For many people , the definition of a satellite was only made clear in 2006 , when the spunky world Pluto was demoted from a satellite to a dwarf planet . Now , a team of astronomers is pushing for “ satellite ” itself to be redefined to encompass bodies that orb stars besides our Sun .
The team’spaperis currently host on the preprint server arXiv and comes in improvement of the International Astronomical Union ’s General Assembly next month . The current definition of satellite was established at the union ’s General Assembly in 2006 , back when Pluto failed to satisfy those standards .
Why are we still talking about Pluto?
To be clear , Pluto is not the main focus of the squad ’s petition . Rather , the team ’s focus is on the thousands of exoplanets — worlds orbiting stars beyond our solar system — that are excluded from the current definition of planet .
NASA has confirmed nearly 6,000 exoplanets in the evident world , but the agency expects that zillion are out there . Exoplanets are fascinate venues for all kinds of enquiry , includingquestions about planetary phylogenesis , thegrowth of star systems , andeven astrobiology — the hunting for life-time beyond our satellite .
“ All the planets in our solar arrangement are dynamically dominant , but other object — including dwarf planet like Pluto and asteroids — are not , ” pronounce Jean - Luc Margot , a planetary scientist at UCLA and the study ’s lead generator , in a universityrelease . “ So this property can be included in the definition of major planet . ”
Pluto as seen by New Horizons© NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
How does the proposed definition of ‘planet’ differ from the existing definition?
In 2006 , the IAU famously cut down Pluto from the pantheon of planets because it did not foregather the union ’s touchstone . As stated on the uniting ’s website , a planet in the solar system :
The recent team ’s definition is all-inclusive , and does not specifically go for to bodies in our solar system , a jolly small subdivision of the galactic backyard , much less the universe of discourse . Their definition of a planet is one that :
When some otherwise - planets are too large , like some gasolene giants , they undergo nuclear spinal fusion , thereby becoming a brownish dwarf rather than a satellite . That ’s why the team put an upper bound on mass in their definition of a planet . And in case you ’re wondering , Plutoweighsapproximately 2.89 * 1022(1.31 * 1022 kg ) . The team remark that scallywag planets — bodies floating through space , unbound by the gravitational field of a star or similar body — should satisfy the second two criterion that they delineate .
An illustration of different types of exoplanet, or planets outside our solar system. © NASA/JPL-Caltech
“ have got definitions anchored to the most easily measurable quantity — aggregated — removes arguments about whether or not a specific target meets the measure , ” said Brett Gladman , a planetary scientist at the University of British Columbia and co - author of the newspaper , in the same release . “ This is a helplessness of the current definition . ”
The definition of planet won’t change immediately
The team is only present its retool definition of planet in the get together next month , so do n’t expect a change to pass overnight . But if the team is successful , the M of worlds we call exoplanets may simply be called planets .
In a certain light , you could say the move would take us away from an isolationistic categorization of our own being ; alternatively of planets just being our cosmic neighbors , planets could refer to any one of the countless cosmos in our world .
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