astronomy

NGC 4395

NGC 4395 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 4395 rather than just read about it. In short: NGC 4395 is a nearby low surface brightness spiral galaxy located about 14 million light-years (or 4.3 Mpc) from Earth in the constellation Canes Venatici. It was discovered by German-British astronomer William Herschel on 2 January 1786.

Key takeaways

NGC 4395 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 4395 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 4395 from memory before moving on to harder problems.

Reference excerpt

NGC 4395 is a nearby low surface brightness spiral galaxy located about 14 million light-years (or 4.3 Mpc) from Earth in the constellation Canes Venatici. It was discovered by German-British astronomer William Herschel on 2 January 1786. The nucleus of NGC 4395 is active and the galaxy is classified as a Seyfert Type I, known for its very low-mass supermassive black hole.

Physical characteristics NGC 4395 has a halo that is about 8′ in diameter. It has several patches of greater brightness running northwest to southeast. The one furthest southeast is the brightest. Three of the patches have their own NGC numbers: 4401, 4400, and 4399 running east to west. The galaxy is highly unusual for Seyfert galaxies, because it does not have a bulge and is considered to be a dwarf galaxy.

Observational history NGC 4395 was imaged and classified as a "spiral nebula" in a 1920 paper by astronomer Francis G. Pease. Now, it is known to be a galaxy distinct from the Milky Way (see Great Debate). Along with several other nearby galaxies, resolved stars in NGC 4395 were used to measure the expansion rate of the Universe by Allan Sandage and Gustav Andreas Tammann in their 1974 paper. More recently, NGC 4395 was discovered to contain a very low-luminosity active galactic nucleus. Since then, its nucleus has been the subject of several academic papers and attempts to measure the mass of its central black hole.

Nucleus NGC 4395 is one of the least luminous and nearest Seyfert galaxies known. The nucleus of NGC 4395 is notable for containing one of the smallest supermassive black holes with a well-measured mass. The central black hole has a mass of "only" 300,000 M☉. However, more recent studies found a black hole mass of just 4,000 M☉ to 20,000 M☉. The low-mass black hole in NGC 4395 would make it a so-called "intermediate-mass black hole". The black hole may have a truncated disk.

NGC 4631 Group According to A.M. Garcia, NGC 4395 is part of the NGC 4631 group (also known as LGG 291) that has at least 14 members. The other members are NGC 4150, NGC 4163, NGC 4190, NGC 4214, NGC 4244, NGC 4308, NGC 4631, NGC 4656, IC 779, UGC 7605, UGC 7698, UGCA 276, and UGCA 292.

See also List of NGC objects (4001–5000)

References

External links Media related to NGC 4395 at Wikimedia Commons NGC4395

Illustrations

Worked examples

Example 1 — a first encounter with NGC 4395

Start with the simplest possible case. Write down what NGC 4395 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 4395 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 4395 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 4395

In research: NGC 4395 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 4395 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 4395 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1786, Canes Venatici, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 4395 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 4395 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 4395 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 4395 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 4395 in simple terms?

Why does NGC 4395 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 4395?

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 4395.