astronomy

Messier 77

Messier 77 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 Messier 77 rather than just read about it. In short: Messier 77 (M77), also known as NGC 1068 or the Squid Galaxy, is a barred spiral galaxy in the constellation Cetus. It is 35 million light-years (11 Mpc) away from Earth, and was discovered by Pierre Méchain in 1780, who originally described it as a nebula.

Key takeaways

Messier 77 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Messier 77 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Messier 77 from memory before moving on to harder problems.

Reference excerpt

Messier 77 (M77), also known as NGC 1068 or the Squid Galaxy, is a barred spiral galaxy in the constellation Cetus. It is 35 million light-years (11 Mpc) away from Earth, and was discovered by Pierre Méchain in 1780, who originally described it as a nebula. Méchain then communicated his discovery to Charles Messier, who subsequently listed the object in his catalog. Both Messier and William Herschel described this galaxy as a star cluster. Today, however, the object is known to be a galaxy. It is one of the brightest Seyfert galaxies visible from Earth and has a D25 isophotal diameter of about 27.70 kiloparsecs (90,000 light-years).

Morphology The morphological classification of Messier 77 in the De Vaucouleurs system is (R)SA(rs)b, where the '(R)' denotes an outer ring-like structure, 'SA' denotes a non-barred spiral, '(rs)' denotes a transitional inner ring/spiral structure, and 'b' denotes the spiral arms are moderately wound. Ann et al. (2015) gave it a class of SAa, suggesting tightly wound arms. However, infrared images of the inner part of the galaxy reveal a prominent bar not seen in visual light, and for this reason it is now considered a barred spiral. Messier 77 is the largest member of a small group of galaxies, which includes NGC 1055, an edge-on spiral galaxy likely twisted by gravitational interactions with Messier 77, and five small irregular galaxies. Messier 77 is an active galaxy with an active galactic nucleus (AGN), which is obscured from view by astronomical dust at visible wavelengths. The diameter of the molecular disk and hot plasma associated with the obscuring material was first measured at radio wavelengths by the Very Long Baseline Array (VLBA) and the Very Large Array (VLA). The hot dust around the nucleus was subsequently measured in the mid-infrared by the MIDI instrument at the Very Large Telescope (VLT) observatory. It is one of the brightest, closest, and best-studied type 2 Seyfert galaxies, forming a prototype of this class.

Research Messier 77 is of key interest to scientists due to its relative proximity and luminosity, allowing for study of its active galactic nucleus. This section contains relevant scientific discoveries that have been made as a result of studying Messier 77. It has been proposed that type 2 Seyfert galaxies are the same class of object as type 1 Seyfert galaxies, viewed from such an angle that the type 1 core is hidden from view. An analysis of Messier 77's spectra using interferometry by Tacconi et al. (1994) suggested that the galaxy's Seyfert 1 core was obstructed by a thick molecular cloud region. It has a radio jet consisting of a northeast and a southwest region, caused by interactions with the interstellar medium. The presence of bow shocks in the northeast region due to these interactions overlap with the edges of molecular outflow, suggesting that the jet is responsible for the outflow. X-ray source 1H 0244+001 in the Cetus constellation was identified as Messier 77 in 1984. In February 2022 astronomers reported a cloud of cosmic dust, detected through infrared interferometry observations, located at the centre of Messier 77 that is hiding a supermassive black hole. In November 2022, the IceCube Neutrino Observatory collaboration, or IceCube, announced the detection of a neutrino source emitted by the active galactic nucleus of Messier 77. It is the second detection by IceCube after TXS 0506+056, and only the fourth known source including SN1987A and solar neutrinos. A potential candidate for the source of these neutrinos is the magnetic corona surrounding the active galactic nucleus, providing powerful enough particle acceleration to cause neutron radiation phenomena. To explain the combination of Messier 77 being an energetic neutrinos source and a weak gamma rays source, a mechanism was suggested whereby helium nuclei collide with ultraviolet photons emitted by the galaxy's central region and break up, releasing neutrons that eventually decay into neutrinos without producing gamma rays.

Supernova SN 2018ivc (Type II, mag. 14.6523) was the only supernova so far observed in Messier 77, discovered by the DLT40 Survey on 24 November 2018.

Gallery

See also List of Messier objects NGC 1106, an active-nucleus galaxy

References

External links

Messier 77 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images "StarDate: M77 Fact Sheet" Spiral Galaxy M77 @ SEDS Messier pages VLBA image of the month: radio continuum and water masers of NGC 1068 Press release about VLTI observations of NGC 1068 ESO:Dazzling Spiral with an Active Heart incl. Potos & Animation Gray, Meghan; Hardy, Liam. "M77 – Globular Cluster". Deep Sky Videos. Brady Haran. NASA Astronomy Picture of the Day: Messier 77 (10 May 2013)

Illustrations

Worked examples

Example 1 — a first encounter with Messier 77

Start with the simplest possible case. Write down what Messier 77 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 Messier 77 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 Messier 77 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 Messier 77

In research: Messier 77 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 Messier 77 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: Messier 77 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 3C objects, 4C objects, Arp objects, so understanding it makes those chapters shorter.
In everyday life: Look for Messier 77 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 Messier 77 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Messier 77 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 Messier 77 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Messier 77 in simple terms?

Why does Messier 77 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 Messier 77?

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 Messier 77.