Biggest Super Earth

When it comes to super-Earth planets, you cannot get any bigger than heavyweight world HD 69830b. Roughly 10 times more massive than our home planet, this rocky world is arguably the largest exoplanet in super-Earth flavour that has so far been uncovered in our high-tech hunt for alien worlds around distant stars.

Orbiting its 41 light-year distant orange dwarf star, HD 69830, which rests in the constellation of Puppis, the large super-Earth is on a tight orbit which it can complete in nearly nine days.

HD 69830b was uncovered by a team of scientists led by veteran exoplanet hunter Christophe Lovis back in May 2006, using the European Southern Observatory’s HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph on the 3.6 metre La Sila telescope in the Atacama desert in Chile. The scientists also noticed that it is not alone around its star.

Behind it in much more distant orbits are its larger companions, two collosal gas giants, HD 69830c and HD 69830d which weigh in at around 12 and nearly 19 Earth-masses respectively.

Biggest Super EarthIt is thought that any world exceeding the mass limit of 10 Earth-masses enters a category of its own and just like HD 69830b, earn their class on the basis of their weights. Planets like HD 6980b are dubbed ‘the super-Neptunes’ due to their masses which are similar to our Solar System neighbour.

Due to its proximity to its star and the fact that it is out of its habitable zone – the distance from a star where it is possible for water to exist – chances of there being life on this super-Earth are really rather slim. But what if we were able to somehow move HD 69830b to a distance where conditions were just right? According to experts, super-Earths are not just scaled-up versions of their prototype, our planet, they’re often presumed to be hostile worlds. Our home hosts a well defined core, mantle and crust, believed to have formed within its first 50 million years, through which heat is transported from the cooling core to the crust before bursting out into volcanoes. Additionally this convection of heat drives the plate tectonics that are crucial for recycling carbon and keeping an ideal climate.

HD 69830bDuring their formation, super-Earths are not so lucky. Under the high temperatures and pressures within them, the viscosity of the rock, which the formation of a planetary core relies on, increases dramatically slowing the formation of the core, mantle and crust. And even if some internal structure formed within exoplanets like HD 69830b, the convection of heat would be slow. This would stop plate tectonics and minimize the volcanic activity which spews out the carbon dioxide that is so important for a planet to form an atmosphere and to keep it warm. Additionally, cooling of the core is reduced and the slowing of the dynamo effect snubs the presence of any water on the surface. The hostility continues as experts believe that the generation of a magnetic field is also out of the question, failing to hold onto any atmospheric water vapours as it is lost to space, and that’s even if an atmosphere was able to be created in the first place. However, despite all of the doom and gloom, and obviously if HD 69830b could somehow move to a more comfortable position and have tectonic plates, large quantities of water found in the lithosphere could actually assist in engineering plate tectonics despite a weak heat flow in the interior.

Due to tidal heating within its interior, planet hunters believe that HD 69830b could throw out heat which would dwarf that outputted by Jupiter’s volcanic moon, Io, by at least 20 times. Could this super-Earth harbour the jagged forms of volcanoes on its surface like Jupiter’s companion or Venus? It is certainly possible but at the current time with current technology we unfortunately cannot say for sure.

HD 69830b Specs

  • Size: 10 times that of Earth
  • Distance from Earth: 41 light years
  • Type: Super-Earth
  • Most like: Earth x 10

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