astronomy

HD 166191

HD 166191 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 166191 rather than just read about it. In short: HD 166191 is a young late-F or early G-type star in the constellation Sagittarius. It is surrounded by a large amount of dust.

Key takeaways

HD 166191 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 166191 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 166191 from memory before moving on to harder problems.

Reference excerpt

HD 166191 is a young late-F or early G-type star in the constellation Sagittarius. It is surrounded by a large amount of dust. In 2019 it was reported in the Astronomer's Telegram that the star had brightened in the infrared, as was seen from Spitzer observations. A study was published in 2022, reporting on the result of a follow-up campaign. This study showed that a dust cloud as large as the star did transit in front of it. This cloud was produced from a giant collision between two planetesimals. In early works the age of the system was not certain and ranged between 10–100 Myrs. The large amount of dust was interpreted as being produced by a recent collision of planetary embryos or by massive ongoing collisional grinding. A later work did determine a younger age. The star was observed with ground-based spectroscopy and with Herschel. The researchers did find that the star is surrounded by a protoplanetary disk with a hole in the center. The silicate feature was also determined to be similar to primordial object. This would make the disk a so-called transitional disk, meaning it lies in between protoplanetary and debris disk. Observations with the Submillimeter Array did however find a high amount of dust and only little amount of gas, indicating that the disk is a debris disk. Another work determined that the disk is made up of two debris belts. An inner belt at ~0.27 AU with a temperature of about 760 Kelvin (K) and an outer belt at ~5 AU with a temperature of about 175 K. It was suggested that HD 166191 co-moves with HD 163296. This was questioned in a later work.

2018–2019 collision event Follow-up observations of the 2018–2019 brightening event were carried out with Spitzer, ASAS-SN and the Hereford Arizona Observatory. The disk has become brighter in the infrared since early 2018, reaching a maximum in mid 2019. ASAS-SN observed a dip during the infrared brightening. 142 ± 0.3 days later the second dip was seen with both Spitzer and ASAS-SN, having a depth of ≳80% in the optical. The new dust from the collision was at first compact, having a size of 1 stellar diameter vertically and about 2–3 stellar diameters horizontally. After two orbital periods the clump grew larger, but also optical thinner and no further dips could be observed. The researchers find a semi-major axis of 0.62 AU for a circular orbit, but the researchers also point out that the orbit is likely eccentric. The collision released dust with a minimum mass of ~1–4 × 1023 g (between 0.3x and 1.2x the mass of Mercury) The researchers think that a collision occurred between two large bodies with a sizes of ≳500 km (larger than 4 Vesta). The event set off a chain reaction of impacts between the fragments of the first collision and other small bodies in the system.

See also List of extrasolar planetary collisions List of stars that have unusual dimming periods 2MASS J08090250-4858172 Giant impact hypothesis

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 166191

Start with the simplest possible case. Write down what HD 166191 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 166191 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 166191 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 166191

In research: HD 166191 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 166191 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 166191 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Circumstellar disks, Extrasolar planetary collisions, F-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for HD 166191 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “HD 166191” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study HD 166191 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 166191 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 166191 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 166191 in simple terms?

HD 166191 is a young late-F or early G-type star in the constellation Sagittarius. It is surrounded by a large amount of dust.

Why does HD 166191 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 166191?

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 166191.