astronomy

Xi Aquilae

Xi 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 Xi Aquilae rather than just read about it. In short: Xi Aquilae is a star in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from ξ Aquilae, and abbreviated Xi Aql or ξ Aql.

Key takeaways

Xi 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 Xi Aquilae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Xi Aquilae from memory before moving on to harder problems.

Reference excerpt

Xi Aquilae is a star in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from ξ Aquilae, and abbreviated Xi Aql or ξ Aql. The star has the official name Libertas, pronounced , a Latin word for liberty. Based on parallax measurements, it is located at a distance of 186 light-years (57 parsecs) from the Sun. This is an aging giant star that is close to a billion years old. A companion star has been detected using speckle interferometry 0.09″ away. As of 2008, an extrasolar planet has been confirmed in orbit around the star. Designated Xi Aquilae b, this massive world was later named Fortitudo.

Nomenclature ξ Aquilae (Latinised to Xi Aquilae) is the star's Bayer designation. Following its discovery the planet was designated Xi Aquilae b. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning names were Libertas for this star and Fortitudo for its planet. The winning names were those submitted by Libertyer, a student club at Hosei University of Tokyo, Japan. The names which were originally proposed were in English and were 'Liberty' and 'Fortitude', but to comply with the IAU's rules they were modified to be Latin versions of the same words, and so the final names became 'Libertas' and 'Fortitudo' respectively. 'Aquila' is Latin for 'eagle', a popular symbol of liberty and embodiment of fortitude—emotional and mental strength in the face of adversity. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. In its first bulletin of July 2016, the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.

Properties This star has an apparent visual magnitude of 4.722, which, according to the Bortle Dark-Sky scale, is bright enough to be viewed with the naked eye from dark suburban skies. The orbital motion of the Earth causes this star to undergo an annual parallax shift of 17.51 milliarcseconds. From this measurement, the distance to this star can be determined, yielding an estimate of approximately 186 light-years with an error of 1 light year. The magnitude of the star is diminished by 0.09 from the extinction caused by interstellar gas and dust. The spectrum of this star is considered a standard example of the stellar classification G9.5 IIIb, where the G9.5 means that it belongs to the category of G-type stars while the luminosity class of IIIb indicates that, at an estimated age of nearly one billion year, is an evolved star that has reached the giant stage. It is in the red clump, meaning it is generating energy through the fusion of helium into carbon at its core. Xi Aquilae has an estimated 174% of the Sun's mass. Its size has been measured using interferometry at the Navy Precision Optical Interferometer, which yields a radius 10.17 times that of the Sun. It is radiating 58.5 times the Sun's luminosity at an effective temperature of 4,841 K, giving it the golden-hued glow of a G-type star. The possibility of a binary stellar companion can be ruled out based upon observations with the CHARA array.

Planetary system In 2008, the presence of a planetary companion was announced, based upon Doppler spectroscopy results from the Okayama Astrophysical Observatory. This object, designated as Xi Aquilae b, has at least 2.8 Jupiter masses and is orbiting at an estimated 0.68 astronomical unit from the star with a period of 136.75 days. Any planets that once orbited to the interior of this object may have been consumed as the star entered the red giant stage and expanded in radius. Later in 2024, astrometric measurements place an upper limit in the mass of 37.1 MJ based on Gaia astrometry.

References

External links "ksi Aql". Exoplanets. Archived from the original on 2009-11-25. Retrieved 2008-06-25. "Notes for star ksi Aql". Extrasolar Planets Encyclopaedia. Archived from the original on March 27, 2008. Retrieved 2008-06-25. HR 7595 Archived 2012-02-11 at the Wayback Machine Image Xi Aquilae wikisky.org

Illustrations

Worked examples

Example 1 — a first encounter with Xi Aquilae

Start with the simplest possible case. Write down what Xi 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 Xi 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 Xi 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 Xi Aquilae

In research: Xi 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 Xi 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: Xi Aquilae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aquila (constellation), Bayer objects, Bright Star Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for Xi 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 Xi Aquilae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Xi 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 Xi Aquilae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Xi Aquilae in simple terms?

Xi Aquilae is a star in the equatorial constellation of Aquila. Its name is a Bayer designation that is Latinized from ξ Aquilae, and abbreviated Xi Aql or ξ Aql.

Why does Xi 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 Xi 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 Xi Aquilae.