astronomy

NGC 3631

NGC 3631 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 3631 rather than just read about it. In short: NGC 3631 is a spiral galaxy located in the constellation Ursa Major. It is located at a distance of about 35 million light years from Earth, which, given its apparent dimensions, means that NGC 3631 is about 60,000 light years across.

Key takeaways

NGC 3631 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 3631 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3631 from memory before moving on to harder problems.

Reference excerpt

NGC 3631 is a spiral galaxy located in the constellation Ursa Major. It is located at a distance of about 35 million light years from Earth, which, given its apparent dimensions, means that NGC 3631 is about 60,000 light years across. It was discovered by William Herschel on April 14, 1789. It is a grand design spiral galaxy seen face on.

Characteristics NGC 3631 is a grand design spiral galaxy and features two principal spiral arms, which begin near the center. The two main arms branch into secondary arms with lower surface brightness. The galaxy shows moderate-to-high star formation rate and bright HII regions are present in all the arms. The star formation rate of the galaxy is 4.6 M☉ per year. Halton Arp observed "straight arms", and an "absorption tube crossing from inside to outside of southern arm" and added the galaxy to his Atlas of Peculiar Galaxies. At inclination of 17 degrees, the galaxy is seen nearly face on. The HI imaging shows the spiral arms distinguished well and HI is also detected in most of the interarm regions. The atomic hydrogen is detected mostly within the limits of the optical disc but also extends one and a half times the radius of the optical disk. The hydrogen forms streaming motions near the spiral arms. The gas features two anticyclonic and four cyclonic vortices, rotating with the spiral pattern. The anticyclones are caused by the differential rotation and the cyclones are the result of a high amplitude in the density wave. The centres of the anticyclones are located between the observed spiral arms and the cyclones lie close to the observed spirals. NGC 3631 has weak diffuse X-ray emission. There are six candidates ultraluminous X-ray sources in disk of the galaxy, two which have an optical counterpart. The nucleus of the galaxy hosts a supermassive black hole with mass 107.4 (25 million) M☉, based on Ks bulge luminosity.

Supernovae Four supernovae have been discovered in NGC 3631:

SN 1964A (type unknown, mag. 17) was discovered by Paul Wild on 4 February 1964. SN 1965L (type unknown, mag. 16) was discovered by Paul Wild on 25 September 1965. SN 1996bu (Type II, mag. 17.3) was discovered by Reiki Kushida on 14 November 1996. SN 2016bau (Type Ib, mag. 17.8) was discovered by Ron Arbour on 13 March 2016, before it reached maximum light. It was also observed in radio waves by the VLA as a radio source with a flux density of 1.0 ± 0.03 mJy at 8.6 GHz.

Nearby galaxies and group NGC 3631 forms a small group with NGC 3657, which is part of the north Ursa Major groups, which is part of the Ursa Major Cloud, which is part of the Virgo Supercluster. According to A.M. Garcia, NGC 3631 is part of the NGC 3631 galaxy group (also known as LGG 241). This group includes at least 10 galaxies, including NGC 3657, NGC 3718, NGC 3729, NGC 3913, NGC 3972, NGC 3998, UGC 6251, UGC 6446, and UGC 6816.

Gallery

Notes

References

External links

NGC 3631 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 3631

Start with the simplest possible case. Write down what NGC 3631 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 3631 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 3631 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 3631

In research: NGC 3631 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 3631 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 3631 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arp objects, Astronomical objects discovered in 1789, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3631 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 3631 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3631 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 3631 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3631 in simple terms?

Why does NGC 3631 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 3631?

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 3631.