astronomy

HD 128311

HD 128311 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 128311 rather than just read about it. In short: HD 128311 is a variable star in the northern constellation of Boötes. It has the variable star designation HN Boötis, while HD 128311 is the star's designation in the Henry Draper Catalogue.

Key takeaways

HD 128311 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 128311 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 128311 from memory before moving on to harder problems.

Reference excerpt

HD 128311 is a variable star in the northern constellation of Boötes. It has the variable star designation HN Boötis, while HD 128311 is the star's designation in the Henry Draper Catalogue. The star is invisible to the naked eye with an apparent visual magnitude that fluctuates around 7.48. It is located at a distance of 53 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −9.6 km/s. Two confirmed extrasolar planets have been detected in orbit around this star. The stellar classification of HN Boo is K3V, which indicates this is a K-type main sequence star. Klaus G. Strassmeier et al. announced that the star's brightness varies, in the year 2000. It was given its variable star designation in 2006. It is a BY Draconis-type variable, randomly varying in brightness by 0.04 in magnitude over a period of 11.54 days due to star spots and high chromospheric activity. The star exhibits strong emission, which suggests an age of 0.5–1.0 billion years. It has 82% of the mass of the Sun and 78% of the Sun's radius. The metallicity of the star, meaning its abundance of heavier elements, appears slightly higher than in the Sun. It is radiating 31% of the luminosity of the Sun from its photosphere at an effective temperature of 4,863 K.

Planetary system

In 2002, the discovery of the exoplanet HD 128311 b was announced by Paul Butler. In 2005, the discovery of a second exoplanet HD 128311 c was announced by Steve Vogt. Most likely, the system has been formed in a very turbulent disc. The authors were able to show with both analytic and numerical models that certain libration modes are readily excited by turbulence. It was initially thought that the system could have been resulted from planet–planet scattering, but this is rather unlikely. In 2014, the true mass of HD 128311 c was measured via astrometry. The same study also proposed a third planetary candidate, but it has not been confirmed. In 2026, the mass of HD 128311 b was also measured with astrometry.

References

External links "Notes for star HD 128311". Extrasolar Planets Encyclopaedia. Archived from the original on July 2, 2007. Retrieved 2008-08-18.

External links GJ 3860 Extrasolar Planet Interactions Archived 2016-05-05 at the Wayback Machine by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona Image HD 128311

Illustrations

Worked examples

Example 1 — a first encounter with HD 128311

Start with the simplest possible case. Write down what HD 128311 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 128311 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 128311 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 128311

In research: HD 128311 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 128311 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 128311 is common in secondary-school and first-year university syllabi. It links to neighbouring topics BY Draconis variables, Boötes, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 128311 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 128311 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 128311 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 128311 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 128311 in simple terms?

HD 128311 is a variable star in the northern constellation of Boötes. It has the variable star designation HN Boötis, while HD 128311 is the star's designation in the Henry Draper Catalogue.

Why does HD 128311 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 128311?

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 128311.