ScottH
May 18th, 2025, 08:58 PM
Malin 1 / VPC 1091 / LEDA 42102
Coma Berenices
Giant Low Surface Brightness Galaxy
RA 12:36:59.3
DEC 14:19:49
Vmag: 16.9
Size 2’
Dist 1.23 billion light-years
In February of 1987, authors Gregory Bothun, Christopher Impey, David Malin, and Jeremy Mould submitted a paper to the Astronomical Journal titled “Discovery of a Huge Low-Surface-Brightness Galaxy: A Protodisk Galaxy at Low Redshift?” [1] A year before, they had been performing a “large, systematic survey designed to detect and measure extremely low-surface-brightness galaxies” in several of the closest known galaxy clusters when they found something peculiar in the region of the Virgo I Cluster. It was a low-surface-brightness (LSB) galaxy that showed conspicuous nucleation and hints of spiral structure. During their subsequent study of it, the authors christened it Malin 1 out of respect and reverence for their coauthor David Malin (1941-).
Follow-up spectroscopy was quickly performed on Malin 1 using the 200-inch on Mount Palomar. It revealed an emission-line from the nucleus…which is more common in distant, compact galaxies (like Markarian Galaxies). The question now was this: Had they simply found a LSB dwarf in the Virgo I Cluster that was accidentally aligned with a background emission-line galaxy? Or was it a first-of-its kind giant LSB spiral with an emission-line nucleus? The authors felt the latter “seemed too preposterous” from the early spectroscopy and would have to wait until the galaxy(s) rose again in the morning sky to get better spectra.
5711
Legacy Sky Survey image with Malin 1 near center and NGC 4571 at the bottom of the field
While they waited, the authors started searching the area with the Arecibo Observatory in October of 1986. They could do this because the Virgo Cluster was highest at noon and radio astronomy is unaffected by the Sun as long as it’s not in the immediate field. They were looking for the 21cm line of neutral hydrogen emission from the galaxy and only found it at a velocity of 25,000 km s-1. This was much, much higher than they expected since galaxies at this velocity in the Virgo Supercluster was somewhat unprecedented at the time. They then felt that the galaxy might be located in the low-density outskirts of the supercluster and have a disk over 350,000 light-years across.
The discovery of such a large, LSB spiral made the authors realize that it’s “likely that the brightness of the night sky really does shroud our understanding of galaxy populations with low central surface brightness and large disks.” They calculated that if Malin 1 was located in the Virgo I Cluster, it might be difficult to recognize with only the bulge component appearing as a prominent 12th-magnitude elliptical galaxy 2’-across. Meanwhile, the disk would be spread over a degree of the sky and “any individual H II regions might appear as unresolved, faint, blue objects.”
In a 1989 followup paper titled “Malin 1: A Quiescent Disk Galaxy” [2], Impey and Bothun argued that Malin 1 “is an example of…a quiescent or non-evolved galaxy.” Later, in a 1997 paper by Pickering et al. [3], it was found that Malin 1 and several other LSB galaxies have a slowly rising rotation curve, which suggests that their kinematics are dominated by their dark matter halos. They also found that its disk has a reservoir of about 60 billion solar masses of neutral hydrogen while later studies confirmed this and found no direct evidence of molecular gas [4].
5712
From Galaz et al. (2016)
Today Malin 1 is believed to lie about 1.2 billion light-years away and have a disk that spans over half a million light-years — making it perhaps the largest disk galaxy known [5]. It’s been found to have a long history of relatively low star formation and few if any post interactions with other galaxies [6]. Plus, recently, emission lines have been detected in numerous regions along the galaxy’s extended disk, indicating that recent star formation is ongoing in those regions [5].
To see this giant (5x the Milky Way's diameter), nearly face-on LSB for yourself, you’ll have to peer through the Virgo I Cluster. On Interstellarum Deep Sky Atlas chart D2, you’ll find it plotted as an ‘X’ just 24.6’ east-southeast of Messier 91. But after finding M91, it’s best if you look for 8.5-magnitude star BD+15 2483 as it lies just 4.7’ southeast of Malin 1. You’ll know you find that star when you see the 11th-magnitude galaxy NGC 4571 next to it.
At this year’s Texas Star Party, Larry Mitchell was kind enough to let me chase it down using his 20-inch f/5 Dobsonian. At just 254x, I was happy to find the nucleus of this monster spiral was visible as a faint little smudge. I know that Larry, Brent Archinal, and possibly even Stephen James O’Meara tried to see it after I triumphantly stepped down off the ladder. But I only remember hearing Larry say that he was able to make it out after I’d gone back to my telescope. So, from my (limited) observations, I’d wager that it would yield to telescopes in the 14—16-inch range at an ideal location with excellent sky conditions. I know I’ve tried with my 16-inch and haven’t yet had success.
As always, “Give it a Go and Let us Know!”
