Aldebaran

Aldebaran, the Hyades and the Pleiades 

Aldebaran is the brightest star in the constellation Taurus at the head of the bull (in the lower left corner of the image).  Although in the image, Aldebaran appears white, it is an orange giant like Arcturus.  It has exhausted the hydrogen in its core but has not yet begun fusing helium.  Aldebaran appears to be a member of the Hyades cluster of young stars at the head of the bull, but it is actually much closer at 20 pc.   Because Aldebaran lies near the ecliptic, it is often occulted by the moon; this has given us many measurements of its angular size of about 20 thousandths of an arcsecond so a diameter of about 40 times that of the Sun.   This measurement provides a calibration for stellar models and interferometric studies of other objects.

A cool question to ask is whether we could detect planets orbiting these giant stars.   Assef, Gaudi and Stanek (http://adsabs.harvard.edu/abs/2009ApJ...701.1616A) argue that although the duration of the transits is long (about 50 hours or longer) and the amplitude is small (less than one part per thousand), the systematics of the photometry can be kept under control that even one-meter telescopes could discover such transiting systems from the ground.   From satellites such as Kepler, COROT and MOST the prospects are even better.