Astro Blog

By ScienceAdvisor.  Excerpt: Most small worlds in the outer Solar System are not expected to have atmospheres. Gas escapes too easily, and there is little to replace it. Pluto, larger and rich in ices that can vaporize into gas, has long been the only known exception. Now,  astronomers have spotted a thin atmosphere around a much smaller object . Known as 2002 XV93, it’s a distant plutino, a Kuiper Belt object ...described in a new paper in  Nature Astronomy . At roughly 250 kilometers in radius, it falls far below the size thought necessary to sustain an atmosphere. But in January 2024, as the object passed in front of a distant star, astronomers noticed something unusual: The starlight did not vanish all at once, but instead dimmed gradually. That subtle fade is the telltale signature of an atmosphere. ...By modeling the signal, researchers estimated a surface pressure of about 100 to 200 nanobars, tens of times thinner than Pluto’s atmosphere, but far denser than expec...

https://www.nytimes.com/2023/02/08/science/quaoar-rings-roche-limit.html By Kenneth Chang , The New York Times.  Excerpt: Quaoar, which orbits the sun in the distant Kuiper belt, is the latest small object shown to have a ring like the ones around Saturn. ...Quaoar (pronounced KWA-wahr ...is a little less than half the diameter of Pluto and about a third of the diameter of Earth’s moon. It is likely to be big enough to  qualify as a dwarf planet , pulled by its gravity into a round shape. ...The ring is not visible in telescope images. Rather, astronomers found it indirectly, when distant stars happened to pass behind Quaoar, blocking the starlight. From 2018 through 2021, Quaoar passed in front of four stars, and astronomers on Earth were able to observe the shadow of the eclipses, also known as stellar occultations. However, they also observed some dimming of the starlight before and after the star blinked out. That pointed to a ring obscuring part of the light, an inte...

https://www.nytimes.com/2019/03/18/science/ultima-thule-new-horizons.html Source:   By Kenneth Chang, The New York Times. Excerpt: ...New Horizons traveled some 4 billion miles to take a close-up look at this 22-mile-long world in the solar system’s icy Kuiper belt beyond Neptune; it is officially designated as 2014 MU69 and nicknamed Ultima Thule. ...a small shard that has been frozen and almost unchanged since it formed 4.5 billion years ago. Ultima Thule was ... full of surprises. The shape turned out to be unlike anything seen in the solar system. ...two objects that at some stage touched and stuck together, like a snowman. Then the scientists discovered that the two lobes of Ultima Thule were not spherical, but more like lumpy pancakes. The larger lobe is also flatter than the smaller one. ...a change from older ideas of planetary formation: that objects called planetesimals grew slowly and steadily in size. Ultima Thule suggests an alternative scenario in which a bunch of...

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20190102 Source:  By New Horizons Mission. Excerpt: Scientists from NASA's New Horizons mission released the first detailed images of the most distant object ever explored — the Kuiper Belt object nicknamed Ultima Thule. Its remarkable appearance, unlike anything we've seen before, illuminates the processes that built the planets four and a half billion years ago. "This flyby is a historic achievement," said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. "Never before has any spacecraft team tracked down such a small body at such high speed so far away in the abyss of space. New Horizons has set a new bar for state-of-the-art spacecraft navigation." The new images — taken from as close as 17,000 miles (27,000 kilometers) on approach — revealed Ultima Thule as a "contact binary," consisting of two connected spheres. End to end, the...

http://pluto.jhuapl.edu/News-Center/ Source:   NASA New Horizons is the superb spacecraft mounted with instruments that gave us all those rich, rich images and data in its flyby of Pluto in July of 2015.  Soon those exquisite instruments can be focused on yet another world in our Solar System, this time a Kuiper Belt object! Ultima is 100 times smaller than Pluto, but was likely formed 4.5 or 4.6 billion years ago, 4 billion miles from the Sun. It's been at near absolute zero temperature ever since, so it's likely the best sample of the ancient solar nebula ever studied. Will Ultima turn out to be a collection smaller bodies? Will it have an atmosphere? Will it have rings? Will it have moons? Any of that could be possible, and soon we'll know the answers to these questions. It flies by Ultima News Years Day — 2019 Jan 1. Get ready to wish New Year to New Horizons.

Source:    European Southern Observatory  Release eso1142 Excerpt: In November 2010, the distant dwarf planet Eris passed in front of a faint background star, an event called an occultation. …Occultations provide the most accurate, and often the only, way to measure the shape and size of a distant Solar System body. …The combined observations from the two Chilean sites indicate that Eris is close to spherical. …Eris… discovery was one of the factors that led to the creation of a new class of objects called dwarf planets and the reclassification of Pluto from planet to dwarf planet in 2006. Eris is currently three times further from the Sun than Pluto. …Eris’s newly determined diameter stands at 2326 kilometres, …This makes its size better known than that of its closer counterpart Pluto, which has a diameter estimated to be between 2300 and 2400 kilometres. …The motion of Eris’s satellite Dysnomia was used to estimate the mass of Eris …27% heavier than Pluto … Eris i...

Source:   Dauna Coulter, Science@NASA Excerpt: At this very moment one of the fastest spacecraft ever launched -- NASA's New Horizons -- is hurtling through the void at nearly one million miles per day. ... headed for the lonely world of Pluto on the outer edge of the solar system. Although astronomers now call Pluto a dwarf planet, "it's actually a large place, about 5,000 miles around at the equator," says Alan Stern, principal investigator for the mission. "And it's never been explored."  science.nasa.gov/science-news/science-at-nasa/2011/02sep_newhorizons/

Source:    NASA RELEASE: 11-234 Excerpt: Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy dwarf planet Pluto. The tiny, new satellite, temporarily designated P4, was uncovered in a Hubble survey searching for rings around the dwarf planet. The new moon is the smallest discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto's largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and Hydra, are in the range of 20 to 70 miles in diameter (32 to 113 km). ...The dwarf planet's entire moon system is believed to have formed by a collision between Pluto and another planet-sized body early in the history of the solar system.  …For images and more information about Hubble, visit: www.nasa.gov/hubble and http://hubblesite.org/news/2011/23    www.nasa.gov/home/hqnews/2011/jul/HQ_11-234_HST_Pluto_Moon.html

Source:   NASA RELEASE: 2011-234     Excerpt: Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy dwarf planet Pluto. The tiny, new satellite, temporarily designated P4, was uncovered in a Hubble survey searching for rings around the dwarf planet. The new moon is the smallest discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto's largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and Hydra, are in the range of 20 to 70 miles in diameter (32 to 113 km). ...The dwarf planet's entire moon system is believed to have formed by a collision between Pluto and another planet-sized body early in the history of the solar system.  …For images and more information about Hubble, visit: www.nasa.gov/hubble and http://hubblesite.org/news/2011/23    www.nasa.gov/home/hqnews/2011/jul/HQ_11-234_HST_Pluto_Moon.html

Source:   Nancy Atkinson, Universe Today Excerpt: … Eris — that pesky big dwarf planet that caused all the brouhaha about planets, dwarf planets, plutoids and the like — has gotten a closer look by a team of astronomers from several different universities, and guess what? Eris and Pluto have a lot in common. Eris appears to have a frozen surface, predominantly covered in nitrogen ice and methane, just like Pluto. …“By combining the astronomical data and laboratory data, we found about 90 percent of Eris’s icy surface is made up of nitrogen ice and about 10 percent is made up of methane ice, which is not all that different from Pluto,” said David Cornelison, coauthor and physicist at Missouri State University…. www.universetoday.com/75123/eris-and-pluto-two-peas-in-a-pod/