111th Uchu Forum
The observationally identifiable total mass of baryons in the present day universe is known to be significantly smaller than the mass derived from the cosmic microwave background radiation and neutral hydrogen absorption line studies of the distant universe. The unobserved baryons in the current universe are sometimes called dark baryons (or missing baryons). The dark baryons are theoretically thought to exist as a dilute plasma called Warm-Hot Intergalactic Medium (WHIM) at the outer edges of the filaments and dark matter haloes of the universe's large-scale structure. In this talk, I will give an overview of the planned X-ray observation program to detect the WHIM, and introduce a new method for observing the WHIM using hyper-fine structure lines of heavy elements.