PlanetStar Wiki
Register
Advertisement
Earth

Our home planet Earth, photographed by Apollo 17

Venus

Venus, photographed by Magellan spacecraft

Mid-Earth, also known as terran planet, is a classification of planet with mass ranging from 0.5 to 2 Earth masses or 0.0016 to 0.0063 Jupiter masses. Hence it is the sixth most massive mass class of planet, mid-Earth is rated M-Class VI and has the symbol Eb.

Characteristics and habitability[]

Mid-Earths typically have rocky surface since they don't usually have enough mass to have predominant fluid composition with gaseous envelope. Many mid-Earths have similar bulk properties to Earth. Those planets tend to have right amount of heat and convection in their interiors to initiate plate tectonics and volcanism. Mid-Earths also tend to have thick atmospheres as they have gravity strong enough to keep gases from escaping. On average, those planets have atmospheres thicker than sub-Earths but thinner than super-Earths, because their gravitational pull of mid-Earths are stronger than sub-Earths but weaker than super-Earths. That amount of atmosphere with abundant supply of oxygen and carbon dioxide would be conducive for multicellular life.

Abundance[]

There are an estimated 185 billion mid-Earths in our galaxy alone, making it the most abundant mass class of planet. This corresponds that 226‰ of all 820 billion planets in our galaxy are mid-Earths.

Known mid-Earths[]

There are over 40 known mid-Earths as of 2015, including two in our solar systemVenus and Earth. Extrasolar mid-Earths are extremely hard to detect because they're so small, that's why there are only less than fifth such exoplanets identified out of nearly 2000 total. The first mid-Earth exoplanet discovered was HD 10180 b (Moneta) on August 24, 2010. In December 2011 Kepler discovered four mid-Earths: Kepler-20e (Tvashtri), Kepler-20f (Shantadurga), Kepler-70b (Yami), and Kepler-70c (Hari). Kepler also found two more mid-Earths in August 2012 — Kepler-54c (Hyacinth) and Kepler-59b (Vili). Two months later, a mid-Earth was discovered in the nearest star system to Earth, Alpha Centauri Bb (Ixionidae), but the planet's existence has not been confirmed. On June 7, 2013 a mid-Earth was discovered around Gliese 667 C, but subsequent observations showed that this and signals of two other planets in the system were artifacts of noise and stellar activity.

Related links[]

Advertisement