While it may not have a catchy name, HD 219134 b is the nearest known rocky planet outside our solar system and it deserves our attention.
The planet orbits the star HD 219134, which is visible to the human eye near the constellation Cassiopeia, only 21 light-years from the sun. Like our own solar system with Mercury, Venus, Earth, and Mars, HD 219134 b has three planetary siblings.
What makes HD 219134 b special is how near it is to us – relatively speaking. We can learn a lot about these close exoplanets by using techniques that would be difficult or impossible for those at greater distances.
For example, using a technique called the radial velocity method it’s possible to deduce an exoplanet’s mass by measuring tiny movements of the star caused by the exoplanet’s gravitational pull. This reveals that HD 219134 b has a mass of between four and five times that of the Earth, making it a type of exoplanet known as a “Super-Earth.”