Bibliography
[1] Bothun et al 1987 (https://ui.adsabs.harvard.edu/abs/1987AJ.....94...23B/abstract)
[2] Impey & Bothun 1989 (https://ui.adsabs.harvard.edu/abs/1989ApJ...341...89I/abstract)
[3] Pickering et al 1997 (https://ui.adsabs.harvard.edu/abs/1997AJ....114.1858P/abstract)
[4] Johnston et al 2024 (https://ui.adsabs.harvard.edu/abs/2024A%26A...686A.247J/abstract)
[5] Junais et al 2024 (https://ui.adsabs.harvard.edu/abs/2024A%26A...681A.100J/abstract)
[6] Boissier et al 2016 (https://ui.adsabs.harvard.edu/abs/2016A%26A...593A.126B/abstract)
Coma Berenices
Giant Low Surface Brightness Galaxy
RA 12:36:59.3
DEC 14:19:49
Vmag: 16.9
Size 2’
Dist 1.23 billion light-years
In February of 1987, authors Gregory Bothun, Christopher Impey, David Malin, and Jeremy Mould submitted a paper to the Astronomical Journal titled “Discovery of a Huge Low-Surface-Brightness Galaxy: A Protodisk Galaxy at Low Redshift?” [1] A year before, they had been performing a “large, systematic survey designed to detect and measure extremely low-surface-brightness galaxies” in several of the closest known galaxy clusters when they found something peculiar in the region of the Virgo I Cluster. It was a low-surface-brightness (LSB) galaxy that showed conspicuous nucleation and hints of spiral structure. During their subsequent study of it, the authors christened it Malin 1 out of respect and reverence for their coauthor David Malin (1941-).
Follow-up spectroscopy was quickly performed on Malin 1 using the 200-inch on Mount Palomar. It revealed an emission-line from the nucleus…which is more common in distant, compact galaxies (like Markarian Galaxies). The question now was this: Had they simply found a LSB dwarf in the Virgo I Cluster that was accidentally aligned with a background emission-line galaxy? Or was it a first-of-its kind giant LSB spiral with an emission-line nucleus? The authors felt the latter “seemed too preposterous” from the early spectroscopy and would have to wait until the galaxy(s) rose again in the morning sky to get better spectra.
5711
Legacy Sky Survey image with Malin 1 near center and NGC 4571 at the bottom of the field
While they waited, the authors started searching the area with the Arecibo Observatory in October of 1986. They could do this because the Virgo Cluster was highest at noon and radio astronomy is unaffected by the Sun as long as it’s not in the immediate field. They were looking for the 21cm line of neutral hydrogen emission from the galaxy and only found it at a velocity of 25,000 km s-1. This was much, much higher than they expected since galaxies at this velocity in the Virgo Supercluster was somewhat unprecedented at the time. They then felt that the galaxy might be located in the low-density outskirts of the supercluster and have a disk over 350,000 light-years across.
The discovery of such a large, LSB spiral made the authors realize that it’s “likely that the brightness of the night sky really does shroud our understanding of galaxy populations with low central surface brightness and large disks.” They calculated that if Malin 1 was located in the Virgo I Cluster, it might be difficult to recognize with only the bulge component appearing as a prominent 12th-magnitude elliptical galaxy 2’-across. Meanwhile, the disk would be spread over a degree of the sky and “any individual H II regions might appear as unresolved, faint, blue objects.”
In a 1989 followup paper titled “Malin 1: A Quiescent Disk Galaxy” [2], Impey and Bothun argued that Malin 1 “is an example of…a quiescent or non-evolved galaxy.” Later, in a 1997 paper by Pickering et al. [3], it was found that Malin 1 and several other LSB galaxies have a slowly rising rotation curve, which suggests that their kinematics are dominated by their dark matter halos. They also found that its disk has a reservoir of about 60 billion solar masses of neutral hydrogen while later studies confirmed this and found no direct evidence of molecular gas [4].
5712
From Galaz et al. (2016)
Today Malin 1 is believed to lie about 1.2 billion light-years away and have a disk that spans over half a million light-years — making it perhaps the largest disk galaxy known [5]. It’s been found to have a long history of relatively low star formation and few if any post interactions with other galaxies [6]. Plus, recently, emission lines have been detected in numerous regions along the galaxy’s extended disk, indicating that recent star formation is ongoing in those regions [5].
To see this giant (5x the Milky Way's diameter), nearly face-on LSB for yourself, you’ll have to peer through the Virgo I Cluster. On Interstellarum Deep Sky Atlas chart D2, you’ll find it plotted as an ‘X’ just 24.6’ east-southeast of Messier 91. But after finding M91, it’s best if you look for 8.5-magnitude star BD+15 2483 as it lies just 4.7’ southeast of Malin 1. You’ll know you find that star when you see the 11th-magnitude galaxy NGC 4571 next to it.
At this year’s Texas Star Party, Larry Mitchell was kind enough to let me chase it down using his 20-inch f/5 Dobsonian. At just 254x, I was happy to find the nucleus of this monster spiral was visible as a faint little smudge. I know that Larry, Brent Archinal, and possibly even Stephen James O’Meara tried to see it after I triumphantly stepped down off the ladder. But I only remember hearing Larry say that he was able to make it out after I’d gone back to my telescope. So, from my (limited) observations, I’d wager that it would yield to telescopes in the 14—16-inch range at an ideal location with excellent sky conditions. I know I’ve tried with my 16-inch and haven’t yet had success.
As always, “Give it a Go and Let us Know!”
Bibliography
[1] Bothun et al 1987 (https://ui.adsabs.harvard.edu/abs/1987AJ.....94...23B/abstract)
[2] Impey & Bothun 1989 (https://ui.adsabs.harvard.edu/abs/1989ApJ...341...89I/abstract)
[3] Pickering et al 1997 (https://ui.adsabs.harvard.edu/abs/1997AJ....114.1858P/abstract)
[4] Johnston et al 2024 (https://ui.adsabs.harvard.edu/abs/2024A%26A...686A.247J/abstract)
[5] Junais et al 2024 (https://ui.adsabs.harvard.edu/abs/2024A%26A...681A.100J/abstract)
[6] Boissier et al 2016 (https://ui.adsabs.harvard.edu/abs/2016A%26A...593A.126B/abstract)