Month: April 2019

Looking at the shadow–The first picture of a black hole

 By Mireia Montes Quiles

Astronomers have captured the first image ever of a black hole. As part of the Event Horizon Telescope (EHT) project, the team simultaneously took observations using telescopes around the globe to take one of the most detailed images ever of a black hole 55 million light-years away from us.

What is all this fuss about?

A collaboration of more than 200 scientists have taken the very FIRST IMAGE of a black hole! This is an incredible achievement and it is technically amazing; they used 8 telescopes observing at the same time…

Left: Can you imagine that our entire solar system can fit inside the black hole’s shadow and still there is plenty of room? Right: Position of the array of telescopes on Earth. Credit: xkcd and Event Horizon Telescope

Wait… what is a black hole, again?

 A black hole is a region of space where the gravitational field is so intense that no matter or radiation can escape. The center of the black hole, the singularity, is a point in spacetime that contains ALL the mass of the black hole; where the density is infinite. The gravity that this singularity produces is so strong that there is a region where not even light can escape. The edge of it, the point of no return, is called the event horizon. Like the telescope! Exactly.

Aaah! Got it. Can you explain this image to me? Why does it look like an orange donut?

Actually, we are not seeing the black hole because no light can escape from it.

An active black hole, like this one, has an accretion disk: a disk of gas and dust surrounding and feeding it. The friction heats this gas to temperatures of billions of degrees and consequently it glows. The path of this light is affected by the strong gravity of the black hole, bending it if it passes nearby. This is what creates the ring of light in the image. If too close, photons (light) are then trapped in orbits around the black hole, and eventually will fall into it. This region of photon orbits is the famous shadow of the black hole, 2.5 time larger than the event horizon, the hole of the donut.

The colour just represents how intense the emission of light is, brighter at the bottom because the black hole is spinning**.

Animation of how the light is bent by the black hole. Credit: Smithsonian Astrophysics Observatory

How did they take this image?

The image has been taken in radio wavelengths, the ones used by radios in the past! Astronomers can take these radio waves and use a technique called interferometry to combine the information from different telescopes. This technique uses the separation between the telescopes to simulate a telescope of the size of this separation. For these observations, they used EIGHT telescopes around the globe, which means that it was basically a telescope the SIZE OF THE EARTH!

Why do we need such a big telescope?

Because we want to take such a detailed picture that we could see objects of the size of the solar system in a galaxy 55 million light-years away. To give you an idea of the detail we need, what we are seeing in this picture is the size of an orange on the moon. What?? Crazy.

Why is this image so important?

Apart from the fact that this is a technical success, with this image we are able to tell that Einstein’s theory of General Relativity accurately predicts what happens in these regions of such strong gravity. The theory predicts that the structure is nearly circular, which is what we have seen.

The combined effort of more than 200 people in 10 different countries have made this possible. You might know of one of the contributors to the algorithm that made the image possible, Dr. Katie Bouman. This is a picture when she saw the image for the first time. This is the face of someone that has seen her years of hard work paying off.

 

*Or a thousand times more massive than Sagittarius A*, the black hole of our galaxy.

** This effect is called relativistic or Doppler beaming. It tells us the direction where the black hole is spinning: clockwise in the sky.

 

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#dataHackEd

By Jennifer Sloane

If you go to twitter, you can see that #dataHackEd was trending just a couple of weeks ago. But what does dataHackEd even mean? What was all the buzz? It may be helpful to start with a definition of hacking: “Computer hacking refers to the practice of modifying or altering computer software and hardware to accomplish a goal that is considered to be outside of the creator’s original objective.” (definition from https://cyber.laws.com/hacking)

The Australian Data Science Education Institute hosted the first ever “Resource Hack Day” on March 27th 2019 in Melbourne. The purpose of the event was for teachers and “hackers” with an interest in data science education to come together and brainstorm ways to support education from primary school to Year 12. The twitter hashtag is, therefore, a play on data hacking for educational purposes.

While the main event took place in Melbourne, with help from Dr. Jenny Richmond, we organized and hosted an event at UNSW and participated remotely. Our goal was to create resources that teachers can use to help students to visualise, analyse, and interpret big datasets. At first, I thought this seemed like a very daunting task and didn’t even know where to begin. However, we had an incredible team of 6 enthusiastic researchers that were eager to get started. We all agreed to work with a dataset that looks at the trends of baby names across different states in Australia.

We spent hours analysing and trying our best to fully understand the dataset… which is not such a simple task considering there are 252,358 rows of data! You can see some of the cool graphs we created on this page using excel and two programming languages (i.e. Python and R). And if you are interested, you can check out the interactive website (https://j-sloane-92.shinyapps.io/babynames/) I created to help visualize this huge dataset. Although, as you can see from the website, I may have been biased in choosing a few of the “best” names (I’m still working on how to include all 57167 names without it crashing). Aside from creating visualizations, we spent time typing up notes, key findings, and step-by-step guides that may be useful for teachers with little to no programming experience.

An example from the interactive website of the popularity of the name “Jenny” between 1950-2000.

Hack Day was a huge success in both Sydney and Melbourne. People were working on several different projects and datasets in a shared space, so now everyone has access to all of the material. We had such a great time in Sydney, we are already planning our next Hack Day. Additionally, one of my long-term goals is to organise and run workshops at local high schools with our new resources to teach younger students all about data science in a fun, interactive, and engaging way.

If you are interested in getting involved in any way, please contact me directly (j.sloane@unsw.edu.au).

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