https://www.cnet.com/news/asteroid-suddenly-shows-off-a-comet-like-tail/

A notice sent to astronomers by the International Astronomical Union said that data from the observations is "consistent with the ejection of material or commencement of activity in early Nov. 2018."

British astronomer Alan Fitzsimmons noted on Twitter that the tail of dust extends over 400,000 km (249,000 miles).