When searching nearby stars for exoplanets, astronomers typically either look for the dimming of the stars’ light as planets pass in front of them or try to see if the stars themselves exhibit a slight wobble due to the gravitational tug of orbiting worlds. But recently scientists using the Hubble Space Telescope have found a curious clue in the disk of gas and dust surrounding a star 192 light-years away: a long, darkened swath that orbits the star every 16 years and may indicate the presence of an orbiting planet.
“The fact that I saw the same motion over 10 billion miles from the star was pretty significant, and told me that I was seeing something that was imprinted on the outer disk rather than something that was happening directly in the disk itself,” said John Debes of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, leader of the research team. “The best explanation is that the feature is a shadow moving across the surface of the disk.”
Read the full story from NASA at Hubble Captures ‘Shadow Play’ Caused by Possible Planet
Recent findings from the New Horizons team reveal that Pluto’s third-largest satellite Nix is covered in the purest water ice yet observed in the dwarf planet system, even purer in spectra than what was seen on its slightly larger sibling Hydra. This analysis further supports the hypothesis that Pluto’s moons were created in an impact event that formed the Pluto-Charon system, over 4 billion years ago.
Discovered in June 2005, distant Pluto’s outermost moon Hydra it thought to have formed during the same collision four billion years ago that created the Pluto-Charon system that we see today. Yet despite its age this 31-mile (50-km) -long moon appears remarkably clean and bright, as witnessed by New Horizons during its close pass through the Pluto system in July 2015.
Whether you want to call it a planet, dwarf planet, Kuiper Belt Object, or some or none of the above, there’s no denying that Pluto and its family of moons are true curiosities in the Solar System. Not only does little Pluto have one moon — Charon — that’s so massive in comparison that they both actually orbit each other around a central point outside the radius of either (if you feel like adding “binary” to whatever term you prefer to use, go right ahead) but it also has four other smaller moons in orbit that kinda sorta break the rules of how moons are “supposed to” behave.
Scientists using the Hubble Space Telescope have identified a new moon in orbit around distant Pluto. Estimated to be between 8 to 21 miles (13 to 31 km) in diameter the moon has been designated P4… at least until a more fitting name can be decided upon.
P4 lies between the orbits of Nix and Hydra, two moons discovered in 2005. It completes an orbit around Pluto about every 31 days.
Pluto’s largest moon Charon is 648 miles (1,043 km) across. Nix and Hydra are each about 20 to 70 miles (32 to 113 km) wide.
Read the press release here.
Credit: NASA, ESA and M. Showalter (SETI Institute)