New All-Sky Map of Milky Way’s Outer Reaches Released – Could Offer a New Test of Dark Matter Theories

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All Sky Map Milky Way Galaxy

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Astronomers have actually launched a brand-new all-sky map of the outer area of our Milky Way galaxy. Credit: NASA/JPL-Caltech/NSF/R.Hurt

The emphasize of the brand-new chart is a wake of stars, stimulated by a little galaxy set to hit the Milky Way. The map might likewise use a brand-new test of dark matter theories.

Astronomers utilizing information from NASA and ESA (European Space Agency) telescopes have actually launched a brand-new all-sky map of the outer area of our galaxy. Known as the stellar halo, this location lies outside the swirling spiral arms that form the Milky Way’s identifiable main disk and is sparsely occupied with stars. Though the halo might appear mainly empty, it is likewise anticipated to include an enormous tank of dark matter, a strange and unnoticeable compound believed to comprise the bulk of all the mass in deep space.

The information for the brand-new map originates from ESA’s Gaia objective and NASA’s Near Earth Object Wide Field Infrared Survey Explorer, or NEOWISE, which ran from 2009 to 2013 under the name WISE. The research study utilizes information gathered by the spacecraft in between 2009 and 2018.


This visualization reveals the main disk of our Milky Way galaxy and a smaller sized neighboring galaxy called the Large Magellanic Cloud. A brand-new, all-sky star map charts the area of stars in the Milky Way’s external reaches (called the stellar halo), about 200,000 light years to 325,000 light years from the Milky Way’s center. Credit: NASA/JPL-Caltech/NSF/R. Hurt/N. Garavito-Camargo & G. Besla

The brand-new map exposes how a little galaxy called the Large Magellanic Cloud (LMC) – so called due to the fact that it is the bigger of 2 dwarf galaxies orbiting the Milky Way – has actually cruised through the Milky Way’s stellar halo like a ship through water, its gravity developing a wake in the stars behind it. The LMC lies about 160,000 light-years from Earth and is less than one-quarter the mass of the Milky Way.

Though the insides of the halo have actually been mapped with a high level of precision, this is the very first map to offer a comparable photo of the halo’s external areas, where the wake is discovered – about 200,000 light-years to 325,000 light-years from the stellar center. Previous research studies have actually meant the wake’s presence, however the all-sky map verifies its existence and uses an in-depth view of its shape, size, and area.

This disruption in the halo likewise offers astronomers with a chance to study something they can’t observe straight: dark matter. While it doesn’t give off, show, or soak up light, the gravitational impact of dark matter has actually been observed throughout deep space. It is believed to develop a scaffolding on which galaxies are developed, such that without it, galaxies would fly apart as they spin. Dark matter is approximated to be 5 times more typical in deep space than all the matter that discharges and/or engages with light, from stars to worlds to gas clouds.

Although there are numerous theories about the nature of dark matter, all of them suggest that it must exist in the Milky Way’s halo. If that’s the case, then as the LMC cruises through this area, it must leave a wake in the dark matter also. The wake observed in the brand-new star map is believed to be the overview of this dark matter wake; the stars resemble leaves on the surface area of this unnoticeable ocean, their position moving with the dark matter.

The interaction in between the dark matter and the Large Magellanic Cloud has huge ramifications for our galaxy. As the LMC orbits the Milky Way, the dark matter’s gravity drags out the LMC and slows it down. This will trigger the dwarf galaxy’s orbit to get smaller sized and smaller sized, till the galaxy lastly hits the Milky Way in about 2 billion years. These kinds of mergers may be an essential chauffeur in the development of huge galaxies throughout deep space. In reality, astronomers believe the Milky Way combined with another little galaxy about 10 billion years earlier.

“This robbing of a smaller sized galaxy’s energy is not just why the LMC is combining with the Milky Way, however likewise why all galaxy mergers take place,” stated Rohan Naidu, a doctoral trainee in astronomy at Harvard University and a co-author of the brand-new paper. “The wake in our map is a really neat confirmation that our basic picture for how galaxies merge is on point!”

