Because it fills up the 24/7 news cycle. If you don't have 24 hours of content then the boomers could decide to change the channel - that's not good for business.
Sure, but that's the BBC. Surely there's enough news in the entirety of the UK that they don't need to resort to astronomical phenomena that are both meaningless and invisible without measuring tools. Hell, tell me what part of the sky the planets will be - at least I can see those.