astronomy

HD 164604

HD 164604 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 HD 164604 rather than just read about it. In short: HD 164604 is a single star in the southern constellation of Sagittarius. It has the proper name Pincoya, as selected in the NameExoWorlds campaign by Chile, during the 100th anniversary of the IAU.

Key takeaways

HD 164604 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 164604 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 164604 from memory before moving on to harder problems.

Reference excerpt

HD 164604 is a single star in the southern constellation of Sagittarius. It has the proper name Pincoya, as selected in the NameExoWorlds campaign by Chile, during the 100th anniversary of the IAU. Pincoya is a female water spirit from southern Chilean mythology who is said to bring drowned sailors to the Caleuche so that they can live in the afterlife. A 2015 survey ruled out the existence of any stellar companions at projected distances from 13 to 340 astronomical units. It is known to host a single super-Jupiter exoplanet. This star is invisible to the naked eye with an apparent visual magnitude of 9.62. It is located at a distance of 130.5 light-years from the Sun based on parallax, and is drifting further away with a radial velocity of +7 km/s. The stellar classification of HD 164604 is K3.5V(k), which indicates this is a K-type main-sequence star. The chromosphere is considered very inactive. It is roughly seven billion years old with 77% of the mass and radius of the Sun. The star is radiating 26% of the luminosity of the Sun from its photosphere at an effective temperature of 4,663 K.

Planetary system A super-Jupiter exoplanet (HD 164604 b, later named Caleuche) was detected by the Magellan Planet Search Program in 2010 based on radial velocity variations of the host star. The orbit of this body does not preclude a hypothetical Earth-mass exoplanet from occupying a dynamically stable orbit within the habitable zone of this star. An astrometric measurement of the planet's inclination and true mass was published in 2022 as part of Gaia DR3. A second planet was found in 2026 from combined analysis of radial velocity and astrometry. This is another super-Jupiter on a wider orbit. There are two possible orbital solutions, with the outer planet's orbit being either prograde or retrograde to the inner planet's orbit. The retrograde solution is dynamically stable, while the prograde solution may be unstable. Gaia DR4 astrometry should make it possible to determine which solution is correct.

References

Further reading Feng, Fabo; et al. (June 2019). "Search for Nearby Earth Analogs. I. 15 Planet Candidates Found in PFS Data". The Astrophysical Journal Supplement Series. 242 (2): 31. arXiv:1904.08567. Bibcode:2019ApJS..242...25F. doi:10.3847/1538-4365/ab1b16. S2CID 121128472. 25.

Worked examples

Example 1 — a first encounter with HD 164604

Start with the simplest possible case. Write down what HD 164604 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 HD 164604 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 HD 164604 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 HD 164604

In research: HD 164604 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 HD 164604 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: HD 164604 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, Henry Draper Catalogue objects, Hipparcos objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 164604 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 HD 164604 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 164604 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 HD 164604 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 164604 in simple terms?

HD 164604 is a single star in the southern constellation of Sagittarius. It has the proper name Pincoya, as selected in the NameExoWorlds campaign by Chile, during the 100th anniversary of the IAU.

Why does HD 164604 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 HD 164604?

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 HD 164604.