APOD: Curly Spiral Galaxy M63 (2020 Dec 04)

[APOD Robot]

Curly Spiral Galaxy M63

Explanation: A bright spiral galaxy of the northern sky, Messier 63 is nearby, about 30 million light-years distant toward the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across, about the size of our own Milky Way. Its bright core and majestic spiral arms lend the galaxy its popular name, The Sunflower Galaxy, while this exceptionally deep exposure also follows faint, arcing star streams far into the galaxy's halo. Extending nearly 180,000 light-years from the galactic center the star streams are likely remnants of tidally disrupted satellites of M63. Other satellite galaxies of M63 can be spotted in this remarkable wide-field image, made with a small telescope, including five newly identified faint dwarf galaxies, which could contribute to M63's star streams in the next few billion years.

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[Ann]

M63 could be an unusually large spiral galaxy. On the other hand, it could be a rather small spiral galaxy.

The smallish starforming disk inside a much larger, disturbed, old star disk with pronounced tidal features, as well as the lack of a well-defined spiral structure in the inner part, suggests to me that this galaxy has undergone a collision and merger that partly wrecked its spiral structure, expelled much of its gas and created large tidal features, while at the same time made the galaxy larger and more massive. These factors suggest to me that M63 is a large galaxy.

On the other hand, M63 has a small inner bulge. That is not common or typical of large galaxies, although M101 might disagree. Also on the one hand (according to Wikipedia), M63 might not have a central black hole at all, but on the other hand, it may have a black hole whose mass is equal to 850 million solar masses! Compare that sort of black hole with the central black hole of the Milky Way, Sgr A*, which is believed to be only 4 million solar masses!

Similarly, according to Wikipedia, the distance to M63 might be some 29 million light-years, but it might also be some 15 million light-years! If M63 is located 29 million light-years away it's big, but if it's only 15 million light-years away it's small!

So is M63 a big or a small galaxy? I'll leave that for you to decide.

Ann

[mcfrank0]

I wonder what the night sky would look like from a position comporable to Earth's in this galaxy. Would the star streams be bright enough to appear as rivulets to its Milky Way?

[Coisius]

Cool. Thanks for the Thread

[sillyworm 2]

Loving this apod..esp with the negative view showing the sattelites.What is that odd faint ghostly galaxy slightly past 12:00? Could it be an additional sattelite?

[sillyworm 2]

There is actually speculation that a central black hole might not exist? How could that even be possible?

[neufer]

Messier 63 seen in infrared by the Spitzer Space Telescope.

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Spiral galaxy M63 (NGC 5055), by HST (450 & 814 nm).

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M63 from GALEX (ultraviolet) Sky Survey, Credit NASA / WikiSky

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[orin stepanek]

Unusual shape; but still a beautiful galaxy! Hard for me to picture
that it as large as our MW, but maybe that's because I can see the
vastness of the home galaxy in the night sky!

[johnnydeep]

Curly Spiral Galaxy M63

Explanation: A bright spiral galaxy of the northern sky, Messier 63 is nearby, about 30 million light-years distant toward the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across, about the size of our own Milky Way. Its bright core and majestic spiral arms lend the galaxy its popular name, The Sunflower Galaxy, while this exceptionally deep exposure also follows faint, arcing star streams far into the galaxy's halo. Extending nearly 180,000 light-years from the galactic center the star streams are likely remnants of tidally disrupted satellites of M63. Other satellite galaxies of M63 can be spotted in this remarkable wide-field image, made with a small telescope, including five newly identified faint dwarf galaxies, which could contribute to M63's star streams in the next few billion years.

A remarkable image! I'm simply astounded that this was taken with a mere 140 mm (5.5") telescope! It's Hubble-worthy to be sure. From the "remarkable wide field image" image link in the text, the scope is a TEC 140 APO. And from a review at https://avt-astro.com/reviews/telescope ... po-review/, apparently it's just about the best that money can buy:

I guess I just wanted to see what all the fuss is all about when you read on the internet astro forums regarding optics that are made to be about as perfect as possible. Would it be worth the ultra-high price? Well to scratch this itch I decided that I would buy an Astrophysics of TEC APO. These two brands of American made refractors are widely regarded as the best that money can buy. After some searching I pulled the trigger on a used TEC 140!

The TEC 140 is a 140mm(5.5”) APO that is made 100% in the state of Colorado by a team of gents that came from the former Soviet Union. The scope has a focal length of 980mm and weighs in at a very manageable 19lb. So what’s the verdict on the best optics that money can buy?

Elsewhere, the consensus on the quality of this scope is unanimously raving. And at around 7000 EU, the price isn't even that bad! Well, ok, maybe it is

[johnnydeep]

Loving this apod..esp with the negative view showing the sattelites.What is that odd faint ghostly galaxy slightly past 12:00? Could it be an additional sattelite?

