The Gizmodo article A Visiting Star Jostled Our Solar System 70,000 Years Ago refers to the the three year old ApJ. paper The Closest Known Flyby of a Star to the Solar System (also arXiv) which describes Scholz’s Star and it's pass close to our solar system about 70,000 years ago.

The Gizmodo article then discusses the newly published paper in MNRAS Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies. However, while I can access the earlier paper, the new result is paywalled and I'm not able to access it (at least not soon).

The second half of the abstract in particular is confusing me.

Here, we perform a systematic numerical exploration of the past orbital evolution of known hyperbolic minor bodies using a full N-body approach and statistical analyses to study their radiants. Our results confirm the theoretical expectations that strong anisotropies are present in the data. We also identify a statistically significant overdensity of high-speed radiants towards the constellation of Gemini that could be due to the closest and most recent known fly-by of a star to the Solar system, that of the so-called Scholz's star. In addition to and besides 1I/2017 U1 (‘Oumuamua), we single out eight candidate interstellar comets based on their radiants’ velocities.

I've heard of a radiant of a meteor shower - it's an apparent position of the source of meteors referenced to the position of the Earth at the time of the shower. But I've= never heard the term applied to the orbit of a minor body unrelated to the Earth's position. What is the "radiant" of a minor body with a hyperbolic orbit in a simulation? Could it be the asymptotic incoming direction of the hyperbola?

But my main question is simply how "statistically significant" is this result in reference to the enhancement in the direction of Gemini? I can't see the data. Is it just a tiny fluctuation, or a fairly obvious and robust feature?

A screen shot of the data would be most welcomed!

Possibly helpful: List of hyperbolic comets.


1 Answer 1


Not an answer, but just on radiants:

Radiant means angle of approach. It's applied to meteor showers because the Earth intersects the dust trail that causes the meteor shower at a specific place in orbit and dust trail has a specific angle of intersection relative to Earth and Earth's orbit.

enter image description here

Source of picture.

What is the "radiant" of a minor body with a hyperbolic orbit in a simulation

Radiant can't be applied to elliptical orbits though extremely elliptical orbits kind of have a radiant, but it can be applied to objects approaching the solar system. A hyperbolic orbit generally implies an object that came from outside the solar-system though it could also be a gravity assisted object from inside the solar system that was accelerated from an elliptical to a hyperbolic orbit.

Here's an article that mentions radiant in association with an exo-solar object

astronomers looked for the radiant it seemed to originate from. Calculations determined that A/2017 U1 came from a radiant located close to (R.A. = 18h 41m 25s ; Dec=+34° 15′) coordinates, which is near the actual position of Vega

exo-solar objects approach the solar system in a mostly straight line until they get close enough for the sun to bend their path. Where they came from before their direction was curved by the sun's gravity is their radiant.


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