08-27-2018, 06:10 PM
The magnetism of our Galaxy's super-massive black hole
https://phys.org/news/2018-08-magnetized...milky.html
This if from UKIRT's sister telescope, the JCMT on MK. I'll let you read the link for the info but thought I'd very briefly explain how astronomers on Mauna Kea measure magnetic fields as it's close to my own research, although my previous work has been on magnetic fields around young protostellar stars.
Many molecules in space are "polar". Carbon monoxide, water and silicates are examples. It means they have a distribution of charge and they should align with magnetic fields in space. However, in the gas-phase, they also rotate which messes up everything. However, if those molecules become trapped in interstellar dust grains, they are no longer able to rotate, but they can still vibrate but only in the direction of their charge. Most dust particles aren't spheres but elongated which means the grains have a charge distribution which isn't symmetrical. Therefore, although it's not very efficient, they tend to align with a magnetic field.
We can measure this. These dust grains are cold and tend to emit radiation in the infrared and submillimeter wavelengths. As your science teacher may have shown you at school, you can use polarizing optics, just like some sunglasses, to detect polarized light. You rotate the optics and it goes from dark to light. Astronomers use this same method especially in the infrared and submillimeter to measure the polarization of light (it's a little more sophisticated than just using your sunglasses though!) and from those measurements can tell the orientation of the dust grains and therefore deduce the distribution of a magnetic field.
https://phys.org/news/2018-08-magnetized...milky.html
This if from UKIRT's sister telescope, the JCMT on MK. I'll let you read the link for the info but thought I'd very briefly explain how astronomers on Mauna Kea measure magnetic fields as it's close to my own research, although my previous work has been on magnetic fields around young protostellar stars.
Many molecules in space are "polar". Carbon monoxide, water and silicates are examples. It means they have a distribution of charge and they should align with magnetic fields in space. However, in the gas-phase, they also rotate which messes up everything. However, if those molecules become trapped in interstellar dust grains, they are no longer able to rotate, but they can still vibrate but only in the direction of their charge. Most dust particles aren't spheres but elongated which means the grains have a charge distribution which isn't symmetrical. Therefore, although it's not very efficient, they tend to align with a magnetic field.
We can measure this. These dust grains are cold and tend to emit radiation in the infrared and submillimeter wavelengths. As your science teacher may have shown you at school, you can use polarizing optics, just like some sunglasses, to detect polarized light. You rotate the optics and it goes from dark to light. Astronomers use this same method especially in the infrared and submillimeter to measure the polarization of light (it's a little more sophisticated than just using your sunglasses though!) and from those measurements can tell the orientation of the dust grains and therefore deduce the distribution of a magnetic field.