Peering at Pluto in preparations for a satellite visit in 2015, the Hubble Space Telescope has spotted a fourth moon orbiting the dwarf planet. The wee moon doesn't even have a name yet — it's called P4 for now — and its estimated diameter is between 8 and 21 miles.
That's right, Hubble spotted something the size of a city from a distance of more than 3 billion miles away.
Pluto's new moon is smaller than the dwarf planet's other companions; the big one, Charon, is 648 miles across, and the other moons, Nix and Hydra, are in the range of 20 to 70 miles in diameter, according to NASA. Hubble discovered those moons back in 2005.
P4 is located between the orbits of Nix and Hydra. Hubble's Wide Field Camera 3 ultraviolet visible instrument, which was installed on the telescope's final servicing mission two years ago, first picked it up on June 28, and then confirmed it in follow-up pictures taken July 3 and July 18. It may appear as a faint smudge in images from 2006, NASA reports, but no one noticed because it was too obscured. This recent set of photos was taken with longer exposures, allowing P4 to resolve more clearly.
Charon, first discovered back in 1978 and first imaged in 1990, is one of the reasons why Pluto was demoted from planet status. It's about half the size of Pluto, and the two bodies act as a binary system, rotating around a common center of gravity. Some astronomers referenced this during debates about planetary classification back in 2006.
Scientists believe Charon and the other moons formed when another object sheared off a huge chunk of Pluto, much the same way that our moon formed when a Mars-sized object sheared off a piece of Earth.
Astronomers planning for the 2015 arrival of NASA's New Horizons spacecraft were excited about the discovery, because now they can plan closeup observations. And NASA was also excited about the discovery's importance for Hubble — "it's a powerful reminder of Hubble's ability as a general purpose astronomical observatory to make astounding, unintended discoveries," said Jon Morse, astrophysics division director at NASA headquarters.
Given that it may be on its own for a while, that's a nice reminder.
FOURTH moon? when last I heard, pluto only had ONE moon? when were the other two found?
Ok as of today, is Pluto a considered a planet or not a planet? If it’s a asteroid, then it has 4 asteroids spinning around it, yes, no? I thought the term moon was reserved for big rocks\asteroids that obit a planet. Then again, our moon is also called a satellite too.
How come Pluto got 4 moons and we only have one.
This is not fair.
Screw you Big Bang.
yeah f that bs, i'm moving to pluto. The night sky would be so much more badass if we had 4 or even TWENTY moons
I was at the Chicago planetarium last week and they have Pluto listed as a planet; guess they never got the memo?
Rebecca, Pluto is not going to be visited by a satellite. A satellite is one object that orbits another. Pluto is being visited by a robotic spacecraft and it's a flyby to boot. Of course fifty years ago, moons were referred to as satellites and orbiting spacecraft were called artificial satellites...
Overall however, I found your article well crafted and informative. Keep up the good work!
Just to clarify, Pluto is currently classified as a "dwarf planet", along with four others in our solar system - Ceres, Haumea, Makemake, and Eris.
"That's no moon ...."
Ok, so its now called a Dwarf Planet, then I suppose it has 4 Dinky Moons? lol.
@kormiko; you stole my line.
They have not started parsing out moons by size yet, but before they get to that they will probably reclassify Pluto and Charon as binary dwarf planets because they orbit around a common center of gravity that is not within either body. In which case Pluto-Charon will have 3 moons which will be later classified as micro moons.
WHAO WHAO WHAO WHAT THE FRACK!!!
ok whait a minute.... pluto and charon are reported as orbiting each other in a binary system, right??
yet, that's not illustrated in the damn drawing... anybody care to update that?!? .. it's drawn incorrectly.
