Popular media is abuzz today with news regarding research by NAOC (National Astronomical Observatories of Chinese Academy of Sciences) on the shape of our galaxy, the Milky Way, published in Nature Astronomy today. A peculiar disk. A new 3D model.
Original article on Nature Astronomy: “An intuitive 3D map of the Galactic warp’s precession traced by classical Cepheids” (February 4, 2019).
Here’re two examples about that article: ABC Science News and Phys.org. The Phys.org article contains visualizations.
Milky Way is ‘S-shaped’, 3D map reveals, in a new way of looking at our celestial home
- We have long thought the Milky Way was warped, but it is also twisted, according to a new study of pulsating stars.
- The new map is the most accurate representation of the Milky Way so far, say astronomers.
- The Gaia telescope will give us a much better picture in the future.
The map provides an “unprecedented view of the Milky Way”, said study co-author Richard de Grijs of Macquarie University.
To create the map, Professor de Grijs and colleagues from the Chinese Academy of Sciences focused on 1,339 pulsating beacons known as Cepheid stars.
To cut through the dust, Professor de Grijs and colleagues based their calculations on observations of Cepheid stars made using the Wide-Field Infrared Survey Explorer, which detects longer wavelengths than visible light.
Joss Bland-Hawthorn of the University of Sydney agreed the new study was a first step, which will be followed up in more detail by observatories such as the Gaia space telescope.
“This is probably the cleanest demonstration of the warp in stars and it looks different from the warp in gas,” said Professor Bland-Hawthorn, who was also not involved in the new study.
But we don’t really know what causes these warps, he added.
The Milky Way galaxy’s disk of stars is anything but stable and flat. Instead, it becomes increasingly warped and twisted far away from the Milky Way’s center, according to astronomers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC).
“Somewhat to our surprise, we found that in 3-D, our collection of 1339 Cepheid stars and the Milky Way’s gas disk follow each other closely. This offers new insights into the formation of our home galaxy,” says Prof. Richard de Grijs from Macquarie University in Sydney, Australia, and senior co-author of the paper. “Perhaps more importantly, in the Milky Way’s outer regions, we found that the S-like stellar disk is warped in a progressively twisted spiral pattern.”
“This new morphology provides a crucial updated map for studies of our galaxy’s stellar motions and the origins of the Milky Way’s disk,” says Dr. DENG Licai, senior researcher at NAOC and co-author of the paper.
We’ve come a long way from “perfect” celestial spheres, eh.
19 thoughts on “The Milky Way’s shape — a peculiar disk”
Milky Way Collided with Dark-Matter Dominated Galaxy Less Than Billion Years Ago (June 18, 2019)
This Space.com article “This 3D Map of the Milky Way Is the Best View Yet of Our Galaxy’s Warped, Twisted Shape” (August 1, 2019) by Charles Q. Choi discusses recent research on the Milky Way’s shape using Cepheid variable stars.
Lots of media coverage recently about research on “bubbles” of gamma and X-ray emissions about 25 thousand light-years distant above and below the Milky Way’s galactic center – Fermi bubbles. This Space.com artcle by Paul Sutter on September 4, 2019 is an example: “Something Strange Is Happening in the Fermi Bubbles.”
There’s a well done animation is this article about galactic evolution.
ESA > “Galactic crash may have triggered Solar System formation” (May 25, 2020).
Beyond visible light, the ultraviolet eyes of NASA’s Hubble Space Telescope continue to provide insights into the history of our very own Milky Way.
Space.com > “Ancient explosion in Milky Way’s core lit up gas outside the galaxy” by Elizabeth Howell (June 4, 2020).
 Andrew Fox, the principal investigator of the study and an astronomer at the Space Telescope Science Institute (STScI) in Baltimore.
Our Milky Way was built via mergers of smaller galaxies … computer simulation …
• Phys.org > “Astronomers discover new ‘fossil galaxy’ buried deep within the Milky Way” by Sloan Digital Sky Survey (Nov 20, 2020)
• Phys.org > “Orbits of ancient stars prompt rethink on Milky Way evolution” by ARC Centre of Excellence for All Sky Astrophysics in 3D (ASTRO 3D) (Nov 16, 2020)
ESA’s Gaia space observatory maps our Milky Way in much better detail.
• Cnet > “Most detailed 3D map ever of Milky Way includes nearly 2 billion stars” by Gael Fashingbauer Cooper (Dec 3, 2020) – The new data it offers provides measurements that are “orders of magnitude” more exact than prior information, scientists say.
• Space.com > “A ‘tsunami’ for astrophysics: New Gaia data reveals the best map of our galaxy yet” by Megan Gannon (Dec 3, 2020)
A much more dynamic history and state of our Milky Way …
• ESA > Science & Exploration > “Gaia’s Milky Way discoveries” (Nov 26, 2020)
• YouTube > ESA > “Gaia’s Milky Way discoveries” (Nov 25, 2020)
Another recap of recent research on galactic formation. The role of new data and digital simulations in crafting a more complex origin story and ongoing saga. Disk, halo, dwarf galaxies, globular clusters. The Gaia spacecraft. Stars of various metallicities. Galactic wreckage. Galactic interlopers.
