[HN Gopher] Volunteers spot almost 100 cold brown dwarfs near ou...
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Volunteers spot almost 100 cold brown dwarfs near our sun
Author : wglb
Score : 146 points
Date : 2020-08-21 02:05 UTC (20 hours ago)
(HTM) web link (www.space.com)
(TXT) w3m dump (www.space.com)
| sradman wrote:
| The paper _Spitzer Follow-up of Extremely Cold Brown Dwarfs
| Discovered by the Backyard Worlds: Planet 9 Citizen Science
| Project_ [1]:
|
| > We present Spitzer follow-up imaging of 95 candidate extremely
| cold brown dwarfs discovered by the Backyard Worlds: Planet 9
| citizen science project, which uses visually perceived motion in
| multi-epoch WISE images to identify previously unrecognized
| substellar neighbors to the Sun.
|
| [1] https://arxiv.org/abs/2008.06396
| throwaway2048 wrote:
| Should be noted that this kind of science in particular will be
| completely destroyed from satellite constellation launches from
| the likes of SpaceX and Blue Origin.
|
| https://phys.org/news/2020-05-costly-collateral-elonmusk-sta...
|
| With the amount of satellites being launched, it will be
| impossible not to have several in frame, especially over a long
| exposure, and they will swamp out pretty much any signal from
| space with their brightness.
| sbierwagen wrote:
| Note that Starlink satellites are visible due to reflected
| sunlight. You can only see them immediately after sunset.
| BurningFrog wrote:
| Satellites are only lit by the sun for a while around
| sunset/sunrise.
|
| Once they're in Earth shade, they have no astronomy impact.
| cookingrobot wrote:
| You don't need long exposure now that we have digital cameras,
| it's better to stack many short exposures. It's trivial to
| throw out the outlier values which removes the satellite
| trails, and other sensor noise. Images with prominent streaks
| are being deliberately processed to only keep the bright
| outliers and delete the clean frames.
| nitrogen wrote:
| Also these observations came from the WISE satellite.
| iso947 wrote:
| Will be far cheaper to launch many observation satellites
| in future too
| akerro wrote:
| What does "cold brown" mean in this context? How can it be cold
| near the sun?
| perlgeek wrote:
| They are still several light years away from the sun, so "near"
| only on astronomical scales.
|
| "Brown dwarf" is an object bigger than a usual planet, but not
| big enough to spark and sustain nuclear fusion in the core.
|
| "cold" means "not hot enough to shine bright like a star".
| LatteLazy wrote:
| Near? (I read the article, it also seems not to know any actual
| distances).
| rement wrote:
| Space.com likes to write those kind of titles. However, the
| observable universe is ~93 billion lights years[0] across so
| 20-60 light years is relatively close.
|
| [0] https://en.wikipedia.org/wiki/Observable_universe
| PenisBanana wrote:
| On the very final page is a table of distances.
|
| 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.
| etangent wrote:
| So that's actually further away than the closest star
| systems. Got freaked out for a second, because having hard-
| to-see massive objects near your sun system is scary!
| mynegation wrote:
| Nearest known brown dwarf (actually a binary) Luhman-16 is
| farther away than Proxima but not by much (relatively
| speaking).
|
| It would be interesting to know if a theoretical smallest
| coolest brown dwarf would be detectable with the current
| technology.
| garmaine wrote:
| Why would it be scary?
| wcoenen wrote:
| In the scifi short story "a pail of air", the Earth is
| yanked away from the Sun by a dark star passing through
| the solar system. The Earth cools until all of the
| atmospheric gasses turn into solids and fall to the
| ground as layers of ultra-cold snow.
|
| It's one of the pieces of fiction that left a deep
| impression on me. Harsh winter days still remind me of
| it.
|
| http://www.gutenberg.org/ebooks/51461
| garmaine wrote:
| I suggest basing your view of reality on facts, not
| fiction.
| sbierwagen wrote:
| A primordial black hole of 1000 Earth masses is only 17
| meters wide. It's effectively impossible to see, with a
| event horizon temperature of 0.02 millikelvin. If it was
| extragalactic, it'd pass through our solar system at a
| pretty good clip. It could certainly do unfortunate
| things to Earth's orbit. A normal stellar mass black hole
| would be even worse.
|
| Very unlikely, of course. But not fictional.
| wcoenen wrote:
| OK, I'll bite. What do the facts say would happen when a
| brown dwarf passes through the inner solar system? Is the
| ejection of planets implausible?
