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Astronomical Observatory of the Jagiellonian University


Astronomy Object of the Month: 2021, August

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J0028+0035 - a fidget spinner like radio galaxy

Fidget spinners are toys that became popular in 2017, typically consisting of four bearings connected with durable plastic, resembling a triangle with a central bearing serving as a handle.

Radio astronomers use powerful radio telescopes to map the sky in a similar way to observations made with optical telescopes, such as the Hubble Space Telescope. However, images taken with a radio telescope reveal the sky in a completely different way. In the radio sky, stars and galaxies are not directly visible, but it shows numerous complex structures linked to supermassive black holes at the centers of galaxies. Most of the dust and gas surrounding a supermassive black hole is swallowed by it, but some matter can be ejected with a very high speed into space. Charged particles that move within a weak magnetic field shine as ghostly structures: radio galaxies, which we can observe using radio telescopes.

Illustration 1: Cygnus A - a typical radio galaxy. The radio core at the centre which resides in a not too distant galaxy (redshift z~0.06) is associated with a supermassive (about 2.5 billion solar masses) black hole. Jets of charged relativistic particles emanate in opposite directions and are topped with hot spots. From the hot spots, particles diffuse towards the centre, creating huge, expanding lobes. The size of the radio galaxy (as measured between hot spots) is approx. 400 thousand light yrs. Source: own composition based on VLA observations presented in the work: Perley, R. A., Dreher, J.W., Cowan, J. J., 1984, ApJ, 285L, 35.

Illustration 2: Left: J0028+0035 radio galaxy with an unusual triple structure in the centre, obtained at 323 MHz with use of the GMRT interferometer. Its size is approximately 3.8 million light yrs (for comparison, the distance between the Galaxy and M31 is about 2.5 million light yrs). Right: Fidget spinner - a popular toy resembling the central structure of J0028+0035. Source: own composition based on the data contained in the team's publication and available on the Internet.

The first picture shows a typical radio galaxy. It consists of a central core, thin jets of relativistic matter terminating with hot spots, and huge lobes. The eponymous radio galaxy J0028+0035 has three components in the centre, thus its morphology resembles a fidget spinner. The central component on the left is a distant blazar, not connected physically with the other objects visible on the map. The other two components on the right, which can be seen better in the right-hand side image, constitute a small radio galaxy consisting of a core and two lobes. J0028+0035 belongs to a rare class of restarting radio galaxies with two pairs of lobes, involving components that emerged from two different cycles of activity of the central object.

Moreover, to make yourself better acquainted with radio galaxies, we invite you to get involved with the "Radio Galaxy Zoo: LOFAR", which is a part of the Zooniverse project, the world's largest and most vibrant community-based research platform based on citizen science community. Participating in the "LOFAR Radio Galaxy Zoo" will become an exciting scientific adventure for you, while helping professional radio astronomers in exploration of the Universe.

Illustration 3: Centre of the radio galaxy J0028+0035. Left: in colours - spectral index map (i.e. weighted ratio of emission at two radio frequencies) between 1.5 and 3 GHz, contours - emission at 3 GHz. The orange colour corresponds to the more energetic particles, and the dark blue ones to the less energetic particles. Right: Map of the centre at 5.5 GHz made with a better resolution than the left-hand one. The cross on the left indicates the position of the distant blazar at redshift z=0.7. The right-hand cross shows the position of the radio core associated with the SDSS galaxy J002838.86+003539.7 at redshift z=0.4. The size of the central structure – from the edge of one lobe to the edge of the other one – is approx. 320 thousand light years (for comparison, the size of the Galaxy is about 100 thousand light years). Source: own composition based on the team's publication.

Original publication: Marecki, A., Jamrozy, M., Machalski, J., Pajdosz-Śmierciak, U., Multifrequency study of a double-double radio galaxy J0028+0035, 2021, MNRAS, 501, 853.

The research was conducted at the Department of Stellar and Extragalactic Astronomy and the Department of Radioastronomy and Space Physic Jagiellonian University’s Astronomical Observatory (OAUJ). The work was supported by the Polish National Science Centre through the grant 2018/29/B/ST9/01793.


Marek Jamrozy
Astronomical Observatory
Jagiellonian University
M.Jamrozy [at] oa.uj.edu.pl