Chandra X-ray Observatory (1999–present)

Chandra's 0.5 arcsecond angular resolution is 100 times finer than any previous X-ray mission, allowing it to map dark matter distribution in galaxy clusters like the Bullet Cluster with 99% confidence. It has imaged superheated gas at temperatures exceeding 10 million Kelvin, revealing black hole environments and neutron star collisions that Hubble cannot detect. Compared to #2 Webb, Chandra operates in a completely different energy band (0.1–10 keV), capturing high-energy processes invisible to infrared telescopes, and its 25-year archive contains over 20,000 unique X-ray sources — 5 times more than Spitzer's infrared catalog.