13 Delphini
Double star in the constellation Delphinus
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13 Delphini is a binary star[2] in the northern constellation of Delphinus, with a combined apparent magnitude of 5.64.[13] The system is located at a distance of 471 light years but is approaching the Solar System with a heliocentric radial velocity of about −7 km/s.[7]
13 Delphini A has an apparent magnitude of 5.66, while its companion has an apparent magnitude of 8.51.[2] As of 2016, the pair have a separation of 1.5″ located at a position angle of 200°.[14]
13 Delphini has a blended stellar classification of A0 V,[5] indicating that it is an ordinary A-type main-sequence star. However, when the components are analysed individually, the primary star is given a class of B9V.[15] It has 2.51 times the mass of the Sun[9] and has an effective temperature of 9,840 K.[4] However, the star is large for its class, having a radius almost 4 times that of the Sun[9] and a luminosity 119 times greater.[4] This is due to 13 Delphini having completed 86.1% of its main sequence lifetime[4] and has led one source to classify it as a subgiant instead.[16] It spins rapidly with a projected rotational velocity of 170 km/s[11] and has an age of 307 million years.[10]
This star has been designated Lambda Delphini by Johann Elert Bode, but the designation is generally unused now.[17]