The intense electromagnetic environment near a black hole can accelerate particles to much of the speed of light, sending the speeding particles along jets extending from each of the object's poles. In the case of the supermassive black holes at the centers of galaxies, these jets are truly colossal, blowing material not only from the galaxy, but possibly from the entire galaxy environment.
But this week scientists described how the jets can also do strange things in a galaxy. Examination of the galaxy M87 has revealed that nova explosions appear to occur at an unusually high frequency near one of the jets from the galaxy's central black hole. But there is absolutely no mechanism to explain why this could happen, and there are no signs of it happening to the plane flying in the opposite direction.
Whether this effect is real, and whether we can come up with an explanation for it, may require some further observations.
Novas and wedges
M87 is one of the larger galaxies in our local part of the universe, and its central black hole has active jets. During an earlier period of regular observations, the Hubble Space Telescope had discovered that stellar explosions called novas appeared to be surrounding the jet.
This makes little sense. Novas occur in systems with a large, hydrogen-rich star, with a nearby white dwarf orbiting Earth. Over time, the white dwarf draws hydrogen from the surface of its companion until it reaches a critical mass on its surface. At that point, a thermonuclear explosion blows the remaining material off the white dwarf and the cycle resets. Because the rate of material transfer is usually quite stable, novas in a stellar system will often repeat at regular intervals. And it's not at all clear why a black hole's radius would change that regularity.
So some of the people involved in the first study were given time on Hubble to go back and take another look. And for the better part of a year, Hubble was pointed at M87 every five days, allowing it to capture novas before they faded out. All told, this picked up 94 novas that occurred near the center of the Milky Way. Combined with the 41 identified during previous work, this left a collection of 135 novas in this galaxy. The researchers then mapped this relative to the black hole and its jets.
The region where the jet is located (top right) experiences significantly more novas than the rest of the galaxy's core.
Lessing et. al.
By dividing the area around the center of the Milky Way into ten equal segments, the researchers counted the novas that occurred in each segment. In the nine segments that did not include the jet on the Earth-facing side of the galaxy, the average number of novas was 12. In the segment that included the jet, the number was 25. Another way to look at this look is that the highest number in a segment without jets was only 16 – and that was in a segment right next to the segment with the jet in it. The researchers calculate the chance of this arrangement happening randomly at about one in 1,310 (which means less than 0.1 percent).
To get a separate measure of how unusual this is, the researchers placed 8 million novas around the center of the galaxy, with the distribution being random but adjusted to the galaxy's brightness, on the assumption that novas will become more common in areas with more stars. . This was then used to estimate how often novas could be expected in each of these segments. They then used a wide variety of wedges: “To reduce noise and avoid p-hacking when choosing wedge size, we average the results for wedges between 30 and 45 degrees wide.”
Overall, the improvement near the jet was low for both very narrow and very wide wedges, as you would expect: narrow wedges take up too much space in the area affected by the jet, while wide wedges contain a lot of space where you gets the normal space. background rate. Things peak in the region of wedges 25 degrees wide, where the enrichment near the jet is about 2.6 times greater. So this seems to be real.
