astronomy

HD 161056

HD 161056 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 161056 rather than just read about it. In short: HD 161056 (HIP 86768, HR 6601) is a bluish-white hued star in the equatorial constellation of Ophiuchus. It has an apparent magnitude of 6.32, placing it near the limit for naked eye visibility under dark skies.

Key takeaways

HD 161056 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 161056 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 161056 from memory before moving on to harder problems.

Reference excerpt

HD 161056 (HIP 86768, HR 6601) is a bluish-white hued star in the equatorial constellation of Ophiuchus. It has an apparent magnitude of 6.32, placing it near the limit for naked eye visibility under dark skies. The object is located approximately 1,340 light-years (410 parsecs) distant according to Gaia DR3 parallax measurements, but it is moving closer at a heliocentric radial velocity of −26.0 km/s. It is a luminous early B-type star, but its spectral type varies from publication to publication, most often between B1.5V, implying a hot main-sequence star, and B3II/III, indicative of a slightly cooler blue giant. It has a mass of 12.5 M☉ and a radius of 11.7 R☉. In Chinese astronomy, the star was given the name Shìlóuliù (Chinese: 市樓六), meaning it was the sixth star of the asterism Shìlóu (市樓, "Municipal Office") in the Heavenly Market enclosure.

Polarimetry In 1985, the star was suggested as a standard for polarimetric observations via the Hubble Space Telescope, since the star's large distance from Earth produces a large interstellar polarization and its high luminosity makes it easily visible at such distances. In 1988, however, it was found that the star was slightly variable in polarization, and thus unsuitable as a standard star. Nevertheless, Hubble observed the star's ultraviolet interstellar polarization, thanks to it having been well-researched in the visible spectrum, presenting results consistent with Serkowski's law—an empirical formula regarding the dependency of interstellar polarization on wavelength. The extensive collected polarization spectrum showed a close match to what would be expected from an interstellar dust composition of pure amorphous forsterite.

Spectroscopy In addition to polarimetry, spectroscopic observations have also been conducted on HD 161056 to provide insight into the interstellar medium. The ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES) detected signatures of diatomic carbon and tricarbon molecules in interstellar clouds surrounding the star. Near-infrared spectroscopy has revealed signs of weak stellar emission lines of singly ionized magnesium and neutral helium (Mg II and He I in spectroscopic notation).

Runaway star HD 161056 is a runaway star and a candidate for producing a bow shock observable in the infrared. Such stars commonly originate in multiple star systems, from which they were ejected due to gravitational interactions or supernovae of their companions, and indeed it is possible that the star could have been in a binary system with the pulsar PSR B1929+10 about 1.1 million years ago, when it was located in the vicinity of IC 4665. However, Zeta Ophiuchi is considered more likely to have been its binary companion, in which scenario the pair possibly split up around 900,000 years ago.

See also Ophiuchus in Chinese astronomy List of Chinese star names

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 161056

Start with the simplest possible case. Write down what HD 161056 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 161056 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 161056 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 161056

In research: HD 161056 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 161056 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 161056 is common in secondary-school and first-year university syllabi. It links to neighbouring topics B-type bright giants, B-type giants, B-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for HD 161056 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 161056 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 161056 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 161056 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 161056 in simple terms?

Why does HD 161056 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 161056?

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 161056.