M77, also known as NGC 1068, is one of the most fascinating galaxies in the Messier catalog due to its bright nucleus and active galactic core. It is a barred spiral galaxy located in the constellation Cetus, near the celestial equator. Here’s an overview of M77:
Basic Characteristics
M77 is classified as a barred spiral galaxy (type SB(s)b), indicating it has a well-defined central bar structure and moderately wound spiral arms. It is located approximately 47 million light-years away from Earth, and spans a diameter of about 170,000 light-years, making it one of the largest galaxies in the Messier catalog.
Structure and Composition
M77 is a Seyfert galaxy, a type of active galaxy with a very bright nucleus powered by a supermassive black hole at its center. The intense gravitational pull of the black hole and the dynamic processes within the galaxy lead to gas being funneled inward toward the core. This inflowing gas feeds the black hole, resulting in the accretion of material, which powers the bright and active nucleus. The inflowing gas is often accelerated by spiral arms, galaxy interactions, or turbulence in the surrounding medium, creating a dynamic environment in the central region of the galaxy.
The spiral arms of M77 contain numerous regions of active star formation, visible as bright knots and H II regions, where young, hot stars ionize the surrounding gas. It contains substantial amounts of dust and gas, which are essential for star formation. Dust lanes can be observed tracing the spiral arms, contributing to the galaxy’s detailed structure.
Studies of M77’s rotation curve provide insights into the distribution of mass within the galaxy, including the presence of dark matter. The galaxy’s rotation speed remains relatively constant beyond the visible edges, suggesting a significant dark matter component.
M77 has also hosted several supernovae, which provide valuable opportunities for studying stellar evolution and explosive events. A notable supernovae is, SN 2018ivc, a Type II supernova observed in 2018, which offered insights into the life cycles of massive stars.
Observational History
M77 was discovered by the French astronomer Pierre Méchain on October 29, 1780. Charles Messier included it in his catalog of non-cometary objects shortly thereafter.
M77 has been observed extensively across multiple wavelengths, from radio to X-rays, revealing detailed information about its structure and active nucleus. As a Seyfert II galaxy, it offers a valuable opportunity to study active galactic nuclei and the dynamics of barred spiral galaxies.
Observing M77
The best time to observe M77 from both hemispheres is during the autumn and winter months (spring to summer in the southern hemisphere) when the constellation Cetus is well-positioned in the night sky. Cetus is located adjacent to the celestial equator, which is why it can be observed from both the northern and southern hemispheres between October and January.
M77 is visible with small to medium-sized telescopes under dark skies with minimal light pollution. It appears as a bright core with surrounding nebulosity. Larger telescopes will reveal its spiral structure. It can also be spotted with binoculars from a dark site.