astronomy

HD 164427

HD 164427 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 164427 rather than just read about it. In short: HD 164427 is a star with a likely red dwarf companion in the southern constellation of Pavo. It has an apparent visual magnitude of 6.88, placing it just below the nominal limit for visibility with the typical naked eye.

Key takeaways

HD 164427 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 164427 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 164427 from memory before moving on to harder problems.

Reference excerpt

HD 164427 is a star with a likely red dwarf companion in the southern constellation of Pavo. It has an apparent visual magnitude of 6.88, placing it just below the nominal limit for visibility with the typical naked eye. The annual parallax shift of 26.0 mas yields a distance estimate of 125 light-years (38 parsecs). It is moving further from the Earth with a heliocentric radial velocity of +3.4 km/s. This is an inactive G-type main-sequence star given a stellar classification of G0+V by Gray et al. (2006), although Evans et al. (1964) classified it as a subgiant star with luminosity class IV. It is 6.6 billion years old with 1.125 times the mass of the Sun and 1.40 times the Sun's radius. The star is somewhat over-luminous for its class, radiating 2.33 times the Sun's luminosity from its photosphere at an effective temperature of 5,876 K.

Companions In 2001, a brown dwarf candidate companion was announced by Anglo-Australian Planet Search program. It was detected by the Doppler velocity technique with an echelle spectrograph attached to the 3.92m Anglo-Australian Telescope. A magnitude 12.60 companion star designated HD 164427 B lies at an angular separation of 28.90″ along a position angle of 336°, as of 2010. This is a suspected common proper motion companion with 52% of the Sun's mass and a physical separation of as much as 1,090 AU. HD 164427 b was initially thought to be a brown dwarf based on its minimum mass of 46 times that of Jupiter. In 2023, an astrometric orbit for this object was published using data from Gaia, showing its true mass to be 0.34 M☉, making it a likely red dwarf star. This stellar companion orbits at nearly half an astronomical unit or Earth-to-Sun distance away from its primary. The angular separation between the two stars as viewed from Earth is 11.76 milliarcseconds. It takes 108.55 Earth days to orbit eccentrically around HD 164427. It has a very high semi-amplitude of almost 1400 m/s, because this is a very massive object which exerts strong gravitational pull on its tugging star.

References

External links "NLTT 45831 -- High proper-motion Star". SIMBAD. Retrieved December 21, 2007.

Worked examples

Example 1 — a first encounter with HD 164427

Start with the simplest possible case. Write down what HD 164427 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 164427 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 164427 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 164427

In research: HD 164427 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 164427 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 164427 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Binary stars, Durchmusterung objects, G-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for HD 164427 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 164427 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 164427 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 164427 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 164427 in simple terms?

Why does HD 164427 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 164427?

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 164427.