Results from a new technique designed to map the structure of the Milky Way appear to support the four spiral arm model of our galaxy. A team of researchers from the Federal University of Rio Grande do Sul, Brazil, used data collected by NASA's Wide-field Infrared Survey Explorer (WISE) spacecraft to pinpoint star clusters located in the resource rich environment of the spiral arms, and use them as markers to trace the structure of our galaxy.
The problem we facewhen attempting to map our galaxy revolves around location. Earthsits roughly two thirds out from the galactic center, surrounded byseemingly chaotic yet structured clouds of dense dust that work toobscure our view, and hamper our efforts to gain an in-depthunderstanding of the large scale structure of our galaxy.
Researchershave, to an extent, been able to work around this impediment using avariety of differing observational techniques paired with insightgained from studies of distant spiral galaxies, in order to develop abasic model of our galaxy. Unfortunately the techniques used up tothis point have left this model riddled with blank spots, but here isa brief outline of our galaxy as it is currently understood.
TheMilky Way is a barred spiral galaxy, and at the heart of thisleviathan structure (it is believed) lurks a supermassive black holeknown as Sagittarius A* (SgrA*), with a mass of around 4 million times that of our Sun.Surrounding Sgr A* is a bar-shaped core region, and from this focalpoint extend four spiral arms that harbor vast quantities of dustand gas, the key ingredients for creating a new generation of stars.
"Spiral arms arelike traffic jams in that the gas and stars crowd together and movemore slowly in the arms" states Denilso Camargo, lead author ofthe paper from the Federal University of Rio Grande do Sul, Brazil. "As material passes through the dense spiral arms, it is compressedand this triggers more star formation."
Thefour spiral arms that make up the Milky Way are known as the Perseus,Sagittarius, Scutum-Centaurus, and Outer arms. Our Sun islocated in the Orion Spur, an offshoot of the Perseus spiral arm.
Recently, scientistshave turned to infrared data collected from NASA's WISE telescope inorder to more precisely map the positions of these arms, updating ourview of the galaxy in which we reside. WISE, now re-designated asNEOWISE, has the ability to pierce the dense veils of dust that wouldotherwise obscure our view, allowing researchers to observe starnurseries embedded in the resource rich spiral arms of the Milky Way.
These nurseries givebirth to clusters of stars that represent the ideal markers fortracing the position of spiral arms, as the relatively young groupsof stars have not yet had the time to drift away from the region inwhich they were created. During its operational period as WISE, thetelescope scanned the entire sky, granting researchers vastquantities of data to further hone their model of the Milky Way. Todate, researchers have discovered around 400 dust-shrouded starclusters in the WISE data.
The researchers thencompared the data from WISE with data from the Two Micron All Sky Survey (2MASS) in order to more accurately determine thedistance, and therefore position, of the clusters. The researchersdiscovered that the positions of these markers strengthened theprevailing model of the Milky Way, which asserts that our solarsystem is located in a barred spiral galaxy with four spiral arms.
A paper outlining theresearch is available online at the Monthly Notices of the Royal Astronomical Society.
Source: NASA