Skip to main content

A Spiral Snowflake


Image: The spiral galaxy NGC 6814. Credit:
ESA/Hubble & NASA. Acknowledgement: Judy Schmidt (Geckzilla)

Spiral galaxies together with irregular galaxies make up approximately 60% of the galaxies in the local Universe. However, despite their prevalence, each spiral galaxy is unique - like snowflakes, no two are alike. This is demonstrated by the striking face-on spiral galaxy NGC 6814, whose luminous nucleus and spectacular sweeping arms, rippled with an intricate pattern of dark dust, are captured in this NASA/ESA Hubble Space Telescope image.

NGC 6814 has an extremely bright nucleus, a telltale sign that the galaxy is a Seyfert galaxy.

Seyfert galaxies account for about 10% of all galaxies and are some of the most intensely studied objects in astronomy, as they are thought to be powered by the same phenomena that occur in quasars, although they are closer and less luminous than quasars. These galaxies have supermassive black holes at their centers which are surrounded by accretion discs of in-falling material. The accretion discs are believed to be the source of the observed ultraviolet radiation. Ultraviolet emission and absorption lines provide the best diagnostics for the composition of the surrounding material.

Seen in visible light, most Seyfert galaxies look like normal spiral galaxies, but when studied under other wavelengths, it becomes clear that the luminosity of their cores is of comparable intensity to the luminosity of whole galaxies the size of the Milky Way.

The luminous heart of NGC 6814 is a highly variable source of X-ray radiation, causing scientists to suspect that it hosts a supermassive black hole with a mass about 18 million times that of the Sun.

As NGC 6814 is a very active galaxy, many regions of ionised gas are studded along  its spiral arms. In these large clouds of gas, a burst of star formation has recently taken place, forging the brilliant blue stars that are visible scattered throughout the galaxy.

Links

Etichette:

Comments

Post a Comment

Popular posts from this blog

QUASARS AND THE COSMIC REIONIZATION

Credit: NASA/ESA Recently it has been suggested that quasars can be primarily responsible for the reionization of the universe.
Post a Comment
Read more

A METHOD TO TEST THE EXISTENCE OF REGULAR BLACK HOLES

Illustration of a black hole. Image Credit & Copyright: Alain Riazuelo The existence of the singularity is an intrinsic problem of the General Relativity (GR). At the fundamentally level, the resolution of the problem of the singularity lies with the expectation that under situations where quantum effects become strong, the behavior of gravity could possibly greatly deviate from that predicted by the classical theory of GR. Regular black hole solution are proposed with the same spacetime geometry outside the horizon as the traditional black hole, but bears no singularity inside. Whether or not black hole singularities should exist, they would be covered by the black hole horizon. The black hole horizon serves as an information curtain hindering outside observers from directly observing the interior structure of the black hole, and determining that whether or not the black hole singularity does really exist. A method is needed to check the correctness of the new constructions ...
Post a Comment
Read more

BOUNCING BLACK HOLES

Image: Illustration of a dusty supermassive black hole. Credit: ESA/NASA, the AVO project and Paolo Padovani Black holes could be bouncing stars as a consequence of quantum gravity: when the density of matter becomes high enough, quantum gravity effects generate sufficient pressure to compensate the matter's weight, the collapse ends, and matter bounces out. In a black hole, matter's collapse could stop before the central singularity is formed.
Post a Comment
Read more