Aldebaran is Alpha Tauri, HD 29139 and HIP 21421, preserved as permanent object 25. It is a K5 III giant with visual magnitude about 0.87. SIMBAD records a parallax near 48.94 milliarcseconds; simply inverting that angle in arcseconds gives an approximate distance of 20.4 parsecs, or 66.7 light-years. That is an original calculation from a catalogue measurement, not an independent distance determination. Source: SIMBAD, https://simbad.cds.unistra.fr/simbad/sim-basic?Ident=Aldebaran.
The Roman numeral III in K5 III marks the giant luminosity class. Aldebaran has exhausted the quiet main-sequence phase represented by an ordinary dwarf star and expanded and cooled at its surface. That cooler photosphere shifts more visible light toward red and orange wavelengths, producing its conspicuous warm colour. “Cool” is comparative: a stellar photosphere remains thousands of kelvin. To the eye the expanded star is still an unresolved point.
Aldebaran appears in the V-shaped face of Taurus, but it is not a Hyades cluster member. NASA's observing guide explicitly treats the orange star as a foreground landmark for finding the more distant cluster. The chance alignment is useful on a sky chart while saying nothing about shared origin. Source: NASA/JPL, https://www.jpl.nasa.gov/videos/whats-up-march-2022/. The name comes through Arabic al-dabaran, “the follower,” traditionally understood as following the Pleiades across the sky; the star's IAU-approved name applies to this specific object, while Alpha Tauri remains its constellation designation.
For more than three decades, astronomers have measured slow changes in Aldebaran's radial velocity—the motion toward or away from us inferred from shifts in its spectral lines. A 2015 analysis found a coherent period near 629 days and fitted a companion with a minimum mass about 6.5 times Jupiter's. The same data contained a less stable signal near 520 days associated with activity indicators, illustrating that a giant star can carry both orbital-looking and intrinsic variations. Source: Hatzes and colleagues (2015), https://arxiv.org/abs/1505.03454.
The companion is not settled fact. A later analysis combined 165 new Lick Observatory measurements with seven earlier data sets. Its best one-companion fit moved to about 607 days, left large residual scatter, lost statistical power during part of the record and showed phase mismatches. The authors concluded that the new data weakened the planet hypothesis and proposed oscillatory convective modes as a plausible alternative. Source: Reichert and colleagues (2019), https://arxiv.org/abs/1903.09157. SIMBAD accordingly labels the proposed planet unconfirmed. A careful story therefore reports a disputed interpretation, not a discovered world.
The stored coordinates are approximately right ascension 4h 36m and declination +16° 31′. At 45° N, Aldebaran reaches about 61.5° altitude at upper culmination. At 35° S it reaches about 38.5°. These geometric values ignore refraction and obstructions. Brightness makes the star accessible from cities, but its orange hue and the Hyades V are clearer when it is comfortably above haze.
Use Orion as the large-scale signpost: extend the line of Orion's Belt northwestward to the first conspicuous orange star. Then verify the two arms of the Hyades V around it. In the accepted Taurus finder, Aldebaran occupies the eastern end of the V and also anchors a longer figure line toward the horns. Do not identify the star by colour alone; trace the pattern. The repository geometry has been inspected for this guidance, but the final rendered finder and story link still need publication review.
Binoculars widen the scene and reveal more Hyades members, while Aldebaran remains a foreground point. Record the colour impression separately from brightness estimates, because eye adaptation and comparison stars affect both. The current week supplies rising, transit, Moon and darkness conditions; none should be frozen into this reusable account.