I agree that the negative image is fascinating, but I marvel that anyone can pick out the satellite galaxies. Seems to me that plenty of other candidate "smudges" could just as well be satellite galaxies. I wonder how they determine which are the real ones? Here's the negative:

Sunflower Galaxy and Labelled Satellites - Negative

As for your "odd faint galaxy slightly past 12:00" I'm not sure what you are referring to. A pic with an arrow would help.

[Chris Peterson]

Loving this apod..esp with the negative view showing the sattelites.What is that odd faint ghostly galaxy slightly past 12:00? Could it be an additional sattelite?

I agree that the negative image is fascinating, but I marvel that anyone can pick out the satellite galaxies. Seems to me that plenty of other candidate "smudges" could just as well be satellite galaxies. I wonder how they determine which are the real ones? Here's the negative:

Satellite galaxies will have similar redshifts to the large galaxy. Small smudges that are not satellite galaxies are much more distant, and will therefore be more redshifted.

[johnnydeep]

Loving this apod..esp with the negative view showing the sattelites.What is that odd faint ghostly galaxy slightly past 12:00? Could it be an additional sattelite?

I agree that the negative image is fascinating, but I marvel that anyone can pick out the satellite galaxies. Seems to me that plenty of other candidate "smudges" could just as well be satellite galaxies. I wonder how they determine which are the real ones? Here's the negative:

Satellite galaxies will have similar redshifts to the large galaxy. Small smudges that are not satellite galaxies are much more distant, and will therefore be more redshifted.

So, are they able to get redshift measurements from all (or lots of) the smudges at once, or do they have to manually pick likely candidates and take separate measurements?

[Chris Peterson]

I agree that the negative image is fascinating, but I marvel that anyone can pick out the satellite galaxies. Seems to me that plenty of other candidate "smudges" could just as well be satellite galaxies. I wonder how they determine which are the real ones? Here's the negative:

Satellite galaxies will have similar redshifts to the large galaxy. Small smudges that are not satellite galaxies are much more distant, and will therefore be more redshifted.

So, are they able to get redshift measurements from all (or lots of) the smudges at once, or do they have to manually pick likely candidates and take separate measurements?

Depends on the instrument. There was an APOD a while back with the image from a multi-channel spectrometer that could simultaneously image dozens or hundreds of objects. Other instruments can only record from a single slit.

[VictorBorun]

There is actually speculation that a central black hole might not exist? How could that even be possible?

Well, are we really sure that there is a central BH in the Milky Way? The Event Horizon Telescope project tried to image it with few hours exposure and failed to get any crisp picture to publish (unlike M87*). What if there is really a binary BH system with an orbit's period of a few hours? A ternary system?
We know that statistically a large star or BH in a galaxy disk would drift toward the center after most encounters (and a smaller star would drift outward). But near the center the galactic gravitational pull is weak and the large stars or BHs there would be asymptomatically free, would not they?

[Chris Peterson]

There is actually speculation that a central black hole might not exist? How could that even be possible?

Well, are we really sure that there is a central BH in the Milky Way? The Event Horizon Telescope project tried to image it with few hours exposure and failed to get any crisp picture to publish (unlike M87*). What if there is really a binary BH system with an orbit's period of a few hours? A ternary system?
We know that statistically a large star or BH in a galaxy disk would drift toward the center after most encounters (and a smaller star would drift outward). But near the center the galactic gravitational pull is weak and the large stars or BHs there would be asymptomatically free, would not they?

We know that there is a central black hole in the Milky Way because it is the only explanation for the orbits of the stars at the very center.

There are a few galaxies that apparently lack central black holes. Why? Can't say for certain, because the role of central black holes and galaxy formation remains unclear. And it is possible that they simply lost them to a collision.

[VictorBorun]

We know that there is a central black hole in the Milky Way because it is the only explanation for the orbits of the stars at the very center.

Do those orbits prove that the central BH is not a binary system with a period of 10 hours, to ruin 5 hours exposure in 2017?
Do those orbits prove that the central BHs are not several with a distance of 100 ly between them — one of them radio-bright and becoming a focus of the astronomic attention?

[Chris Peterson]

We know that there is a central black hole in the Milky Way because it is the only explanation for the orbits of the stars at the very center.

Do those orbits prove that the central BH is not a binary system with a period of 10 hours, to ruin 5 hours exposure in 2017?
Do those orbits prove that the central BHs are not several with a distance of 100 ly between them — one of them radio-bright and becoming a focus of the astronomic attention?

The orbits are consistent with a point source central BH.

[neufer]

We know that there is a central black hole in the Milky Way because it is the only explanation for the orbits of the stars at the very center.

