A very old white dwarf star with rings?
The uncertainty of science: A citizen scientist has discovered a very old white dwarf star that apparently has one or more dust rings it should not have.
The star, LSPM J0207+3331 or J0207 for short, is forcing researchers to reconsider models of planetary systems and could help us learn about the distant future of our solar system. “This white dwarf is so old that whatever process is feeding material into its rings must operate on billion-year timescales,” said John Debes, an astronomer at the Space Telescope Science Institute in Baltimore. “Most of the models scientists have created to explain rings around white dwarfs only work well up to around 100 million years, so this star is really challenging our assumptions of how planetary systems evolve.”
In other words, we don’t really yet understand the processes that form solar systems or even stars. This isn’t because we can’t figure this out, but because we don’t yet have enough information on hand. What we do know tells us that stars and solar systems both form from accretion disks. The information also gives us a general idea of the pattern of formation, but not much more.
For example, one question I have asked a number of astronomers is: Why are some stars gigantic monsters and others dwarfs? Based on present theories of stellar evolution, it seems to me that all stars should be the same size, as accretion is thought to end when the star reaches a heavy enough mass to ignite its nuclear engine. Yet this is not what we find. Why? I’ve never gotten a good answer.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The uncertainty of science: A citizen scientist has discovered a very old white dwarf star that apparently has one or more dust rings it should not have.
The star, LSPM J0207+3331 or J0207 for short, is forcing researchers to reconsider models of planetary systems and could help us learn about the distant future of our solar system. “This white dwarf is so old that whatever process is feeding material into its rings must operate on billion-year timescales,” said John Debes, an astronomer at the Space Telescope Science Institute in Baltimore. “Most of the models scientists have created to explain rings around white dwarfs only work well up to around 100 million years, so this star is really challenging our assumptions of how planetary systems evolve.”
In other words, we don’t really yet understand the processes that form solar systems or even stars. This isn’t because we can’t figure this out, but because we don’t yet have enough information on hand. What we do know tells us that stars and solar systems both form from accretion disks. The information also gives us a general idea of the pattern of formation, but not much more.
For example, one question I have asked a number of astronomers is: Why are some stars gigantic monsters and others dwarfs? Based on present theories of stellar evolution, it seems to me that all stars should be the same size, as accretion is thought to end when the star reaches a heavy enough mass to ignite its nuclear engine. Yet this is not what we find. Why? I’ve never gotten a good answer.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Good stuff.
That, is a highly interesting question, you pose at the end….
‘Star Formation’
backgrounder & commentary
w/ data/observations from the Atacama Large Millimeter Array
https://youtu.be/swdHgkhwBcg
50:49
haven’t watched this yet, but very topical and recent:
“Linking the Scales of Star Formation”
CfA Colloquium 1-31-19
Daniela Calzetti U.Mass, Amherst
https://youtu.be/RfdQZnzLaJ4
1:00:04
Perhaps it‘s not a dust ring but a Ringworld? “Paging Larry Niven!”
Off the cuff, perhaps star size is related to the density of the formation field. The density of coalescing material and in-fall velocity exceed the ignition wavefront velocity until an equilibrium is reached.
Blair–
Good stuff.
“Three-dimensional Simulation of Massive Star Formation in the Disk Accretion Scenario”
Rolf Kuiper
https://youtu.be/mibtU0mBjz8
0:22
“The movie is based on data of a three-dimensional high-resolution radiation hydrodynamics simulation of the collapse of a pre-stellar core of cold gas and dust of 120 solar masses.
The initial rotation of the pre-stellar core leads to the formation of a massive disk around the central star.
The high luminosity of this massive star exerts a radiation pressure, which stops further mass inflow from the low-density bipolar direction and yields the launching of a radiation pressure driven outflow.
However, the massive accretion disk around the central star strongly diminishes the radiation pressure in the midplane. Due to the self-gravity of the disk, a close-in gravitational instability in the disk drives an angular momentum transport outwards. The resulting accretion flow through the disk is able to overcome the diminished radiation pressure of the massive star. These mechanisms allow the formation of the most massive stars known in the present day universe!”
[see Kuiper et al. (2011), Astrophysical Journal, vol. 732 pp. 20]
Wayne:
Better stuff.
wayne’s description is roughly how I have understood star formation. Gravitational attraction causes a large cloud to accumulate matter until a protostar forms. Wikipedia describes processes that occur as specific densities.
https://en.wikipedia.org/wiki/Star_formation#Protostar
However, the Wikipedia article gets less specific about just when the hydrogen begins to fuse — ignites — starting the process of radiation pressure stopping the inflow of matter and sweeping the immediate region of the star (matter seems to accumulate in farther regions where planets may to form).
My conclusion is that sometimes the fusion process is delayed and more matter is accumulated resulting in the more massive stars. Why fusion would be delayed is still a mystery to me.