Astronomers discover another object in an orbit so extreme it reaches the outskirts of the theorized Oort Cloud
Astronomers analyzing a dark energy survey by a ground-based telescope have discovered what might be another dwarf planet orbiting the Sun, but doing so in an orbit so extreme that it reaches the outskirts of the theorized Oort Cloud more than 151 billion miles out.
This object, dubbed, 2017 OF201, was found in 19 different observations from 2011 to 2018, allowing the scientists to determine its orbit. The map to the right is figure 2 from their paper [pdf], with the calculated orbit of 2017 OF201 indicated in red. As you can see, this new object — presently estimated to be about 450 miles in diameter — is not the first such object found in the outer solar system with such a wide eccentric orbit. However, the object also travels in a very different region than all those other similar discoveries, suggesting strongly that there are a lot more such objects in the distant outer solar system.
Its existence also contradicts a model that proposed the existence of a larger Planet X. That theory posited that this as-yet undetected Planet X was clustering the orbits of those other distant Trans-Neptunian objects shown on the map.
As shown in Figure 2, the longitude of perihelion of 2017 OF201 lies outside the clustering region near π ≈ 60◦ observed among other extreme TNOs [Trans-Nepturnian Objects]. This distinction raises the question of whether 2017 OF201 is dynamically consistent with the Planet X hypothesis, which suggests that a distant massive planet shepherds TNOs into clustered orbital configurations. Siraj et al. (2025) computed the most probable orbit for a hypothetical Planet X by requiring that it both reproduces the observed clustering in the orbits of extreme TNOs.
…These results suggest that the existence of 2017 OF201 may be difficult to reconcile with this particular instantiation of the Planet X hypothesis. While not definitive, 2017 OF201 provides an additional constraint that complements other challenges to the Planet X scenario, such as observational selection effects and the statistical robustness of the observed clustering.
Planet X might exist, but if so it is likely simple one of many such objects in the other solar system. It is also likely to be comparable in size to these other objects, which range from Pluto-sized and smaller, making it less unique and less distinct.
In other words, our solar system has almost certainly far more planets than nine (including Pluto).
Hat tip to BtB’s stringer Jay.
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Astronomers analyzing a dark energy survey by a ground-based telescope have discovered what might be another dwarf planet orbiting the Sun, but doing so in an orbit so extreme that it reaches the outskirts of the theorized Oort Cloud more than 151 billion miles out.
This object, dubbed, 2017 OF201, was found in 19 different observations from 2011 to 2018, allowing the scientists to determine its orbit. The map to the right is figure 2 from their paper [pdf], with the calculated orbit of 2017 OF201 indicated in red. As you can see, this new object — presently estimated to be about 450 miles in diameter — is not the first such object found in the outer solar system with such a wide eccentric orbit. However, the object also travels in a very different region than all those other similar discoveries, suggesting strongly that there are a lot more such objects in the distant outer solar system.
Its existence also contradicts a model that proposed the existence of a larger Planet X. That theory posited that this as-yet undetected Planet X was clustering the orbits of those other distant Trans-Neptunian objects shown on the map.
As shown in Figure 2, the longitude of perihelion of 2017 OF201 lies outside the clustering region near π ≈ 60◦ observed among other extreme TNOs [Trans-Nepturnian Objects]. This distinction raises the question of whether 2017 OF201 is dynamically consistent with the Planet X hypothesis, which suggests that a distant massive planet shepherds TNOs into clustered orbital configurations. Siraj et al. (2025) computed the most probable orbit for a hypothetical Planet X by requiring that it both reproduces the observed clustering in the orbits of extreme TNOs.
…These results suggest that the existence of 2017 OF201 may be difficult to reconcile with this particular instantiation of the Planet X hypothesis. While not definitive, 2017 OF201 provides an additional constraint that complements other challenges to the Planet X scenario, such as observational selection effects and the statistical robustness of the observed clustering.
Planet X might exist, but if so it is likely simple one of many such objects in the other solar system. It is also likely to be comparable in size to these other objects, which range from Pluto-sized and smaller, making it less unique and less distinct.
In other words, our solar system has almost certainly far more planets than nine (including Pluto).
Hat tip to BtB’s stringer Jay.
Readers!
My annual February birthday fund-raising drive for Behind the Black is now over. Thank you to everyone who donated or subscribed. While not a record-setter, the donations were more than sufficient and slightly above average.
As I have said many times before, I can’t express what it means to me to get such support, especially as no one is required to pay anything to read my work. Thank you all again!
For those readers who like my work here at Behind the Black and haven't contributed so far, please consider donating or subscribing. My analysis of space, politics, and culture, taken from the perspective of an historian, is almost always on the money and ahead of the game. For example, in 2020 I correctly predicted that the COVID panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Every one of those 2020 conclusions has turned out right.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
This agrees with recent paper about another planetary candidate, in an orbit which rules out the Brown-Batygin Planet Nine (which you’re calling X).
That’s Fortuna or Greek Tyche, here –
https://arxiv.org/abs/2504.17288
David Ross: Minor point: I’m not calling it X, this was the term the researchers used in the paper.
They mention this other work you refer to here, which also suggests this theorized “ninth” planet doesn’t exist. Calling a “ninth planet” is in itself foolish, because this research is showing that there are a lot more than the nine planets known (I include Pluto, as do most planetary scientists). I am willing to bet that a large number of these Kuiper and Trans-Neptunian objects will be large enough so that gravity will forced them into a spherical shape, the definition for a planet that works best for the scientists who study these things.
Thus, our solar system likely has dozens more planets in its outer reaches. We just have to find them.
As to 2017 OF201: they project albedo 0.15. That is dark and I suspect assumes tholins, as seen on (half of) Pluto. Tholins form under sunlight, however weak. Sedna, further out, shines over 0.4. Eris is bright too.
I think this object is smaller than the 700 km they’ve given it. It might not be spherical after all.