astronomy

NGC 6872

NGC 6872 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 6872 rather than just read about it. In short: NGC 6872, also known as the Condor Galaxy, is a large barred spiral galaxy of type SB(s)b pec in the constellation Pavo. It is 212 million light-years (65 Mpc) from Earth.

Key takeaways

NGC 6872 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 6872 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 6872 from memory before moving on to harder problems.

Reference excerpt

NGC 6872, also known as the Condor Galaxy, is a large barred spiral galaxy of type SB(s)b pec in the constellation Pavo. It is 212 million light-years (65 Mpc) from Earth. NGC 6872 is interacting with the lenticular galaxy IC 4970, which is less than one twelfth as large. The galaxy has two elongated arms with a diameter based on ultraviolet light of over 522,000 light-years (160,000 pc), and a D25.5 isophotal diameter of over 717,000 light-years (220,000 pc), making it the largest known spiral galaxy. The galaxy contains a central black hole with a mass of 269 million solar masses (M☉). It was discovered on 27 June 1835 by English astronomer John Herschel.

Star formation rates When observed in the ultraviolet and mid-infrared, the central region and bar of NGC 6872 show old stars and low rates of star formation, with rates increasing along the spiral arms as distance from the core increases. The most active region of star formation, located in the northeast arm, shows a stellar flux around 1,000 times higher than in the central region, though this may be affected by the density of stellar dust in the core. The extended portions of both arms exhibit young star cluster formations with ages ranging from one to one hundred million years. Star formation rates in the northeast extended arm are twice that of the southwest extended arm, and five times the formation rate in the sections of the arms closer to the central region.

Interaction with IC 4970

IC 4970 is a nearby lenticular galaxy, located only a few arcseconds away, and is known to be interacting with NGC 6872. Horrelou and Koribalski (2007), using a computer simulation to determine how the two galaxies were interacting, reported that IC 4970 approached NGC 6872 nearly along the plane of its spiral disk, making its closest approach approximately 130 million years ago and resulting in the latter's current highly elongated shape. An ultraviolet-to-infrared study by Eufrasio, et al. (2013), using data from GALEX, Spitzer, and other resources found that the interaction between the two galaxies appears to have triggered significant star formation in the northeastern arm of NGC 6872 beginning about 130 thousand light-years (40 kpc) from its nucleus. The same appears to have also occurred in the southwestern arm. A bright ultraviolet source was discovered at the end of the northeastern arm, around 290 thousand light-years (90 kpc) from the nucleus, which may be a tidal dwarf galaxy formed out of the interaction between IC 4970 and NGC 6872. The bright ultraviolet nature of this cluster indicates that it contains stars less than 200 million years old, which roughly coincides with the timeframe of the collision. Mihos, et al. (1993), and Eufrasio, et al. (2014), suggest that prior to its interaction with IC 4970, the galaxy's disk may have been non-uniform with an extended mass distribution.

Possible interaction with NGC 6876 Machacek, et al. (2005), reported on a 290–330-thousand-light-year (90–100 kpc) X-ray trail that exists between NGC 6872 and the nearby elliptical galaxy NGC 6876. NGC 6872 is moving away from NGC 6876 at 849 ± 28 km/s (528 ± 17 mi/s) in approximately the same trajectory as the X-ray trail, suggesting a link between the two galaxies. Four possibilities for the trail's existence were given: gas stripped from the two galaxies during a close fly-by, intergalactic medium that has been gravitationally focused behind NGC 6872 as it moves, interstellar medium that was stripped from NGC 6872 by ram pressure as it passed through the densest part of the Pavo group, and interstellar medium stripped from NGC 6872 by turbulent viscosity as it passes through Pavo. Any or all of these processes may be responsible for the trail. If NGC 6872 and NGC 6876 did interact in the past, the latter may have affected NGC 6872's arms and gas distribution as much as its interaction with IC 4970.

See also Antennae Galaxies NGC 2207 and IC 2163 NGC 5090 and NGC 5091

Notes

References

External links

NGC 6872 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images NGC 6872 at SIMBAD

Illustrations

Worked examples

Example 1 — a first encounter with NGC 6872

Start with the simplest possible case. Write down what NGC 6872 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 6872 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 6872 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 6872

In research: NGC 6872 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 6872 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 6872 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1835, Barred spiral galaxies, ESO objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 6872 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 6872 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 6872 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 6872 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 6872 in simple terms?

NGC 6872, also known as the Condor Galaxy, is a large barred spiral galaxy of type SB(s)b pec in the constellation Pavo. It is 212 million light-years (65 Mpc) from Earth.

Why does NGC 6872 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 6872?

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 6872.