The author is Sir Martin Rees, the leading astronomer in the UK (Astronomer Royal), and former president of the Royal Society. It's not some random journalist.

https://en.wikipedia.org/wiki/Martin_Rees

He's The Right Honourable Lord Rees these days.

It's common for journalists to be told science news before an official announcement if they agree not to publish on it until afterward. This is called an embargo.

If it is a rumor it's probably on very good authority. The author appears to be extremely reputable.