| garmaine wrote:
| The facts say that such an event has an extremely low
| probability of happening, as our solar system is still
| intact after 4.5 billion years and solar systems remain
| around nearly all stars we look at, so the probability of
| this happening is so low as to not worry about it.
| Rebelgecko wrote:
| The fact is that 250 light-years is not "near" the sun.
| Unless you're an astronomer, there's no practical
| difference between something that is 2 light years or
| 2,000,000 light years away. Both distances are equally
| unattainable. Saying that something is near "the sun" (as
| opposed to a more generic area like "the solar system")
| makes it sound like it's much closer than it actually is.
| Imagine if the article said that the stars were near
| "Dallas Texas". It would be equally true (+-0.001%), but
| IMO the extra specificity is misleading
| FalconSensei wrote:
| Exactly. They are not specifically near 'our sun'. They
| are near our system. The title (because of the
| specificity), seems to say that they are in our solar
| system, or so close that you could consider it like that
| lostlogin wrote:
| If 2020 has shown us anything, it's that some far fetched
| scenarios can actually happen.
| lrem wrote:
| What has happened in 2020 that was far fetched?
| samatman wrote:
| This is a recipe for missing out on a certain amount of
| anxiety at the expense of a great deal of joy.
| garmaine wrote:
| I read and enjoy science fiction. I don't worry about the
| stuff in these stories unless I have independent reality-
| based evidence that I should.
| jacquesm wrote:
| Yesterdays science fiction more often than not is today's
| science. As long as you leave time travel, wormholes,
| fusion and aliens out of it has surprising applicability.
| ivalm wrote:
| If a brown dwarf scatters into the solar system it might
| dramatically shift orbits potentially making earth
| uninhabitable. To say nothing of a direct hit on
| anything, even hitting the sun might strip atmosphere
| from earth, hitting any planet would create world ending
| debris fields
| jvm___ wrote:
| Because eventually that body would have gravitational
| effects on our stable system and could throw everything
| out of whack.
| kabdib wrote:
| The solar system is actually not stable in the long term.
| Early planetary development was violent and chaotic, and
| the planets shifted around a lot more than you might
| think.
|
| 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.
| btilly wrote:
| Our next such approach is
| https://en.wikipedia.org/wiki/Gliese_710 in 1.281 million
| years.
|
| 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.
| garmaine wrote:
| If it were in our solar system then it would be in a
| gravitationally stable arrangement--because if it weren't
| it would have already thrown things out of whack in the
| last 4.5 billion years.
| adenozine wrote:
| Could be an object at high speed, waiting for the right
| gravity assist directly into us?
|
| 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?
| garmaine wrote:
| > Could be an object at high speed, waiting for the right
| gravity assist directly into us?
|
| 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?
| adenozine wrote:
| Then I guess the morons with careers in astrophysics are
| investigating it for no reason then.
|
| 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
| thombat wrote:
| New things are interesting, and astrophysicists like
| investigating interesting things. If these brown dwarfs
| posed the slightest threat to us they'd be even more
| interesting than they already are.
| mindcrime wrote:
| _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?_
|
| https://en.wikipedia.org/wiki/Problem_of_induction
| throwaway316943 wrote:
| Don't worry, there could still be somewhat smaller less
| detectable objects nearby.
| eloff wrote:
| It's amazing that we could detect an object that cold, that
| small, at those distances. How does that work?
| asdasfasdfasdf wrote:
| Often it's only because they pass in front of objects that
| we can see.
| doctoboggan wrote:
| From my understanding they took 2 pictures of the same spot
| at different times and then had volunteers ("citizen
| scientists") look at those pictures to see if anything
| moved. You can see some examples of the kinds of pictures
| in the paper linked in another comment above.
| unzadunza wrote:
| I had to look it up, because I'm curious too. It looks like
| volunteers are given images from NASA's Wide-field Infrared
| Survey Explorer (WISE) telescope. The volunteers then just
| look for moving objects.
| https://www.zooniverse.org/projects/marckuchner/backyard-
| wor...
| nitrogen wrote:
| I was unable to find a table matching wavelengths to
| visible temperatures in a bit of searching. Closest I
| could find is the chromaticity diagram on Wikipedia's
| Black-body Radiation article, which puts 1000K around
| 0.7nm red light.
|
| The WISE article lists 22mm 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 22mm, 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...
