# Third interstellar body discovered in our solar system **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [July 4, 2025, 5:26am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471 "2025-07-04T05:26:13Z")\ **Posts on this page:** 1\ **Showing post:** 7
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [July 4, 2025, 7:09am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/7 "2025-07-04T07:09:40Z")
I thought I had once posted a more detailed response on this topic before. I found it here: > [@First object from another solar system](https://boards.straightdope.com/t/first-object-from-another-solar-system/800014/10): > > Playing around with numbers a bit–[the estimate is](https://en.wikipedia.org/wiki/Interstellar_comet) that there are between 1 trillion and 10 trillion interstellar comets per cubic parsec. One cubic parsec is 2.72x10[sup]17[/sup] cubic astronomical units. So the chance of any interstellar comet to randomly be within one AU of the Earth is from 1 in 272,000 to 1 in 27,200. And from the Wikipedia article I linked: Astronomers estimate that several interstellar objects of extrasolar origin (like ʻOumuamua) pass inside the [orbit of Earth](https://en.m.wikipedia.org/wiki/Orbit_of_Earth) each year,[[11]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-NASA-FAQ-11) and that 10,000 are passing inside the [orbit of Neptune](https://en.m.wikipedia.org/wiki/Orbit_of_Neptune) on any given day.[[12]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-12) Interstellar comets occasionally pass through the inner [Solar System](https://en.m.wikipedia.org/wiki/Solar_System)[[1]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-Valtonen-1) and approach with random velocities, mostly from the direction of the constellation [Hercules](https://en.m.wikipedia.org/wiki/Hercules_(constellation)) because the Solar System is moving in that direction, called the [solar apex](https://en.m.wikipedia.org/wiki/Solar_apex).[[13]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-Struve-13) Until the discovery of [ʻOumuamua](https://en.m.wikipedia.org/wiki/%CA%BBOumuamua), the fact that no comet with a speed greater than the [Sun](https://en.m.wikipedia.org/wiki/Sun)’s escape velocity[[14]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-MacRobert2008-14) had been observed was used to place upper limits to their density in interstellar space. A paper by Torbett indicated that the density was no more than 1013 (10 [trillion](https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(numbers)#1012)) comets per cubic [parsec](https://en.m.wikipedia.org/wiki/Parsec).[[15]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-Torbett-15) Other analyses, of data from [LINEAR](https://en.m.wikipedia.org/wiki/LINEAR), set the upper limit at 4.5×10−4/[AU](https://en.m.wikipedia.org/wiki/Astronomical_unit)3, or 1012 (1 trillion) comets per cubic [parsec](https://en.m.wikipedia.org/wiki/Parsec).[[2]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-Francis-2) A more recent estimate by [David C. Jewitt](https://en.m.wikipedia.org/wiki/David_C._Jewitt) and colleagues, following the detection of [ʻOumuamua](https://en.m.wikipedia.org/wiki/%CA%BBOumuamua), predicts that “The steady-state population of similar, ~100 m scale interstellar objects inside the orbit of Neptune is ~1×104, each with a residence time of ~10 years.”[[16]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-Jewitt2017-16) --- _[View the full topic](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471)._