astronomy

NGC 3393

NGC 3393 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 3393 rather than just read about it. In short: NGC 3393 is a barred spiral galaxy located in the constellation Hydra. It is located at a distance of circa 180 million light-years from Earth, which, given its apparent dimensions, means that NGC 3393 is about 231,000 light-years across.

Key takeaways

NGC 3393 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 3393 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3393 from memory before moving on to harder problems.

Reference excerpt

NGC 3393 is a barred spiral galaxy located in the constellation Hydra. It is located at a distance of circa 180 million light-years from Earth, which, given its apparent dimensions, means that NGC 3393 is about 231,000 light-years across. It was discovered by John Herschel on March 24, 1835. It is a Type II Seyfert galaxy, known to host two supermassive black holes, which are the nearest known pair of supermassive black holes to Earth.

Characteristics The galaxy is characterised as a barred spiral galaxy. At both ends of the bar H II regions are present. There is also evidence of a fainter inner bar. The fainter outer arms of the galaxy form a nearly complete ring.

Active galactic nucleus NGC 3393 has been characterised as a Seyfert galaxy, a galaxy category which features bright point-like nuclei. NGC 3393 is a type II Seyfert galaxy. Its X-ray spectrum is more consistent with a Compton-thick cold reflection source, which means that the source is hidden behind dense material, mainly gas and dust, and the X-rays observed have been reflected.

Supermassive black holes

The source of activity in the active galactic nuclei is a supermassive black hole (SMBH) lying at the centre of the galaxy. Observations by the Chandra X-ray Observatory revealed evidence for a pair of supermassive black holes in the centre of NGC 3393. The observation in hard X-rays, including emission from iron, showed two separate peaks, which were identified as black holes that are actively growing, generating X-ray emission as gas falls towards the black holes and becomes hotter. The obscured regions around both black holes block the copious amounts of optical and ultraviolet light produced by infalling material. They are the first pair of black holes found in a spiral galaxy like our Milky Way. The two black holes are separated by only 490 light years. The two black holes in NGC 3393 are likely the remnant of a merger of two galaxies of unequal mass a billion or more years ago. Other evidence that supports the hypothesis of the galaxy merger include high pre-shock densities in the narrow-line region and low O/H and Mg/H abundances. However the N/H is more than predicted, probably due to the creation of Wolf–Rayet stars in the central region of the galaxy during the merger. The total mass of the pair is estimated to be between 21 and 35 million M☉.

Supernova One supernova has been observed in NGC 3393.

SN 2018aqi was discovered by ASAS-SN on April 6, 2018, and had an apparent magnitude of 16.4 at discovery. By its spectrum, it was identified as a Type Ia supernova 6 days before maximum brightness.

Nearby galaxies NGC 3393 is the brightest galaxy in the NGC 3393 group, which also includes NGC 3369, NGC 3383, and ESO 501-086. NGC 3463 has also been proposed to be a member of the group. The group is part of the Hydra Supercluster.

References

External links

NGC 3393 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 3393

Start with the simplest possible case. Write down what NGC 3393 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 3393 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 3393 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 3393

In research: NGC 3393 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 3393 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 3393 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1835, Barred spiral galaxies, Discoveries by John Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3393 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 3393 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3393 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 3393 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3393 in simple terms?

Why does NGC 3393 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 3393?

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 3393.