PubhD #28: Astronomy Special

First up is Sally, whose research is based on the Sun. Not the pro-Brexit newspaper detested by many, but our nearest star.

Sally is looking at pictures of the Sun's magnetic field at the surface. Here there are active regions where a lot of the sun's activity appear as flares, and coronal mass ejections occur. These active regions appear dark in the visible spectrum and we refer to them as Sun spots. The field strength is measured by a satellite orbiting Earth that takes images in seven different wavelengths.

There is an eleven year solar cycle that is driven by the magnetic field. The field changes over these eleven years due to the motion of the charged particles in the sun. This change happens quicker at the equator as the plasma there moves faster than at the poles.

This all happens in the Sun's middle layers. A strong magnetic field breaks through the surface and causes Sun spots. As the active regions emerge, they start dispersing. Eventually, it returns to the start point but the magnetic field has flipped. The key thing that Sally is interested in, is how the distribution of the magnetic field values change as the active regions disperse.

Over the eleven year cycle, the Sun moves from a solar minimum to a solar maximum and back again. The solar maximum is a time of more Sun spots and the Sun actually emits more light at this time. When the river Thames froze over, it coincided with a long solar minimum.

Key learning: The sun takes a month to rotate

Next up is Sarah, who is UCL's outreach coordinator and is looking at how science is taught in schools.

Part of her work also involves talking with university lecturers about what their undergraduates will know when they first walk through the door – they won't just magically know physics. Sarah is also speaking with students about where studying physics can lead to. When going into primary schools, it's clear that kids love space. However, by age eleven, they have already decided whether or not they like science and a lot of primary school teachers have no science background. At the end of one her days in school, Sarah asked the pupils to draw a scientist – most drew the classic ‘Einstein’ - white man in a lab coat. None of them seemed to realise that Sarah is a scientist.

Kids also love black holes, which is what Sarah researched for her PhD. However, they aren’t the ‘space hoovers’ that children think of them as, they are actually more like the Cookie Monster, with more stuff being spewed out than swallowed. Astronomers, who are awful at naming things, refer to them as Active Galactic Nuclei. In images, they are the bright (active) spot at the centre (nuclei) of a galaxy (galactic)

In fact when Sarah says that she has studied black holes, she actually means that they study the part before the event horizon, as we still don't know what happens when we reach the event horizon. But, we can see the energy given off when things collide near the event horizon. From looking at this energy, we know that black holes are the most efficient converters of mass into energy in the universe.

Back onto science in schools, Sarah talks about whether things like Tim Peake's lettuce seeds from space can help encourage children to be interested in science. But how do we keep them interested? How do we get more science graduates into teaching? Only 9% of primary school teachers did some science in their degree course. Sarah still has some work to do.

Key learning: You can model space/time using a ball and a trampoline

Finally, we have Daniel, who arrives late after playing football, but whose research is on gravitational waves.

The study of gravity started down the A52 in Grantham with Isaac Newton. Then, Albert Einstein completely rethought physics. He saw that mass bends space-time, which affects all objects. He also predicted gravitational waves. These are ripples that travel out from objects as they move. Einstein's gravitational waves paper was rediscovered in the sixties.

But how do we detect them? We measure the distance between two masses, but the size of movement caused by gravitational waves is a tenth of the diameter of a hydrogen atom's nucleus. So, detectors have to be very sensitive and they also need to be big. But this means that on Earth, detectors can be affected by earthquakes, tides hitting the coast on the other side of the country or even birds. One early detector in Germany was upset by rabbits jumping up and down outside.

But what kinds of objects cause gravitational waves? The first two detections were caused by black hole collisions. These binary black holes can teach us about stellar formation, but the first detection spawned many new questions as they appeared to be the ‘wrong type’ of black hole. Eventually, it is hoped that we will be able to detect gravitational waves from neutron star collisions and from super nova.

Black hole collisions are very rare occurrences – they happen once every 250,000 years. It was pure luck that the first collision was discovered as the detector wasn't due to be switched on until two days later.

Key learning: Every non-symmetrical mass produces gravitational waves, but they are usually too small to detect.

PubhD returns to the Vat and Fiddle on the Wednesday 20 July, 7.30pm with talks on Classics, Chemistry and History. 

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