The musician – real name Terence Wilson – was a part of the Birmingham-based band for more than 30 years.
Breakaway band UB40 featuring Ali Campbell and Astro announced the news on Twitter, writing: “We are absolutely devastated and completely heartbroken.”
The statement added: “The world will never be the same without him.”
Astro, who was set to perform as part of the breakaway group on a 2022 tour, died after a short illness.
As part of UB40, Astro sold more than 70 million records. They had three UK number one hits, including “Red Red Wine” and Elvis Presley cover “Can’t Help Falling in Love”.
Astro sang the lead vocals on “Rat In Mi Kitchen”, which was released in 1987.
Astro left the band in 2013, teaming up with Campbell, who quit in 2000, for a new music project.
UB40 continue to perform with their current line-up.
In a statement on Twitter, Astro’s former band wrote: “We have heard tonight, the sad news that ex-member of UB40, Terence Wilson, better know as Astro, has passed away after a short illness. Our sincere condolences to his family.”
In an interview in 2016, Astro told UK Music Reviews that he was given his nickname as a child because he owned a pair of Dr Martens boots that featured the label “Astronaut”.