Last year, the Event Horizon Telescope (EHT) presented the observations of Sagittarius A* (Sgr A*), located at the Galactic Center of the Milky Way. Their results confirm the presence of a supermassive black hole at the center of our galaxy (see Fig. 1 or this interview). Such an astrophysical object is expected to be described by the Kerr spacetime, which is a solution of Einstein’s equation for a rotating black hole. Furthermore, they also investigated potential deviations from the Kerr prediction, such as the traversable Morris–Thorne wormhole! See my previous blogpost for more context about wormholes. The visual difference between simulations of the accretion flow from the two spacetime geometries is shown in…

One thing that has always confused me since I was a bachelor: What is a power law? According to Wikipedia: “In statistics, a power law is a functional relationship between two quantities (y, x), where a relative change in one quantity results in a proportional relative change in the other quantity, independent of the initial size of those quantities: one quantity varies as a power of another.” That is, y = c x –k, where c is a constant and k is the power-law index. Well apparently, it seems that a power law is just a mathematical definition! However, you might feel surprised when I tell you that more than a hundred power-law relationships have been identified in multiple…

Tune in today (21 June 2022) at 8pm CET as host, Melanie During interviews our PhD student, Wanga Mulaudzi. In this interview, Wanga will tell us about our black hole, Sagittarius A*, and how the Event Horizon Telescope collaboration went about imaging it for the very first time in history! Watch the livestream here https://youtu.be/jWsC8HJ5d4k.

For translations of this post in Xhosa, Xitsonga, Afrikaans and Arabic, see here! If you have ever been lucky enough to be in a remote area, far away from the buzz of city life, then you might have looked up at the sky as the wonders of the Milky Way were revealed to you. Seeing the Milky Way with your own eyes is a truly magical experience. But what is the Milky Way and why does it look like a starry band of milk. Well, the Milky Way is the galaxy we live in. From our point of view, which is from Earth, when we look towards the centre of…

…that’s amore! The moon is one of the most beautiful objects in the sky to photograph. Not only is it close enough for us to resolve its craters, its apparent size is also large enough for its light to be distorted by the Earth’s atmosphere. This distortion is what causes the moon to appear to be different colours. It is important to note, however, that the moon does not produce its own light. The moon’s surface reflects light from the sun! If we were to take a photo of the moon outside of the Earth’s atmosphere, it would always appear to be a shade of grey. When viewed from inside…

Many celestial objects have certain limitations on their physical properties, governed by the laws of nature. For example, if a planet gains enough mass (around 10 times as massive as Jupiter), they become massive enough to fuse deuterium or lithium, effectively categorizing them as a star. A similar case happens for stars, which are, for most of their lives, in a stable equilibrium between the inward gravitational force of the gas and the outward radiation pressure from the energy generated by the nuclear reactions in the core. The luminosity (and by extension the radiation pressure) is highly proportional to its mass, which means that if you continue to add mass…

In this blog, I will introduce the mathematical concept of wormholes in general relativity, the possible implications in serious astrophysical research, and how this became an inspiration for the german science fiction series: Dark. With mathematics, it is possible to duplicate the geometry of spacetime, for example, we can make a copy of the Schwarzschild geometry (describing a static Black Hole) in reverse. In this reversed version, the copy behaves as a White Hole where all objects are destined to escape from it, contrary to the case of a black hole. In Fig. 2, if we consider region I being the universe where we live, then by traveling to the…

This past month, we bid farewell to Doosoo Yoon who has been a postdoctoral fellow in our group since September 2018. His work focused on using the GRMHD code H-AMR to study the dynamics of accretion disks, winds, and jets around black holes. He is also a member of the Event Horizon Telescope (EHT) project, where his main focus is to study supermassive black holes such as Sgr A* and M87. For Doosoo’s farewell dinner, we went to The Madras Diaries in Leidseplein to have some authentic South Indian dishes. A big hit for the group were the dosas, which are a crispy savoury crepe made from lentils and rice.…