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from the waiting-for-Snow-White-planets dept.
ESO Telescope Reveals What Could be the Smallest Dwarf Planet Yet in the Solar System
Astronomers using ESO's SPHERE instrument at the Very Large Telescope (VLT) have revealed that the asteroid Hygiea could be classified as a dwarf planet. The object is the fourth largest in the asteroid belt after Ceres, Vesta and Pallas. For the first time, astronomers have observed Hygiea in sufficiently high resolution to study its surface and determine its shape and size. They found that Hygiea is spherical, potentially taking the crown from Ceres as the smallest dwarf planet in the Solar System.
As an object in the main asteroid belt, Hygiea satisfies right away three of the four requirements to be classified as a dwarf planet: it orbits around the Sun, it is not a moon and, unlike a planet, it has not cleared the neighbourhood around its orbit. The final requirement is that it has enough mass for its own gravity to pull it into a roughly spherical shape. This is what VLT observations have now revealed about Hygiea.
"Thanks to the unique capability of the SPHERE instrument on the VLT, which is one of the most powerful imaging systems in the world, we could resolve Hygiea's shape, which turns out to be nearly spherical," says lead researcher Pierre Vernazza from the Laboratoire d'Astrophysique de Marseille in France. "Thanks to these images, Hygiea may be reclassified as a dwarf planet, so far the smallest in the Solar System."
The team also used the SPHERE observations to constrain Hygiea's size, putting its diameter at just over 430 km. Pluto, the most famous of dwarf planets, has a diameter close to 2400 km, while Ceres is close to 950 km in size.
Ceres, Vesta, Pallas, and Hygiea are the four largest asteroid belt objects. Saturnian moon Mimas is the smallest astronomical body known to be rounded due to self-gravitation, with a diameter of just 396 km.
Impact simulation video (34s).
Also at Ars Technica.
A basin-free spherical shape as outcome of a giant impact on asteroid Hygiea (open, DOI: 10.1038/s41550-019-0915-8) (DX)
(Score: 0) by Anonymous Coward on Wednesday October 30 2019, @05:37AM (5 children)
The classification boundary between such objects seems subjective and fuzzy to me. For example, if it gets hit by another object and loses a big chunk, it's no longer "round" and changes category.
(Score: 0) by Anonymous Coward on Wednesday October 30 2019, @07:03AM (2 children)
It isn't round anyway, not even the Earth is round. There is a compelling consensus forming in conspiracy circles that the earth is more cone shaped with a dome over the top and antartica as a ring around the outer rim. You'll find debunkers on both sides of course, but that many people around the world couldn't be wrong... Unless that is just a distracting existential narrative designed to keep the powers that be in control.
(Score: 0) by Anonymous Coward on Wednesday October 30 2019, @10:37AM (1 child)
I have something that is cone shaped with a dome over the top. Maybe it's a planet too.
(Score: 0) by Anonymous Coward on Wednesday October 30 2019, @03:42PM
Made out of aluminum foil, no doubt.
(Score: 1, Insightful) by Anonymous Coward on Wednesday October 30 2019, @01:09PM (1 child)
Life is "fuzzy."
To pretend that things fit into categories is silly. We need to acknowledge that there aren't fine lines, but thick ones between categories and several things will end up on that line. Still the categories are useful, even if the borders are ill-defined because most of the category isn't on the border.
I mean we can all agree that Pluto is a dwarf planet, right?
(Score: 2, Interesting) by Anonymous Coward on Wednesday October 30 2019, @03:53PM
I realize that, but the latest attempts are growing ever more unhelpful.
I suggest instead we toss out the "clearing out its orbit" crap and give category names based on their average diameter. Mass is probably more useful, but most humans relate to diameter better. Plus, it's usually easier to measure diameter than mass of distant objects.
Rough example:
501 to 1000 miles - Dibs
1001 to 1500 miles - Eebs
1501 to 2000 miles - Floogs
2001 to 3000 miles - Gurts
Etc.
Notice how the first letters are in alphabetical order (DEFG...). This gives one a way to quickly compare without looking up the ranges.
Genius, right?! Where's my Nobel now?
It's more objective and more intuitive.