AeternusDoleo t1_ixz93mv wrote on November 27, 2022 at 3:37 PM

Is the fact that the nebula is blue at the bottom but not at the top due to the material being blueshifted? IE are we seeing matter being ejected from the protostar at a decent fraction of light speed?

BrooklynVariety t1_iy4glge wrote on November 28, 2022 at 6:03 PM

Astronomer here.

Protostellar disks do have powerful winds and jets, the latter of which especially would produce a measurable blueshift and redshift exactly in the pattern you describe. However, protostellar disk jets tend not to be relativistic (maxing out at about 1000 km/s), while just the PROJECTED velocity required to produce shifts in this image is in 90,000 to 150,000 km/s (30% to 50% of the speed of light). This is based on the filters used to create this image. If there was a jet here, it would be detectable in spectroscopic data, but it wouldn't produce the dramatic color difference we see here.

From the press release, the blue light we see in the lower right is due to the fact that there is less dust (which tends to absorb bluer light) in that region.

TheBurninator99 t1_iy4qw3c wrote on November 28, 2022 at 7:11 PM

Out of curiosity, why are the jets shot off along the axis of rotation, and not say, along the equator?

BrooklynVariety t1_iy4v49a wrote on November 28, 2022 at 7:39 PM

We definitely see outflows of material along the equator: disk winds! In fact, we think that in protoplanetary disks and accreting black holes, you can have winds and jets launched by the same magnetocentrifugal mechanism, where magnetic field lines coming out of the surface of the disk rotate while "anchored" to the surface and material is driven out centrifugally along the magnetic field line. The jet is then a special case where the opening angle of the global magnetic field closes around the rotation axis. This is not the only mechanism for driving jets, and certainly not the only way off driving winds though.

The key here is that jets are strongly thought to be a fundamentally magnetic process, where the strong magnetic field of the accretion disk near the accreting object interacts with the fastest rotating material in the disk. The magnetic field geometry of the disk is driven entirely by the rotation of ionized gas in the disk, so the close connection to the rotation axis of the disk is not incidental. Curiously, the jet does not have to be perfectly aligned, and the jet may be misaligned or begin precessing.

Another way to think about it is that everything in the disk is basically axially symmetric around the rotation axis. When the disk spits out material, it does the same in the form of winds. Jets are a special case of this.