astronomy

NGC 4278

NGC 4278 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 4278 rather than just read about it. In short: NGC 4278 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 55 million light years from Earth, which, given its apparent dimensions, means that NGC 4278 is about 65,000 light years across.

Key takeaways

NGC 4278 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 4278 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 4278 from memory before moving on to harder problems.

Reference excerpt

NGC 4278 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 55 million light years from Earth, which, given its apparent dimensions, means that NGC 4278 is about 65,000 light years across. It was discovered by William Herschel on March 13, 1785. NGC 4278 is part of the Herschel 400 Catalogue and can be found about one and 3/4 of a degree northwest of Gamma Comae Berenices even with a small telescope.

Charasteristics NGC 4278 is an elliptical galaxy. Its nucleus has been found to be active (AGN) and based on its spectrum has been identified as a LINER. The most accepted theory for the power source of active galactic nuclei is the presence of an accretion disk around a supermassive black hole. In the centre of NGC 4278 lies a supermassive black hole with an estimated mass (3.09±0.54)×108 M☉ based on stellar velocity dispersion. The X-ray emission of the nucleus is consistent with one of a black hole fed by a low radiative efficiency accretion flow. The nucleus is a source of radio waves and two small symmetric S-shaped radio jets have been observed spanning for 20 mas each, which corresponds to 1.4 parsec at the distance of NGC 4278, emanating from the central source. The nucleus also hosts a compact ultraviolet source, which features strong variability in the form of flares. One such flare was observed between June 1994 and January 1995, when the nuclear source became 1.6 times brighter in six months. Similar flares have also being observed in other low luminosity AGN.

Variability has also being observed in X-rays. The galaxy has been found to brighten 5 times within three years, while fluctuations have been observed in shorter time periods, even within an hour, with the flux increasing by a factor of 10% in one observation by XMM-Newton. The spectrum obtained by XMM-Newton can be accounted for by an absorbed power-law, with column density of the order of 1020 cm-2. The FeKα emission line has not been detected, as is typical for LINERs. The spectral energy distribution of NGC 4278 resembles a LINER at lower fluxes while at higher fluxes it resembles a low luminosity Seyfert galaxy. Dust features have been observed in the central part of the galaxy and the area that appears northwest of the nucleus. The dust forms knots and filaments that spiral down to the nucleus. Moreover, the galaxy, contrary to most elliptical galaxies which lack neutral hydrogen emission, has been found to possess a massive HI disk, probably formed after the accretion of a dwarf satellite galaxy. The total mass of the HI disk is estimated to be 6.9×108 M☉. The disk rotates at the same sense as the stars, but is misaligned by 20° to 70°. Molecular clouds, as pointed by CO emission, have also been detected in the galaxy. The galaxy has been observed with the InfraRed Spectrograph (IRS) onboard Spitzer Space Telescope, examining the dust features of NGC 4278. Multiphase gas and dust have been observed in the same elongated features. Another uncommon finding for an elliptical galaxy is the detection of emission by polycyclic aromatic hydrocarbons (PAHs) and of strong [Si II] 34.8-μm emission. PAHs in other elliptical galaxies are believed to be destroyed by the hot interstellar medium. Emission by molecular hydrogen and ionised gas has also been reported. The observed emission of the gas in the nuclear region has been suggested to be the result of the accretion of cold gas by the HI disk. NGC 4278 is home to a larger than average number of globular clusters compared with galaxies of similar luminosity, with an estimated total number of 1378+32−194. As it has been found in other galaxies, the colour distribution of the globular clusters in the galaxy features bimodiality, with the clusters forming a red and a blue subpopulation. The blue clusters have been found to be larger than the red ones at the same galactocentric distance, while the size of the clusters increases with galactocentric radius.

Nearby galaxies

NGC 4278 has been identified as a member of a galaxy group known as NGC 4274 or NGC 4062 group. Other members of this group are NGC 4020, NGC 4062, NGC 4136, NGC 4173, NGC 4203, NGC 4245, NGC 4251, NGC 4274, NGC 4283, NGC 4310, NGC 4314, NGC 4359, NGC 4414, NGC 4509, and NGC 4525. Another survey placed NGC 4278 in the same group with NGC 4631, NGC 4656, NGC 4559, NGC 4448, and NGC 4414. It is part of the Coma I Group which is part of the Virgo Supercluster. NGC 4283 lies 3.5 arcminutes to the northeast and NGC 4286 9 arcminutes northeast of NGC 4278 in the sky. NGC 4274 lies about 20 arcminutes north of NGC 4278.

See also IC 1459 - a similar elliptical galaxy

References

External links

NGC 4278 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images NGC 4278 on SIMBAD

Illustrations

Worked examples

Example 1 — a first encounter with NGC 4278

Start with the simplest possible case. Write down what NGC 4278 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 4278 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 4278 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 4278

In research: NGC 4278 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 4278 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 4278 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1785, Coma Berenices, Coma I Group, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 4278 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 4278 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 4278 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 4278 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 4278 in simple terms?

Why does NGC 4278 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 4278?

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 4278.