astronomy

NGC 4725

NGC 4725 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 4725 rather than just read about it. In short: NGC 4725 is an intermediate barred spiral galaxy with a prominent ring structure, located in the northern constellation of Coma Berenices near the north galactic pole. It was discovered by German-born British astronomer William Herschel on April 6, 1785.

Key takeaways

NGC 4725 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 4725 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 4725 from memory before moving on to harder problems.

Reference excerpt

NGC 4725 is an intermediate barred spiral galaxy with a prominent ring structure, located in the northern constellation of Coma Berenices near the north galactic pole. It was discovered by German-born British astronomer William Herschel on April 6, 1785. The galaxy lies at a distance of approximately 40 megalight-years from the Milky Way. NGC 4725 is the brightest member of the Coma I Group of the Coma-Sculptor Cloud, although it is relatively isolated from the other members of this group. This galaxy is strongly disturbed and is interacting with neighboring spiral galaxy NGC 4747, with its spiral arms showing indications of warping. The pair have an angular separation of 24′, which corresponds to a projected linear separation of 370 kly. A tidal plume extends from NGC 4747 toward NGC 4725.

NGC 4725 is a suspected type 2 Seyfert galaxy with a supermassive black hole at the core. The morphological classification of this galaxy is SAB(r)ab pec, indicating a peculiar, weakly-barred spiral galaxy (SAB) with a complete ring surrounding the bar (r) and somewhat tightly-wound spiral arms (ab). It is actually double-barred, a feature found among about a third of all barred spirals. The galactic plane is inclined by approximately 46° to the line of sight from the Earth. The ring structure of the galaxy is a region of star formation. It is offset from the galactic center and displays non-circular motion. There is a compact radio source positioned approximately 6.2 kly from the nucleus of NGC 4725. Since there is no optical counterpart at that position, this may be a star forming region that is heavily obscured by dust.

Supernovae Multiple supernova candidate events have been detected in this galaxy:

SN 1940B was discovered by Josef J. Johnson on a photograph taken May 5, 1940, about 2.5′ northeast of the galactic core. The light curve indicates this was a Type II supernova. SN 1969H (Type I, mag. 15) was discovered by Anthony Fairall on 8 July 1969. [Note: Many sources incorrectly report the discovery date as 17 June 1969.] Candidate SN 1987E was detected April 24, 1987 with a magnitude of 15.65. A follow-up studies failed to detect this event, and it is believed to be the result of a high proper motion foreground star. SN 1999gs (type unknown, mag. 19.3) was discovered by the Lick Observatory Supernova Search (LOSS) on 28 December 1999. It was positioned 3″ west and 105″ south of the nucleus of NGC 4725. On automated images taken July 5, 2016, a magnitude 17.0 transient source was discovered at an angular separation of 324″ from the galactic nucleus. Designated ASASSN-16gu (AT 2016cyu), with an estimated absolute visual magnitude of –13.6, it was initially thought to be a supernova. However, it was determined that the sighting was actually Kuiper belt object Makemake, a dwarf planet.

References

External links

NOAO: NGC 4725 NGC 4725 NASA Astronomy Picture of the Day: One-Armed Spiral Galaxy NGC 4725 (1 September 2005) NGC 4725 in Coma-Berenices

Illustrations

Worked examples

Example 1 — a first encounter with NGC 4725

Start with the simplest possible case. Write down what NGC 4725 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 4725 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 4725 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 4725

In research: NGC 4725 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 4725 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 4725 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Barred spiral galaxies, Coma Berenices, Coma I Group, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 4725 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 4725 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 4725 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 4725 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 4725 in simple terms?

Why does NGC 4725 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 4725?

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 4725.