Zeta Aquarii

Starbox begin
name=ζ Aquarii Starbox image


caption = ζ Aquarii Starbox observe
epoch=J2000
ra=22^h 28^m 49.912^s
dec= -00° 01′ 11.9″
appmag_v=4.42
constell=Aquarius Starbox character
class=F3V
b-v=0.42
u-b=0.01
variable= Starbox astrometry
radial_v=24.9
prop_mo_ra=191
prop_mo_dec=37
parallax=13
p_error=5
absmag_v=4.8 Starbox detail
mass=1,7
radius=1,4
luminosity=6 | temperature=6,000–7,500
metal=?
rotation=?
age=? Starbox visbin
name=ζ Aquarii B
period=856
axis=5.055
eccentricity=0.495
inclination=131.25
node=
periastron=1957.6

Starbox visbin
name=ζ Aquarii C
period=
axis=94.8
eccentricity=
inclination=273
node=
periastron=

Starbox catalog
names=55 Aquarii, HR 8558 +
HR 8559, HD 213051 +
HD 213052, BD-00°4365,
HIP 110960, SAO 146107 +
SAO 146108, GC 31398,
ADS 15971, CCDM 22288-0001. Starbox reference
Simbad=HD+213052 Starbox reference
Simbad=ADS+15971

Zeta Aquarii (ζ Aqr / ζ Aquarii) is a binary star,the central star in the “water jar” asterism (Click [http://www.dibonsmith.com/aqr_z.htm here] to see the "water jar") in the constellation Aquarius. It is approximately 103 light years from Earth.

The brighter component, ζ² Aquarii, is a yellow-white F-type main sequence dwarf with an apparent magnitude of +4.42. Its companion, ζ¹ Aquarii, is a yellow-white F-type subgiant with an apparent magnitude of +4.59. The fact that their brightness is so close makes the pair easy to measure and resolve. The binary system has a combined brightness of +3.65 magnitudes. The two stars are 1.67 arcseconds apart and have an orbital period of 760 years.

Christian Mayer, director of the Mannheim Observatory, is considered the first to have observed Zeta Aquarii to be double. He did so in 1777. A couple of years later, William Herschel also discovered this duality.

Zeta Aquarii has only been observed through half its orbit; hence, the size and shape of the orbit, and therefore, the orbital period, are undetermined. According to Martin Gaskell, the latest orbital calculation was made in 1968, and gave a period of 856 years. (This information was catalogued in Norton’s, 2000.)

The greatest distance in the elliptical orbit of the two components, which appears to be a clockwise movement, is approximately four times greater than their closest distance, which is about the distance of our Sun and Pluto.

The stars currently have an ephemeris of about 2.5". It is projected that at the end of the twenty-third century, the stars should be about 6.4" apart. The change per year a very slight, however.

The two components, simply labeled star A and star B, each have a mass of 1.1 solar masses and 0.9 solar masses, respectively. Despite this similitude in mass, they are about seven times more luminous than our sun, which means they are more evolved. The spectroscopic interpretation of both stars classifies them as subgiants. This supports the prediction that the hydrogen in their cores is exhausted and that they are becoming red giants.

There have been claims that there is a third component orbiting star B with a period of 25.5 years. But, it is possible that this is simply an over-interpretation of residuals, as has been the case with other perceived third components of binary systems. Such tertiaries have a luminosity too low to be seen directly. The speculated tertiary in the Zeta Aquarii system allegedly has a mass of 0.28 solar masses and is likely a red or white dwarf. It is located at 9 astronomical units from star B, the same distance as Saturn from our Sun.

Zeta Aquarii is currently a northern hemisphere object. In 2004 it was directly above the celestial equator, and before that it was located south of it.

Location

Components

References

1. Martin Gaskell. Double Stars to Follow, Part IV: Zeta Aquarii and Mu Cygni. Prairie Astronomy Club Home Page. [http://www.prairieastronomyclub.org/dblstar4.htm]

2. Richard Jaworski. “This Months Double Stars” [http://www.asnsw.com/universe/1997/tmds-1197.htm]

* [http://www.alcyone.de/cgi-bin/search.pl?object=HR8558 HR 8558]
* [http://aladin.u-strasbg.fr/AladinPreview?-c=NLTT+53956&ident=NLTT+53956&submit=Aladin+previewer Image ζ Aquarii]