• Quanta Magazine > Astrophysics > “The New History of the Milky Way” by Charlie Wood (December 15, 2020) – Over the past two years, astronomers have rewritten the story of our galaxy.
• Space.com > “A galactic sideswipe 3 billion years ago warped our Milky Way galaxy” by Elizabeth Howell (January 21, 2021) – New data from the Sloan Digital Sky Survey and Europe’s Gaia spacecraft suggest that a brush with another galaxy caused the strange, potato chip-like “warp” in our Milky Way galaxy.
A jar of stars?
When I was a kid, there was a family day event at the local YMCA. The activities included a “how many jelly beans in the jar” contest. The prize was a stuffed animal. Well, I looked at a drawing of the jar in the contest poster and at the real (large) jar, which was sort of cube like. I decided to guess the count by estimating the number of beans along each dimension and multiplying. Obviously not considering some factors, I think I fudged that mental calculation by adding a number. I don’t remember how close I was to the actual count; but my guess was the closest one.
This Space.com article on estimating the number of stars in our galaxy hints at the complexity of any such effort. A galaxy’s not just a bunch of stars packed closely together within a well-defined spatial “jar.”
• Space.com > “How many stars are in the Milky Way?” by Elizabeth Howell (June 9, 2021)
Galaxy’s mass – solar mass vs. number of stars
Spectroscopy, star types
Dark matter %
Answer: Billions … how many billions, eh.
How many stars?
An overview of how astronomers know the distance to a star or a distant galaxy. The cosmic distance ladder.
• Space.com > “Some celestial yardsticks are visible in the night sky” by Joe Rao (Nov 7, 2021) – Here’s where to look to see some key landmark stars.
Available for viewing via PBS’ smartphone app, a helpful overview of our galaxy’s history & dynamics, 3D visualizations, and future interactions.
Particularly, an overview of how Gaia, a spacecraft in an orbit ~1 million miles from Earth [Sun–Earth Lagrange point L2 located approximately 1.5 million kilometres from Earth], uses parallax [with an accuracy of 10 microarcseconds] to measure positions & distances of ~1 billion stars – astrometry.
• PBS > NOVA > S46 > E16 > “Universe Revealed: Milky Way”
Research on our galaxy’s evolution finds signs of another merger.
• Universe Today > “Gaia Finds Ancient Satellite Galaxy Pontus Embedded in Milky Way” by David Dickinson (February 23, 2022) – A recent study looked at stellar streams hidden in Gaia data, to uncover evidence of an ancient remnant dubbed Pontus.
Image credit: Edge on view of the Milky Way with several structures indicated, 22 February 2013, (as is) by Gaba p, licensed under Creative Commons.
While “the age of a star is one of the most difficult parameters to determine,” analysis of a galactic set of particular stars’ brightness and position and spectroscopic data indicates an older age for a part of our Milky Way.
• ESA > “Gaia finds parts of the Milky Way much older than expected” (Mar 23, 2022)
Suspected Milky Way timeline:
Here’s a wonderfully visualized recap of our galactic story – the evolution of our Milky Way and the evidence for that.
• YouTube > PBS Space Time > “The Evolution of the Modern Milky Way Galaxy” hosted by Matt O’Dowd (May 25, 2022)
Note this resource for the PBS series:
• Search the Entire Space Time Library
Research on galactic evolution abounds with yet another Gaia data dump: “Gaia is currently the scientific mission that generates the most scientific papers …”
• Space.com > “4 big Milky Way mysteries the next Gaia mission data dump may solve” by Tereza Pultarova (May 31, 2022)
More research on our galaxy’s oldest star populations.
• Space.com > “First ever map of Milky Way’s galactic graveyard revealed” by Elizabeth Rayne (10-10-2022) – The nascent Milky Way appeared drastically different to the galaxy we see today.
A plug for gamma-ray astronomy: More research using the Fermi Gamma Ray Space Telescope, looking for the source of the Milky Way’s so-called “Fermi bubbles.” Something besides our central black hole, Sagittarius A*.
• Space.com > “Gamma rays from a dwarf galaxy solve an astronomical puzzle” by Roland Crocker published (Oct 2, 2022) – A glowing blob known as “the cocoon” has puzzled astronomers since it was discovered in 2012.
(Wiki image) Gamma-Ray bubble at the center of the Milky Way
Credit: NASA’s Goddard Space Flight Center
Using data from the European Space Agency’s Gaia space observatory, here’s another article on research about how the Sagittarius dwarf galaxy, which orbits the Milky Way, has shaped our home galaxy.
• Space.com > “The Milky Way is ‘rippling’ like a pond, and scientists may finally know why” by Brandon Specktor (Sept 29, 2022) – the Sagittarius dwarf galaxy just can’t keep its hands off of us.
Credit: NASA/Adler/U. Chicago/Wesleyan/JPL-Caltech
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