Do those orbits prove that the central BH is not a binary system with a period of 10 hours, to ruin 5 hours exposure in 2017?

Do those orbits prove that the central BHs are not several with a distance of 100 ly between them — one of them radio-bright and becoming a focus of the astronomic attention?

The orbits are consistent with a point source central BH.

Inferred orbits of 6 stars around supermassive black hole candidate Sagittarius A* at the Milky Way's center

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<<Observations of several stars orbiting Sagittarius A*, particularly star S2, have been used to determine the mass and upper limits on the radius of the object. Based on mass and increasingly precise radius limits, astronomers have concluded that Sagittarius A* is the Milky Way's central supermassive black hole. Reinhard Genzel and Andrea Ghez were awarded the 2020 Nobel Prize in Physics for their discovery that Sgr A* is a supermassive compact object, for which a black hole is the only currently known explanation.

There are a number of stars in close orbit around Sagittarius A*, which are collectively known as "S stars" in various catalogues. These stars are observed primarily in K band (an atmospheric transmission window centered on 2.2 μm) infrared wavelengths, as interstellar dust drastically limits visibility in visible wavelengths. This is a rapidly changing field—in 2011, the orbits of the most prominent stars then known were plotted in the diagram at right, showing a comparison between their orbits and various orbits in the solar system. Since then, S62 and then S4714 have been found to approach even more closely than those stars.

The high velocities and close approaches to the supermassive black hole makes these stars useful to establish limits on the physical dimensions of Sagittarius A*, as well as to observe general-relativity associated effects like periapse shift of their orbits. An active watch is maintained for the possibility of stars approaching the event horizon close enough to be disrupted, but none of these stars are expected to suffer that fate. The observed distribution of the planes of the orbits of the S stars limits the spin of Sagittarius A* to less than 10% of its theoretical maximum value.

As of 2020, S4714 is the current record holder of closest approach to Sagittarius A*, at about 12.6 AU, almost as close as Saturn gets to the Sun, traveling at about 8% of the speed of light. These figures given are approximate, the formal uncertainties being 12.6±9.3 AU and 23,928±8,840 km/s. Its orbital period is 12 years, but an extreme eccentricity of 0.985 gives it the close approach and high velocity.>>

[neufer]

Click to play embedded YouTube video.

This animation shows the orbits of the stars S29 and S55 as they move close to Sgr A* (centre), the supermassive black hole at the heart of the Milky Way. As we follow the stars along in their orbits, we see real images of the region obtained with the GRAVITY instrument on ESO’s Very Large Telescope Interferometer (VLTI) in March, May, June and July 2021. In addition to S29 and S55, the images also show two fainter stars, S62 and S300, the latter having only been discovered following these new VLTI observations.

<<They were able to determine the mass of the Sgr A* to be: 4.297 million solar masses (±0.25%) and the distance from the Earth to the center of the galaxy: 26,983 (±29) light years.>>

Inferred orbits of 6 stars around supermassive black hole candidate Sagittarius A* at the Milky Way's center

---

<<Observations of several stars orbiting Sagittarius A*, particularly star S2, have been used to determine the mass and upper limits on the radius of the object. Based on mass and increasingly precise radius limits, astronomers have concluded that Sagittarius A* is the Milky Way's central supermassive black hole. Reinhard Genzel and Andrea Ghez were awarded the 2020 Nobel Prize in Physics for their discovery that Sgr A* is a supermassive compact object, for which a black hole is the only currently known explanation.

There are a number of stars in close orbit around Sagittarius A*, which are collectively known as "S stars" in various catalogues. These stars are observed primarily in K band (an atmospheric transmission window centered on 2.2 μm) infrared wavelengths, as interstellar dust drastically limits visibility in visible wavelengths. This is a rapidly changing field—in 2011, the orbits of the most prominent stars then known were plotted in the diagram at right, showing a comparison between their orbits and various orbits in the solar system. Since then, S62 and then S4714 have been found to approach even more closely than those stars.

The high velocities and close approaches to the supermassive black hole makes these stars useful to establish limits on the physical dimensions of Sagittarius A*, as well as to observe general-relativity associated effects like periapse shift of their orbits. An active watch is maintained for the possibility of stars approaching the event horizon close enough to be disrupted, but none of these stars are expected to suffer that fate. The observed distribution of the planes of the orbits of the S stars limits the spin of Sagittarius A* to less than 10% of its theoretical maximum value.

As of 2020, S4714 is the current record holder of closest approach to Sagittarius A*, at about 12.6 AU, almost as close as Saturn gets to the Sun, traveling at about 8% of the speed of light. These figures given are approximate, the formal uncertainties being 12.6±9.3 AU and 23,928±8,840 km/s. Its orbital period is 12 years, but an extreme eccentricity of 0.985 gives it the close approach and high velocity.>>