In the 17th century, Galileo Galilee aimed his telescope at the stars and showed (for the very first time) that the Milky Way was not a nebulous band however a collection of far-off stars. This led to the discovery that our Sun was simply one of the numerous stars in a much larger structure: the Milky Way Galaxy. By the 18th century, William Herschel ended up being the first astronomer to produce a map that tried to capture the shape of the Milky Way. Even after all that time and discovery, astronomers are still plagued by the issue of point of view.
While we have actually been able to identify galaxies we see throughout the cosmos with relative ease, it is challenging for astronomers to study the size, shape, and population of the Milky Way because of how our Solar System is embedded in its disk. Luckily, there are methods to prevent this problem of viewpoint, which have offered astronomers with clues to these concerns. In a recent paper, a group from the Astronomical Observatory at the University of Warsaw (AstroUW) utilized a large collection of Mira variable stars to trace the shape of the Milky Way, which yielded some fascinating outcomes!
For the sake of their research study, the team examined information on 65,981 Mira-type stars observed by the Optical Gravitational Lensing Experiment (OGLE), a long-term sky study of variable stars based at the University of Warsaw. Given that 1992, OGLE has actually kept track of the brightness of about two billion stars in the Milky Way and the Magellanic Clouds, supplying insight into a large range of astronomical phenomena.
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This Hubble image shows RS Puppis, a kind of variable star called a Cepheid variable. Credit: NASA/ESA/H. Bond/STScI/AURA/ PSU.
The 3D map of the Milky Way from this newest research study offers brand-new clues about the structure of the Galactic Bulge, which might also assist astronomers understand the structure of other disallowed spiral galaxies. As Iwanek emphasized, all 66,000 Miras variables were chosen and classified from the OGLE study “by hand.” In other words, the light curve of every star was examined by an experienced astronomer to identify if they varied and what type they were. This, stated Iwanek, provides chances for future studies that rely on machine knowing:.
” Our big collection of Mira variables, thanks to its purity and efficiency, along with the long-term and precise OGLE light curves, can be utilized to train the device learning algorithms for the automated classification of variable stars in future sky surveys conducted with bigger telescopes.”.
Additional Reading: arXiv.
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The shape of the Milky Way galaxy is disturbed by tidal interactions with a dwarf galaxy, as forecasted by N-body simulations. Credit: T. Mueller/C. Laporte/NASA/JPL-Caletch
The OGLE project, likewise called the Optical Gravitational Lensing Experiment, is among the largest-scale sky surveys worldwide. It is a long-term sky survey that monitors the brightness of about 2 billion stars in the Milky Way and the Magellanic Clouds. During its long history, the OGLE study has actually contributed considerably to the study of a large range of huge phenomena, including gravitational lensing and microlensing, extrasolar planets, variable stars, cosmic distance scale, and the structure and evolution of the Milky Way and Magellanic Clouds.
As stars approach completion of their main series stage, they exhaust their supply of hydrogen fuel and start consuming helium. This triggers them to broaden to a number of times the initial size and to become dimmer and cooler than main sequence stars– thus the term Red Giants. Mira variables are a special class of pulsating red giants that have long durations ranging from 80 to more than 1000 days. They belong to the Asymptotic Giant Branch (AGB) of the Hertzsprung– Russell Diagram, that includes all stars with less than 5-8 solar masses.
The remarkable changes in brightness of pulsating stars (like other variable stars) make them really useful to astronomers for measuring ranges and the spatial distribution of stars in galaxies. As Iwanek described Universe Today via email:
” These stars follow a distinct period-luminosity relation, which indicates that [by] knowing their pulsation durations, it is possible to determine their outright magnitudes and after that identify their distances. This function makes Miras an outstanding cosmic distance indicator. Using their specifically determined distances, it is possible to study the three-dimensional distribution of stars in our galaxy.
” Moreover, the high luminosity of Miras, which is orders of magnitude greater than that of the Sun, makes it possible to observe these stars not just in the Milky Way but also in other neighboring galaxies (e.g., M31 or the Magellanic Clouds). Studying the Mira variables might assist to understand the structure and development of galaxies.”
For the sake of their research study, the group taken a look at data on 65,981 Mira-type stars observed by the Optical Gravitational Lensing Experiment (OGLE), a long-lasting sky study of variable stars based at the University of Warsaw. During its long history, the OGLE survey has actually contributed considerably to the study of a wide variety of astronomical phenomena, including gravitational lensing and microlensing, extrasolar planets, variable stars, cosmic range scale, and the structure and evolution of the Milky Way and Magellanic Clouds.
For this research study (released in 2019), Iwanek and his associates utilized data on Cepheid variable stars to produce a 3D map of the Milky Way.
This improved image reveals the X-shaped circulation around the bulge based on information from the NASA area telescope WISE. Credit: NASA/JPL-Caltech/D. Lang
For their study, the group utilized 65,981 stars mapped by OGLE that fall into the classification of Mira variables. They also considered the distance unpredictabilities by implementing the Bayesian Hierarchical Method (BHM), a statistical model where inferences are made about a bigger population based upon information from smaller sized samples (grouped hierarchically). From this, they had the ability to produce a detailed 3D map of our galaxy made up of intermediate-age and young stellar populations. Their analysis supplies independent evidence of an X-shaped bulge component and a flared disk.
The X-shape is an extra structure in the dense, main part of the Milky Way, the Galactic bulge, formed by 2 overlapping groups of stars. This structure is believed to be triggered by the movements and interactions of stars within the bulge. It might be a common feature of disallowed spiral galaxies (comparable to our Milky Way).”.
This research study constructs on previous work performed by astronomers from the University of Warsaw, Ohio State University (OSU), and the University of Warwick (of which Iwanek was a co-author). For this research study (launched in 2019), Iwanek and his coworkers used data on Cepheid variable stars to create a 3D map of the Milky Way. This map revealed the structure of the Milky Way and permitted the group to constrain the distorted nature of the Milky Ways disk. As Iwanek explained:.
” Classical Cepheids and Mira variables are stars from different populations. In the most current research, we also used mid-infrared observations to precisely measure distances to the Mira stars, however this time we focused mainly on the Galactic center, where Miras predominate.”.
In the 17th century, Galileo Galilee aimed his telescope at the stars and demonstrated (for the first time) that the Milky Way was not an ambiguous band however a collection of far-off stars. In a recent paper, a group from the Astronomical Observatory at the University of Warsaw (AstroUW) used a big collection of Mira variable stars to trace the shape of the Milky Way, which yielded some intriguing results!
