astronomy

NGC 3109

NGC 3109 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 3109 rather than just read about it. In short: NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.35 Mly away in the direction of the constellation of Hydra. It was discovered by John Herschel on March 24, 1835 while he was in what is now South Africa.

Key takeaways

NGC 3109 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 3109 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3109 from memory before moving on to harder problems.

Reference excerpt

NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.35 Mly away in the direction of the constellation of Hydra. It was discovered by John Herschel on March 24, 1835 while he was in what is now South Africa.

Size and morphology NGC 3109 is classified as a Magellanic type irregular galaxy, but it may in fact be a small spiral galaxy. Based on the D25.5 isophote at the B-band with an angular diameter of 1,980 arcseconds, it has an isophotal diameter approximately 12.80 kiloparsecs (41,700 light-years) across, slightly larger than the Large Magellanic Cloud but smaller than the Triangulum Galaxy. If it is a spiral galaxy, it would be the smallest in the Local Group. NGC 3109 has a mass of about 2.3×109 times the mass of the Sun (M☉), of which 20% is in the form of neutral hydrogen. It is oriented edge-on from our point of view, and may contain a disk and a halo. The disk appears to be composed of stars of all ages, whereas the halo contains only very old and metal-poor stars. NGC 3109 does not appear to possess a galactic nucleus. From measurements of the neutral atomic hydrogen in the galaxy, it has been found that the disk of NGC 3109 is warped. The warp has the same radial velocity as gas in the Antlia Dwarf galaxy, indicating that the two galaxies had a close encounter approximately one billion years ago.

Composition Based on spectroscopy of blue supergiants in NGC 3109, it is known that the galaxy has a low metallicity, similar to that of the Small Magellanic Cloud. It is one of the most metal-poor star-forming galaxies in the Local group. NGC 3109 seems to contain an unusually large number of planetary nebulae for its luminosity. It also contains a substantial amount of dark matter.

Location NGC 3109 is located about 1.33 megaparsecs (4.3 Mly) away, in the constellation Hydra. This puts it at the very outskirts of the Local Group. Its membership of the Local Group has been questioned, because it seems to be receding faster than estimates of the Local Group's escape velocity. It is distant enough from the largest members of the Local Group that it has not been tidally influenced by them. NGC 3109 has two satellite galaxies, the Antlia Dwarf and Antlia B.

Luminous blue variable Although no supernovae have been observed in NGC 3109 yet, a luminous blue variable, designated AT 2018akx (type LBV, mag. 17.5), was discovered by the All Sky Automated Survey for SuperNovae on 22 March 2018.

Gallery

Notes

See also List of NGC objects (3001–4000)

References

Further reading Grebel, Gallagher, Harbeck (2003) The Progenitors of Dwarf Spheroidal Galaxies ArXiv.org. retrieved November 2007

External links

NGC 3109 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 3109

Start with the simplest possible case. Write down what NGC 3109 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 3109 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 3109 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 3109

In research: NGC 3109 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 3109 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 3109 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1835, Barred spiral galaxies, Hydra (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3109 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 3109 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3109 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 3109 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3109 in simple terms?

Why does NGC 3109 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 3109?

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 3109.