NGC 3311

Key takeaways

NGC 3311 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 3311 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3311 from memory before moving on to harder problems.

Reference excerpt

NGC 3311 is a super-giant elliptical galaxy (a type-cD galaxy) located about 190 million light-years away in the constellation Hydra. The galaxy was discovered by astronomer John Herschel on March 30, 1835. NGC 3311 is the brightest member of the Hydra Cluster and forms a pair with NGC 3309 which along with NGC 3311, dominate the central region of the Hydra Cluster. NGC 3311 is surrounded by a rich and extensive globular cluster system rivaling that of Messier 87 in the Virgo Cluster.

Physical characteristics The central region of NGC 3311 is obscured by a dust cloud with an estimated diameter of 1,700 ly (0.53 kpc). It has an amorphous and complex structure and its small size and disturbed morphology suggests that the cloud originated from a merger event with another galaxy that occurred within the past 10 million years. Oddly though, there are no shells or isophote distortions in the outer regions of NGC 3311 that would have been the result of such a recent merger. Other scenarios for the origin of the dust cloud are by a cooling flow or by galactic wind failure. The total estimated mass of the dust cloud is 4,600 solar masses (4.6×104 M☉). In NGC 3311, it has been detected that there is an excess blue population in the central region of the galaxy. The spectrum of the galaxy appears to resemble that of an H II region. This suggests that the excess blue population represents an ongoing formation of young bright stars.

Outer halo The outer halo of NGC 3311 appears to have formed from the accretion and mergers of massive satellite galaxies in vicinity of the galaxy. The halo is made up of intra-cluster stars with a dominant part of these stars coming from the outskirts of bright early-type galaxies and the rest originating from dwarf galaxies. However, the build-up of its extended halo is still ongoing due to the infall of a group of 14 dwarf galaxies including the galaxies HCC 026 and HCC 007 that are currently being tidally disputed and adding their stars to the outer halo. In contrast, the inner galaxy formed from the mergers of gas-rich lumps reminiscent of the first phase of galaxy formation.

Stellar populations The stars in the central region of NGC 3311 and in the halo are very old, with ages of over 10 Gyrs. However, the stars in the central galaxy have a higher metallicity than the halo suggesting the stars in the stars in the central galaxy formed in a rapid but short period of star formation that occurred early on though a gas-rich dissipative collapse while the stars in halo formed in smaller accreted satellite galaxies with more extended star formation.

Off-centered envelope NGC 3311 contains an off-centered envelope that was first detected by Arnaboldi et al. The off-centered envelope has a higher metallicity than the outer halo and is located close to the infalling group of dwarf galaxies. The envelope appears to have been offset from the center of NGC 3311 by a tidal interaction with the dark matter halos of the infalling group of dwarf galaxies or halo associated with NGC 3309. This tidal interaction would have also stripped gas and dust from the outer halo of NGC 3311.

Intracluster planetary nebulae Around 60 intracluster planetary nebulae have been detected surrounding NGC 3311.

Supermassive black hole NGC 3311 is host to a supermassive black hole with an estimated mass of 126 million solar masses (1.26 × 108 M☉).

Dark matter halo NGC 3311 appears to have a cored dark matter halo.

Radio source NGC 3311 has a weak radio source with a total 6 cm flux density of 0.3 mJy. Although NGC 3311 has a weak radio source, it is bright in X-rays.

Globular clusters NGC 3311 has one of the largest globular cluster systems known in the local universe. With an estimated population of about 16,500 ± 2,000 globular clusters, NGC 3311's globular cluster system rivals that of Messier 87's, which has about 13,000 globular clusters. NGC 3309, another nearby giant elliptical has an unusually low number of globular clusters. This suggests that NGC 3311 stripped part of NGC 3309's globular clusters, with some of its globular clusters becoming members of NGC 3311's system. NGC 3311's globular cluster system was initially detected in 1976 and was found by Harris et al. in 1983 to contain a massive globular cluster system similar to Messier 87. An analysis by Secker et al. in 1995 using Washington photometry from the Cerro Tololo Inter-American Observatory concluded that NGC 3311 had the most metal-rich globular cluster system known, with a complete absence of populations of metal-poor and intermediate-metallicity globular clusters. However, Brodie et al. and Wehner et al. determined that the globular cluster system shows a bimodal color distribution with equal numbers of metal-rich and metal-poor clusters.

Ultra-compact dwarf galaxies A large population of about 50 ultra-compact dwarf galaxies (UDCs) have been detected in the Hydra Cluster, with most of them being dynamically associated to NGC 3311. It appears that the UDCs, especially the brighter and more massive ones such as HUCD1 with a mass of 5×107 and a half-light radius of 83 ly (25.4 pc), are the remnant nuclei of dwarf galaxies whose stellar envelopes were stripped off during an interaction with another galaxy or the cluster itself.

See also List of NGC objects (3001–4000) NGC 3309 Messier 87 NGC 4874 NGC 4889

References

External links

NGC 3311 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 3311

Start with the simplest possible case. Write down what NGC 3311 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 3311 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 3311 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 3311

In research: NGC 3311 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 3311 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 3311 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1835, Discoveries by John Herschel, Elliptical galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3311 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.

How to study NGC 3311 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3311 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 3311 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3311 in simple terms?

NGC 3311 is a super-giant elliptical galaxy (a type-cD galaxy) located about 190 million light-years away in the constellation Hydra. The galaxy was discovered by astronomer John Herschel on March 30, 1835.

Why does NGC 3311 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 3311?

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 3311.