60-Second Adventures in Astronomy. Number
3: Exoplanets. Like fussy holidaymakers looking for a home from home, astronomers
are fascinated by finding planets similar to earth beyond our solar system. But
planets outside our solar system, known as exoplanets, are difficult to spot
because they get lost in the glare from the star they orbit, like a mosquito
flying around a streetlamp. So how do you see something that’s effectively
invisible? Observing the changing appearance of some stars, astronomers
found that an exoplanet could be detected by measuring the effect of its
gravitational pull on the star it orbits. Some can also be detected if they passed
in front of their star causing its light to dim slightly, like a wink. You can even
work out the planet’s mass and size from the amount of the star’s wobble and the
depth of its wink, which gives us a pretty good idea of what it’s made of.
Some exoplanets may even contain water because they orbit their stars in the
Goldilocks zone. Any further away they’d be too cold, any closer too hot and
although hundreds of exoplanets have been discovered, astronomers haven’t yet
found one that’s just like the Earth. Who needs a second home anyway?