Starship Asterisk*

starsurfer wrote:
Your post reminds me of the galaxy UGC 1382. Did you know there is a Malin 2?

NASA wrote:

A new study to be published in the Astrophysical Journal reveals the secret of UGC 1382, a galaxy that had originally been thought to be old, small and typical. Instead, scientists using data from NASA telescopes and other observatories have discovered that the galaxy is 10 times bigger than previously thought and, unlike most galaxies, its insides are younger than its outsides, almost as if it had been built using spare parts.

"This rare, 'Frankenstein' galaxy formed and is able to survive because it lies in a quiet little suburban neighborhood of the universe, where none of the hubbub of the more crowded parts can bother it," said study co-author Mark Seibert of the Observatories of the Carnegie Institution for Science, Pasadena, California. "It is so delicate that a slight nudge from a neighbor would cause it to disintegrate."

Ann wrote:

neufer wrote:

• M101 has a disk mass on the order of 100 billion solar mass.
  
  That clearly excludes dark matter mass and other components.
  
  (M101 also has over twice the number of stars as the Milky Way.)

I've tried and tried to confirm your claim that M101 has over twice the number of stars as the Milky Way. The claim that M101 has a trillion stars, 10¹² comes from Wikipedia. But Wikipedia itself doesn't provide a link to its claim.

But I decided to try to find out how many stars there are in Malin 1, a tremendously huge low-mass surface brightness galaxy. That, too, provided extremely frustrating. Nevertheless, I did find this:

Click to view full size image

Malin 1. Galaz et al., 2016/NASA/JPL-Caltech

Ken Croswell wrote:

Discovered in 1986, Malin 1 is the largest spiral galaxy known. Its spiral disk is 650,000 light-years across--several times bigger than the Milky Way's--but the stars are so spread out from one another that the disk looks extremely diffuse, having what astronomers call a low surface brightness.
...
Despite its diffuse light, Malin 1 emits eight times more light than the entire Milky Way, which is itself a giant galaxy. Furthermore, Malin 1 abounds with gas, containing 50 billion solar masses of atomic hydrogen gas--more than ten times the amount in the Milky Way.
...
Within 30,000 light-years of Malin 1's center lies a normal barred spiral galaxy having a Hubble type of SB0 or SBa. The galaxy's central bulge is 10,000 light-years across, and its bar is 30,000 light-years long. The disk is smooth with no signs of dust lanes or star-forming regions.
...
(Aaron) Barth calculates that 80 percent of Malin 1's light comes from that extended disk, not from the normal disk he has discovered.

According to Wikipedia, which links to Barth, Aaron J. (March 2007). "A Normal Stellar Disk in the Galaxy Malin 1". The Astronomical Journal. 133 (3): 1085–1091. arXiv:astro-ph/0701018], Malin 1 has a mass of about 10¹² solar masses. That would be about ten times more than the disk mass of M101, according to https://en.wikipedia.org/wiki/Pinwheel_ ... 01_mass-11] and Comte, G.; Monnet, G. & Rosado, M. (1979). "An optical study of the galaxy M 101 - Derivation of a mass model from the kinematic of the gas". Astronomy and Astrophysics. 72: 73–81.

Okay, let's see now. Malin 1 emits eight times more light than the Milky Way - doesn't that mean that it must contain many more stars than Milky Way? Alternatively, it might mean that the individual stars of Malin 1 are, on average, brighter than the stars of the Milky Way. Okay, that's possible:

S. Boissier et al. wrote:
Based on our model, the extreme disk of Malin 1 is found to have a long history of relatively low star formation (about 2 M_⊙ yr−1).

The star formation rate of the Milky Way is believed to be about 1 M_⊙ yr−1, so Malin 1 would convert twice as much gas into stars as the Milky Way during a given year. This higher rate of star formation in Malin 1 would also produce a larger number of high-mass and therefore more luminous stars. As for M101, it has definitely produced a terrific number of high-mass stars!

Let's assume that the number of stars of Malin 1 is either somewhat similar to the number of stars in the Milky Way, or somewhat higher, perhaps double that of the Milky Way. But Malin 1 has ten times more gas than the Milky Way. Of course, Malin 1 is definitely more massive than the Milky Way, too, perhaps twice as massive. To me, it's hard to believe that Malin 1 doesn't contain a lot of dark matter, too. Or perhaps it doesn't? Could it be that Malin 1 has formed out of a huge blob of gas that has somehow "come loose" from its dark matter moorings. So perhaps the Milky Way contains more dark matter than Malin 1 - and perhaps more dark matter than M101, too?

