Starship Asterisk*

M63: The Sunflower Galaxy from Hubble

Explanation: One of the bright spiral galaxies visible in the north sky is M63, the Sunflower Galaxy. M63, also catalogued as NGC 5055, can be found with a small telescope toward the constellation of Hunting Dogs (Canes Venatici). The featured picture from the Hubble Space Telescope exhibits the center of M63, complete with long winding spiral arms glowing blue from a few bright young stars, emission nebulae glowing red from hot ionized hydrogen gas, and dark dust in numerous filaments. M63 interacts gravitationally with M51 (the Whirlpool Galaxy) and several smaller galaxies. Light takes about 35 million years to reach us from M63, and about 60,000 years to cross the spiral galaxy. Stars in the outer regions of the Sunflower Galaxy rotate about the center at a speed so high that, given the matter seen and assuming normal gravity, they should fly off into space. The fact that the stars remain indicates the presence of sort of invisible, gravitationally-binding, dark matter.

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"All right Mr. DeMille, I'm ready for my close-up," Norma Desmond... Sunset Blvd. 1950...

And so too was M63, it would seem...

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Funny how the explanation explicitly mentions dark matter, with the recent headline news of challenging ideas on gravity, without the need for dark matter, by professor Erik Verlinde.

Case wrote:Funny how the explanation explicitly mentions dark matter, with the recent headline news of challenging ideas on gravity, without the need for dark matter, by professor Erik Verlinde.

Yeah, because dark matter is the overwhelmingly more likely explanation, the one accepted by mainstream physics. The new idea doesn't even warrant a mention in the caption of an image in a forum like this. It has a long way to go to demonstrate itself as a reasonable theory worth taking seriously.

I recall recently seeing an image similar to this, but showing the Milky Way and having an arrow pointing to the place of our solar system in the galaxy. Not sure if it was an APOD or other. Have searched the APOD archive for it, but thus far without success. If anyone can provide a link to this image I'd be deeply grateful. Thanks.

A google search for "you are here galaxy" will get a huge pile of images for you. From there you should be able to find the specific variant you're looking for.

smitty wrote:I recall recently seeing an image similar to this, but showing the Milky Way and having an arrow pointing to the place of our solar system in the galaxy. Not sure if it was an APOD or other. Have searched the APOD archive for it, but thus far without success. If anyone can provide a link to this image I'd be deeply grateful. Thanks.

Possibly one of the images in a search result elsewhere.
https://www.google.com/search?q=earth+l ... Gu8bmMM%3A

smitty wrote:I recall recently seeing an image similar to this, but showing the Milky Way and having an arrow pointing to the place of our solar system in the galaxy. Not sure if it was an APOD or other. Have searched the APOD archive for it, but thus far without success. If anyone can provide a link to this image I'd be deeply grateful. Thanks.

Perhaps it was yesterday's A.P.O.D. for the good people living on a planet in the outskirts of M63.
(Sorry, I don't have an answer that is actually helpful. )

Are the bright blue knots of light star clusters? They seem much too bright and resolved to be individual stars. Or are they also nebulae like the red knots?

SeedsofEarth wrote:Are the bright blue knots of light star clusters? They seem much too bright and resolved to be individual stars. Or are they also nebulae like the red knots?

They're stars. Some could be individual stars, but it's likely that many are multi-star systems and clusters, just as they are in our own Milky Way.

I'm with Case on this one. I've noted for many years how so much of the astronomical community speak of "dark matter" (what I call "fantasy matter") as though it were some sort of proven theory of gravity. This without it being directly detected, in spite of many years of attempts using ingenious experiments by brilliant astronomers. It's a genuine theory in the scientific sense, yet until someone detects the stuff it's a theory still in the hypothesis stage. Until we resolve this, other theories at the same stage ought occasionally to be acknowledged. Such as MOND, which has been around for decades.
This issue seems rather like the 19th century belief in "luminiferous aether" (also completely undetectable by any test) to explain how light waves could move through a matterless vacuum. Significantly, that was resolved by revolutionary new equations from Einstein, not by some mysterious, undetectable "aether" that permeated space. I've an uneasy suspicion that fifty years from now people will snicker behind their hands when someone mentions "dark matter", just as they did through most of the 20th century when someone mentioned the old "aether".

geckzilla wrote:

smitty wrote:I recall recently seeing an image similar to this, but showing the Milky Way and having an arrow pointing to the place of our solar system in the galaxy. Not sure if it was an APOD or other. Have searched the APOD archive for it, but thus far without success. If anyone can provide a link to this image I'd be deeply grateful. Thanks.

