life on exoplanets. Kevin described how finding life is extremely rare due to a number of reasons such as distance (sending them a signal could take millions of years to reach them) , likening the search for extra-terrestrial life to trying to find fish in an ocean using nothing but a cup! Next, we met with Dr Gerdhardt who, to my surprise, demonstrated to us that the pretty pictures of galaxies found on the internet are created using only 3 colour filters – red, blue and green. After lunch, Ruby, a PhD candidate introduced us to an entertaining app called Stellarium, which allows users to see the stars, planets, galaxies, nebulas and constellations in their location. We concluded our first day by conversing with Jen, another PhD candidate researching the angular momentum of galaxies. She gave us insight into her research, discussing how the rotation of galaxies can help us figure out how galaxies form as well as act as indirect evidence of dark matter which are particles abundant in the universe but do not interact with light, only gravity.
We started our second day off with a cosmology video lecture by Dr Alan Duffy. He explained how the universe is expanding, likely flat, 13.8 billion years old and constitutes of three main components – dark energy (74%), dark matter (22%) and atoms (4%).The most fascinating thing I comprehended from this lecture was that the universe is expanding. Every atom emits a certain wave frequency, Dr Alan Duffy explained. If space is expanding then waves emitted by galaxies is expected to ‘stretch’, resulting in a lower frequency, towards the right (redder) side of the electromagnetic spectrum – This is referred to as redshift. Scientists know that the universe is expanding as nearly everything (i.e. stars) shows a redshift in its spectrum. In fact, Hubble noted that everything was redder than usual. After the lecture Tristan, a post doctorate radio astronomer who studies the gas content in galaxies using ASKAP came to talk to us. He emphasized the importance of understanding the gas content in galaxies as it can help us understand a number of things including the early formation of stars, the rotation, the age, the number of stars and future star formation in the galaxy. He described ASKAP, a type of radio infermometer telescope that is essentially a number of parabolic dish antennae in an array which all work together, forming one large telescope. Tristian also gave us insight into his PhD research, explaining how galaxies can pass one another in the intergalactic medium and if they are close enough, gas can be pulled and stripped off one making one galaxy denser and the faster the galaxies are moving; the more gas is likely to be stripped. Next, we conversed with Luca, a senior observer from Italy whose research involves how our galaxy is likely to be formed, why some galaxies are different and the ability of galaxies to convert gas into stars. Similarly, to Dr Gerhardt, he exposed how the colour of galaxies in images are superimposed by placing red, blue and green filters to produce the aesthetic alluring pictures we know. But in fact, if we were to visit a galaxy, we would likely see it as 1 particular colour rather than different colours as the variation in wavelengths of the gases may be too small for our eyes to differentiate. This is why they impose distinctive colours – to display the variations in wavelengths and properties. Lastly, we met with Jen, Katie, Jess and Maddie, PhD candidates who prepared an interactive presentation for us about black holes, stars and supernova.
Today, Omima, a PhD student specialising in cosmic dust came to talk to us first. Dust in the intergalactic medium is from the death of stars (e.g. supernovas which spew the dust out in a spectacular explosion). In a star’s life hydrogen is fused into helium and later in its life can convert into other elements such as lithium, carbon, oxygen, iron and magnesium. When a star dies, it expands and cools, depositing these ‘metals’ into space and as it cools some can solidify. This deposited matter is dust. She explained to us how dust makes stars appear redder and darker because as photons from the stars interact with the dust in front, the dust particles scatters any blue light only allowing red light to go through. Dust in galaxies can also block a star’s light. This is why we see dark patches on the milky way. The most intriguing piece of information about dust I learnt from Nina was that dust acts as a catalyst for the formation of nuclear hydrogen and thus stars. The intergalactic medium is chaotic – it is hot and possesses lots of energy, so the hydrogen atoms within it collide with such intense energy, they just bounce off each other. However, dust acts as a surface that hydrogen atoms to stick to. There they can meet with other atoms attached to the surface and form a bond, allowing gas particles to stick together as molecules, forming the building blocks of stars. After our discussion with Omima, Chris, an ICRAR professor who runs the cosmology theory group came to talk to us. I learnt from Chris, stellar streams which are an association of stars orbiting a galaxy that was once a small galaxy or Globular cluster which has now been torn and stretched out along its orbit around a large galaxy by tidal forces. He also introduced to me galactic jets – beams of matter ejected from a galaxy with a supermassive black hole in the centre and the theories of cold (slow) and warm (fast) dark matter. After lunch, we learnt about supercomputers and simulations by Dr Lilian Smithson and Dr Kate Harbourne. Dr Lilian Smithson, a theoretical astrophysicist outlined about how in a simulation of a galaxy you need to consider gas SPH particles, star formation laws, cooling, stellar feedback, blackholes and dark matter. Continuing on simulations, Dr Kate Harbourne emphasized the importance of coding, advising us to learn Python.
We began the day with a brief 5-minute walk to the spirit telescopes in the UWA campus. Inside one of the domes stood the telescope and around the walls were pictures of nebulae and galaxies it had taken. Unfortunately, all we could do was gaze at the telescope. We could not lift the roof up or look into it due to the rainy weather. After morning tea, Greg gave us the task to determine the mass of the galaxy NGC 7531, my favourite part of the day. The more mass a galaxy contains, the faster the orbits have to be. If it is not fast enough then the orbital radius will decrease. To maintain its circular motion, the galaxy’s centripetal force (mv2/r) needs to be balanced by gravitational force (GMm/r2). So mv2/r = GMm/r2 and therefore we can find the mass of the galaxy (M) by rearranging the equation M = rv2 /G. I learnt that to obtain v, you can use hydrogen spectrum. Using the spectrum, we first needed to find the velocity width of the galaxy in m/s and then divide by two to find the rotational velocity at the edge of the galaxy. I also learnt that to find the radius of galaxy NGC 7531, we can use optical or infrared image. We then moved on to talk about exoplanets. The most fascinating thing I learnt today was that we can detect planets using the wobble method or the transit method. When an exoplanet’s mass is significant in comparison to its star’s mass, its gravity can cause the star to wobble. We can notice a wobble in this centre of mass, via a shift in the star’s light frequencies – blue shift and red shift. As the star moves closer to us, it is blue shifted and as it moves further, it is red shifted. This is the wobble method. The transit method involves measuring the change in brightness of a star. If a planet was orbiting a star, then the planet can be positioned in front of the star relative to the observer, causing a change in brightness as it is obstructing it. After lunch, we then talked to Dr David Gozzard and Lewis Howard, experimental physicists. Lewis talked about a major project his team recently finished which involved stabilizing the signal from interspace. He then escorted us around labs working on lasers, quantum physics and gravitational waves, which I found fun to look at. We concluded our last day by playing with VR googles. We were able to see the SKA array in the desert and the milky way in different frequencies of the electromagnetic spectrum.
My week at ICRAR has truly been an enjoyable and enlightening experience. I loved learning about so many new concepts every day and not only have these past 4 days deepened my knowledge of astrophysics, but they have also sparked a deeper desire to pursue this career in the future. I highly recommend this work experience to anyone thinking of a career in physics and engineering or even looking to spend a week learning about fascinating things. Thank you to Greg and the passionate researchers at ICRAR for making this experience worthwhile.