Changes

[[File:Spiral galaxy.jpg|right]]

[[File:Spiral galaxy.jpg|right]]

A '''spiral galaxy''' is a [[galaxy]] consisting of a rotating disk of [[star]]s, [[gas]] and [[dust]] which has a number of arms extending outwards from the galactic centre.<ref>[https://www.britannica.com/topic/galaxy/Types-of-galaxies#ref559197 Galaxies] from britannica.com</ref> Some spiral galaxies have a prominent bulge around the centre, while others have a bar crossing the centre with the spiral arms extending from the ends of the bar. They tend to be fairly large and blue in color.

A '''spiral galaxy''' is a [[galaxy]] consisting of a rotating disk of [[star]]s, [[gas]] and [[dust]] which has a number of arms extending outwards from the galactic centre.<ref>[https://www.britannica.com/topic/galaxy/Types-of-galaxies#ref559197 Galaxies] from britannica.com</ref> Some spiral galaxies have a prominent bulge around the centre, while others have a bar crossing the centre with the spiral arms extending from the ends of the bar. They tend to be fairly large and blue in color. Approxmately 77% of all known galaxies are spiral galaxies.<ref>[http://cas.sdss.org/dr6/en/proj/basic/galaxies/spirals.asp Spiral galaxies] from cas.sdss.org, Sloan Digital Sky Survey</ref>

Some Creation scientists have argued that spiral galaxies are [[Arguments for a recent creation|evidence of a young universe]].<ref>[https://answersingenesis.org/astronomy/cosmology/galaxies-unexplained-spirals/ Galaxies-unexplained spirals] from answersingenesis.org</ref> Specifically, the spiral arms in the galaxy should smear out after several rotations as the inner stars orbit faster than the outer stars. This is known as the "winding problem." A young universe solves the winding problem as it means there has not been enough time for galaxies to rotate even once, the Milky Way takes around 200 million years to complete a single revolution, and so not enough time for the arms to smear out.<ref>[https://phys.org/news/2015-02-milky-rotate.html Why does the Milky Way rotate?] from phys.org</ref>  

Some Creation scientists have argued that spiral galaxies are [[Arguments for a recent creation|evidence of a young universe]].<ref>[https://answersingenesis.org/astronomy/cosmology/galaxies-unexplained-spirals/ Galaxies-unexplained spirals] from answersingenesis.org</ref> Specifically, the spiral arms in the galaxy should smear out after several rotations as the inner stars orbit faster than the outer stars. This is known as the "winding problem." A young universe solves the winding problem as it means there has not been enough time for galaxies to rotate even once, the Milky Way takes around 200 million years to complete a single revolution, and so not enough time for the arms to smear out.<ref>[https://phys.org/news/2015-02-milky-rotate.html Why does the Milky Way rotate?] from phys.org</ref>