(Subject is Astronomy, but that's not an option.) What part of GAIA is used to determine the angular positions of stars to better measure their distances and motions?

A. The radial-velocity instrument
B. The infrared light instrument
C. The photometric instrument
D. The astrometry instrument

Not all tiles will be usedidentify the element present in each star based on the gaps observed in wavelengths of its light refer to this table containing absorption wavelengths (in nm) of several different elements the table ishelium 447, 502 ,587 ,668carbon 427 ,515, 600 ,678sulfur 425, 565, 639, 675xenon 484, 590, 687calcium 429 ,527, 593, 645silver 421 ,521, 662

What property is a characteristic of a substance that can be observed and does not change the identity of the substance

Which quantities are scalars? choose all that apply a.distance b.speed c. acceleration d.velocity