There is a second source of powerful X-rays coming from the aftermath of a pair of colliding neutron stars, which indicates either the debris from the explosion is slamming into material that surrounds the event, or that the merger created a black hole, and now material is falling onto it.
Either way.
There is a bit of background.
A new window on the Universe opened up on August 17th, when the consequences of two stars colliding were felt.
When the core of a massive star collapses, the outer layers of the star explode in a supernova. Two massive stars can leave behind two smaller stars. They create ripples in the fabric of spacetime called gravitational waves, which expand away at the speed of light. The pair spiral together because of this. They finally merged, creating a single wave of waves.
Black holes emit no light when they collide. The material around the stars can explode at high speed if they collide. That creates a lot of light, less than a nova, but still powerful. Astronomers call this event a kilonova. It is thought that a significant amount of elements like Platinum, strontium, and gold are made in kilonovae.
The LIGO/Virgo observatory, which can detect ripples in the fabric of space and time, had only found one other black hole merger. The first such event seen this way was when the event was seen by LIGO/Virgo. Multimessenger astronomy is when you can see an event in the Universe not just through light or waves, but both.
Things got weird after that.
A team of scientists used the Chandra X-ray observatory to observe the event, but did not see anything. Nine days after the initial explosion, X-rays were seen, and it kept looking.
The dense disk of matter around the stars was created by the intense force felt by the stars as they whirled around each other. This resulted in two beams of energy and matter being blasted away from the event. One of the jets was pointed towards Earth, but tipped away from us.
The material that already existed around the stars would slow down as the jet screamed away at a decent fraction of the speed of light. The jet loses its collimation when it slows to a critical speed. We started seeing X-rays after nine days, when the beam was wide enough to include Earth.
The fading of the X-rays stopped in March 2020. The jet should fade until we can no longer see it.
This means there must be a second source of X-rays, one that has been there for a while but was nowhere near as bright as they jet, so we did not see it. X-rays are still seen because the source was visible once the jet faded.
3.4 years after the initial explosion, it's still cranking out energy at a rate 125,000 times the Sun's power, and that's just in X-rays! That is a lot of energy.
There are two possible explanations for this source. The debris from the explosion is hitting material at large in the galaxy, the thin gas between the stars. The shock waves travel through the gas. Magnetic fields in the expanding debris are compressed by shock waves, which in turn can cause them to accelerate subatomic particles to incredibly high speeds. These emit X-rays through a process called inverse Compton scattering.
If the two stars were large enough, they would have merged into a black hole. Material falling toward the black hole doesn't fall straight in; it piles up in a disk around it that gets extremely hot and can emit X-rays.
Which is it? There is a way to tell here. Over time, the X-rays from the debris colliding with other stuff will fade. The x-rays from the black hole should be better. Black holes eat more material than shock waves, so it's better to look for radio waves. It is possible to see radio light from this object and figure out what it is.
The milliseconds after the stars collide is an interesting aspect of this. It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 The bounce of a neutrons star can give a huge kick to material, speeding it away at high speed. If the X-rays show the blast hitting the material around the event, models suggest it would have accelerated.
The gift that keeps giving is this event. We are learning about what happens when huge events occur, and nothing like this has ever been seen before. Platinum is used in computer hard drives and circuit boards, meaning that the machine you are reading about may have had some of its parts created billions of years ago. How cool is that?
This new work is based on observations taken of the kilonova in the year of 2017, and due to the way I phrased it, it sounded like all the work was done by a different team. I changed the text to make it more clear.
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