[MDriver1981 (OP)]

Lars Von Trier, the Danish film director and screenwriter known for his optimism, practicality and love of all things, recently released a science fiction film called Melancholia, which is about Earth colliding with a "counter earth" planet called Melancholia.  The planet, Lars explained in an interview, is a Terrestrial Planet (AKA Rocky Planet) ten times the size of Earth. Despite the fact that we all know that if such a planet existed we would know of it's existence, is it possible for a rocky planet to be that big?  I don't think there is enough material in a solar system to form such a planet.  Planets that big are either gas giants or ice giants, made of much denser material than rock.  Am I wrong? 

[RD]

According to this table the maximum is between 4.35 and 10.55 Earth masses, depending on what it is made of ...

"MASS-RADIUS RELATIONSHIPS FOR SOLID EXOPLANETS
S. Seager,  M. Kuchner, C. A. Hier-Majumder, B. Militzer
Draft version February 1, 2008

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[MDriver1981 (OP)]

I've heard the term "Super Earth", describing such a planet.  From what I now understand the biggest Terrestrial Planet ever found is the extrasolar planet HD 69830 b, which is, like the fictional planet Melancholia, 10 times the size of Earth.  However, whether the planet is Terrestrial is simply a theory.  I think the planet is probably an Ice Giant like Uranus and Neptune. Some scientists believe that the cores of Jupiter and extrasolar planet HD 149026 b have rocky cores more than 10 times the size of Earth, but again, just a theory.