# 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:** 20\ **Page:** 1
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [July 4, 2025, 5:26am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/1 "2025-07-04T05:26:13Z")
On July 1, the NASA-funded [ATLAS](https://atlas.fallingstar.com/) (Asteroid Terrestrial-impact Last Alert System) survey telescope in Rio Hurtado, Chile, first reported observations of a comet that originated from interstellar space. Arriving from the direction of the constellation Sagittarius, the interstellar comet has been officially named 3I/ATLAS. It is currently located about 420 million miles (670 million kilometers) away. > **[NASA Discovers Interstellar Comet Moving Through Solar System - NASA Science](https://science.nasa.gov/blogs/planetary-defense/2025/07/02/nasa-discovers-interstellar-comet-moving-through-solar-system/)** > > On July 1, the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Rio Hurtado, Chile, first reported observations of a ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [July 4, 2025, 5:29am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/2 "2025-07-04T05:29:32Z")
Very cool. Makes me wonder how much of that stuff we never see that is out there? ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [July 4, 2025, 5:31am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/3 "2025-07-04T05:31:53Z")
I’m sure it’s a lot. Think of the long trip it’s made. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [July 4, 2025, 5:38am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/4 "2025-07-04T05:38:24Z")
> **[Astronomers spot an interstellar object zipping through our solar system | CNN](https://amp.cnn.com/cnn/2025/07/03/science/interstellar-object-comet-3i-atlas)** > > Astronomers have observed an object that originated from beyond our solar system, thought to be an interstellar comet, speeding through our celestial neighborhood. More info and observatory’s “video”. ---
**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, 6:28am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/5 "2025-07-04T06:28:56Z")
> [@Whack-a-Mole](#): > > Very cool. Makes me wonder how much of that stuff we never see that is out there > Norris pointed to modeling estimating that there could be as many as 10,000 interstellar objects drifting through the solar system at any given time, though most would be smaller than the newly discovered object. > **[Third-ever confirmed interstellar object blazing through solar system (Update)](https://phys.org/news/2025-07-astronomers-track-solar.html)** > > Astronomers on Wednesday confirmed the discovery of an interstellar object racing through our solar system—only the third ever spotted, though scientists suspect many more may slip past unnoticed. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [July 4, 2025, 6:33am UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/6 "2025-07-04T06:33:48Z")
> [@Darren\_Garrison](#): > > Norris pointed to modeling estimating that there could be as many as 10,000 interstellar objects drifting through the solar system at any given time, though most would be smaller than the newly discovered object. That is actually more than I thought (not sure how small they are going though). ---
**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) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 4, 2025, 2:44pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/8 "2025-07-04T14:44:15Z")
> [@Darren\_Garrison](#): > > > Norris pointed to modeling estimating that there could be as many as 10,000 interstellar objects drifting through the solar system at any given time, though most would be smaller than the newly discovered object. > > [Third-ever confirmed interstellar object blazing through solar system (Update)](https://phys.org/news/2025-07-astronomers-track-solar.html) That’ll depend on how big it needs to be before you call it an “object”. You probably don’t want to count dust grains, and you probably do want to count things the size of a comet, but there’s no clear, discrete cutoff size in between them. ---
**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, 2:46pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/9 "2025-07-04T14:46:02Z")
Read my next post any you’ll see it is objects above 100 m. ---
**Author:** ![burpo\_the\_wonder\_mutt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/burpo_the_wonder_mutt/32/365_2.png) [@burpo\_the\_wonder\_mutt](https://boards.straightdope.com/u/burpo_the_wonder_mutt)\ **Post date:** [July 4, 2025, 2:55pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/10 "2025-07-04T14:55:47Z")
Hey! You other solar systems, keep your trash outta our region. ---
**Author:** ![Coriolanus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/coriolanus/32/18769_2.png) [@Coriolanus](https://boards.straightdope.com/u/Coriolanus)\ **Post date:** [July 4, 2025, 3:35pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/11 "2025-07-04T15:35:15Z")
> [@Whack-a-Mole](#): > > Very cool. Makes me wonder how much of that stuff we never see that is out there? My thoughts exactly. Whatever was once between Jupiter and Mars and essentially Jupiters’ gravity broke it up. Thus the Asteroid belt. And the Russians were the first to film the other side of the Moon and really every astro-type-person was amazed at how much more impact it had taken, compared to the side of Moon that we see. We (meaning nine billion people) are capable of dealing with known asteroids/comets that might come pretty close to earth. These out-of-solar-system objects are great that we have (and have not de-funded) the tech and generally a miniscule chance that it’s headed to the third rock from the sun. Yet we do or we don’t have the ability to do anything about them. Blowing up shit in space is tantamount to blowing up Beijing. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 4, 2025, 4:34pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/12 "2025-07-04T16:34:19Z")
> [@Coriolanus](#): > > My thoughts exactly. Whatever was once between Jupiter and Mars and essentially Jupiters’ gravity broke it up. Or more precisely, prevented it from coalescing in the first place. Not that there was ever all that much there to begin with. Ceres all by itself is over a third of the total mass. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [July 4, 2025, 4:51pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/13 "2025-07-04T16:51:29Z")
The Ramans do everything in threes. ---