Possibly one of the images in a search result elsewhere.
https://www.google.com/search?q=earth+l ... Gu8bmMM%3A

Yes, thank you! A useful bit of perspective as we consider current events.

Reminder: It's ok to present your opinion that maybe our current theories have something wrong, maybe dark matter is wrong, etc. What is not ok is to present your opinion as if it is a fact or somehow better than established mainstream science. I have and will continue to ban guests and nascent users who come forth with their own personal theories especially if they include broad and flippant dismissal of mainstream science.

It will never be anyone's job at Asterisk to vet the bleeding edge of science, much less any random visitor's own personal ideas. See the rules.

MuluTrail wrote:I'm with Case on this one. I've noted for many years how so much of the astronomical community speak of "dark matter" (what I call "fantasy matter") as though it were some sort of proven theory of gravity. This without it being directly detected, in spite of many years of attempts using ingenious experiments by brilliant astronomers. It's a genuine theory in the scientific sense, yet until someone detects the stuff it's a theory still in the hypothesis stage. Until we resolve this, other theories at the same stage ought occasionally to be acknowledged. Such as MOND, which has been around for decades.

What astronomers observe is that the behaviour of visible matter is not described by our known laws of gravity and visible matter alone. This means that either a) our theory of gravity (general relativity) is incomplete b) there exists other type of invisible matter, called dark matter or c) a combination of a&b. Many physicist work on option a. MOND is one of such theories and has problems describing observations. The APOD caption does acknowledge this discussion with the assuming normal gravity link, so need to complain. However, option b) is the one that best describes a multitude of observations, with the least amount of unknown parameters. The exact nature of dark matter still alludes us and that is why many experiments search for it and theories try to describe it. The issue is far from being settled.

While the theory of dark matter may not as of yet have been proven, I believe there is enough extenuating evidence to support such a theory. Take for instance gravitational lensing. The fact that there are images in the archives of galaxies stretched into a circular or arc-like pattern by the powerful gravitational forces of something intervening between the "stretched" galaxy and our point of observation indicates incontrovertibly that something is causing this anomaly, and the only force we are aware of that can do this is gravity, and gravity only manifests itself in the presence of mass. Since we cannot see that mysterious mass, it is deemed to be invisible, or “dark” meaning that it does not interact with photons (does not reflect them), but it does influence them by deflecting them, meaning that it has mass. What we see is the deflected light, bent around the invisible mass, or dark matter. I stand with you, Geckzilla on this. I find the idea of dark matter to be an intriguing and challengin one, like its sibling dark energy. I am glad scinetists are persuing this theory, and until something better comes along, we must continue to try and understand it.

As ever, xkcd manages to put it succinctly and with the benefit of humor.

Yes, everybody has already had the idea, "Maybe there's no dark matter—Gravity just works differently on large scales!" It sounds good but doesn't really fit the data.

geckzilla wrote:

SeedsofEarth wrote:Are the bright blue knots of light star clusters? They seem much too bright and resolved to be individual stars. Or are they also nebulae like the red knots?

They're stars. Some could be individual stars, but it's likely that many are multi-star systems and clusters, just as they are in our own Milky Way.

I always imagined that in distant galaxies the stars appear in the photos more like a luminous fog. I assumed that the bright spots in those galaxies were always clusters of stars, even in the most detailed (Hubble) photos. Have I guessed wrong about that?

EArHog wrote:I always imagined that in distant galaxies the stars appear in the photos more like a luminous fog. I assumed that the bright spots in those galaxies were always clusters of stars, even in the most detailed (Hubble) photos. Have I guessed wrong about that?

Even amateur images made from the ground with small telescopes resolve some stars in other galaxies. Large telescopes and space-based ones resolve large numbers.