so they looked for the spectral lines<\/a> in the same location of Kinman and – they were gone. The star was apparently gone. What could have happened?<\/p>\nThe astronomers have put forth two hypotheses. The first is more mundane – if the star was in an eruptive phase, perhaps it shed a lot of its mass, rapidly becoming a much smaller and dimmer star (sometime between 2011 and 2019). This alone would not be enough to explain the disappearance, and so over this same time the star might also have been obscured by dust. This combination of factors could explain the disappearance.<\/p>\n
The second hypothesis, however, is more interesting. Perhaps the star turned into a black hole. This would explain the complete absence of any spectral lines which previously indicated its presence. There is a problem with this hypothesis, however – stars typically don’t just silently collapse into black holes. They typically transition with a bang, specifically a supernova. But no supernova was observed in this galaxy, and the remnants of such a recent supernova are not detected.<\/p>\n
Stars are not supposed to do this, but they speculate this could be a very rare event. Normally massive enough stars, when they finish burning fuel in their core, no longer produce the energy necessary to push out against the inward pull of their own gravity. As soon as the core fusion winks out, therefore, the star collapses in on itself. This is a rapid and powerful event, especially for the most massive stars because their gravity is so intense. The collapse is so energetic, in fact, that there is enough energy to fuse even the heavy elements now in the core, resulting in an explosion we call a supernova. If the core remnant left behind after this explosion is massive enough (3-5 solar masses), it will finish its collapse down into a black hole.<\/p>\n
Black holes made this way are not more massive than the stars they come from, but all that mass is in a much smaller area. Actually, no area at all, they are a singularity. Very close to a black hole, therefore, has all the gravity of a massive star in a tiny space, and so the gravitational fields are so strong at some point close enough (the event horizon) they can capture even light and keep it from escaping. That’s why they are black.\u00a0 We can detect such black holes only by their gravity (unless they are feeding off a close neighbor and this swirling material can give off light).<\/p>\n
In this case, if the star collapsed into a black hole that would explain its current absence, but now the astronomers will have to figure out how it did this without going supernova first. If I had to guess (wild speculation alert) I would say something kept the core from collapsing all at once. Perhaps the physics of this highly energetic and eruptive star allowed for a mixing of material so that the core was running out of fuel, but not completely, so fusion stopped slow enough for the star to slowly collapse, rather than catastrophically collapse and lead to a supernova. In any case, we’ll see what the experts come up with. I suspect computer models will be involved.<\/p>\n
Either way (shrinking behind dust or supernova-less black hole) this was a rare event. But here’s the thing – astronomers see even extremely rare events all the time. This is because the visible universe is a really big place, and we can look at entire galaxies worth of stars to see if anything unusual is happening. I hope we hear some follow up, and I will try to keep track of this myself. Often we hear about the exciting discoveries, but not necessarily the follow through.<\/p>\n","protected":false},"excerpt":{"rendered":"
Stars do not just disappear – except when they do. Using the Very Large Telescope (part of the European Southern Observatory) astronomers have been tracking a massive unstable star. The star is located in the Kinman Dwarf galaxy, which is a distant, small, and metal poor galaxy (PHL 293B – at a distance of 23.1 […]<\/p>\n","protected":false},"author":7,"featured_media":12147,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[73],"tags":[],"class_list":["post-12146","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-astronomy"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t
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