**Author:** ![Coriolanus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/coriolanus/32/18769_2.png) [@Coriolanus](https://boards.straightdope.com/u/Coriolanus)\ **Post date:** [July 4, 2025, 6:05pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/14 "2025-07-04T18:05:57Z")
Dunno that we know much about the Asteroid belt other than what we might surmise from Saturn’s creation of the “rings” I am not an astrophycist (and even if I had a phD would that be enough?) yet I don’t know if it’s been determined the asteroids ever accreted into a body that Jupiter’s gravity would then destroy or if they are just rocks that Jupiter would not allow. I mean: Gravity: How does it work? It is good that we can detect interstellar objects flying into the solar system proper, and hopefully add to our knowledge. What and why are these things flying interstellar? It’s possible for the gas giants or the sun to “grab” these things yet would likely be in a highly elliptical orbit that never comes close to the third rock. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [July 4, 2025, 6:39pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/15 "2025-07-04T18:39:04Z")
What does the asteroid belt have to do with this topic? This is an object that came from outside the solar system, not from the asteroid belt. And it’s a comet, not an asteroid. ---
**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, 6:46pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/16 "2025-07-04T18:46:15Z")
> [@markn\_1](#): > > And it’s a comet, not an asteroid. We have no idea what it is yet. Whether it should be called an asteroid or a comet depends on how much of it is made up of volatiles. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [July 4, 2025, 6:48pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/17 "2025-07-04T18:48:45Z")
Well, the NASA page linked in the OP unequivocally calls it a comet, so I assumed that they have some evidence for such nomenclature. ---
**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, 7:00pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/18 "2025-07-04T19:00:46Z")
I see that more recent observations support that > Initial observations of 3I/ATLAS were unclear on whether it is an [asteroid](https://en.m.wikipedia.org/wiki/Asteroid) or a [comet](https://en.m.wikipedia.org/wiki/Comet).[[13]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-Conv-20250702-15)[[15]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-IFLSci-20250702-17)[[6]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-UT-20250702-6) Observations on 2 July 2025 by the Deep Random Survey ([X09](https://en.m.wikipedia.org/wiki/List_of_observatory_codes#X09)) at Chile, [Lowell Discovery Telescope](https://en.m.wikipedia.org/wiki/Lowell_Discovery_Telescope) ([G37](https://en.m.wikipedia.org/wiki/List_of_observatory_codes#G37)) at [Arizona](https://en.m.wikipedia.org/wiki/Arizona), and [Canada–France–Hawaii Telescope](https://en.m.wikipedia.org/wiki/Canada%E2%80%93France%E2%80%93Hawaii_Telescope) ([T14](https://en.m.wikipedia.org/wiki/List_of_observatory_codes#T14)) at [Mauna Kea](https://en.m.wikipedia.org/wiki/Mauna_Kea) showed a marginal [coma](https://en.m.wikipedia.org/wiki/Coma_(comet)) and a short [tail](https://en.m.wikipedia.org/wiki/Comet_tail) 3 [arcseconds](https://en.m.wikipedia.org/wiki/Arcsecond) in [angular length](https://en.m.wikipedia.org/wiki/Angular_distance), which indicated the object is a comet.[[2]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-MPEC-2025-N12-2)[[16]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-CBET5578-18) On the other hand, various astronomers including [Alan Hale](https://en.m.wikipedia.org/wiki/Alan_Hale_(astronomer)) reported no cometary features on 3I/ATLAS.[[16]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-CBET5578-18) On 2 July 2025, the MPC announced the discovery of 3I/ATLAS and gave it the [interstellar object designation](https://en.m.wikipedia.org/wiki/Interstellar_object#Nomenclature) “3I”, signifying it being the third interstellar object confirmed.[[2]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-MPEC-2025-N12-2)[[16]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-CBET5578-18) The MPC also gave 3I/ATLAS the [non-periodic comet](https://en.m.wikipedia.org/wiki/Non-periodic_comet) designation C/2025 N1 (ATLAS).[[2]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-MPEC-2025-N12-2) By the time 3I/ATLAS was announced, the MPC had collected 122 observations of the comet from 31 different observatories.[[2]](https://en.m.wikipedia.org/wiki/3I/ATLAS#cite_note-MPEC-2025-N12-2) (From Wikipedia.) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 5, 2025, 1:16pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/19 "2025-07-05T13:16:32Z")
> [@Coriolanus](#): > > I am not an astrophycist (and even if I had a phD would that be enough?) yet I don’t know if it’s been determined the asteroids ever accreted into a body that Jupiter’s gravity would then destroy or if they are just rocks that Jupiter would not allow. I mean: Gravity: How does it work? I answered that two posts prior. Yes, we do know. The asteroid belt was never a single object. > [@Coriolanus](#): > > It’s possible for the gas giants or the sun to “grab” these things yet would likely be in a highly elliptical orbit that never comes close to the third rock. Possible, but highly unlikely. More relevantly, the reverse can also happen: Interactions with a planet could cause an object that was previously bound to our solar system to be ejected. This is probably the origin of some of these interstellar objects. It happens very, very rarely in an old, mature system like ours, because almost anything in an orbit such that it could be ejected already has been, but it was probably fairly common when the solar system was new. ---
**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 5, 2025, 2:24pm UTC](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471/20 "2025-07-05T14:24:14Z")
> [@Chronos](#): > > More relevantly, the reverse can also happen: Interactions with a planet could cause an object that was previously bound to our solar system to be ejected. This is probably the origin of some of these interstellar objects. I would say that is the origin of _all_ interstellar objects. From [the Wikipedia article I referenced earlier](https://en.wikipedia.org/wiki/Interstellar_object): > Current models of [Oort cloud](https://en.m.wikipedia.org/wiki/Oort_cloud) formation predict that more comets are ejected into interstellar space than are retained in the Oort cloud, with estimates varying from 3 to 100 times as many.[[2]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-Francis-2) Other simulations suggest that 90–99% of comets are ejected.[[17]](https://en.m.wikipedia.org/wiki/Interstellar_object#cite_note-Choi-17) [Next page](https://boards.straightdope.com/t/third-interstellar-body-discovered-in-our-solar-system/1020471.md?page=2)