astronomy

NGC 6621

NGC 6621 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 6621 rather than just read about it. In short: NGC 6621 is an interacting spiral galaxy in the constellation Draco. It lies at a distance of about 260 million light-years.

Key takeaways

NGC 6621 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 6621 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 6621 from memory before moving on to harder problems.

Reference excerpt

NGC 6621 is an interacting spiral galaxy in the constellation Draco. It lies at a distance of about 260 million light-years. NGC 6621 interacts with NGC 6622, with their closest approach having taken place about 100 million years ago. The pair was discovered by Edward D. Swift and Lewis A. Swift on June 2, 1885. Originally NGC 6621 was assigned to the southeast galaxy, but now it refers to the northern one. NGC 6621 and NGC 6622 are included in the Atlas of Peculiar Galaxies as Arp 81 in the category "spiral galaxies with large high surface brightness companions". NGC 6621 is the larger of the two, and is a very disturbed spiral galaxy. The encounter has pulled a long tail out of NGC 6621 that has now wrapped at the north behind its body. The collision has also triggered extensive star formation between the two galaxies. The most intense star formation takes place in the region between the two nuclei, where a large population of luminous clusters, also known as super star clusters, has been observed. At this region is observed the most tidal stress. Many large clusters are also observed in the tail and the nucleus of NGC 6621. The brightest and bluest clusters are less than 100 million years old, with the youngest being less than 10 million years old. The side of the galaxy further from the companion features noticeably less star formation activity. NGC 6621 is characterised as a luminous infrared galaxy, with its infrared luminosity being 1011.24 L☉. NGC 6621 contributes nearly all of the radio and far infrared flux of the pair. When observed in H-alpha, the centre of the galaxy has two bright sources separated by 3 arcseconds, with the southwest being brighter while the northeastern one coincides with the nucleus of NGC 6621.

Supernovae Two supernovae have been detected in NGC 6621:

SN 2010hi (type unknown, mag. 18), was discovered by Ron Arbour on 1 September 2010, lying 30" east and 4" north of the center of the galaxy. SN 2019hsx (Type Ic-BL, mag. 18.62), was discovered by the Zwicky Transient Facility on 2 June 2019.

See also List of NGC objects (6001–7000)

References

This article incorporates text available under the CC BY 3.0 license.

External links

NGC 6621 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 6621

Start with the simplest possible case. Write down what NGC 6621 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 6621 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 6621 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 6621

In research: NGC 6621 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 6621 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 6621 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arp objects, Draco (constellation), Interacting galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 6621 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 6621 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 6621 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 6621 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 6621 in simple terms?

NGC 6621 is an interacting spiral galaxy in the constellation Draco. It lies at a distance of about 260 million light-years.

Why does NGC 6621 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 6621?

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 6621.