Starship Asterisk*

ShaileshS wrote:Is this galaxy rotating clockwise or counter clockwise ? I read that scientist expect half the galaxies to be of each type but are there any signs or indications based on observations and studies done of so many galaxies by which we can say if this is spinning one way or the other ? Thanks in advance to all who respond.

ShaileshS wrote:Most visualizations I have seen of event horizon, the matter is collapsing in in the black hole and that would make sense when the galaxies are spinning in (counter clockwise, arms rotating inwards towards the black hole). But if half the galaxies are expected/assumed to be rotating out (spinning arms going out as if thrown away from the black hole) then in that case, since spinning is happening away from the black hole, there won't be any matter falling in the block hole and if so, it may starve resulting in <???> ?

Chris Peterson wrote:

ShaileshS wrote:Most visualizations I have seen of event horizon, the matter is collapsing in in the black hole and that would make sense when the galaxies are spinning in (counter clockwise, arms rotating inwards towards the black hole). But if half the galaxies are expected/assumed to be rotating out (spinning arms going out as if thrown away from the black hole) then in that case, since spinning is happening away from the black hole, there won't be any matter falling in the block hole and if so, it may starve resulting in <???> ?

The black hole in the center of most galaxies has almost no impact on the galaxies, nor do most receive much matter from their galaxies (except for active galaxies, which are in a transient phase). Nothing you see in a spiral galaxy is moving either inward or outward. The stars are in substantially circular orbits, and nothing would change if their central black holes disappeared.

As NGC 6814 is a very active galaxy, many regions of ionized gas are studded along its spiral arms.

In these large clouds of gas, a burst of star formation has recently taken place, forging the brilliant blue stars that are visible scattered throughout the galaxy.

https://en.wikipedia.org/wiki/Spiral_galaxy#Alignment_of_spin_axis_with_cosmic_voids wrote:
<<Recent results suggest that the orientation of the spin axis of spiral galaxies is not a chance result, but instead they are preferentially aligned along the surface of cosmic voids. That is, spiral galaxies tend to be oriented at a high angle of inclination relative to the large-scale structure of the surroundings. They have been described as lining up like "beads on a string," with their axis of rotation following the filaments around the edges of the voids.>>

https://en.wikipedia.org/wiki/Void_(astronomy) wrote:

[b][color=#0000FF]Matter distribution in a cubic section of the Universe. The blue fiber structures represent the matter (primarily dark matter) and the empty regions in between represent the cosmic voids.[/color][/b]

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<<Cosmic voids are the vast empty spaces between filaments (the largest-scale structures in the Universe), which contain very few or no galaxies. Voids typically have a diameter of 10 to 100 megaparsecs; particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids. They have less than one-tenth of the average density of matter abundance that is considered typical for the observable Universe.

Voids are believed to have been formed by baryon acoustic oscillations in the Big Bang, collapses of mass followed by implosions of the compressed baryonic matter. Starting from initially small anisotropies from quantum fluctuations in the early Universe, the anisotropies grew larger in scale over time. Regions of higher density collapsed more rapidly under gravity, eventually resulting in the large-scale, foam-like structure or “cosmic web” of voids and galaxy filaments seen today. Voids located in high-density environments are smaller than voids situated in low-density spaces of the universe.

Voids appear to correlate with the observed temperature of the cosmic microwave background (CMB) because of the Sachs–Wolfe effect. Colder regions correlate with voids and hotter regions correlate with filaments because of gravitational redshifting. As the Sachs–Wolfe effect is only significant if the Universe is dominated by radiation or dark energy, the existence of voids is significant in providing physical evidence for dark energy.>>

Dad is watching wrote:
In a spiral galaxy, to be actually considered an 'arm', how far around the galaxy does a trail of stars and matter have to extend?

https://en.wikipedia.org/wiki/Orion_Arm wrote:

[b][color=#0000FF]Observed (normal lines) and extrapolated (dotted lines) structure of the spiral arms. The gray lines radiating from the Sun's position (upper center) list the three-letter abbreviations of the corresponding constellations.[/color][/b]

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<<The Orion Arm is a minor spiral arm of the Milky Way some 3,500 light-years across and approximately 10,000 light-years in length. The Solar System, including the Earth, lies within the Orion Arm. It is also referred to by its full name, the Orion–Cygnus Arm, as well as Local Arm, Orion Bridge, Local Spur and Orion Spur.

