The Parallax of ? Centauri Measured from Gaia EDR3 and a Direct, Geometric Calibration of the Tip of the Red Giant Branch and the Hubble Constant

We use data from the ESA Gaia mission Early Data Release 3 (EDR3) to measure trigonometric parallax of $\omega$ Cen, first high precision measurement for most massive globular cluster in Milky Way. a combination positional and quality proper motion EDR3 identify over 100,000 members, which 67,000 are magnitude color range where parallaxes best calibrated. find estimated be robust, demonstrating good control systematics within color-magnitude diagram cluster. $0.191\pm0.001$ (statistical) $\pm0.004$ (systematic) mas (2.2\% total uncertainty) corresponding distance $5.24\pm0.11$ kpc. The Cen provides unique opportunity directly geometrically calibrate luminosity Tip Red Giant Branch (TRGB) because it is only with sufficient mass provide enough red giant stars, more than 100 one below tip, precise, model-free tip. Combined pre-existing widely-used measurements tip foreground Way extinction, we $M_{I,TRGB}=-3.97\pm0.06$ mag $I$-band blue edge. Using TRGB calibrated SNIa results value Hubble constant $H_0=72.1\pm2.0$ km s$^{-1}$ Mpc$^{-1}$. make stars available electronically encourage independent analyses presented here.