A team of scientists discovered that the galaxy’s Milky Way (or our galaxy) is at most 50% larger than many estimates. They also found out that the galactic disc is shaped into concentric ripples. The Milky Way has corrugated. Prof. Heidi Jo Newberg, Rensselaer Polytechnic institute in Troy, New York led the study. She reexamined Sloan Digital Sky Survey data, which in 2002, showed that there was an expanding ring of stars above the Milky Way’s known plane. Professor Newberg is an American Astrophysicist who is well-known for her research into the structure and function of the Milky Way. It radiates from the sun and we can see at most four ripples in its disk. (Image: Rensselaer) “While we can only look at part of the galaxy with this data, we assume that this pattern is going to be found throughout the disk.” Notably, their findings demonstrate that features previously observed as rings are in fact part of the galactic disk, extending the Milky Way’s known width from 100,000 to 150,000 light years across, said lead author Yan Xu, a scientist who works at the National Astronomical Observatories of China, part of the Chinese Academy of Science, Beijing. Rensselaer’s former visiting scientist, Mr. Xu. Apparent ring is a ripple in the disk Mr. Xu said: “Going into the research, astronomers had observed that the number of Milky Way stars diminishes rapidly about 50,000 light years from the center of the galaxy, and then a ring of stars appears at about 60,000 light years from the center.” “What we see now is that this apparent ring is actually a ripple in the disk. It is possible that more ripples exist further out than we are aware of.” This study was partially funded by NASA. A rippling contour is revealed by the Milky Way’s density of light. Image: Rensselaer. Newberg, Xu, and their colleagues used data taken from the SDSS to demonstrate an oscillating asymmetry between the star count sequences on each side of the galaxies. They started from the Sun, and looked outwards from the centre of the galaxy. The disk’s mid-plane is affected by the Sun when it looks outward. It then goes up and down again. Glen Langston (NSF program manager) stated that “Extending our knowledge about our galaxy’s structures is fundamentally essential.” NSF proudly supports their efforts to map our galaxy’s shape beyond what was previously known limits. This study is based on the 2002 discovery in which Prof. Newberg discovered the existence of the “Monoceros Ring” – a ‘over-density of stars near the edges of the galaxy, that bulges over the galactic plane. How high is this ‘over-density of stars’? Professor Newberg noticed evidence of an additional over-density between the Sun, the Monoceros Ring and stars in but was unable to investigate more. Scientists recently returned to solving the mystery using additional data from the SDSS. Professor Newberg stated that he wanted to find out the reason for this other excess density. These stars had previously been considered disk stars, but the stars don’t match the density distribution you would expect for disk stars, so I thought ‘well, maybe this could be another ring, or a highly disrupted dwarf galaxy.” When the team re-examined the data, they found four anomalies: one south of the galactic plane at 4-6 kilo-parsecs (kpc), one north of the plane at 2 kpc, a third to the north at 9-10 kpc, plus evidence of a fourth to the south at 12-16 kpc from the Sun. Parsecs are an astronomical unit for distance. They measure approximately 3. 26 lightyears (3. 086 x 1013 kilometers, 31 trillion kilometers or 19 trillion miles). With the third ripple, is also associated the Monoceros Ring. Scientists also discovered that oscillations align with locations of the galaxy’s spiral arms. Professor Newberg stated that their results support previous studies. This includes a theory that dark matter or dwarf galaxies passing through the Milky Way might produce similar ripple effects. These ripples may be used in the future to determine how much dark matter is in our galaxy. Professor Newberg stated that the ripples could be used to measure the lumpiness of dark matter in our galaxy. The Astrophysical Journal. Published 11 February, 2015. DOI: 10.1088/0004-637X/801/2/105. Video: The Corrugated Milky Way
