Theta Apodis
{{Short description|Star in the constellation Apus}}
{{Starbox begin
| name = θ Apodis
}}
{{Starbox image
| image=
{{Location mark
|image=Apus constellation map.svg|alt=|float=center|width=240
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=θ Apodis
|x=728|y=624
}}
|caption=Location of θ Apodis (circled)
}}
{{Starbox observe
| epoch = J2000
| constell = Apus
}}
{{Starbox character
| variable = SRb
}}
{{Starbox astrometry
| prop_mo_ra = −88.586
| prop_mo_dec = −32.655
| parallax = 8.3808
| p_error = 0.3574
}}
{{Starbox detail
| luminosity = {{val|3050|460|fmt=commas}}
| temperature = {{val|2850|160|fmt=commas}}
| rotational_velocity =
| age_gyr =
}}
{{Starbox catalog
| names = {{odlist | B=θ Apodis, Theta Aps | CD=-76°615 | FK5=1363 | HD=122250 | HIP=68815 | HR=5261 | SAO=257112 | AAVSO=1355-76 }}
}}
{{Starbox reference
|Simbad=tet+Aps
}}
{{Starbox end}}
Theta Apodis is a variable star in the southern circumpolar constellation of Apus. Its identifier is a Bayer designation that is Latinized from θ Apodis, and abbreviated Tet Aps or θ Aps, respectively. This is a variable star with an apparent visual magnitude range of 4.65 to 6.20, which, according to the Bortle Dark-Sky Scale, means it is a faint star but visible to the naked eye from dark suburban skies. The distance to Theta Apodis is approximately {{Convert|390|ly|pc|abbr=off|lk=on}}, based upon parallax measurements made from the Gaia telescope. It is unusual in that it is a red star with a high proper motion (greater than 50 milliarcseconds a year).
File:ThetaApsLightCurve.png for Theta Apodis, adapted from Moon et al. (2008)]]
Benjamin Apthorp Gould announced that Theta Apodis is a variable star, in 1879.
It is a semiregular pulsating variable and its brightness changes over a range of 0.56 magnitudes with a period of 119 days. A longer period of around 1,000 days has also been detected.
This is an evolved red giant that is currently on the asymptotic giant branch, with a stellar classification of M7 III. It shines with a luminosity approximately 3879 times that of the Sun and has a surface temperature of {{val|3131|ul=K|fmt=commas}}. It is losing mass at the rate of {{nowrap|1.1 × 10−7}} times the mass of the Sun per year through its stellar wind. Dusty material ejected from this star is interacting with the surrounding interstellar medium, forming a bow shock as the star moves through the galaxy. The stand-off distance for this front is located at about {{Convert|0.134|ly|pc|abbr=on|sigfig=2}} from Theta Apodis.
Theta Apodis has been identified as an astrometric binary, indicating that it has an orbiting companion that causes gravitational perturbation of the primary star.
References
{{reflist|30em|refs=
{{cite Gaia DR3|5786929090848333568}}
{{citation | display-authors=1 | last1=Yeşilyaprak | first1=C. | last2=Aslan | first2=Z. | title=Period-luminosity relation for M-type semiregular variables from Hipparcos parallaxes | journal=Monthly Notices of the Royal Astronomical Society | volume=355 | issue=2 | pages=601–607 |date=December 2004 | doi=10.1111/j.1365-2966.2004.08344.x | bibcode=2004MNRAS.355..601Y | postscript=. | doi-access=free }}
}}
{{Stars of Apus}}
{{DEFAULTSORT:Theta Apodis}}
Category:Semiregular variable stars
Category:Asymptotic-giant-branch stars