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 outer 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.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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 outer 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.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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.
The observational astronomers score yet another point against the theoreticians. So it goes.
other solar system => outer solar system…
Michael McNeil: Fixed. Thanks.
I don’t think we are in a position yet to say that the Brown-Batygin hypothesis is ruled out. But it is an interesting development, and it does suggest that there’s a lot more out there in the Kuiper Belt and Scattered Disc that we still haven’t found.
We’ll learn a lot more once the Vera Rubin telescope (first light planned for July 2025) is operational.