The Orion Arm is named for the Orion constellation, which is one of the most prominent constellations of Northern Hemisphere winter (Southern Hemisphere summer). Some of the brightest stars and most famous celestial objects of this constellation (Betelgeuse, Rigel, the stars of Orion's Belt, the Orion Nebula) are located within the Orion Arm, as shown on the interactive map below.

The Orion Arm is located between the Carina–Sagittarius Arm (toward the Galactic Center) and the Perseus Arm (toward the outside Universe), the latter one of the two major arms of the Milky Way. Long thought to be a minor structure, a "spur" between the two longer adjacent arms Perseus and Carina-Sagittarius, evidence was presented in mid 2013 that it might be a branch of the Perseus Arm, or possibly an independent arm segment itself.

Within the Orion Arm, the Solar System, including Earth, is located close to the inner rim in the Local Bubble, about halfway along the Orion Arm's length, approximately 8,000 parsecs (26,000 light-years) from the Galactic Center.>>

Dad is watching wrote:In a spiral galaxy, to be actually considered an 'arm', how far around the galaxy does a trail of stars and matter have to extend?

nycpaull wrote:Is there an animation that would simulate/demonstrate the full life of a galaxy from formation to end? Would a possible end of a galaxy look like water flowing down a drain as its black hole devours it?

Ann wrote:

Dad is watching wrote:In a spiral galaxy, to be actually considered an 'arm', how far around the galaxy does a trail of stars and matter have to extend?

Click to view full size image

NGC 2857. Photo:
European Southern Observatory - NASA/IPAC Extragalactic Database

Click to view full size image

NGC 7793. Photo: Josef Pöpsel.

Ann, I am thinking with NGC 7793, there were many, many, many, small mergers... and it is still in a state of "settling"....

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NGC 2857 has fantastically long arms that extend more than 360^o around the galaxy's center. NGC 2857 is a perfect example of a grand design galaxy with two long elegant arms.

But what about NGC 7793? Its disk appears to be "exploding" with short arms in all directions. Is NGC 7793 a spiral galaxy? Yes, it is classified as an Sd galaxy, the loosest of all spiral galaxies. Are those things arm? I guess they are.

Ann

Fred the Cat wrote:Is the name for such a galaxy a euphemism? Grand design is a philosophically loaded gun. Taken individually the words might portray an impressive structure but put together their meaning has been very divisive. Hawking and Mlodinow attempt to use their similarly-titled book to take us through the history of scientific learning into a universe of 10 dimensions and M-theory. The "grand" part is obvious but the "design" part of the name implies much more. :?

Chris Peterson wrote:

Fred the Cat wrote:Is the name for such a galaxy a euphemism? Grand design is a philosophically loaded gun. Taken individually the words might portray an impressive structure but put together their meaning has been very divisive. Hawking and Mlodinow attempt to use their similarly-titled book to take us through the history of scientific learning into a universe of 10 dimensions and M-theory. The "grand" part is obvious but the "design" part of the name implies much more.

You can have a design without a designer.

Chris Peterson wrote:

ShaileshS wrote:Is this galaxy rotating clockwise or counter clockwise ? I read that scientist expect half the galaxies to be of each type but are there any signs or indications based on observations and studies done of so many galaxies by which we can say if this is spinning one way or the other ? Thanks in advance to all who respond.

Nearly all spiral galaxies rotate such that their arms are trailing. A few appear to rotate with their arms leading- probably because of past interactions with other galaxies. Of course, "clockwise" and "counterclockwise" are meaningless in any absolute sense. But from our perspective, we see galaxies rotating both directions, with close to a 50/50 split, as would be expected. However, a large survey a few years back suggested that their might be a small imbalance. If so, the cause remains uncertain. This one, from our perspective and in the coordinate frame of the image is likely rotating counterclockwise.

geckzilla wrote:

Chris Peterson wrote:

Fred the Cat wrote:Is the name for such a galaxy a euphemism? Grand design is a philosophically loaded gun. Taken individually the words might portray an impressive structure but put together their meaning has been very divisive. Hawking and Mlodinow attempt to use their similarly-titled book to take us through the history of scientific learning into a universe of 10 dimensions and M-theory. The "grand" part is obvious but the "design" part of the name implies much more.

You can have a design without a designer.

Especially when you've got a brain capable of seeing designs in purely random data, much less something with structure formed through physical interactions.

Evermore wrote:

geckzilla wrote:

Chris Peterson wrote: You can have a design without a designer.

Especially when you've got a brain capable of seeing designs in purely random data, much less something with structure formed through physical interactions.

Then why do newborn mamals, without any previous instruction or patterning, automatically seek out the nipple?