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>But observations using the world’s largest radio telescope are casting doubt on this long gestational period. Researchers have zoomed in on a prestellar core i

by 37 5y ago

>But observations using the world’s largest radio telescope are casting doubt on this long gestational period. Researchers have zoomed in on a prestellar core in a giant gas cloud—a nursery for hundreds of baby stars—and found the tiny embryo may be forming 10 times faster than thought, thanks to weak magnetic fields. I'm sure this has been taken into account already (by actual scientists much smarter than me) but, how do we know it isn't dark matter causing the collapse to happen faster than thought? Seems like a reasonable question to me. Lack of gravitational lensing? (edit:) Also >thanks to weak magnetic fields ... Zeeman effect etc This is a bit questionable to me. I understand the Zeeman effect, or thought I did, but I don't understand how it can be thanks to a "weak" magnetic field.

pdonis 5y ago
> how do we know it isn't dark matter causing the collapse to happen faster than thought? The average density of dark matter is way too small. It's significant on the scale of a galaxy because it doesn't clump, so its density is basically the average density everywhere (denser towards the center and less dense further out, but still of the same rough order of magnitude), instead of being isolated clumps surrounded by huge expanses of empty space, as with ordinary matter. But on the scale of a single stellar system the density of dark matter is so small that its effect on the dynamics is negligible.
- 37 5y ago
  This is a excellent response! Thank you!
- treeman79 5y ago
  https://xkcd.com/2186/ https://xkcd.com/2186/ Good explanation of low density of dark matter as measured by squirrels.
dtgriscom 5y ago
The observations didn't measure the speed of the collapse; they measured the strength of the magnetic field which guides models of the collapse. Magnetic fields tend to slow the gas collapsing, so finding that the fields were lower than expected decreases the expected time of collapse.
- 37 5y ago
  Thank you! This is also a great response! Now I'm wondering how they measure magnetic fields. But of course I'm sure there's about a million youtube videos explaining that. >Magnetic fields tend to slow the gas collapsing, so finding that the fields were lower than expected decreases the expected time of collapse. I think this part might be backwards, wouldn't it increase the expected time of collapse, which is to say stars may form faster than thought? (edit: no, I'm just tired and wrong, yet again...)
  - antognini 5y ago
    At a very simplified level, in these kinds of astrophysical contexts you can kind of think of magnetic field lines as strings, and the particles in the gas are forced to follow the strings. The stronger the field, the more closely the particles have to follow those strings. So if the magnetic field is large, they can have the effect of redirecting particles from where they otherwise would go due to gravitational collapse, and slow the process down.
  - simonh 5y ago
    They explain the measurement approach in the article. The Zeeman effects occurs when spectral absorption lines 'split' due to the influence of magnetic fields. They measure this effect at radio wavelengths.

by 37 5y ago

pdonis 5y ago

> how do we know it isn't dark matter causing the collapse to happen faster than thought? The average density of dark matter is way too small. It's significant on the scale of a galaxy because it doesn't clump, so its density is basically the average density everywhere (denser towards the center and less dense further out, but still of the same rough order of magnitude), instead of being isolated clumps surrounded by huge expanses of empty space, as with ordinary matter. But on the scale of a single stellar system the density of dark matter is so small that its effect on the dynamics is negligible.

37 5y ago
This is a excellent response! Thank you!
treeman79 5y ago
https://xkcd.com/2186/ https://xkcd.com/2186/ Good explanation of low density of dark matter as measured by squirrels.

dtgriscom 5y ago

The observations didn't measure the speed of the collapse; they measured the strength of the magnetic field which guides models of the collapse. Magnetic fields tend to slow the gas collapsing, so finding that the fields were lower than expected decreases the expected time of collapse.

37 5y ago
Thank you! This is also a great response! Now I'm wondering how they measure magnetic fields. But of course I'm sure there's about a million youtube videos explaining that. >Magnetic fields tend to slow the gas collapsing, so finding that the fields were lower than expected decreases the expected time of collapse. I think this part might be backwards, wouldn't it increase the expected time of collapse, which is to say stars may form faster than thought? (edit: no, I'm just tired and wrong, yet again...)
- antognini 5y ago
  At a very simplified level, in these kinds of astrophysical contexts you can kind of think of magnetic field lines as strings, and the particles in the gas are forced to follow the strings. The stronger the field, the more closely the particles have to follow those strings. So if the magnetic field is large, they can have the effect of redirecting particles from where they otherwise would go due to gravitational collapse, and slow the process down.
- simonh 5y ago
  They explain the measurement approach in the article. The Zeeman effects occurs when spectral absorption lines 'split' due to the influence of magnetic fields. They measure this effect at radio wavelengths.