.. also one for the evil pricks that demoted pluto ... uh so what if they're more like a binary... that just makes them more intersting as planets.. quiky even... PLUS YOU SMUG BAST*RDS... you can't have your cake and eat it too! you forget that when i jump into the air, my own gravity pulls at the earth.. making it and anything else below me want to orbit me.. however so weakly.... and infact, the MOON.. the earths moon pulls at the earth at a MUCH greater magnitude.. one so great that i would wager a large amount of money that i bet the earth and moon share a binary orbit as well.... no matter how fractional it may be, it is without a doubt happening. .let's not forget the moon is about 1/4 (3.7:1 ratio actually) the size of the earth... infact since pluto was demoted, the moon (our moon) is the 5th largest in the solar system, yet our planet is the 4th smallest.... we should demote earth because it's a binary too. :)
"when i grow up i want to be a masterdebater" :)
@ptv83, don't confuse a gravitational "tug" causing a wobble around an axis with binary orbit.
The Moon does pull on the earth and it does cause it to wobble slightly, however, the earth does not share a central gravitational point with the moon like Pluto and Charon do, yes, the diagram is incorrect.
Playing Devil's Advocate since 1978
"The only constant in the universe is change"
-Heraclitus of Ephesus 535 BC - 475 BC
RE: "wobble" when i hear wobble, i think of either 1. A spinning top, with the bottom stationary and the top wobbling around in a circle as it rotates... or 2. the earth being anchored in the center and the top and bottom wobbling around in a circle as it rotates.
If i remember correctly from highschool the earth does do what what's described in #2. but the moon's orbit is moving away from us, which just thinking in my head would lead me to think that the earth's central wobble ancor does itself move in a small orbit. my reason for thinking this is that: why a gravity assisted method of 'sling shoting' a spacecrft around a planet works is that the planet is moving, if the planet or moon wasn't moving it would just slow the spacecrat down and pull it back as much as it accelerated it in the approach. If the moon is slowly escaping us (and it is) then the earth would have to be moving in relation to the moon in order for that to happen.... now this is just a guess by a guy who never went to college and only got his GED because actually going to school was far too boring... but it is a hypothesis that would work.
also the moon orbits 20 or 30'ish (i forget) degrees off the equator this path of gravitational force around the earths own centralised force of gravity is close enough to center to move the earth very slightly off what would otherwise(without a moon this close in size) its centered rotational anchor point. thus making that point move in a small circle/oval/elipse/whatever
the moon is damn near 1/4 the size of the earth.. and that's a LOT of force.... and if the earth wasn't moving too, why is the moon escaping like a sling shotted space craft around mars or venus?
.. one man's thoughts that seem to him that make perfect sense.. in his own head atleast...
i forgot to say.. and while this is not the same as pluto roating around a point that is located outseide of its own mass... the earth would be orbiting around a point located within its own mass, caused by the moons pull.
unless i'm missing something, which is very likely possible... (once i hit 16 i quit school and went to work... asked for the exams to enough credits to get my GED early, skipped studying for them and took them all in a the following 2 weekends.. as such there's a whole whack i skipped past and aren't aware of.. plus all the stuff i never took when i never went to college)
is there a law of physics related to the 4 fundimental forces that applies here and i'm missing?
In theory any two objects in gravitational equilibrium orbit around a common center of granity (CG). However in most cases the orbital radius of the major body is trivial.
The Pluto-Charon CG about 2,110 km from Pluto's center( r1) . Pluto's radius is 1,150 km (R1). r1/R1 = 1.83
The Earth-moon CG is about 4,670 kms from Earth's center. Earth's radius is 6,380 km. Thus for this system r1/R1 = 0.73.
There is no official definition separating a planet-moon system from a binary (or double) planet, but the general conciseness is if r1/R1 > 1 then it is a binary planet.
The moon's orbital radius is slowing growing. If this continues there could be a point in time (a few billion years from now) where the r1/R1 for the Earth-Moon system becomes greater then 1.
a, a, yea, what he said.
glad to see another gut feeling was correct :) & grade 10 science was enough... again ! lol