astronomy

NGC 6951

NGC 6951 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 6951 rather than just read about it. In short: NGC 6951 (also catalogued as NGC 6952) is a barred spiral galaxy located in the constellation Cepheus. It is located at a distance of about 75 million light-years from Earth, which, given its apparent dimensions, means that NGC 6951 is about 100,000 light-years across.

Key takeaways

NGC 6951 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 6951 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 6951 from memory before moving on to harder problems.

Reference excerpt

NGC 6951 (also catalogued as NGC 6952) is a barred spiral galaxy located in the constellation Cepheus. It is located at a distance of about 75 million light-years from Earth, which, given its apparent dimensions, means that NGC 6951 is about 100,000 light-years across. It was discovered by Jérôme Eugène Coggia in 1877 and independently by Lewis Swift in 1878.

Characteristics

NGC 6951 has a large stellar bar with dust lanes running across it. These lanes come in contact with the circumnuclear ring at its north and south points. Gas is channeled inwards, towards the ring, through the bar. Observations in CO revealed also the presence of molecular gas with inflow motion towards the galactic nucleus. Since there are no signs of interaction with another galaxy in the isolated NGC 6951 for the last one billion years, it is believed that the origin of the gas is internal. Gas kinematics have also been observed for the rest of the galaxy, where the gravitational torques caused by the bar have a dominant role.

Active nucleus The nucleus of NGC 6951 is active. It has been classified both as a type 2 Seyfert galaxy and a LINER and it has been suggested that it is in transition form, between a Seyfert galaxy and a very-high-excitation LINER, with very strong [N II] and [S II] lines. A supermassive black hole which accretes material in the centre of the galaxy is believed to be the cause of the nuclear activity. The upper mass limit of the supermassive black hole at the centre of NGC 6951 is estimated to be between 6 and 14 million M☉ based on velocity dispersion. Molecular gas, most probably a circumnuclear dust disk or torus less than 50 parsec in radius, has been detected around the nucleus.

Circumnuclear ring Around the nucleus of NGC 6951 has been observed a star formation ring with a radius of 5 arcseconds. It also emits radio waves. The total gas mass at and inside the ring is estimated to be 3×108 M☉. Inside the ring is detected a spiral-like structure, with two spiral arms, that extends up to 0.5 arcseconds from the nucleus, while no inner bar was detected in the images obtained by Hubble Space Telescope. The central part of the nuclear area contains red supergiant stars. The ring is complete and features H II regions. It is characterised by a gradient in stellar population ages, with the younger stars being a few million years old while the older are more than a hundred million years old. The stars in the ring form star clusters with masses between 104 and 106.8 M☉. Although there have been observed clusters with ages as little as 4 million years or over one billion years, the star clusters predominantly have intermediate ages, with average ages of 200–300 million years, and are massive. Based on the ages of the clusters it is suggested that the most intense star formation in the ring took place 800 million years ago, then lowered, only to increase again 400 million years ago.

Supernovae Five supernovae have been observed in NGC 6951:

SN 1999el (Type IIn, mag 15.4) was discovered by the Beijing Astronomical Observatory on 20 October 1999. SN 2000E (Type Ia, mag 14.3) was discovered by the Collurania-Teramo Observatory on 26 January 2000. This supernova was visible at the same time as SN 1999el. SN 2015G (Type Ibn, mag 15.5) was discovered by Kunihiro Shima on 23 March 2015. SN 2020dpw (Type II-P, mag. 17) was discovered by Patrick Wiggins on 26 February 2020. SN 2021sjt (Type IIb, mag. 18.58) was discovered by the Zwicky Transient Facility on 7 July 2021.

See also NGC 5135 - a similar active galaxy List of NGC objects (6001–7000)

References

External links

NGC 6951 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images NGC 6951 on SIMBAD

Illustrations

Worked examples

Example 1 — a first encounter with NGC 6951

Start with the simplest possible case. Write down what NGC 6951 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 6951 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 6951 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 6951

In research: NGC 6951 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 6951 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 6951 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1877, Barred spiral galaxies, Cepheus (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for NGC 6951 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study NGC 6951 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 6951 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 6951 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 6951 in simple terms?

Why does NGC 6951 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 6951?

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 6951.