In journal club today, we discussed the recent study by Matsakos and Königl that investigated the possibility that hot Jupiters can be ingested by their host stars.
The idea that stars might ingest hot Jupiters has been around since the planets were first discovered. The putative accomplice in this type of astrophysical murder is tidal interaction between the planet and host star (the same kind of interactions that cause the Moon to recede from the Earth).
Tides cause the hot Jupiters to slowly spiral into their host stars, while spinning up the host star, but the strength of the interactions drops off rapidly with distance between the planet and star. The first hot Jupiters were far enough from their stars that they are probably safe from tidal destruction.
However, astronomers have continued to find planets closer and closer to their host stars, raising again the specter of planetary tidal destruction.
These same tidal interactions also align a host star’s equator to its planet’s orbital plane. So stellar equators that start out highly inclined to their hot Jupiter’s orbit (and there are a surprisingly large number) can end up completely aligned, but, as Matsakos and Königl argue, only at the cost of the planet’s orbital angular momentum.
The upshot of this is that many of the exoplanet host stars with equators aligned to their planets’ orbital planets may have eaten a hot Jupiter early in their lives. Under some reasonable assumptions, Matsakos and Königl show that the observed distribution of inclination angles for host star equators is consistent with about half of the stars having eaten a hot Jupiter.
Fortunately, the planets in our solar system will not suffer the same fate — at least not for a few billion years. But once the Sun leaves the Main Sequence and enters stellar senescence in a few billion years, its radius will blow up, destroying Mercury and Venus. Whether the Earth is also consumed by the approaching cloud of plasma is not clear, but if exoplanet studies have taught us anything, it’s that the universe is a tough place to be a planet.
Today’s attendees included Jennifer Briggs, Emily Jensen, and Tyler Wade.