{"id":15777,"date":"2018-03-28T15:39:09","date_gmt":"2018-03-28T19:39:09","guid":{"rendered":"http:\/\/hobbyspace.com\/Blog\/?p=15777"},"modified":"2018-03-28T15:39:09","modified_gmt":"2018-03-28T19:39:09","slug":"hubble-discovers-a-local-galaxy-without-dark-matter","status":"publish","type":"post","link":"https:\/\/hobbyspace.com\/Blog\/?p=15777","title":{"rendered":"Hubble discovers a local galaxy without dark matter"},"content":{"rendered":"

The latest finding from the Hubble Space Telescope<\/a>:<\/p>\n

Hubble finds first galaxy in the local Universe without dark matter<\/a><\/strong><\/p>\n

An international team of researchers using the NASA\/ESA Hubble Space Telescope and several other observatories have, for the first time, uncovered a galaxy in our cosmic neighborhood that is missing most \u2014 if not all \u2014 of its dark matter. This discovery of the galaxy NGC 1052-DF2 challenges currently-accepted theories of and galaxy formation and provides new insights into the nature of dark matter. The results are published in Nature.<\/p>\n

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NGC 1052-DF2 resides about 65 million light-years away in the NGC 1052 Group, which is dominated by a massive elliptical galaxy called NGC 1052. This large, fuzzy-looking galaxy is so diffuse that astronomers can clearly see distant galaxies behind it. This ghostly galaxy is not well-formed. It does not look like a typical spiral galaxy, but it does not look like an elliptical galaxy either. Based on the colours of its globular clusters, the galaxy is about 10 billion years old. However, even the globular clusters are strange: they are twice as large as typical groups of stars. All of these oddities pale in comparison to the weirdest aspect of this galaxy: NGC 1052-DF2 is missing most, if not all, of its dark matter. The galaxy contains only a tiny fraction of dark matter that astronomers would expect for a galaxy this size. But how it formed is a complete mystery. Hubble took this image on 16 November 2017 using its Advanced Camera for Surveys.<\/em><\/figcaption><\/figure>\n

Astronomers using Hubble and several ground-based observatories have found a unique astronomical object: a galaxy that appears to contain almost no dark matter\u00a0[1]<\/a>. Hubble helped to accurately confirm the distance of NGC 1052-DF2 to be 65 million light-years and determined its size and brightness. Based on these data the team discovered that NGC 1052-DF2 larger than the Milky Way, but contains about 250 times fewer stars, leading it to be classified as an\u00a0ultra diffuse galaxy<\/a>.<\/p>\n

“I spent an hour just staring at this image,”\u00a0lead researcher Pieter van Dokkum of Yale University says as he recalls first seeing the Hubble image of NGC 1052-DF2.\u00a0“This thing is astonishing: a gigantic blob so sparse that you see the galaxies behind it. It is literally a see-through galaxy.”<\/em><\/p>\n

Further measurements of the dynamical properties of ten\u00a0globular clusters<\/a>\u00a0orbiting the galaxy allowed the team to infer an independent value of the galaxies mass. This mass is comparable to the mass of the stars in the galaxy, leading to the conclusion that NGC 1052-DF2 contains at least 400 times less\u00a0dark matter<\/a>\u00a0than astronomers predict for a galaxy of its mass, and possibly none at all\u00a0[2]<\/a>. This discovery is unpredicted by current theories on the distribution of dark matter and its influence on galaxy formation.<\/p>\n

“Dark matter is conventionally believed to be an integral part of all galaxies \u2014 the glue that holds them together and the underlying scaffolding upon which they are built,”\u00a0explains co-author Allison Merritt from Yale University and the Max Planck Institute for Astronomy, Germany. And van Dokkum adds:\u00a0“This invisible, mysterious substance is by far the most dominant aspect of any galaxy. Finding a galaxy without any is completely unexpected; it challenges standard ideas of how galaxies work.”<\/em><\/p>\n

Merritt remarks:<\/p>\n

“There is no theory that predicts these types of galaxies \u2014 how you actually go about forming one of these things is completely unknown.”<\/em><\/p>\n

Although counterintuitive, the existence of a galaxy without dark matter negates theories that try to explain the Universe without dark matter being a part of it\u00a0[3]<\/a>: The discovery of NGC 1052-DF2 demonstrates that dark matter is somehow separable from galaxies. This is only expected if dark matter is bound to ordinary matter through nothing but gravity.<\/p>\n