astronomy

Zeta Aquilae

Zeta Aquilae is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Zeta Aquilae rather than just read about it. In short: Zeta Aquilae is a binary star system in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from ζ Aquilae, and abbreviated Zeta Aql or ζ Aql.

Key takeaways

Zeta Aquilae belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Zeta Aquilae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Zeta Aquilae from memory before moving on to harder problems.

Reference excerpt

Zeta Aquilae is a binary star system in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from ζ Aquilae, and abbreviated Zeta Aql or ζ Aql. This system is readily visible with the naked eye as a point of light, having a combined apparent visual magnitude of 2.983. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 83 light-years (25 parsecs) distant from the Sun. It is a candidate member of the TW Hydrae association of co-moving stars. Zeta Aquilae's two components can be designated Zeta Aquilae A and B. The former is officially named Okab, pronounced , the traditional name for the system. Zeta Aquilae has a number of companions listed and together they are designated WDS J19054+1352. As the primary star of this group, Zeta Aquilae also bears the designation WDS J19054+1352A. The companions are then designated WDS J19054+1352B, C, D and E.

Nomenclature ζ Aquilae, Latinised to Zeta Aquilae, is the binary's Bayer designation. The designations of the two components as Zeta Aquilae A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). WDS J19054+1352 is the entry of the wider system of which Zeta Aquilae is a member in the Washington Double Star Catalog. Zeta and Epsilon Aquilae together bore the traditional name Deneb el Okab, from an Arabic term ذنب العقاب Dhanab al-ʽuqāb "the tail of the eagle", which they mark (Aquila is Latin for 'eagle'). In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Okab for the component Zeta Aquilae A on 1 June 2018 and it is now so included in the List of IAU-approved Star Names. Epsilon and Zeta Aquilae also bore the Mandarin names Woo and Yuë , derived from and representing the old states Wú (吳) (located at the mouth of the Yangtze River) and Yuè (越) (in Zhejiang province). In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, Zeta Aquilae was designated Dzeneb al Tair (from the Arabic ذنب الطائر ðanab aṭ-ṭā’ir), which was translated into Latin as Cauda (Vulturis) Volantis, meaning the eagle's tail. In Chinese, 天市左垣 (Tiān Shì Zuǒ Yuán), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven old states in China and is marking the left borderline of the enclosure, consisting of Zeta Aquilae; Delta, Lambda, Mu, Omicron and 112 Herculis; Theta¹ and Eta Serpentis; Nu Ophiuchi, Xi Serpentis and Eta Ophiuchi. Consequently, the Chinese name for Zeta Aquilae itself is 天市左垣六 (Tiān Shì Zuǒ Yuán liù, English: the Sixth Star of Left Wall of Heavenly Market Enclosure), representing the state mentioned above.

Properties The primary, designated component A, has a stellar classification of A0 Vn, with the luminosity class 'V' indicating is a main sequence star that is generating energy through the nuclear fusion of hydrogen at its core. It has more than double the mass of the Sun and is radiating more than 39 times the Sun's luminosity. The effective temperature of the star's outer envelope is about 9620 K, which gives it the white hue typical of A-type stars. The estimated age of this star is 50–150 million years. This star is rotating rapidly, with a projected rotational velocity of 306 km s−1 giving a lower bound on the azimuthal velocity along the equator. As a result, it has an oblate shape, with its equatorial radius measuring 2.76 solar radii (R☉) and its polar radius measuring 2.15 R☉. Gravity darkening due to the fast rotation also make its effective temperature and surface gravity vary across latitudes, from 8,680 K and 3.60 cgs in the equator to 11,000 K and 4.15 cgs in the poles. Because of the Doppler effect, this rapid rotation makes the absorption lines in the star's spectrum broaden and smear out, as indicated by the 'n' suffix in the stellar class. It likely exhibits differential rotation along different latitudes. The star is rotating nearly edge-on relative to Earth, with an inclination of 85°. Astronomers use Zeta Aquilae as a telluric standard star. That is, the spectrum of this star is used to correct for telluric contamination from the Earth's atmosphere when examining the spectra of neighboring stars. Observation of this star in the infrared band during the 2MASS survey appeared to reveal excess emission. However, the distribution of this emission could not be readily explained by a conjectured disk of circumstellar dust. Instead, in 2009 the detection was ascribed to errors caused by saturation of the near-infrared detectors. Precise infrared interferometric observations during 2008–2011 was able to resolve infrared emission within the first astronomical unit from the star. A 2017 study proposed hot exozodiacal dust extended from 0.14 to 1.0 au with a mass of (1.79–10.2)×10−9 M🜨. Scenarios to explain the presence of this dust include a collision between orbiting bodies, or the sublimation of a super comet.

Companions The primary forms a binary star system with component B. This is a magnitude 12.0 star at an angular separation of 7.20″ along a position angle of 46°, as of 2009. The pair have a projected separation of 185.1 AU. The secondary has an estimated mass equal to one half the mass of the Sun. The 16th magnitude star WDS J19054+1352E is also considered to be a co-moving companion with a mass of 0.14 M☉, at a projected separation of 38,000 AU from the primary. The Washington Double Star Catalog lists a second 12th magnitude star at 160" (WDS J19054+1352C) plus an 11th magnitude star separated by 200" (WDS J19054+1352D). The Catalog of Components of Double and Multiple Stars lists the two 12th magnitude companions at 6.5" and 160".

References

External links Image Zeta Aquilae

Illustrations

Worked examples

Example 1 — a first encounter with Zeta Aquilae

Start with the simplest possible case. Write down what Zeta Aquilae claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Zeta Aquilae before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Zeta Aquilae ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Zeta Aquilae

In research: Zeta Aquilae appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Zeta Aquilae in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Zeta Aquilae is common in secondary-school and first-year university syllabi. It links to neighbouring topics A-type main-sequence stars, Aquila (constellation), Bayer objects, so understanding it makes those chapters shorter.
In everyday life: Look for Zeta Aquilae outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Zeta Aquilae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Zeta Aquilae means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Zeta Aquilae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Zeta Aquilae in simple terms?

Zeta Aquilae is a binary star system in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from ζ Aquilae, and abbreviated Zeta Aql or ζ Aql.

Why does Zeta Aquilae matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Zeta Aquilae?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Zeta Aquilae.