Making a Stellar Tossed Salad

When I was in high school, I worked for a while in a local restaurant, washing dishes. Sometimes the restaurant got so busy I was given the pleasure of making tossed salad. I suppose being the dishwasher my hands were expected to be super clean, eh? The chief cook gave me a lesson and away I went, tearing up iceberg lettuce into a huge stainless-steel bowl. The beginning of my tossed salad career.

In September, 2021, a group of researchers from the University of Arizona published in the Astrophysical Journal, their report about a star getting shredded into tossed salad, like a giant head of iceberg lettuce. What can do this? Maybe an adolescent black hole, just starting its working life? As in most things about science, new findings bring about new questions.

But first, a black hole primer or refresher if you will.

A black hole is space, a spherical hole of space…in space.  It’s called black because we cannot see it directly, light cannot escape it. Really, it is a spherical (we think) hole of extreme gravity surrounding an infinitesimal point of incredible mass. Does that clarify things? Black holes are still enigmatic and not well described by physics as we know it.

We are aware of four possible scenarios that form black holes:  1-Collapse of a white dwarf after sucking a companion stars mass away, 2-core collapse of a very massive star (8-40 x the Sun’s mass), 3-neutron star merger, and 4-direct collapse of molecular hydrogen (called primordial black holes – hydrogen mass densities sufficient for this were likely only existent in the early universe). The black holes identified so far are either stellar mass or super massive (millions to billions of solar masses and found in the center of galaxies).

A black hole is a mean little bugger if you get too close! Keep your distance and no problem but if you arrive at the event horizon (Schwarzschild radius) beware.  Any closer and you become part of the black hole. That goes for stars too.

Getting back to the University of Arizona team, they had been on the hunt for intermediate-mass black holes, those with tens to hundreds of thousands of times the Sun’s mass. The Chandra X-ray and XMM-newton space telescopes had been observing a star cluster they think contains an intermediate-mass black hole. Upon compiling 12 years’ worth of data from those observations they saw something. A star apparently got too close and got shredded – there it was, the salad maker. They measured the timing and extent of this tidal-disruption event and concluded they had identified a black hole with the mass of 20,000 Suns!

Of course, this new finding is not without questions.  The black hole’s spin seems to not fit expected scenarios for black hole formation.

What’s in the Sky?

January 12; about 45 minutes after sunset; west-southwest: Jupiter, Saturn, and Mercury grace the low evening sky.