You know about exomoons, don’t you? Moons orbiting a planet that is going around a distant star are referred to as exomoons. Even though finding exoplanets has become straightforward and we now achieve it with great success, the same isn’t the case with exomoons. In fact, we haven’t confirmed the detection of even one exomoon. A recent research has come up with a possible reason as to why this has been the case so far.
Transit technique
In order to detect exoplanets, orbiting space telescopes stare at many stars for as long as possible. When an exoplanet crosses in front of the face of its star from our point of view, the brightness of that star reduces a bit. This dip in brightness thus corresponds to an exoplanet transit and provides evidence of such planets orbiting other stars.
The problem with detecting exomoons stems from the fact that we need to identify a transit within a transit. Add to it the fact that moons are usually much smaller than planets, and it calls for stronger observations and equipment with higher sensitivity.
In this research, scientists used simplified simulations to find out if we are simply not good at finding exomoons or if exomoons itself are relatively rare. Turns out, it is the former for now.
Stable moons
Researchers found that planets close to their stars lose their moons rather quickly and the probability of having a stable moon increases for planets farther away from their star.
These findings are in tune with what we see in the solar system, where Mercury and Venus do not have any moons, while Earth’s moon is a permanent fixture.
The transit method that we use to detect exoplanets works best when we are looking for planets that are close to their stars. So based on this recent research, it naturally follows that our planet-finding technique is biased towards finding planets that are less likely to retain their moons. It is no surprise, therefore, that we haven’t identified exomoons yet.
As our techniques and instruments improve, we will soon start detecting exoplanets that are farther away from their stars. And when we start doing that, the likelihood of finding exoplanets with exomoons would also improve significantly.
Picture Credit : Google