|
| ----
|
| _Edit:_ found it: https://commons.m.wikimedia.org/wiki/F
| ile:Blackbody_peak_wav...
|
| Looks like 20mm 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.
| eloff wrote:
| Wow, that's amazing that it can detect light from objects
| at 200K. That's about the temperature of dry ice.
| Roboprog wrote:
| For anyone missing how little radiation that is,
| radiation is proportional to the 4th power of the
| temperature in Kelvin.
|
| 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.
| messe wrote:
| > From 8 parsec to 70 parsec
|
| 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
| ErikVandeWater wrote:
| I find the phrasing odd as well. Why specify near our sun as
| opposed to near us? If it's specifically near our sun as
| opposed to near us that would imply something closer to the sun
| than us.
| repsilat wrote:
| They should have said "near Mars", it would have been more
| exciting.
| adrianmonk wrote:
| They could have also gone with near Topeka, Kansas.
| jessaustin wrote:
| They're trying not to sound provincial, to the many
| scientists based in other solar systems who will read this
| paper in centuries to come.
| adrianmonk wrote:
| Maybe, but I'm not sure how "our sun" is less provincial
| than "us".
| Someone wrote:
| https://www.nationalastro.org/news/cool-new-worlds-found-in-...
| tries to hide it, too, but says, in note 1: The closest of
| these new discoveries is roughly 23 light-years away from the
| Sun. Many more of these brown dwarfs are in the 30-60 light-
| year distance range.
| martyvis wrote:
| Why do they always reference the nearness to the Sun, rather
| than just to us? With 8 light minutes between us and our
| nearest star, and light years to the dwarf stars they are as
| close to us as the Sun. Your average person is going to read
| the statement as being near to the Sun almost as if they are
| close to it but far from us.
| lopmotr wrote:
| If this "average person" is going to get such a false
| impression from clear and correct information, then maybe
| there's no use them knowing it anyway? They're obviously
| not even trying. I know someone who thinks the Milky Way is
| the same thing as the solar system. That person won't be
| reading an article about astronomy and it's OK. They have
| their own life and don't care about it.
| coronadisaster wrote:
| It would have made more sense if they would have said
| that they are close to our solar system.
| conductr wrote:
| Feels like you're calling me an idiot because, I'll admit
| it, that's exactly what I thought. You're right in that I
| care significantly less now than I know the scale of
| "close" is not actually close in my terms. But it made it
| sound like a more impressive discovery than I perceive it
| to be. So, what they did is astronomical linkbaiting.
| Someone wrote:
| I think the best way to phrase it would be "close to the
| solar system", but even then, "close to", IMO, doesn't
| really carry the message for the general public. Neptune is
| 4 light hours from the sun. 20 light years is 40,000 times
| that distance, so that's like saying somebody 40 km away is
| "close to you".
| sudoaza wrote:
| Pff since the closest star system is just 4ly away I was
| expecting something closer...
| [deleted]
| Robotbeat wrote:
| There may still be some cold brown dwarf nearer than
| Proxima.
| [deleted]
| fernly wrote:
| Credit where it's due, "Backyard Worlds" is one of a large number
| of "citizen science" projects hosted at Zooniverse[1]. The
| specific project is at [2], but the Zooniverse platform hosts
| many others affording pleasant hours of internet contribution.
|
| [1]https://www.zooniverse.org
|
| [2] https://www.zooniverse.org/projects/marckuchner/backyard-
| wor...
| hyperpape wrote:
| What's the connection between the brown dwarfs being cold and
| being exoplanets? Are planets definitionally not hot, or does it
| tell us something about how the dwarfs formed?
| mturmon wrote:
| One place where brown dwarf (BD) and exoplanet science overlap
| is atmospheric characterization by spectral methods. If you get
| reasonably well-resolved spectra from the BD, you can invert to
| obtain information about its atmosphere's composition and
| density/temperature profile.
|
| The BD is going to be more emissive than an exoplanet (and a BD
| has no light contamination from a nearby host star) so the BD
| is not an exact analog, but BDs provide a workshop for
| development of inversion approaches.
|
| [e.g.: https://arxiv.org/pdf/1410.6512.pdf]
| T-hawk wrote:
| The definition of a brown dwarf is enough mass to cause nuclear
| fusion of deuterium (roughly 13x Jupiter's mass) but not enough
| for hydrogen-1 (roughly 75x Jupiter or 0.08x the Sun.)
