
Volunteers spot almost 100 cold brown dwarfs near our sun - wglb
https://www.space.com/citizen-scientists-discover-95-brown-dwarfs.html
======
throwaway316943
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.

~~~
totetsu
We can't ignore how this verse matches the tune of piano man.
[https://www.polygon.com/2018/1/22/16919632/cthulhu-
lovecraft...](https://www.polygon.com/2018/1/22/16919632/cthulhu-lovecraft-
billy-joel-piano-man-cover-hp-joelcraft)

~~~
mikeappell
Aaand now I can't un-hear it. Thanks a lot.

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sfifs
So a question for the knowledgeable on this subject. Over the last few years,
we continually keep seeing discoveries large number of intra and extra solar
system astronomical bodies that do not radiate at high luminosities or
frequencies. Presumably all these add to the mass of galaxies.

How much of the dark matter hypothesis is dependent on observations of
rotation of high luminosity bodies? If we assume there are large numbers of
these non luminous bodies distributed between stars, does the necessity for
postulating exotic dark matter go away?

~~~
catmistake
Dark matter is going away, regardless, because it is not necessary to explain
galaxy rotation curves.
[https://www.youtube.com/watch?v=PL0ewiwqoTw](https://www.youtube.com/watch?v=PL0ewiwqoTw)
Dark matter was always just a way to fudge what was observed. It is hard to
believe most physicists, astronomers and cosmologists still believe in and are
still looking for something that never existed.

~~~
dwaltrip
My understanding is that MOND is essentially dead at this point and that there
aren't any other promising alternative theories left on the table.

I enjoyed a podcast on the topic by the highly respected physicist Sean
Carroll (along with his guest, MIT physicist Lina Necib). It was very
interesting and insightful. They cover in-depth why we are so confident that
dark matter is a thing that exists.

Here's a link to it:
[https://www.preposterousuniverse.com/podcast/2020/05/11/96-l...](https://www.preposterousuniverse.com/podcast/2020/05/11/96-lina-
necib-on-what-and-where-the-dark-matter-is/)

~~~
catmistake
Simulation in video I linked is not MOND. Dark Matter is postulated due to
observations of galaxies in isolation. BUT galaxies are not gravitationally
isolated. They gravitationally affected by all the other galaxies in their
neighborhood. The video and simulation is pretty straight forward. Dark Matter
is simply unnecessary to explain galaxy rotation curves.

~~~
dwaltrip
Even if you are correct about the galaxy rotation curves -- which everything
I've read and heard leads to me believe is rather unlikely -- those curves are
only one of several pieces of evicence that point to the existence of dark
matter. The wikipedia page list many of these:
[https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...](https://en.wikipedia.org/wiki/Dark_matter#Observational_evidence)

I only mentioned MOND as it is one of the more widely-known plausible
alternatives that have been pursued.

~~~
catmistake
And I and the video creators are only claiming dark matter is not needed to
explain galaxy rotation curves. Whatever other spaghetti lumped into the need
for dark matter, have at it... but galaxy rotation curves are explained quite
neatly looking at two things: 1) dark matter was initially postulated and
never reexamined because galaxies were observed as gravitationally isolated
and 2) when not unnaturally gravitationally isolating galaxies from their
neighborhood group, the rotation curves make precisely exact and perfect sense

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LatteLazy
Near? (I read the article, it also seems not to know any actual distances).

~~~
PenisBanana
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
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!

~~~
garmaine
Why would it be scary?

~~~
wcoenen
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](http://www.gutenberg.org/ebooks/51461)

~~~
garmaine
I suggest basing your view of reality on facts, not fiction.

~~~
lostlogin
If 2020 has shown us anything, it’s that some far fetched scenarios can
actually happen.

~~~
lrem
What has happened in 2020 that was far fetched?

~~~
amanaplanacanal
That our collective response to the pandemic could be so terrible.

~~~
lrem
The response of various countries mostly follows pre-pandemic approach of the
respective governments to science, public services and making hard decisions.
Personally, the only major surprise here is the level of defending the stock
market.

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fernly
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](https://www.zooniverse.org)

[2] [https://www.zooniverse.org/projects/marckuchner/backyard-
wor...](https://www.zooniverse.org/projects/marckuchner/backyard-worlds-
planet-9)

------
hyperpape
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?

~~~
T-hawk
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
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
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.

~~~
kdmccormick
An exoplanet is just any planet outisde our own star system. You're thinking
of "rogue planets".

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LargoLasskhyfv
Yay! Jump points!
[https://en.wikipedia.org/wiki/Jump_(Alliance%E2%80%93Union_u...](https://en.wikipedia.org/wiki/Jump_\(Alliance%E2%80%93Union_universe\))

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sradman
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](https://arxiv.org/abs/2008.06396)

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hinkley
Are any of them situated in a place that would be useful to us for getting to
other places?

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cable2600
Which one is the mythical "Nemesis" that throws comets and asteroids at Earth?

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akerro
What does "cold brown" mean in this context? How can it be cold near the sun?

~~~
perlgeek
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".

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cevn
Could we live on a brown dwarf?

~~~
taf2
I imagine the gravity would be too strong?

~~~
throwaway316943
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
How would you float something in a hydrogen atmosphere?

~~~
estebanisko
Not float, but you can keep aloft while spending minimal energy using
[https://en.wikipedia.org/wiki/Dynamic_soaring](https://en.wikipedia.org/wiki/Dynamic_soaring)

Jupiter seems to have sufficiently dynamic atmosphere. Not sure about cold
brown dwarfs...

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ryanmarr
This was misleading, they made it sound like they were inside our solar
system.

~~~
sadfev
Almost a Clickbait

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tazedsoul
Misleading headline.

------
wkjagt
If you look closely, you can often also spot a warm brown dwarf near Uranus.

------
throwaway2048
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...](https://phys.org/news/2020-05-costly-collateral-elonmusk-starlink-
satellite.html)

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.

~~~
cookingrobot
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
Also these observations came from the WISE satellite.

~~~
iso947
Will be far cheaper to launch many observation satellites in future too

