Delta Persei
Delta Persei (Delta Per, δ Persei, δ Per) is a double star in the northern constellation of Perseus. It has an apparent visual magnitude of 3.01, making it readily visible with the naked eye. Parallax measurements give it a distance of about from the Earth.

The spectrum of this star matches a stellar classification of B5 III, which indicates it is a giant star that has evolved away from the main sequence after exhausting the hydrogen at its core. It has about seven times the Sun's mass and has an estimated age of 6.8 million years. The effective temperature of the outer envelope is 14,890 K, with the energy being emitted at this temperature giving it the blue-white hue that is a characteristic of a B-type star. It is rotating rapidly with a projected rotational velocity of 190 km s−1, which gives a lower bound for the actual azimuthal velocity along the star's equator.

This is most probably a binary star and may be a triple star system. It has an optical companion with an apparent magnitude of +6.17 at an angular separation of 0.330 arcseconds and a position angle of 221°, but it is uncertain whether this is an optical double star or a gravitationally bound companion. The star has also been categorized as a spectroscopic binary, indicating that it has an orbiting companion that has not been separately resolved with a telescope. Finally, this star may be a member of the Melotte 20 open cluster, which would make it the second-brightest member after Mirfak.

Observation with the IRAS shows an extended, ring-like feature that may be a bow wave driven by radiation pressure from the star, rather than a bubble being generated by the stellar wind. This feature has an angular size of 15 × 25 arcminutes and a peak temperature of 38 K. It has an estimated peculiar velocity of more than 30 km s−1, making it a runaway star.
Q13890
double star
Concept
Q8928
constellation
Concept
Q10511
Perseus
CEL
Q124313
apparent visual magnitude
Concept
Q165074
Parallax
Concept
Q752171
spectrum
Concept
Q25377588
stellar classification
Concept
Q5875
giant star
Concept
Q6472
evolved
Concept
Q3450
main sequence
Concept
Q180892
Sun's mass
Concept
Q854050
effective temperature
Concept
Q6464
projected rotational velocity
Concept
Q124274
azimuth
Concept
Q50053
binary star
Concept
Q12097402
arcsecond
Concept
Q2105737
position angle
UNK
Q13890
optical double
Concept
Q50053
spectroscopic binary
Concept
Q1072618
Melotte 20
DIS
Q11387
open cluster
Concept
Q13790
Mirfak
CEL
Q724913
IRAS
MISC
Q649036
radiation pressure
Concept
Q654396
stellar wind
Concept
Q718647
angular size
Concept
Q12097402
arcminute
Concept
Q1253791
peculiar velocity
Concept
Q6440
runaway star
Concept
Q2743026
Delta Persei
CEL
+3.01^^http://www.w3.org/2001/XMLSchema#decimal
3.01
NUMBER
+5^^http://www.w3.org/2001/XMLSchema#decimal
5
NUMBER
+6.8^^http://www.w3.org/2001/XMLSchema#decimal
6.8
NUMBER
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
++6.17^^http://www.w3.org/2001/XMLSchema#decimal
+6.17
NUMBER
+0.330^^http://www.w3.org/2001/XMLSchema#decimal
0.330
NUMBER
+20^^http://www.w3.org/2001/XMLSchema#decimal
20
NUMBER
+15^^http://www.w3.org/2001/XMLSchema#decimal
15
NUMBER
+25^^http://www.w3.org/2001/XMLSchema#decimal
25
NUMBER
+38^^http://www.w3.org/2001/XMLSchema#decimal
38
NUMBER
+30^^http://www.w3.org/2001/XMLSchema#decimal
30
NUMBER
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
constellation
apparent magnitude
instance of
instance of