Is there really no consumer program to show orbit relative to Earth? Can't you just shove orbital parameters into Universe Sandbox and press "center camera on" Earth?
One statement in the article needs a little clarification:
"This so-called “quasi-moon” isn’t a true moon or a mini-moon, because it orbits the Sun rather than our planet."
Our Moon also orbits the Sun rather than the Earth, in the sense that its orbit is always concave towards the Sun--in other words, the pull of the Sun's gravity on the Moon is always stronger than the pull of the Earth's gravity, so the Moon's net acceleration due to gravity is always towards the Sun.
Our Moon's orbit is of course much more closely tied to the Earth's than 2005 PN7, but one still has to be careful about exactly how that works.
If we want to be really pedantic, the earth doesn't even orbit the sun. Rather, both bodies orbit a point that's (roughly) their combined center of mass (which in our case just happens to be somewhere inside the sun). And of course that "roughly" is standing in for a lot of other variables, too.
> the earth doesn't even orbit the sun. Rather, both bodies orbit a point that's (roughly) their combined center of mass
Yes, that's true. Indeed, when we take into account other planets (and the Moon, and the asteroids, etc., etc.), all of these objects orbit a common barycenter.
However, that doesn't change the fact that the Moon does not orbit the Earth in this sense; its net acceleration (in a barycentric inertial frame) is never towards the Earth, or towards a common barycenter of the Earth-Moon system. Only if we ignore the motion around the solar system barycenter do we get the approximation in which the Moon and Earth orbit a common center of mass.
Ok, but this (the whole subthread, not just this msg I'm replying to) gets so deep into pedantry that it becomes borderline meaningless. The moon circles the earth approx every 28 days. When people -- even reasonably well-educated ones like me, with a couple semesters of astronomy from a world-class university -- say "orbit", that is what they mean. I'm deliberately omitting caveats about sidereal month vs synodic period, to avoid the same slippery slope I'm gently criticizing. Given there's no absolute spatial frame of reference, I'd argue that piling such caveats atop each other doesn't "move" us closer to a truer understanding.
> The moon circles the earth approx every 28 days.
In what sense? You state this like it's an obvious fact. It isn't. It contains a number of hidden assumptions, not all of which stand up to close scrutiny.
> Given there's no absolute spatial frame of reference, I'd argue that piling such caveats atop each other doesn't "move" us closer to a truer understanding.
I disagree, because "there's no absolute frame of reference" is not the same as "all frames of reference are equally useful". The former is true. The latter is not.
Once you face up to the fact that different frames are useful for different purposes, you should realize why you can't just state things like "the moon circles the earth" as obvious facts. At the very least, you have to explain why you've picked the frame of reference (centered on the Earth) in which that's (approximately) true. Basically, that would be because you're ignoring the rest of the universe and you only care about the Earth and the Moon. Which is fine for many purposes (it worked for sending humans to the Moon and back), but not for others (like saying "the moon orbits the earth" as opposed to "the moon orbits the sun"--which is simply not true, once we bring the Sun into the picture, you can no longer ignore the Sun's effect on the moon).
> Can you go further and say that the Earth and sun "really" are orbiting the center-of-mass of the milky way?
Not according to the definition I gave. Calculate the acceleration of the Earth and Sun towards the center of the Milky Way and compare it with the Earth's acceleration towards the Sun.
The description makes me think it might be a Horseshoe Orbit [0], where something spends time in about the same circular orbit, but slowly bounces back and forth through the unoccupied portion.
Looking up 2025 PN7 [1], it says:
> Over time, it may transition between quasi-satellite and horseshoe orbits due to gravitational perturbations.
It's like a bit from The Smoke Ring (or Integral Trees) by Larry Niven, where a very weird planetary configuration made a human-habitable ecosystem out of an orbiting ring of gas. [0]
The locals refer to "East" as in the direction of orbit (prograde), "In" as towards the central star, and teach their children: "East takes you Out, Out takes you West, West takes you In, In takes you East, North and South take you back."
Would be neat to be able to get some photographs of it. Curious if it's a near-Earth asteroid or yet another case of a rocket's upper stage re-entering Earth orbit (like with 2020 SO and J002E3). An expected appearance of 1957 would be pretty early for the latter case (that's when the USSR launched Sputnik 1 and 2, and I'm pretty sure both those upper stages came back down a long time ago), but who knows?
I'm just going to believe, for no good reason in particular, that it's actually an alien probe sent to watch our planet after the detection of particles from the nuclear detonations that started in the 1940s. And yes, this is very much influenced by Star Trek and the detection of our first warp drive by the Vulcan's flying by our solar system.
I'm amused
It's been at least 3 days since first news articles about it appeared, and there's not a single image of its orbit relative to Earth
best I can find it https://earthsky.org/upl/2025/09/2025-PN7-NASA-Sep-7-2025-e1... showing orbit relative to Sun
Is there really no consumer program to show orbit relative to Earth? Can't you just shove orbital parameters into Universe Sandbox and press "center camera on" Earth?
Here you go, here is its orbit from 1900 to 2100 in the earth's rotating frame, sun is at -1 on the x axis.
https://dahlend.github.io/2025_PN7_Orbit_1900-2100.png
Its hanging out for a while near us.
Shameless plug for my software I used compute it:
https://github.com/dahlend/kete
This is excellent, thank you.
Thank you!
Maybe you can get a Kerbal Space mod to add it?
One statement in the article needs a little clarification:
"This so-called “quasi-moon” isn’t a true moon or a mini-moon, because it orbits the Sun rather than our planet."