|
| Planets by definition are anything that doesn't meet the
| deuterium threshold. Stars meet the hydrogen threshold. "Cold"
| in this context means relative to hydrogen-fusing stars. It's
| referring to the object's own energy production, not like
| measuring the surface temperature of a planet illuminated by a
| star.
|
| That we are finding "cold" brown dwarfs now is observational
| bias. We already found the hotter ones because they're more
| luminous and detectable. "Near the sun" (up to about 250 light-
| years here) is also observational bias, we just can't detect
| cold ones any farther.
| throwaway316943 wrote:
| I wonder what the ratio is of dark bodies to the star systems
| we can see? Are there vast numbers of invisible worlds hiding
| between the stars?
| zlynx wrote:
| Yes, as far as I know, astronomers think so. Those are
| exoplanets. Planets without any nearby stars.
|
| Even in our own solar system we don't know whats out in our
| Kuiper Belt. Probably nothing too big or we'd be able to
| measure the gravity effect.
|
| But in the Oort cloud, we could have multiple Pluto sized
| things out there and have no idea.
| mixmastamyk wrote:
| Sounds like we've found our dark matter.
| Igelau wrote:
| One of the proposed dark matter explanations is "massive
| astrophysical compact halo objects" (MACHOs). Brown
| dwarfs are among some of the possible MACHO candidates.
| mynegation wrote:
| I think the brown dwarf still fuse deuterium but then the
| question is - how can it be so cold? And if it is so cold - is
| it a planet. But then why is it so (relatively) hot? Could be
| that the new discovered object is (thus far) a missing piece on
| a spectrum between brown dwarfs and gas giants?
| qayxc wrote:
| One of the difficulties in astronomy is determining the age
| of astronomical objects.
|
| Brown dwarfs and small red dwarfs have about the same
| temperature in the early stages of their formation. The main
| difference between the two is the drop in temperature over
| time.
|
| A super cool brown dwarf might just be an old brown dwarf.
| The (arbitrary) line between planemos and brown dwarfs can be
| drawn via mass (e.g. no matter the temperature, if it's too
| small for deuterium fusion, it's not a brown dwarf) and
| composition (e.g. via testing for lithium), though both
| criteria are not perfect.
|
| A cool brown dwarf can basically just be very old.
| wkjagt wrote:
| If you look closely, you can often also spot a warm brown dwarf
| near Uranus.
| ryanmarr wrote:
| This was misleading, they made it sound like they were inside our
| solar system.
| sadfev wrote:
| Almost a Clickbait
| hinkley wrote:
| Are any of them situated in a place that would be useful to us
| for getting to other places?
| cevn wrote:
| Could we live on a brown dwarf?
| taf2 wrote:
| I imagine the gravity would be too strong?
| throwaway316943 wrote:
| Perhaps a floating colony like those proposed for Venus?
| There might be a Goldilocks zone in the atmosphere. If not
| then there may still be a comfortable location in near orbit
| where the heat would be tolerable. It's interesting to think
| of ways to overcome an extreme gravity environment though,
| perhaps suspension in a liquid would counteract some of the
| effects?
| fhars wrote:
| How would you float something in a hydrogen atmosphere?
| estebanisko wrote:
| Not float, but you can keep aloft while spending minimal
| energy using
| https://en.wikipedia.org/wiki/Dynamic_soaring
|
| Jupiter seems to have sufficiently dynamic atmosphere.
| Not sure about cold brown dwarfs...
| rini17 wrote:
| Hot hydrogen would.
| hinkley wrote:
| > Some of these weird worlds are even relatively close to
| Earth's temperature and could be cool enough to have
| water clouds in their atmospheres, according to the
| statement.
| tazedsoul wrote:
| Misleading headline.
| throwaway316943 wrote:
| I have seen the dark universe yawning Where the black planets
| roll without aim, Where they roll in their horror unheeded,
| Without knowledge, or lustre, or name.
| 7373737373 wrote:
| https://youtube.com/watch?v=lHgnrN8vhVs
| lostlogin wrote:
| Thanks. To save a few click for those like me - H. P.
| Lovecraft.
|
| https://www.hplovecraft.com/writings/texts/poetry/p121.aspx
| mindcrime wrote:
| _" There are worlds out there where the sky is burning, where
| the sea's asleep and the rivers dream, people made of smoke and
| cities made of song. Somewhere there's danger, somewhere
| there's injustice and somewhere else the tea is getting cold.
| Come on, Ace, we've got work to do."_
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(page generated 2020-08-21 23:00 UTC)