From 8 parsec to 70 parsec, so 28 to 250 light years or 240 trillion kms to 2170 trillion kms away (-ish)
Many are comparatively cold. While most seem to be 400 Celsius plus, one (couldn't find in the article, but mentioned elsewhere) seemed to be -10 Celsius.
Roughly (waving my hands and talking vaguely here) about 10% plus minus in distance and temperature.
It would be interesting to know if a theoretical smallest coolest brown dwarf would be detectable with the current technology.
We can't project orbits out indefinitely, either; multiple studies show that our ability to go out more than a few hundred million years are suspect and very dependent on starting conditions, which can obviously be easily perturbed by unknown bodies. Since we get star-sized approaches at Oort Cloud distances on the order of every few million years, that probably puts an upper bound on things.
However the rate at which such encounters happen varies greatly. We are in an orbit bobs up and down from the galactic ecliptic with a period of roughly 60 million years. There are more encounters near the ecliptic, with very few encounters when we are above or below. We cross the ecliptic about every 30 million years, and last did so about 3 million years ago. So we are still in the dangerous period.
It is not entirely a coincidence that the dinosaurs were wiped out 66 million years ago, during another relatively dangerous period.
Could be a strange object with capability to disrupt the sun somehow?
Why would an object hitherto unbeknownst to us and close to the sun NOT be scary?
An object larger than Jupiter doesn't change its course because of chance encounters with other random small bodies.
> Could be a strange object with capability to disrupt the sun somehow?
This doesn't make physical sense.
> Why would an object hitherto unbeknownst to us and close to the sun NOT be scary?
Because it's had no observable effect on us for the last 4.5 billion years of our solar system's existence, and we've postulated nothing that would change this stable dynamical relationship?
Beyond your wildly unfounded and I daresay naive assumption that the objects have had no effect on the solar system, perhaps they need to hear YOUR postulations.
If only they were reading all of your grayed out comments, I see your dismissive and arrogant condescending remarks are leading to such fruitful insights and conversations. /s
Feel better soon
There's a lot of safe objects in space. There's a lot of safe plants in the jungle. Still, truth must be uncovered day by day.
That's all I was meaning to convey.
It's like you climbing a volcano that has been dormant for 1000 years, and it suddenly, explosively erupting right while you're walking towards the peak. Could happen out of the blue right during those few hours, sure, but it really, really probably won't.
It's one of the pieces of fiction that left a deep impression on me. Harsh winter days still remind me of it.
It reads as if it is either between us and the sun, or close enough that you'd see it roughly up to the same distance we are from the sun.
My point? That even this was a much better candidate for a far-fetched event in 2020 than this pandemic ever could be. Scientists, academics, reporters, policy makers and even some more astute or honest politicians have been predicting it for literally years as something that was probably just around the corner.
I had interpreted your "why would it be scary" question as "what kind of bad things would happen if a brown dwarf did get close?", but I guess it was instead a rethorical question implying something about low probability. Hence the confusion.
That said, there is a problematic selection bias in your statement about our solar system. Only stable systems can produce observers, so of course we find ourselves in a stable system. For now ;-)
Like, we just found out the universe is a way, way bigger place--full of planets between the stars. Maybe humans will visit these worlds someday as we planet-hop between the stars. What civilization could we make near these cold, but resource-rich worlds? What if they had tidally-heated moons with liquid oceans... what sort of life would evolve without the energy of a star?
But no, people's first reaction is "OMG is this going to kill me?!" I've even had someone get angry at me for bringing up the topic (that the sun will go nova billions of years from now) and making them depressed. I just don't get it.
> That said, there is a problematic selection bias in your statement about our solar system. Only stable systems can produce observers, so of course we find ourselves in a stable system. For now ;-)
That's why I mentioned other exosolar systems. So far as we can see, basically every stellar object that we look at has stable planetary system. We mostly find planets by periodic transit events, which requires the plane of formation to be aligned with us. You can calculate the statistical chance that this is the case, and sure enough when we look we find roughly that percentage of stable planetary systems. If there were rogue planets or primordial black holes out there likely to encounter us, then those other systems would be just as vulnerable and we would expect to see fewer percentage of visible stable planetary systems than predicted. That is not the case.
We would also expect consistent groups of long-period comets from the interactions of these passing objects with the Kuiper belt and Oort cloud, but there is no consistent grouping.
We would expect a history of random heavy bombardment periods in the crater history of the moon, mars, mercury, and other datable planetary bodies in the solar system. Instead we see just one period, the late heavy bombardment which coincides with the synchronization of the orbits of Jupiter and Saturn in the late stages of solar system formation.
Etc. etc. When I first saw the headline I thought "wait a minute, that cannot be right." And sure enough, it's not. There aren't 100's of rogue planets in our particular stellar neighborhood, but rather scattered around the nearby region.
Very unlikely, of course. But not fictional.
The WISE article lists 22μm as its longest wavelength, though that might no longer be attainable since WISE is out of coolant. If one can find out what blackbody temperature has its peak at 22μm, then we could maybe see how close to the edge of WISE's temperature range the 400C (673K) and -10C (263K) dwarves are.
https://en.m.wikipedia.org/wiki/Wide-field_Infrared_Survey_E...
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Edit: found it: https://commons.m.wikimedia.org/wiki/File:Blackbody_peak_wav...
Looks like 20μm is a bit below 200K, so if I'm interpreting this right, WISE should have had no temperature-related problem (leaving aside brightness) spotting a -10C brown dwarf.
200 K is a bit below (water) freezing. 400 K is just over boiling. The 400 K object emits 16 times (2 ^ 4) more radiation than the same object at 200 K.
Really minor correction, but 7.1±1.4 is the lower bound. 1 parsec is a tad over 3 lightyears, so it's a somewhat significant difference when the distances are that small.
EDIT: corrected my correction