Lesson plan
mega-Earth
(center), a very dense Neptune-sized exoplanet believed to be nearly entirely made of solid rock, metal, and water. A mega-Earth or massive solid planet is a type of terrestrial exoplanet that is very massive and dense — more massive than super-Earths. The term "mega-Earth" was coined in 2014, though it remained an informal category until a quantitative definition was proposed for it in 2026. Based on the measured radii and densities of known exoplanets , mega-Earths appear to be a distinct category of exoplanets that are between 2.1 and 5.0 Earth radii ( ) and have densities higher than Earth's ( ). Based on their observed high densities, mega-Earths are inferred to be largely made of solid material, such as rock, metal, and ice. If the mega-Earth is rich in volatiles like water, it may harbor a supercritical ocean under a thin atmosphere of hydrogen, helium, and other gases. The existence of mega-Earths challenges conventional theories for planetary formation, as massive planets should accrete large amounts of gas in addition to solid material from the host star's protoplanetary disk. It has been hypothesized that mega-Earths may either be remnant cores of evaporated gas giants or white dwarfs or products of consecutive collisions between super-Earths.…
Article summary
(center), a very dense Neptune-sized exoplanet believed to be nearly entirely made of solid rock, metal, and water. A mega-Earth or massive solid planet is a type of terrestrial exoplanet that is very massive and dense — more massive than super-Earths. The term "mega-Earth" was coined in 2014, though it remained an informal category until a quantitative definition was proposed for it in 2026. Based on the measured radii and densities of known exoplanets , mega-Earths appear to be a distinct category of exoplanets that are between 2.1 and 5.0 Earth radii ( ) and have densities higher than Earth's ( ). Based on their observed high densities, mega-Earths are inferred to be largely made of solid material, such as rock, metal, and ice. If the mega-Earth is rich in volatiles like water, it may harbor a supercritical ocean under a thin atmosphere of hydrogen, helium, and other gases. The existence of mega-Earths challenges conventional theories for planetary formation, as massive planets should accrete large amounts of gas in addition to solid material from the host star's protoplanetary disk. It has been hypothesized that mega-Earths may either be remnant cores of evaporated gas giants or white dwarfs or products of consecutive collisions between super-Earths.…
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.