I think it was later proposed it could be a galaxy that we are viewing from side on/angle - https://www.space.com/runaway-black-hole-tail-stars-mystery-solved h

I think it was later proposed it could be a galaxy that we are viewing from side on/angle - https://www.space.com/runaway-black-hole-tail-stars-mystery-solved https://www.space.com/runaway-black-hole-tail-stars-mystery-...