The article says that 5% of the matter in the universe is normal matter but they can’t detect half of it. How do they know it is 5% normal matter then and not 2.5%?
Student astronomer finds missing galactic matter
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Re: Student astronomer finds missing galactic matter
#12Can’t say I’m surprised. Confirms my opinion that dark matter is just literally that: dark, cold interstellar matter
Most scientists also thought it was crazy at first--surely there must be some simpler explanation than just conjuring up a new type of matter. But at this point, the dark matter theory is by far the most popular.
There are a lot of reasons we know that dark matter is (almost certainly) non-baryonic. For one, we know how much baryonic matter there is (based on models of the big bang, etc.) And while no one has seen dark matter in a laboratory, we have observed it indirectly (eg by gravitational lensing).
[1] https://www.nasa.gov/vision/universe/starsgalaxies/dark_matt...
Re: Student astronomer finds missing galactic matter
#13Would it be possible for all the missing matter to be just unseen baryonic matter? How are we sure that most of this is exotic dark matter?
Re: Student astronomer finds missing galactic matter
#14A copy of the paper for anyone who can't read the journal site: https://arxiv.org/pdf/2101.06048.pdf
On reading it, one thing I'm a little stylistically critical of (and this is minor):
They go through all the principles, methodology, findings -- distances, dimensions, (0.1 pc at 4 pc distance), velocity, properties, etc. etc. of this thing.
But I guess in keeping with the tradition of hiding the headline worthy thing that the BBC would want to write about, not once did they just outright clearly say "we believe this is a filament of dark gas in our own galaxy causing this"!
The terms "galaxy" and "interstellar" appear about 4 times total, and only incidentally to describe the history or context. They never simply clarify in plain language that:
-- This is a piece of gas inside our galaxy (versus outside)
-- It's big, and long, floating around between us and other stuff
Maybe writing for an academic audience, you assume everyone understands the obvious and need to make it sound very detailed, but they could sure have done a better job of making it not just sound like a technical addendum paper. Maybe after months of staring at the details, they got the enthusiasm for making a clear simple statement beaten out of them! But there are good examples of paper writing in astronomy that read simply and clearly. Not everything has to sound technical and swamped by the details to be credible.
I might've called it "First detection of a dark matter filamentary cloud in our Galaxy through pulsar scintillation" or something like that.
Re: Student astronomer finds missing galactic matter
#15Would it be possible for all the missing matter to be just unseen baryonic matter? How are we sure that most of this is exotic dark matter?
In the article, it specifically says that the matter she found is, in fact, unseen baryonic matter, and not dark matter. She found a method for detecting it even though it's cold and not emitting any EM waves.
Re: Student astronomer finds missing galactic matter
#16So, I'm going to bypass all of the really cool things about the excellent work that this Ph.D. candidates, Ms. Yuanming Wang, has done here and just comment on my amusement that this female Ph.D. candidate and her supervisor, Professor Tara Murphy, were working with Manly Astrophysics (http://manlyastrophysics.org/index.html) on this project. I picture a bunch of buff, bearded, rock-jawed astrophysicists who smoke Marlboro's and wear plaid flannel shirts and cowboy boots while staying up all night in the observatory.
Re: Student astronomer finds missing galactic matter
#17The article says that 5% of the matter in the universe is normal matter but they can’t detect half of it. How do they know it is 5% normal matter then and not 2.5%?
The baryon to photon number density in the early universe plays a role during big bang nucleosynthesis as well as baryon acoustic oscillations, imprinted on the microwave background. We know that the total energy density must be (close to) the critical density (again from CMB measurements).
I can't really provide more details without doing some reading myself first, though...
Re: Student astronomer finds missing galactic matter
#18Would it be possible for all the missing matter to be just unseen baryonic matter? How are we sure that most of this is exotic dark matter?
In the article, it specifically says that the matter she found is, in fact, unseen baryonic matter, and not dark matter. She found a method for detecting it even though it's cold and not emitting any EM waves.
It's also clear meaning light passes through this baryonic matter.
My question is, how do we know that the "dark matter" we assume to be littered all over the universe isn't just clear baryonic matter?
I know that we infer the existence of dark matter through gravity so how do we know that this dark matter isn't just "clear" baryonic matter?
Any astronomers care to share their expertise?
Re: Student astronomer finds missing galactic matter
#19Can’t say I’m surprised. Confirms my opinion that dark matter is just literally that: dark, cold interstellar matter
Most scientists also thought it was crazy at first--surely there must be some simpler explanation than just conjuring up a new type of matter. But at this point, the dark matter theory is by far the most popular. There are a lot of reasons we know that dark matter is (almost certainly) non-baryonic. For one, we know how much baryonic matter there is (based on models of the big bang, etc.) And while no one has seen da…
I did a thought experiment once about wormholes, and how gravity would pass through them creating quite a messy curvature of space (potentially dangerously so near a planet or sun).
Don’t we think wormholes would look like gravitational lensing?
Re: Student astronomer finds missing galactic matter
#20So, I'm going to bypass all of the really cool things about the excellent work that this Ph.D. candidates, Ms. Yuanming Wang, has done here and just comment on my amusement that this female Ph.D. candidate and her supervisor, Professor Tara Murphy, were working with Manly Astrophysics ( http://manlyastrophysics.org/index.html ) on this project. I picture a bunch of buff, bearded, rock-jawed astrophysicists who smoke…
Manly people stopped smoking thirty years ago.