Astronomy Picture of the Day: One Arm Against the Dark!

 

#NASA, #Space, #astronomy, #διάστημα

Black Hole Most spiral galaxies unfurl in elegant pairs of arms. NGC 4378 refuses the convention. In this luminous view from the Vera C. Rubin Observatory, the galaxy reveals itself as a near-perfect asymmetry: a single, tightly wound arm that nearly completes a ring around a bright central bulge, as if the second arm simply never arrived. Roughly 80–140 million light-years away in the Virgo Cluster, this early-type spiral is thought to owe its solitary arm to a grazing encounter with a smaller companion long ago—an impulsive tidal wake that never settled into the usual two-armed pattern. At its heart sits a Seyfert II nucleus: a supermassive black hole roughly a hundred million times the mass of the Sun, quietly powering a bright, high-energy core while the surrounding disk still shines with the light of younger stars. The result is both graceful and slightly uncanny—a galaxy that looks almost complete, yet forever missing its matching half. (Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA)