This is really brilliant.

This is really brilliant. Astronomers knew that there are X-rays coming from the solar wind and X-rays coming from the local bubble, but had no good way of telling what fraction came from each. So they took advantage of a hack with the “helium-focusing cone” (I never heard of that before today).

That cone comes from the fact that the Sun is moving in our galaxy. It leaves something like a wake of particles behind it. Unlike a boat wake, the Sun has higher helium density in its wake because gravity slingshots the helium into a clump behind it.

That high-density cone of helium behind the Sun causes an increase of solar wind X-rays due to more stuff for the wind to collide with. So, by launching an rocket above our atmosphere with an X-ray detector at a point in time when the Earth was in the midst of that helium cone, astronomers detected an increase in X-rays above what had been previously detected. The amount of the increase indicated what fraction of X-rays came from the wind vs. an unchanged quantity of X-rays from the bubble.

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Sounding rocket solves one cosmic mystery, reveals another – In the last century, humans realized that space is filled with types of light we can’t see – from infrared signals released by hot stars and galaxies, to the cosmic microwave background that comes from every corner of the universe. Some of this invisible light that fills space takes the form of X-rays, the source of which has been hotly contended over the past few decades.