An international teamof astronomers has discovered a previously unknown component of theMilky Way – a thin disk of variable stars hidden in the galacticbulge. The observations, made using the ESO's Visible and InfraredSurvey Telescope for Astronomy (VISTA) telescope conflict withcurrent theories regarding the composition of the center of ourgalaxy.
As we understand it,the Milky Way is a barred spiral galaxy, with four main spiral armsextending from a galactic core with a supermassive black hole knownas Sagittarius A at its heart. Earth sits roughly two thirds out fromthe center of the Milky Way in the Orion Spur, an offshoot of thePerseus spiral arm.
Our view to thegalactic center is obscured by vast choking clouds of dust and gas,which hamper our efforts to form a unified view of the Milky Way.Therefore, the potential discovery of a new galactic component inspite of these impediments is of great importance in understandingthe characteristics and evolution of the vast cosmic structure thatwe call home.
Astronomers used theVISTA telescope's infrared imaging capabilities to peer through theclouds of dust and gas that would ordinarily mask the interior of ourgalaxy, capturing multiple shots of the central region of the MilkyWay in order to search for variable stars known as Cepheids.
Cepheids are stars thatfluctuate dramatically in observable brightness of the course ofdays, or months, as they expand and contract. It has been discoveredthat, by observing the rhythmic fluctuations of one of the unusualstellar bodies, that astrophysicists can estimate the star's age.
Variable stars likeCephids are particularly useful tools for astronomers attempting totrace out vast galactic structures, as the relatively well understoodprecise nature of the pulsations allow scientists to accuratelydiscern their distance relative to Earth.
In all, VISTA sampled655 Cephids in the galactic bulge, of which 35 were found to belongto a subgroup known as Classical Cepheids, which in turn wherediscovered to be significantly younger than their more prevalentcousins.
“All of the 35classical Cepheids discovered are less than 100 million years old"states co-author of a paper on the research, Dante Minniti, of theUniversidad Andres Bello, Santiago, Chile. "The youngest Cepheidmay even be only around 25 million years old, although we cannotexclude the possible presence of even younger and brighter Cepheids,”
The team then used theaccurately defined positions of the Cepheids to trace out theposition of a thin disk of younger stars residing in the centralbulge – an entirely new component for our galactic model.
Furthermore, therelative youth of these stars shakes up the current model we have theMilky Way, which dictates that the galactic bulge consists ofenormous quantities of very ancient stars. Instead, the results ofthe study hint at a previously undetected source creating new, youngstars for the past 100 million years.
Moving forward, the team hopes to establish whether the newlydetected stars where born in their presently observed locations, orwhether they migrated inward from regions outside of the galacticbulge.
A paper detailing the discovery has been published in The Astrophysical Journal. The findings are illustrated in the video below.
Source: ESO
