Del-2

Its story

Delta-2 Gruis is a deeply evolved red giant, cool down to about 3000 degrees and some seven hundred times more luminous than the Sun, hanging at 330 light-years in the southern sky. It pulses on several periods at once —twenty, twenty-four, thirty-two days— like an organ tuning many pipes at the same time without ever resolving the chord. With its optical twin Delta-1 it forms a striking pair that looks double yet is merely a line-of-sight coincidence.