The giant cosmic cotton ball is so scattered and its ancient stars so spread out that remote galaxies in the background can be seen through it. Astronomers measured the luminosities of faint stars at the suggestion of the red giant branch in this galaxy to enhance the accuracy of its distance and to conclude that, in agreement with earlier studies, it does appear to be really deficient in dark matter. The galaxy NGC 1052-DF2 resides in a field of galaxies about sixty-five million light-years away.
Referral: “A Tip of the Red Giant Branch Distance of 22.1 ± 1.2 Mpc to the Dark Matter Deficient Galaxy NGC 1052– DF2 from 40 Orbits of Hubble Space Telescope Imaging” by Zili Shen, Shany Danieli, Pieter van Dokkum, Roberto Abraham, Jean P. Brodie, Charlie Conroy, Andrew E. Dolphin, Aaron J. Romanowsky, J. M. Diederik Kruijssen and Dhruba Dutta Chowdhury, 9 June 2021, The Astrophysical Journal Letters.DOI: 10.3847/ 2041-8213/ ac0335.
CfA astronomer Charlie Conroy was a member of a team of astronomers that figured out a new range for the galaxy. Rather than rely on its speed/ redshift to get the distance, a value that may be puzzled by its local motion within the group of galaxies, they derived the range using the brightness of faint red huge stars at the suggestion of the red huge branch, a well-established and basic approach when the stars are intense adequate to be accurately studied.
As a low-mass star burns through almost all of its hydrogen and begins to fuse helium in its core, the shift is accompanied by a diminishing in size, a quick rise in the core temperature level, a shift towards a bluer color, and an abrupt reduction in luminosity. This rapid modification in brightness is readily obvious in optical and near-infrared wavelengths; the outright luminosities of those stars can then be determined and, from their obvious luminosities, their range computed.
The astronomers used forty orbits of the Hubble Space Telescope to measure the brightness of the red giant stars in NGC 1052-DF2 and from that information to identify their distance: 72.7 million light-years plus-or-minus 5%.
This brand-new range validates the unusual characteristics of the galaxy including its puzzling scarcity of dark matter and that its globular clusters are incredibly luminous (in reality the brand-new range makes them even more luminescent). The outcome likewise indicates the information will not be suitable for tests of the proposed alternative theory of gravity.
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The giant cosmic cotton ball is so diffuse and its ancient stars so spread out that distant galaxies in the background can be seen through it. Astronomers measured the luminosities of faint stars at the tip of the red giant branch in this galaxy to enhance the accuracy of its range and to conclude that, in agreement with earlier studies, it does appear to be very deficient in dark matter.
The galaxy NGC 1052-DF2 lives in a field of galaxies about sixty-five million light-years away. Its low mass, just about 2 hundred million solar-masses, makes it a “dwarf” and its size, about fifteen thousand light-years in size, positions it in the regime of ultra-diffuse galaxies. It is likewise differentiated by hosting a big population of luminous globular clusters.
Two years ago a second, comparable faint dwarf galaxy was discovered near it, and the relative movements of these two galaxies highly suggest they have extremely little or no dark matter; for comparison, in the Milky Way (a regular galaxy) the dark matter contains nearly ten times more mass than the stellar matter.
Astronomers also noted that, if these mass and movement measurements are accurate, they may be utilized to turn down and test (or confirm) one long-standing alternate theory of gravity to Einsteins. Initially the range to the galaxy needs to be understood more accurately and precisely, given that the worths for numerous of the galaxys homes like movement, luminosity and inferred mass rely on the presumed range.