6. Stars Can Be Smaller (And Colder) Than Planets
We picture even the wimpiest stars being far more substantial than, say, a planet. But astronomers have just discovered the cutest, littlest star ever, EBLM J0555-57Ab.
It’s only 600 light-years away, and its radius and mass are only about 8 percent that of the Sun. In fact, it’s so small that it’s only a hair larger than Saturn. So it wouldn’t even be the largest planet in our solar system thanks to Jupiter. It’s even colder than some gas giant exoplanets.
EBLM J0555-57Ab really straddles the threshold of stellar mass, just barely beefy enough to fuse hydrogen into helium and avoid a fate of undignified brown dwarfiness.
5. TRAPPIST-1 Is Too Old For Life
The seven-planet TRAPPIST-1 system discovered in February 2017 is a prime suspect in the search for alien life, with multiple potentially habitable planets. At least it was when its age was estimated at 500 million years old.
But new criteria, including the system’s speed around the center of the galaxy, the star’s metal content, and chemical absorption lines, suggest that the TRAPPIST family is at least as old as our solar system and potentially twice as old at 9.8 billion years.
So it’s unlikely to host life as it was probably sterilized by flares long ago, a cosmic tragedy and reminder of how rare life may be.