But they say that even accounting for the uncertainties in the observations, the largest possible Eris is smaller than the smallest possible Pluto.
He tells his addressees that, by living in such-and-such a way, they weigh themselves down ('tibi gravis eris'; On Peace of Mind 3.6), or become a problem to themselves ('tu tibi molestus es'; Letter 21.1).
Astronomers led by Bruno Sicardy of the Paris Observatory measured how long the star disappeared behind Eris and, from that, calculated the width of Eris.
Eris was the Greek goddess of strife (the Roman Discordia).
They must have been advocates of Mr Boyle's friendly nemesis, Mike Brown, author of How I Killed Pluto and a discoverer of Eris, an object near to and similar to Pluto.
Eris is almost as large as Pluto (with a diameter of 1,163km, compared with 1,184km for Pluto) and is about 25% more massive.
(The other three—Haumea, Eris and Makemake are all, like Pluto, out beyond the orbit of Neptune).In this section Harvest festival Did dark matter do in the dinosaurs?
A generation of schoolchildren has thus grown up learning that solar system has only eight planets, and that Pluto is, like astronomical also-rans such as Ceres, Eris and Makemake, merely of the "dwarf planets".
It was Eris who cunningly dropped a golden apple with the inscription "to the fairest" into a feast, inciting three goddesses—Hera, Athena and Aphrodite to bicker over who deserved it and thus launching the ten-year Trojan War.
If Pluto counted as a planet, there seemed no reason why Eris should not as well.
Two of the dwarf planets, Pluto and Eris, are plutoids; Ceres, because of its location in the asteroid belt, is not.
