astronomy

NGC 5617

NGC 5617 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 NGC 5617 rather than just read about it. In short: NGC 5617 is an open cluster in the constellation Centaurus. NGC 5617 forms a binary open cluster with Trumpler 22.

Key takeaways

NGC 5617 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NGC 5617 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 5617 from memory before moving on to harder problems.

Reference excerpt

NGC 5617 is an open cluster in the constellation Centaurus. NGC 5617 forms a binary open cluster with Trumpler 22. It lies one degree west-northwest of Alpha Centauri.

Observation history

It was discovered by James Dunlop in 1826. He described it on May 8, 1826 as "a cluster of small stars of mixed magnitudes, considerably congregated towards the centre, 4' or 5' in diametre" and added it to his catalog as number 302. John Herschel described as "Class IV object, very rich; irregularly round; pretty much compressed in the middle but scattered at borders; 15'; there are three stars of 10th magnitude, 5 or 6 stars of 11th magnitude; the rest below 11th" and added it to General Catalogue as No. 3570. In the New General Catalogue it is described as "large (10'), richer in stars to the west (about 80 total), with a compressed middle. It contains stars of magnitude 8 and fainter."

Characteristics NGC 5617 is located nearly 2 kpc (6.500 light years) away from Earth, at the further border of Carina-Sagittarius arm. Various photometric studies have produced different results concerning the age and the distance of the cluster; Moffat & Vogt (1975) studied and calculated a distance of 1.34 kpc from the Sun, Haug (1978) found its distance to be 1.82 kpc, a CCD photometry by Kjeldsen & Frandsen (1991) found the distance to be 2.05 ± 0.2 kpc and the age 70 Myr and Carra & Munari (2004) used BVI photometry to obtain reddening EB−V= 0.48 ± 0.05, age of 80 Myr, and a distance of 2.0 ± 0.3 kpc. De Silva et al. (2015) calculated its distance at 2.1 ± 0.3 kpc. Bisht et al. found an age of 90 ± 10 Myr and a parallax-derived distance of 2.43 ± 0.08 kpc, in good agreement with isochrone-derived values. There are 175 probable member stars within the angular radius of the cluster and 65 within the central part of the cluster. The tidal radius of the cluster is 7.4 - 10.2 parsecs (24 - 33 light years) and represents the average outer limit of NGC 5617, beyond which a star is unlikely to remain gravitationally bound to the cluster core. One blue straggler is a possible member of the cluster. Other possible members of the cluster are delta Scuti variable, gamma Doradus variable and eclipsing variable stars. NGC 5617, along with its companion Trumpler 22, appear to be dynamically relaxed, with massive stars concentrated near the center and less massive stars in the periphery.

Relation with Trumpler 22 NGC 5617 appears to be gravitationally bound to Trumpler 22. The two clusters share similar radial velocities (-38.63 ± 2.25 km/s for NGC 5617 and -38.46 ± 2.08 km/s for Trumpler 22), mean metallicity (-0.18 ± 0.02 for NGC 5617 and-0.17 ± 0.04 for Trumpler 22), similar abundances across various elements, and have similar age, forming a primordial binary cluster pair. Their orbits were initially almost circular and their separation less than 20 pc.

References

External links

NGC 5617 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Illustrations

Worked examples

Example 1 — a first encounter with NGC 5617

Start with the simplest possible case. Write down what NGC 5617 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 NGC 5617 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 NGC 5617 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 NGC 5617

In research: NGC 5617 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 NGC 5617 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: NGC 5617 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1826, Centaurus, Discoveries by James Dunlop, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 5617 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 NGC 5617 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 5617 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 NGC 5617 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 5617 in simple terms?

NGC 5617 is an open cluster in the constellation Centaurus. NGC 5617 forms a binary open cluster with Trumpler 22.

Why does NGC 5617 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 NGC 5617?

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 NGC 5617.