Magnetically gated accretion bursts in MV Lyrae

MV Lyrae is a binary system consisting of a white dwarf accreting material from the envelope of a nearby star. This animation shows the brightness variations of the binary system MV Lyrae observed by the Kepler space-based observatory during a period where the system was found to be in an extremely deep low luminosity state (the moving image is the actual Kepler data). During this period, bursts of light are seen from MV Lyrae approximately every 2 hours. Because the white dwarf in MV Lyrae possesses a weak, but dynamically important, magnetic field, material trying to fall onto the white dwarf is halted by the spinning magnetospheric boundary. Once enough material has piled-up at the inner accretion disk edges, it pushes its way in and eventually falls onto the white dwarf, releasing bursts of light. As the inner disk has emptied, the process then repeats.

Credit: Christian Knigge, Simone Scaringi, Helena Uthas

Wave file number 1

Wave file number 2

Wave file number 3

Wave file number 4

Wave file number 5

Welcome to the feast: the munching sound of the cosmos

Accretion is the process by which objects in the Universe grow in mass through gravitationally collecting material from nearby gas, dust, or indeed companion stars. Accretion is thus responsible for the growth and evolution of most celestial objects, from young protostars still in the star forming process, to ancient supermassive black holes at the centre of galaxies. The accretion process itself is chaotic and stochastic, governed by the complex viscous processes within the disks themselves.

Accreting systems emit throughout the entire electromagnetic spectrum, but depending on the nature of the accreting object (black holes, neutron stars, white dwarfs or young-stellar objects), most of the radiation is emitted at X-ray, ultraviolet, optical or infrared wavelengths. The emitted light is far from being constant, with brightness variations occurring on timescales from milliseconds to days. These light variations (lightcurves) can be transformed into audio files by shifting the relevant frequencies into the human audible range.

These five audio files mimic what accreting systems might sound like, from giant disks the size of the Earth-Sun distance (file number 1) to small disks the size of a city (file number 5). For big systems like supermassive black holes and young stellar objects, the "sounds" will be lower in pitch when compared to smaller systems like galactic black holes. You can have a listen, or watch this video.

Here are some media coverage articles and press releases related to this:
Now We Know What A Black Hole 'Sounds' Like
Eavesdropping on Black Holes: Feasting Giants Sound Like Static
What does a black hole sound like?
Black Holes Sound Like Static
Shedding light on the growth of stars and black holes
Young stars' flickering light reveals remarkable link with matter-eating black holes
New paper shines light on little-understood process in astronomy
Universelles Gesetz für kosmischen Materiezustrom (in German)
L'accrescimento è uguale pe tutti (in Italian)
Miltä musta aukko kuulostaa? Televisio voi antaa maallikollekin vastauksen (in Finnish)
A quoi ressemble le "son" d'un trou noir? Des astronomes ont trouvé la répoe (in French)
Así suena un agujero negro (in Spanish)
¿Cuál sería el sonido que emitiría un agujero negro en el espacio? (in Spanish)

To learn more about how accretion disks of different sizes scale with each other have a look at my research page, or have a look at my article on this matter published in Science Advances.

The globular cluster M4 in the eyes of Kepler/K2

Here is a video showing nearly 3 months in the life of the globular cluster M4 as seen with the NASA K2 Mission. Each frame corresponds to 30 minutes. Clearly visible are the occasional spacecraft jitters caused by the spacecraft attitude tweaks to correct for solar pressure. Also clear are periodic variables known as RR Lyrae variables in the globular cluster. RR Lyrae stars are pulsating, old, horizontal branch stars, with a mass of around half the Sun's and pulsation periods between 4 hours and 1 day. The pulsations of these stars are thought to be caused by periodic changes in the opacity of the stars' atmospheres, known as the kappa-mechanism. When a layer of a stellar atmosphere moves inward due to gravity, it becomes hotter and denser. Usually this combination results in lower opacity in normal stars, but on the contrary RR Lyrae stars become more opaque. This causes a build-up of pressure that pushes the layer back out again, lowering the opacity, resulting in a cyclic process as the layer repeatedly moves inward and then is forced back out again.


The Crab nebula through the eyes of MAIA

Here is a pretty image of the famous Crab nebula I took on the 1.2 meter Mercator telescope on La Palma (Spain) with the MAIA camera. Two 5 minute exposures were taken in both the r- and g- bands, as well as a 10 minute exposure in the u-band. I used to align the the images (if you don't know about it, you should definitely check it out!), and DS9 to enhance the false colours. Have a read at the image caption to learn more!