The Mysterious Interstellar Object May Be Slamming on the Brakes, Scientist Says

[Buster's Uncle]

Futurism
The Mysterious Interstellar Object May Be Slamming on the Brakes, Scientist Says
Joe Wilkins
Sat, October 25, 2025 at 12:45 PM EDT
2 min read



Jewitt and Luu 2025


In case you missed it, there’s a fascinating object from another part of the universe visiting our neck of the woods.

Dubbed 3I-ATLAS — “three” as in the third known interstellar object from outside of our solar system — the bizarre entity has had the astronomical community in a quiet fervor since it was first spotted in early July.

The object is widely believed to be an interstellar comet, although a handful of experts, including Harvard’s ever-controversial astronomy researcher Avi Loeb, have suggested that it might be a visitor from an alien civilization. Many of Loeb’s peers have dismissed that possibility, but that hasn’t quieted the firebrand researcher.

The object is currently hidden behind the Sun, where it’s slated to remain unobservable from Earth for the better part of a month — a blind spot that Loeb had already speculated the object might use to do something unexpected. Now, the latest images from Nordic Optical Telescope, located in the Canary Islands, have provided him with new fodder.

Those images suggest that a “tail” of debris the object sprouted as it neared the Sun has now changed directions, and is instead facing toward the Sun. Astronomers call this an “anti-tail,” a phenomenon which has been observed in a number of other comets going back decades.

Anti-tails have a simple explanation: as the object approaches the sun, our relative position makes the long trail of particulate appear to flip, when in reality it hasn’t changed. Basically, we’re getting a 3D optical illusion, exacerbated by the Sun’s gravity and our relative position in space.

Loeb, though, has another explanation. In his latest blog on the interstellar object, Loeb posits that the anti-tail could show an alien craft applying “braking thrust” — slamming on the brakes, essentially, as it seeks to prolong its sojourn through our star system.

“If the object is an alien spacecraft slowing down, and the anti-tail is braking thrust, then this change from anti-tail to tail would be entirely expected near perihelion,” Loeb wrote, referencing an idea shared by his colleague Adam Hibberd at the Institute for Interstellar Studies.

“In that case,” Loeb continues, the “transition would constitute a technosignature in the form of an unexpected phenomenon indicative of controlled maneuvering, possibly with the intention of achieving a bound heliocentric orbit between Mars’s and Jupiter’s orbits.”

Either way, it’ll be a while before we know for sure. The object isn’t expected to reappear until December 19, at which point it’ll be clear whether its trajectory has been altered by a braking maneuver — or if it’s still simply hurtling through space like the inert snowball that most scientists believe it to be.

https://www.yahoo.com/news/articles/mysterious-interstellar-object-may-slamming-164500888.html

[Lorizael]

The object is currently hidden behind the Sun, where it’s slated to remain unobservable from Earth for the better part of a month — a blind spot that Loeb had already speculated the object might use to do something unexpected.

Now, the latest images from Nordic Optical Telescope, located in the Canary Islands, have provided him with new fodder.

ZOOM IN

The object is currently hidden behind the Sun, where it’s slated to remain unobservable

Now, the latest images from Nordic Optical Telescope

ENHANCE

unobservable

images

There's a simple explanation here, which is that, duh, the images are from before perihelion. But the seeming lack of awareness here speaks to how totally mangled the explanation for what's going on is. Dunno if that's due to this writer or Loeb, or translation between the two. Anyway, from the paper being talked about but not actually referenced...

The earliest NOT observations of comet 3I[/b] (UT 2025 July 2, DOY25 = 183 showed, upon close examination, a faint coma in the west (sunward) direction but no anti-sunward tail (Jewitt & Luu (2025b), see Figure 1). The same sunward extension was reported almost simultaneously by Seligman et al. (2025) and Bolin et al. (2025). Syndynes and synchrones computed for these early dates all project to the east, meaning that the sunward material cannot be an effect of projection, instead indicating a real projection of material towards the Sun (Jewitt et al. 2025). Sunward ejection from comets is completely normal, where it results from the preferential sublimation of ices on the hot, Sun-facing day side of the nucleus (e.g., Sekanina (1987)). What is unusual in 3I is the relative weakness of any anti-sunward tail in the early imaging observations. However, by early August (when rH ∼ 3.0 to 3.5 au), the morphology had evolved to present a dominant tail of particles roughly aligned with the eastward (antisolar) direction, and this tail brightened and lengthened towards the last pre-perihelion observations in September (Figure 6).

...

The dominant morphology of 3I/ATLAS changes from a sunward dust fan in observations taken before 2025 August to an antisunward tail on later dates. The delayed emergence of the antisunward tail is attributed to the weak action of solar radiation pressure on coma dust particles. We infer an effective particle radius ∼100 µm and ejection velocity ∼5 m s−1 . These properties are similar to 2I/Borisov, where large, slowly ejected dust grains dominated the optical appearance of the coma.

It's had a tail pointing toward the sun for awhile. It's not an optical effect. Sunward tails are completely normal. More recently, it's been observed with a tail pointing away from the sun, i.e. antisunward. Not seeing an antisunward tail earlier is considered unusual. The paper suggests this is due to the coma being made up of big dust particles that are slow to react to radiation pressure from the Sun, which other observations support, and which is something that has been seen before in other comets.

[Buster's Uncle]

I wondered about the behind-the-sun stuff - and didn't believe the optical illusion crap, when it's plainly an effect of material escaping with greater momentum than light pressure can easily overcome.

That's the state of much science reporting for you...

[Lorizael]

There are cometary tails that appear to be pointing in weird directions due to viewing geometry; that's just not the case here. It's one of the tricky things about solar system astronomy (which Loeb knows nothing about), where we can get weird effects from viewing angles, fast moving objects, phases, aperture sizes, etc.