Our Moon also orbits the Sun rather than the Earth, in the sense that its orbit is always concave towards the Sun--in other words, the pull of the Sun's gravity on the Moon is always stronger than the pull of the Earth's gravity, so the Moon's net acceleration due to gravity is always towards the Sun.
Our Moon's orbit is of course much more closely tied to the Earth's than 2005 PN7, but one still has to be careful about exactly how that works.
If we want to be really pedantic, the earth doesn't even orbit the sun. Rather, both bodies orbit a point that's (roughly) their combined center of mass (which in our case just happens to be somewhere inside the sun). And of course that "roughly" is standing in for a lot of other variables, too.
> the earth doesn't even orbit the sun. Rather, both bodies orbit a point that's (roughly) their combined center of mass
Yes, that's true. Indeed, when we take into account other planets (and the Moon, and the asteroids, etc., etc.), all of these objects orbit a common barycenter.
However, that doesn't change the fact that the Moon does not orbit the Earth in this sense; its net acceleration (in a barycentric inertial frame) is never towards the Earth, or towards a common barycenter of the Earth-Moon system. Only if we ignore the motion around the solar system barycenter do we get the approximation in which the Moon and Earth orbit a common center of mass.
Ok, but this (the whole subthread, not just this msg I'm replying to) gets so deep into pedantry that it becomes borderline meaningless. The moon circles the earth approx every 28 days. When people -- even reasonably well-educated ones like me, with a couple semesters of astronomy from a world-class university -- say "orbit", that is what they mean. I'm deliberately omitting caveats about sidereal month vs synodic period, to avoid the same slippery slope I'm gently criticizing. Given there's no absolute spatial frame of reference, I'd argue that piling such caveats atop each other doesn't "move" us closer to a truer understanding.
All that said, it is kind of fun to consider.
> The moon circles the earth approx every 28 days.
In what sense? You state this like it's an obvious fact. It isn't. It contains a number of hidden assumptions, not all of which stand up to close scrutiny.
> Given there's no absolute spatial frame of reference, I'd argue that piling such caveats atop each other doesn't "move" us closer to a truer understanding.
I disagree, because "there's no absolute frame of reference" is not the same as "all frames of reference are equally useful". The former is true. The latter is not.
Once you face up to the fact that different frames are useful for different purposes, you should realize why you can't just state things like "the moon circles the earth" as obvious facts. At the very least, you have to explain why you've picked the frame of reference (centered on the Earth) in which that's (approximately) true. Basically, that would be because you're ignoring the rest of the universe and you only care about the Earth and the Moon. Which is fine for many purposes (it worked for sending humans to the Moon and back), but not for others (like saying "the moon orbits the earth" as opposed to "the moon orbits the sun"--which is simply not true, once we bring the Sun into the picture, you can no longer ignore the Sun's effect on the moon).
Can you go further and say that the Earth and sun "really" are orbiting the center-of-mass of the milky way?
And does it end there? I guess that galaxies are far enough apart from one another to escape this logic with their relative escape velocity.
> Can you go further and say that the Earth and sun "really" are orbiting the center-of-mass of the milky way?
Not according to the definition I gave. Calculate the acceleration of the Earth and Sun towards the center of the Milky Way and compare it with the Earth's acceleration towards the Sun.
The description makes me think it might be a Horseshoe Orbit [0], where something spends time in about the same circular orbit, but slowly bounces back and forth through the unoccupied portion.
Looking up 2025 PN7 [1], it says:
> Over time, it may transition between quasi-satellite and horseshoe orbits due to gravitational perturbations.
[0] https://en.wikipedia.org/wiki/Horseshoe_orbit
[1] https://en.wikipedia.org/wiki/2025_PN7
The math on that orbit is making my head hurt beautifully—thank you!
It's like a bit from The Smoke Ring (or Integral Trees) by Larry Niven, where a very weird planetary configuration made a human-habitable ecosystem out of an orbiting ring of gas. [0]
The locals refer to "East" as in the direction of orbit (prograde), "In" as towards the central star, and teach their children: "East takes you Out, Out takes you West, West takes you In, In takes you East, North and South take you back."
[0] https://kaiserscience.wordpress.com/physics/gravity/physics-...
Would be neat to be able to get some photographs of it. Curious if it's a near-Earth asteroid or yet another case of a rocket's upper stage re-entering Earth orbit (like with 2020 SO and J002E3). An expected appearance of 1957 would be pretty early for the latter case (that's when the USSR launched Sputnik 1 and 2, and I'm pretty sure both those upper stages came back down a long time ago), but who knows?
I'm just going to believe, for no good reason in particular, that it's actually an alien probe sent to watch our planet after the detection of particles from the nuclear detonations that started in the 1940s. And yes, this is very much influenced by Star Trek and the detection of our first warp drive by the Vulcan's flying by our solar system.
Don't go giving Avi Loeb any ideas now...
Sure, it's the home base for the alien saucers (drones)
Bit small at 19m, unless it's managing to hide most of the bulk and only presenting a smaller cross section.
If it's an asteroid it could be a good opportunity pick up some samples, given its proximity.
You would wonder if it could even be coaxed into a Lagrange point for longer term study.
That would mean that Earth has not cleared its orbit... therefore... is Earth not a planet?
/Justice for Pluto/
Sure, as long as you're willing to make your children memorize the names of thousands of “planets”.
I thought the aggregate coverage of this on particle.news was pretty good. https://particle.news/share/_0fff
> New Quasi-Moon Discovered Orbiting Earth, but It's Been Around for Decades
My new grandma is also orbiting Earth, but it's been around for decades /s