Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2021 September 1
The picture shows the radio jets emitted from distant active galaxies.
The jets, made of electrons, appear like dancing ghosts.
Please see the explanation for more detailed information.

Dancing Ghosts: Curved Jets from Active Galaxies
Image Credit: Jayanne English & Ray Norris, EMU-ASKAP, DES; Text: Jayanne English (U. Manitoba)

Explanation: Why would galaxies emit jets that look like ghosts? And furthermore, why do they appear to be dancing? The curled and fluffy jets from the supermassive black holes at the centers of two host galaxies (top center and lower left) are unlike anything seen before. They were found by astronomers using the Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope when creating maps tracing the evolution of galaxies. Images preceding this Evolutionary Map of the Universe survey only showed amorphous blobs. Eventually, comparisons of relative amounts of energy emitted revealed the glowing elongated structures were created by electrons streaming around magnetic field lines. Overlaying the radio data on an optical view of the sky (Dark Energy Survey) confirmed that the electron streams originated from the centers of active galaxies. Usually such Active Galactic Nuclei (AGN) produce straight jets. A leading hypothesis for the geometric origin of these unusually graceful shapes involves the flow of large-scale intergalactic winds.

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