HD 84810
HD 84810, also known as l Carinae (l Car), is a star in the southern constellation of Carina. Its apparent magnitude varies from about 3.4 to 4.1, making it readily visible to the naked eye and one of the brightest members of Carina. Based upon parallax measurements, it is approximately from Earth.

From the characteristics of its spectrum, l Carinae has a stellar classification of G5 Iab/Ib. This indicates the star has reached a stage in its evolution where it has expanded to become a supergiant with 169 times the radius of the Sun. As this is a massive star with 8–13 times the mass of the Sun, it rapidly burns through its supply of nuclear fuel and has become a supergiant in roughly , after spending as a main sequence star.

l Carinae is classified as a Cepheid variable star and its brightness varies over an amplitude range of 0.725 in magnitude with a long period of 35.560 days. This unusually long period makes it essential for calibrating the period-luminosity relation for Cepheid variables; additionally, it is one of the nearest Cepheid variables, making it relatively easy to observe. The radial velocity of the star likewise varies by 39 km/s during each pulsation cycle. Its radius varies by about as it pulsates, reaching maximum size as its brightness is decreasing towards minimum.

It has a compact circumstellar envelope that can be discerned using interferometry. The envelope has been resolved at an infrared wavelength of 10μm, showing a radius of 10–100 AU at a mean temperature of 100 K. The material for this envelope was supplied by mass ejected from the central star.

The period of l Carinae is calculated to be slowly increasing and it is thought to be crossing the instability strip for the third time, cooling as it evolves towards a red supergiant after a blue loop.
Q523
star
Concept
Q8928
constellation
Concept
Q10470
Carina
CEL
Q124313
apparent magnitude
Concept
Q165074
parallax
Concept
Q2
Earth
CEL
Q752171
spectrum
Concept
Q25377588
stellar classification
Concept
Q6472
evolution
Concept
Q193599
supergiant
Concept
Q3450
main sequence
Concept
Q188593
Cepheid
Concept
Q6243
variable star
Concept
Q3424054
period-luminosity relation
Concept
Q240105
radial velocity
Concept
Q850283
interferometry
Concept
Q1811
AU
Concept
Q280157
instability strip
Concept
Q5898
red supergiant
Concept
Q60772858
blue loop
Concept
Q2715955
HD 84810
CEL
+3.4^^http://www.w3.org/2001/XMLSchema#decimal
3.4
NUMBER
+4.1^^http://www.w3.org/2001/XMLSchema#decimal
4.1
NUMBER
+5^^http://www.w3.org/2001/XMLSchema#decimal
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NUMBER
+8^^http://www.w3.org/2001/XMLSchema#decimal
8
NUMBER
+13^^http://www.w3.org/2001/XMLSchema#decimal
13
NUMBER
+0.725^^http://www.w3.org/2001/XMLSchema#decimal
0.725
NUMBER
+35.560^^http://www.w3.org/2001/XMLSchema#decimal
35.560
NUMBER
+39^^http://www.w3.org/2001/XMLSchema#decimal
39
NUMBER
+10^^http://www.w3.org/2001/XMLSchema#decimal
10
NUMBER
+10^^http://www.w3.org/2001/XMLSchema#decimal
10
NUMBER
+100^^http://www.w3.org/2001/XMLSchema#decimal
100
NUMBER
instance of
constellation
instance of
instance of