A Rare Opportunity

The authors of the paper likewise believe the brand-new map – in addition to extra information and theoretical analyses – might offer a test for various theories about the nature of dark matter, such as whether it includes particles, like routine matter, and what the residential or commercial properties of those particles are.

“You can imagine that the wake behind a boat will be different if the boat is sailing through water or through honey,” stated Charlie Conroy, a teacher at Harvard University and an astronomer at the Center for Astrophysics | Harvard & Smithsonian, who coauthored the research study. “In this case, the properties of the wake are determined by which dark matter theory we apply.”

Conroy led the group that mapped the positions of over 1,300 stars in the halo. The obstacle emerged in attempting to determine the precise range from Earth to a big part of those stars: It’s frequently difficult to find out whether a star is faint and nearby or intense and far. The group utilized information from ESA’s Gaia objective, which offers the area of numerous stars in the sky however cannot determine ranges to the stars in the Milky Way’s external areas.

After recognizing stars more than likely situated in the halo (due to the fact that they were not clearly inside our galaxy or the LMC), the group tried to find stars coming from a class of huge stars with a particular light “signature” noticeable by NEOWISE. Knowing the fundamental residential or commercial properties of the chosen stars made it possible for the group to find out their range from Earth and develop the brand-new map. It charts an area beginning about 200,000 light-years from the Milky Way’s center, or about where the LMC’s wake was anticipated to start, and extends about 125,000 light-years beyond that.

Conroy and his associates were motivated to hunt for LMC’s wake after discovering a group of astrophysicists at the University of Arizona in Tucson that makes computer system designs anticipating what dark matter in the stellar halo need to appear like. The 2 groups collaborated on the brand-new research study.

One design by the Arizona group, consisted of in the brand-new research study, anticipated the basic structure and particular area of the star wake exposed in the brand-new map. Once the information had actually validated that the design was appropriate, the group might validate what other examinations have actually likewise meant: that the LMC is most likely on its very first orbit around the Milky Way. If the smaller sized galaxy had actually currently made numerous orbits, the shape and area of the wake would be considerably various from what has actually been observed. Astronomers believe the LMC formed in the exact same environment as the Milky Way and another neighboring galaxy, M31, which it is close to finishing a long very first orbit around our galaxy (about 13 billion years). Its next orbit will be much shorter due to its interaction with the Milky Way. 

“Confirming our theoretical prediction with observational data tells us that our understanding of the interaction between these two galaxies, including the dark matter, is on the right track,” stated University of Arizona doctoral trainee in astronomy Nicolás Garavito-Camargo, who led deal with the design utilized in the paper.

The brand-new map likewise offers astronomers with an uncommon chance to evaluate the residential or commercial properties of the dark matter (the notional water or honey) in our own galaxy. In the brand-new research study, Garavito-Camargo and associates utilized a popular dark matter theory called cold dark matter that fits the observed star map fairly well. Now the University of Arizona group is running simulations that utilize various dark matter theories to see which one finest matches the wake observed in the stars. 

“It’s a really special set of circumstances that came together to create this scenario that lets us test our dark matter theories,” stated Gurtina Besla, a co-author of the research study and an associate teacher at the University of Arizona. “But we can only realize that test with the combination of this new map and the dark matter simulations that we built.”

Launched in 2009, the SMART spacecraft was put into hibernation in 2011 after finishing its main objective. In September 2013, NASA reactivated the spacecraft with the main objective of scanning for near-Earth items, or NEOs, and the objective and spacecraft were relabelled NEOWISE. NASA’s Jet Propulsion Laboratory in Southern California handled and ran WISE for NASA’s Science Mission Directorate. The objective was chosen competitively under NASA’s Explorers Program handled by the firm’s Goddard Space Flight Center in Greenbelt, Maryland. NEOWISE is a job of JPL, a department of Caltech, and the University of Arizona, supported by NASA’s Planetary Defense Coordination Office.



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