astronomy

NGC 7552

NGC 7552 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 7552 rather than just read about it. In short: NGC 7552 (also known as IC 5294) is a barred spiral galaxy in the constellation Grus. It is at a distance of roughly 60 million light years from Earth, which, given its apparent dimensions, means that NGC 7552 is about 75,000 light years across.

Key takeaways

NGC 7552 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 7552 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 7552 from memory before moving on to harder problems.

Reference excerpt

NGC 7552 (also known as IC 5294) is a barred spiral galaxy in the constellation Grus. It is at a distance of roughly 60 million light years from Earth, which, given its apparent dimensions, means that NGC 7552 is about 75,000 light years across. It forms with three other spiral galaxies the Grus Quartet.

Observation history

NGC 7552 was discovered on 7 July 1826 by James Dunlop. John Herschel added it to the General Catalogue of Nebulae and Clusters as number 3977. However, Lewis Swift reported the galaxy independently on 22 October 1897, at right ascention 9 arcseconds off the location of the galaxy and it was included in Index Catalogue as IC 5294.

Structure NGC 7552 is a barred spiral galaxy, with two spiral arms forming an outer pseudo-ring. The galaxy is seen nearly face on, at an inclination of ~ 28°. The one arm is more prominent and the less prominent arm shows no clear continuation with the bar. The bar is dusty, and four huge HII regions are detected in it. The disk features numerous scattered HII regions in an asymmetric pattern. The total infrared luminosity of the galaxy is 1011.03 L☉, and thus is categorised as a luminous infrared galaxy. The SIMBAD database lists NGC 7552 as a Seyfert I Galaxy, i.e. it has a quasar-like nucleus with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, the host galaxy is clearly detectable.

Starburst ring

In 1994, Forbes et al. observed a partial starburst ring with 1 kpc radius at Br-gamma with various hot spots. They also detected a small-scale molecular bar and a large reservoir of molecular material, however, no evidence of current activity was detected at the nucleus. The ring is more than 100 parsecs wide. The ring is brighter north of the nucleus and there is inhabited by the younger star populations. Brandl et al. detected in near- and mid-infrared nine prominent structures within the ring they identified as star clusters with stellar ages ranging between 5.5 Myr and 6.3 Myr. These clusters account for the 75% of the bolometric luminosity of the starburst ring, with total luminosity of the clusters 2.1 × 1010 L⊙. Numerous supernova remnants have been observed in the ring. Further observations of the galaxy in radio waves showed that NGC 7552 contains three star forming rings of radii 1.0 kpc, 1.9 kpc, and 3.4 kpc as observed by the Very Large Array at 46.9 MHz and the Australia Telescope Compact Array.

Supernova and Luminous Red Nova One supernova has been observed in NGC 7552: SN 2017bzc (Type Ia, mag. 12.8) was discovered by Stuart Parker as part of the Backyard Observatory Supernova Search (BOSS) on 7 march 2017. In addition, a luminous red nova has also been observed in NGC 7552: AT 2014ej (type LRN, mag. 18.0), also known as NGC7552-2014OT1, was discovered by Peter Marples also as part of BOSS on 24 September 2014.

Galaxy group NGC 7552 belongs in NGC 7582 group, also known as the Grus group. Other members of the group include the spiral galaxies NGC 7599, NGC 7590, and NGC 7582, which along with NGC 7552 form the Grus Quartet. A large tidal extension of HI reaches from NGC 7582 to NGC 7552, which is indicative of interactions between the group members, yet NGC 7552 does not have highly disturbed morphology.

See also NGC 1672 - a similar-looking barred spiral galaxy List of NGC objects (7001–7840)

References

External links

NGC 7552 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 7552

Start with the simplest possible case. Write down what NGC 7552 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 7552 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 7552 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 7552

In research: NGC 7552 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 7552 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 7552 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1826, Barred spiral galaxies, Discoveries by James Dunlop, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 7552 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 7552 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 7552 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 7552 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 7552 in simple terms?

Why does NGC 7552 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 7552?

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 7552.