Milky Way's Black Hole's Magnetic Fields Measured
Black holes are usually talked about in terms of their gravity. This is perfectly natural, of course, given both the fundamental nature of black holes and how we humans happened upon them (theoretical anomaly in General Relativity). However, there's no reason to ignore their magnetic fields. Luckily, they aren't being ignored. The Event Horizon Telescope (EHT) took measurements of our own galaxy's central black hole. For the first time, the resolution of our measurements was able to look almost right down to the event horizon of the Milky Way's central black hole. This will provide valuable information regarding how jets form around black holes.
Given all there is surrounding a galaxy's central black hole, optical imaging is impossible. Instead, the EHT looked at "light" with a 1.3mm wavelength. While the black hole is particularly bright there, the important feature of the light was the polarization. That gives the most information regarding the local magnetic fields. It should also be noted that EHT is making use of very long baseline interferometry (VLBI) to mimic a much larger telescope. This technique improved resolution to the degree needed to make such detailed observations. Though black holes are hugely massive, their density makes them smaller than one might think. This particular study was doing the equivalent of looking at a golf ball on the moon.
Given all there is surrounding a galaxy's central black hole, optical imaging is impossible. Instead, the EHT looked at "light" with a 1.3mm wavelength. While the black hole is particularly bright there, the important feature of the light was the polarization. That gives the most information regarding the local magnetic fields. It should also be noted that EHT is making use of very long baseline interferometry (VLBI) to mimic a much larger telescope. This technique improved resolution to the degree needed to make such detailed observations. Though black holes are hugely massive, their density makes them smaller than one might think. This particular study was doing the equivalent of looking at a golf ball on the moon.
Planetary Nebulae
A new way to determine the distance to planetary nebula was announced. The name "planetary nebula" is a misnomer in that they have nothing to do with planets. However, the name has stuck for historical reasons. Planetary nebula are actually the remnants of now-dead stars. Studying them gives great insight into the stellar life cycle. One thing that has plagued people studying them, however, is that the distances to them is difficult to measure. Unlike stars, planetary nebula are diffuse in the sky and, as can be seen in the picture below, their diversity makes it hard to pick any given feature to home-in on as an age signifier.
However, scientists have indeed found a characteristic that will allow them to gauge the distance to planetary nebula. Though not new, it used much more up-to-date and accurate corroborating data. In addition to publishing the method, which combines reddening and hydrogen emission lines, a catalog of over 1000 distances using this new method was created.
Highest Mass-to-light Ratio Galaxy Found
A galaxy with a record mass-to-light ratio was discovered. Well, we've known about Triangulum II for some time, but we just discovered that its mass-to-light was a whopping 3500 or so (for reference, the Universe's mass-to-light is about 100). Mass-to-light is used as a measure of dark matter. If a lot of mass can be inferred at a location, but we see very few stars, we now assume the difference is predominantly dark matter. If this result stands, it would be an incredible opportunity to study dark matter, as Triangulum II is quite close on a cosmic scale, just barely beyond the furthest edges of our own galaxy, the Milky Way.
Personally, I'm a touch skeptical of this result. The study is basing its results on the velocities of six stars. Others have already put forth the alternative hypothesis that the Milky Way is pulling and tugging on those stars to alter their motion. Nonetheless, I do hope the result is correct and look forward to the follow-on work.
Cheshire Cat Fossil Galaxy
Well, some good science is coming out of this one, but mostly, it's a pretty picture.
This is the Cheshire Cat group of galaxies. It was posted by NASA the week of the 100th anniversary of Einstein's publication of his General Theory of Relativity. That theory predicted gravitational lensing and this picture is a particularly amusing example of that prediction realized. You can read the NASA post for full details about the what's where in this image. The main features are the eyes, which are two galaxies on a collision course with each other, and four background galaxies that are gravitationally lensed into arcs forming the facial outlines and smile of the cat.
