For a period, astronomers referred to 55 Cancri e as a "super-Earth." A super-Earth is a planet that is far larger than our own—in this example, twice the size. 55 Cancri e is so near to its star that it orbits it in just 18 days, despite being 40 million light-years away in the Cancer constellation. One of its most astounding attributes, because to its proximity to its star, is its temperature, which registers a stunning 4,900 degrees Fahrenheit (2,700 degrees Celcius). That heat, along with the density of 55 Cancri e, led scientists to hypothesise that the planet's core was composed of carbon in the form of diamonds and graphite.