Pluto's new moon

  • Thread starter jarroe
  • Start date
Is there any chance the New Horizons probe could collide with an unseen or unknown object while making its flyby? I would assume the odds are astronmical, but if such a small body such as pluto has 5 moons, smaller icy bodies might be more frequent/common than we expected? Does anyone know if they can adjust the trajectory of the probe in time if needed?


Staff Emeritus
Science Advisor
2018 Award
The possibility always exist with anything in spaceflight. We have virtually no chance of turning the probe in time, as real time communication is impossible due to the vast distance from Earth the probe has reached. We would have to see it coming several days out at least most likely.
Objects with a size of ~1mm to 10cm are the most dangerous objects, as they are much more frequent than moons. And we have no way to detect them in this distance.

The small pluto moons have an objectradius/orbitalradius ratio of ~1/3000. The relative area is this number squared. Therefore, a random flight through the system has a probability of about 1 in 10 million to hit them (depends a bit on the parameters). This is negligible compared to all the other risks in space missions.
Thanks for the good info. I guess at the speed its moving an object the size of a dime could cripple the mission. Cant imagine the dissapointment for the team if it fails after such a long wait.

Wondering why they don't try to capture some images further out right now or even next year? Must be able to get a better picture than hubble by now? I know Kuiper belt objects are in the future, perhaps energy must be conserved and energy limits this option? Annual power loss of 0.8%. Couldn't it snap some pics now? Perhaps the resolution wouldn't be enough to accomplish anything yet? Thoughts????

The spacecraft electrical power source is a
radioisotope thermoelectric generator (RTG) with a design baseline of 10.9 kilograms of plutonium-238 dioxide,
housed in 18 general purpose heat source (GPHS) modules3, Fig. 4. The nuclear fuel provides a source thermal
energy that is converted to electrical power using silicon-germanium thermoelectric devices (solid state unicouples).
The efficiency for a GPHS style RTG is 6.4%5 and has an annual power loss of approximately 0.8% due to the
radioactive decay of the isotope fuel6.
It is currently about 1 billion km away from Pluto, while Hubble is ~6 billion km away. At this distance ratio, Hubble is better, and there are already a lot of low-resolution images.

According to Wikipedia:
Observations of Pluto, with LORRI plus Ralph, will begin about 6 months prior to closest approach. The targets will be only a few pixels across. 70 days out, resolution will exceed the Hubble Space Telescope's resolution, [Broken] lasting another two weeks after the flyby.
Last edited by a moderator:
Thanks for the info. I figured if they had the resolution now, they would've tried it already, but now I know the rest of the story. Thanks again!
They might want to avoid all the Lagrangian spots in the Pluto system too.

Don't think a ring system around Pluto would be much of a possibility, I suspect the height of the atmosphere (despite it's low density) would exceed the Roche limit for rings, and any atmosphere at all over the age of the solar system would collapse a ring a very long time ago.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving