Discover Top Posts Tagged with #dragonfly 44

Esta galaxia de materia oscura ocultaba un misterio. Y ahora fue resuelto

La galaxia Dragonfly 44 era un misterio cuando se descubrió por primera vez en 2016. Con base en…

LEE MÁS

#astrofisica #dark matter #dragonfly 44 #galaxia #materia oscura #teymoor saifollahi

Dark Matter Riches? Why Some Galaxies Have More Than Others

“Dark matter, in a 5:1 ratio to normal matter, accounts for everything from the formation of the largest cosmic structures to galaxies' internal motions to the fluctuation patterns in the cosmic microwave background. Present in a large, diffuse halo surrounding galaxies and clusters, its gravity is observable even when collisions separate out the normal matter.”

Everything in the Universe was born with the same ratios of dark matter to normal matter: approximately 5-to-1. It shows up in everything from the cosmic microwave background to galaxy clustering to internal motions of spiral and elliptical galaxies, including the Milky Way. But some galaxies, particularly dwarf galaxies and rapidly moving galaxies within clusters, show a significant enhancement of dark matter over what’s expected. Ratios of even hundreds-to-1 aren’t unheard of. This is a difficulty for theorists to explain, but it doesn’t mean that dark matter is wrong.

On the contrary, it might mean that astrophysics, and how these galaxies evolve, explains exactly what the Universe gives us!

#dark matter #galaxies #Dragonfly 44 #astronomy #astrophysics #ghost #dragonfly #invisible #physics #cosmology #gas stripping #forces #science

SCIENTISTS DISCOVER A ‘DARK’ MILKY WAY Using the world’s most powerful telescopes, an international team of astronomers has found a massive galaxy that consists almost entirely of dark matter. The galaxy, Dragonfly 44, is located in the nearby Coma constellation and had been overlooked until last year because of its unusual composition: It is a diffuse “blob” about the size of the Milky Way, but with far fewer stars. “Very soon after its discovery, we realized this galaxy had to be more than meets the eye. It has so few stars that it would quickly be ripped apart unless something was holding it together,” said Yale University astronomer Pieter van Dokkum, lead author of a paper in the Astrophysical Journal Letters. Van Dokkum’s team was able to get a good look at Dragonfly 44 thanks to the W. M. Keck Observatory and the Gemini North telescope, both in Hawaii. Astronomers used observations from Keck, taken over six nights, to measure the velocities of stars in the galaxy. They used the 8-meter Gemini North telescope to reveal a halo of spherical clusters of stars around the galaxy’s core, similar to the halo that surrounds our Milky Way galaxy. Star velocities are an indication of the galaxy’s mass, the researchers noted. The faster the stars move, the more mass its galaxy will have. “Amazingly, the stars move at velocities that are far greater than expected for such a dim galaxy. It means that Dragonfly 44 has a huge amount of unseen mass,” said co-author Roberto Abraham of the University of Toronto. Scientists initially spotted Dragonfly 44 with the Dragonfly Telephoto Array, a telescope invented and built by van Dokkum and Abraham. Dragonfly 44’s mass is estimated to be 1 trillion times the mass of the Sun, or 2 tredecillion kilograms (a 2 followed by 42 zeros), which is similar to the mass of the Milky Way. However, only one-hundredth of 1% of that is in the form of stars and “normal” matter. The other 99.99% is in the form of dark matter -- a hypothesized material that remains unseen but may make up more than 90% of the universe. The researchers note that finding a galaxy composed mainly of dark matter is not new; ultra-faint dwarf galaxies have similar compositions. But those galaxies were roughly 10,000 times less massive than Dragonfly 44. “We have no idea how galaxies like Dragonfly 44 could have formed,” said Abraham. “The Gemini data show that a relatively large fraction of the stars is in the form of very compact clusters, and that is probably an important clue. But at the moment we’re just guessing.” Van Dokkum, the Sol Goldman Family Professor of Astronomy and Physics at Yale, added: “Ultimately what we really want to learn is what dark matter is. The race is on to find massive dark galaxies that are even closer to us than Dragonfly 44, so we can look for feeble signals that may reveal a dark matter particle.”

#space #science #Astronomy #astrophysics #dragonfly 44 #physics

The Invisible Galaxy

A new form of diffuse galaxy has been discovered inside the Coma Cluster. This place is made 99.99% of dark matter, totally invisible as it doesn’t interact with light.

The galaxy is known as Dragonfly 44 and was discovered by astronomers Pieter van Dokkum and his colleagues.

The way star systems orbit around the center of a galaxy is inexplicable with “normal” physics. To account for the velocity variations and patterns we need to add a new ingredient to the gravitational pot: dark matter.

Dragonfly 44 in particular has so few stars that were the dark matter to be taken away, the galaxy would fly apart the same way you’d go flying if the cord holding the swing to a swing set were severed.

(Image credit: NASA, JPL-CalTech and L. Jenkins)

#astronomy #dark matter #space #dragonfly 44 #coma cluster #science #stars #galaxy #nasa

New galaxy with same mass as the Milky Way discovered

Scientists yet to understand the phenomenon.

A group of scientists has found a new galaxy which has approximately the same mass as the Milky Way and is entirely made of dark matter, reported The Washington Post.

About 99.99 percent of the galaxy named Dragonfly 44 is made up of dark matter, an unidentified type of matter comprising approximately 27% of the mass and energy in the observable…

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#Astrophysical Journal Letters #Coma galaxy cluster #dark matter #Dragonfly 44 #Gravity #milky way #new galaxy #Pieter van Dokkum #University of Toronto #Yale University

Het 'geest-sterrenstelsel' Dragonfly 44 bestaat voor 99,99% uit donkere materie

Sterrenkundigen van de Yale Universiteit onder leiding van de Nederlandse sterrenkundige Pieter van Dokkum hebben met behulp van twee grote telescopen een sterrenstelsel ontdekt dat voor maar liefst 99,99% uit donkere materie bestaat. Het sterrenstelsel heet Dragonfly 44, genoemd naar het zoekprogramma ‘Dragonfly Telephoto Array’ waarmee het vorig jaar werd ontdekt, gelegen op een afstand van 330 miljoen lichtjaar in het sterrenbeeld Haar van Berenice (Coma Berenice). Het is een ultradifuus sterrenstelsel, dat hier en daar ook al als ‘geest-sterrenstelsel’ wordt aangeduid. En da’s niet voor niets. De Yale groep heeft met de Gemini North-telescoop en Keck Telescoop, beiden op Mauna Kea, Hawaï, gekeken naar de bolvormige sterrenhopen rondom Dragonfly 44 (de vlekjes in de cirkels op de afbeelding hierboven) en daaruit kon men de massa van het sterrenstelsel bepalen: pakweg één biljoen zonsmassa, vergelijkbaar met de massa van de aarde. Maar als je naar de lichtkracht van Dragonfly 44 kijkt ziet men dat slechts een honderdste van een procent van die massa uit gewone sterren bestaat. Dat betekent dus dat de rest van de massa, 99,99% om precies te zijn, bestaat uit de mysterieuze donkere materie – een record. De vorige recordhouder was een stelsel in Maagd (Virgo), dat voor 99,96% uit donkere materie bestaat, VCC 1287 genaamd. OK, nou op naar een sterrenstelsel dat voor 100% uit donkere materie bestaat – mmmm, hoe zou je dat kunnen zien? Hier het vakartikel van de groep Van Dokkum, dat gisteren verscheen in The Astrophysical Journal Letters. Bron: Keck Observatorium.

Astroblogs: http://www.astroblogs.nl/2016/08/26/het-geest-sterrenstelsel-dragonfly-44-bestaat-voor-9999-uit-donkere-materie/

#Dragonfly 44 #geest-sterrenstelsels #ultradifuse sterrenstelsels