I read recently that metal-rich planetary systems around large (>5 solar masses) O- and B-type stars can form enormous solid planets (potentially bigger than Jupiter) relatively quickly, photoevaporating their atmospheres to ensure that they don't become gas giants. Unfortunately these types of stars tend to have lifespans of 50 million years or less; not enough time for really interesting planets to arise before the inevitable supernova.
How can I have a high-metallicity system older than 50 million years that has an O- or B-type star with at least 5 solar masses which is expected to last for at least another 10 million years?
I'd like to get as long of a lifespan as possible while still keeping the star massive enough to have the UV radiation and solar winds to form massive solid planets in a reasonable timeframe. Habitability isn't a concern, but I'd like at least a couple of the inner-system solid planets to be able to maintain an atmosphere of at least a couple bars with average surface temperatures under 1000 °K.
Unless there are ways to make a star like this last for quite a bit longer than is listed on the lifespan chart, my best bet is probably to have a non-blue star transition into a blue star.
A couple of theories based on my research:
- Blue stragglers can form in stellar clusters via stellar collision or mass-transfer from a binary companion. This results in a star that has 2-3 times as much mass as other stars in its cluster, potentially allowing for a star to form planets normally and then grow to (hopefully) over 5 solar masses, turning its inner gas giants into chthonian planets.
- Horizontal-branch blue giants can pass from a red giant phase to a blue giant phase before moving on to the asymptotic giant branch (which caps the star at 10 solar masses, precluding it from being O-type). Since blue giants tend to have upwards of 7 solar masses, this definitely meets my size requirement, but I haven't been able to find out how long the period between the formation of the star and the end of the blue giant phase would be.