It wouldn't be a planet. Gaseous or earthlike. They are using other telescopes to monitor the search in that area.
Planets don't emit Xrays, which is the viewing component of Chandra. Although planets can reflect xrays passing infront of a sun for a corona affect, I would highly doubt they are using it for that.
More like quasars coming out of a black hole, super novas, galaxy collisions, peering into nebula clouds to see star formation. Things that emit light. Being that xray is a spectrum of light...
My guess is a super nova. That's been their main target lately.
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