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We present Atacama Large Millimeter/submillimeter Array (ALMA) observationsfrom the 2014 Long Baseline Campaign in dust continuum and spectral lineemission from the HL Tau region. The continuum images at wavelengths of 2.9,1.3, and 0.87 mm have unprecedented angular resolutions of 0.075 arcseconds (10AU) to 0.025 arcseconds (3.5 AU), revealing an astonishing level of detail inthe circumstellar disk surrounding the young solar analogue HL Tau, with apattern of bright and dark rings observed at all wavelengths. By fittingellipses to the most distinct rings, we measure precise values for the diskinclination (46.72pm0.05 degrees) and position angle (+138.02pm0.07 degrees).We obtain a high-fidelity image of the 1.0 mm spectral index ($\alpha$), whichranges from $\alpha\sim2.0$ in the optically-thick central peak and twobrightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings arenot devoid of emission, we estimate a grain emissivity index of 0.8 for theinnermost dark ring and lower for subsequent dark rings, consistent with somedegree of grain growth and evolution. Additional clues that the rings arisefrom planet formation include an increase in their central offsets with radiusand the presence of numerous orbital resonances. At a resolution of 35 AU, weresolve the molecular component of the disk in HCO+ (1-0) which exhibits apattern over LSR velocities from 2-12 km/s consistent with Keplerian motionaround a ~1.3 solar mass star, although complicated by absorption at lowblue-shifted velocities. We also serendipitously detect and resolve the nearbyprotostars XZ Tau (A/B) and LkHa358 at 2.9 mm.

First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region