Digital photography

Thats going to be a really hard criterior to satisfy with a compact. Anything that cheap will be extremely noisy at the ISOs required for star trails. Maybe a second hand canon s100 could get something resembling acceptable at smaller sizes.
For space stuff you really need ultra wide angle, fast aperture lenses in front of a big sensor beyond Iso 3200.

What? It's the complete opposite. Low speed and smaller aperture for best results. Wide angle would be helpful for sure. All you technically need is a B mode.