Questions, questions. I will stop discussing the mass and the number of stars of M101, Malin 1 and the Milky Way now!

Ann

neufer wrote:

• M101 has a disk mass on the order of 100 billion solar mass.
  
  That clearly excludes dark matter mass and other components.
  
  (M101 also has over twice the number of stars as the Milky Way.)

Ken Croswell wrote:

Discovered in 1986, Malin 1 is the largest spiral galaxy known. Its spiral disk is 650,000 light-years across--several times bigger than the Milky Way's--but the stars are so spread out from one another that the disk looks extremely diffuse, having what astronomers call a low surface brightness.
...
Despite its diffuse light, Malin 1 emits eight times more light than the entire Milky Way, which is itself a giant galaxy. Furthermore, Malin 1 abounds with gas, containing 50 billion solar masses of atomic hydrogen gas--more than ten times the amount in the Milky Way.
...
Within 30,000 light-years of Malin 1's center lies a normal barred spiral galaxy having a Hubble type of SB0 or SBa. The galaxy's central bulge is 10,000 light-years across, and its bar is 30,000 light-years long. The disk is smooth with no signs of dust lanes or star-forming regions.
...
(Aaron) Barth calculates that 80 percent of Malin 1's light comes from that extended disk, not from the normal disk he has discovered.

S. Boissier et al. wrote:
Based on our model, the extreme disk of Malin 1 is found to have a long history of relatively low star formation (about 2 M_⊙ yr−1).

APOD Robot wrote: A View Toward M101
About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way galaxy.

Deborah Byrd of Earthsky wrote:
Astronomers have peered into eight relatively nearby elliptical galaxies and made a discovery suggesting that small, dim red dwarf stars in these sorts of galaxies might be 20 times more plentiful than in our spiral-shaped Milky Way galaxy.
...
Until now, astronomers hadn’t been able to detect them in galaxies other than our own Milky Way and its nearest neighbors. Astronomers have used powerful instruments on the Keck Observatory in Hawaii to detect the faint signature of red dwarfs in eight massive, relatively nearby galaxies called elliptical galaxies, which are located between about 50 million and 300 million light-years away. They discovered that the red dwarfs, which are only between 10 and 20 percent as massive as the sun, were much more bountiful than expected.
...
The team discovered that there are about 20 times more red dwarfs in elliptical galaxies than in the Milky Way, said Charlie Conroy of the Harvard-Smithsonian Center for Astrophysics, who was also involved in the research.

neufer wrote:
(M101 also has over twice the number of stars as the Milky Way.)

Ann wrote:

Wikipedia wrote about M101:
M101 is a large galaxy comparable in size to the Milky Way. With a diameter of 170,000 light-years it is roughly equal the size of the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.

Well, I thought the diameter of the Milky Way was considered to be "only" about 100,000 light-years. On the other hand, the Milky Way may well be more massive than the Pinwheel galaxy.

https://en.wikipedia.org/wiki/Milky_Way wrote:
<<The Milky Way is the second-largest galaxy in the Local Group, with its stellar disk approximately 100,000 ly in diameter, and, on average, approximately 1,000 ly thick. A ring-like filament of stars wrapping around the Milky Way may belong to the Milky Way itself, rippling above and below the relatively flat galactic plane. If so, that would mean a diameter of 150,000–180,000 light-years.

Estimates of the mass of the Milky Way vary, depending upon the method and data used. At the low end of the estimate range, the mass of the Milky Way is 5.8×10¹¹ solar masses (M_☉), somewhat less than that of the Andromeda Galaxy.>>

Ann wrote:
I think 5.8×10¹¹ is equal to 560 [sic] billion solar masses, which suggests that the Milky Way is 5.6 times more massive than M101.

• M101 has a disk mass on the order of 100 billion solar mass.
  
  That clearly excludes dark matter mass and other components.
  
  (M101 also has over twice the number of stars as the Milky Way.)

Wikipedia wrote about M101:
M101 is a large galaxy comparable in size to the Milky Way. With a diameter of 170,000 light-years it is roughly equal the size of the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.

Wikipedia wrote about the Milky Way:
The Milky Way is the second-largest galaxy in the Local Group, with its stellar disk approximately 100,000 ly (30 kpc) in diameter, and, on average, approximately 1,000 ly (0.3 kpc) thick.
...
Estimates of the mass of the Milky Way vary, depending upon the method and data used. At the low end of the estimate range, the mass of the Milky Way is 5.8×10¹¹ solar masses (M_☉), somewhat less than that of the Andromeda Galaxy.

JohnNoe wrote:Bad link to Leviathan (telescope) in latest APOD.