Gliese 581 d

Gliese 581d (often shortened to Gl 581d or GJ 581d) is an extrasolar planet orbiting within the Gliese 581 system, approximately 20.4 light-years away in the Libra constellation. It is the third planet claimed in the system and (assuming a five-planet model) the fifth in order from the star.
Though not confirmed to be a terrestrial planet and significantly more massive than Earth (at 6.98 Earth masses), the Super-Earth is the first exoplanet of terrestrial mass regarded as orbiting within the habitable zone of its parent star.
Assuming its existence, computer climate simulations have confirmed the possibility of the existence of surface water and these factors combine to a relatively high measure of planetary habitability.
== Hello from Earth ==
As part of the 2009 National Science Week celebrations in Australia, Cosmos magazine launched a website called "Hello from Earth" to collect messages for transmission to Gliese 581d. The maximum length of the messages was 160 characters, and they were restricted to the English language. In total, 25,880 messages were collected from 195 countries around the world. The messages were transmitted from the DSS-43 70 m radio telescope at the Canberra Deep Space Communication Complex at Tidbinbilla, Australia, on 28 August 2009.
== See also ==
* Gliese 581 (system)
* Exoplanet
* Earth similarity index
* Kepler-186f
* HD 85512 b
Category:Exoplanets
Category:Gliese 581 System