M081

M81 is a famous spiral galaxy in Ursa major that anchors a group of galaxies. It is thought to be just under 12 million light-years distant. It was discovered several times. First by Johann Bode on December 31, 1774. Guess he wasn't out celebrating New Year's Eve. For this reason, it is often called Bode's Nebula (at the time galaxies weren't known but some incorrectly, in my opinion, call it Bode's Galaxy). Or maybe he wasn't the first. Sometime between 1772 and 1778 Johann Koehler found it but didn't record it until 1779 so most say he loses out to Bode. Then in August 1780 Pierre Méchain discovered it. Messier observed and recorded it on February 9, 1781 likely having heard of it from Méchain.

Several parallel dust lanes can be seen above the core of the galaxy straight down and to the right, not following the spiral of the galaxy in the slightest. Some sources say these are due to a close pass with M82. Others say these are due to dust in our own galaxy. I've also seen about everything possible in between these two ideas. There's also another odd lane crossing these to the upper right of the core that is much more vertical and wider. It too doesn't fit the galaxy's structure nor can I fit it with the idea these are due to interaction with M81. For me, they are still unexplained. It is classified by NED as an SA(s)ab; LINER Sy1.8 galaxy. Using a simplified system the NGC Project says Sb I-II.

To the east is the irregular Magellanic dwarf galaxy Holmberg IX (PGC 28757). This is a very young galaxy with little hydrogen. Some think it was formed from gas and dust drawn out by the near collision of M81 and M82 in the past and therefore a very young galaxy. Star streams in deep photos show it as an enhancement in a long stream of stars all of which may be due to this interaction. Or not, depends on who you read. I tend to think there may be something to this idea.

Assuming a distance of 11.8 million light-years for both I get a size of 76,000 and 11,600 light-years respectively measuring their longest length. Holmberg IX is rather drawn out by tidal forces making its long dimension larger than it likely would otherwise be.

For information on the M81 galaxy group and a radio image showing the various streams of hydrogen gas see: http://messier.seds.org/more/m081gr.html Note the far left red spot is NGC 3077. Also, the text incorrectly identifies Holmberg IX as UGC 5423 rather than the correct 5336 shown in the table.

I took this image back in 2007 when my techniques were poor. As was my image processing abilities. I really need to reprocess this one as I doubt the color balance is all that great. Also while the label on the image says 60 minutes of luminance data I can only find 50 minutes worth. I have no idea which is right but will go with 50 as that's all I can find was taken. My notes also indicate the master luminance file contained 9 frames, not 10 or 12 to add to the confusion. I really didn't keep good notes back in 2007 it appears.

For more on this galaxy see: http://messier.seds.org/m/m081.html

14" LX200R @ f/10, L=~10x5' RGB=3x5', STL-11000XM, Paramount ME

Related Designations for M081

M082

Sometime, probably after January 11 and before January 19, the light of a type 1A supernova in the starburst galaxy M82 hit the earth. It wasn't "discovered" until the night of January 21 in England. A group of students got an unexpected introduction to what to do when an event such as this is first seen. You can read about it at http://www.ucl.ac.uk/maps-faculty/maps-news-publication/maps1405. I've seen images taken as early as January 19 that show it but those taking the images didn't realize what they had or didn't look at the data until days later. Earlier images likely exist. These are referred to as pre-discovery images. I first heard of it on the 22nd but it was cloudy. It sort of cleared Wednesday night, the 23rd of January (all times and dates are UT, not local time). I had rather poor seeing but took what data I could prior to moonrise. The temperature here was running down around -35°C when I started and dropped 3 more degrees while I was taking the data which meant my image scale changed adding to my processing steps. Due to other issues, I couldn't get it processed until Friday morning so I'm a bit late to this party. My red data was taken when the moon was brightening the sky though not yet risen. This prevented me from capturing the H alpha streamers caused by the starburst activity in the galaxy.

Starburst activity creates many short lived massive stars that go supernova after only a few million years of life. Such supernovas are called type II supernovae. So you'd expect such a massive star's death to be the cause of the supernova. But, just to be contrary I suppose, this is a type 1a which is caused by the sudden destruction of one or maybe 2 white dwarf stars. White dwarf stars are much less massive stars and live at least a billion years or longer. So the star or stars that caused this supernova predate the starburst activity in M82. Such supernovae are thought to be standard candles so if you know the apparent brightness as well as how much dust and gas between us and the supernova dims the light the distance to the supernova can be calculated. Thus this supernova might help better determine the distance to M82 which is currently put at about 12 million light-years. The problem is the light of a fresh type 1a supernova should be blue. This one is somewhat red. Not because the supernova is red but because it went off deep inside the dusty M82's disk. Dust reddens starlight same as it reddens our sunsets and sunrises. This will make estimating the loss to dust and gas rather difficult. I'm sure all sorts of methods of adjusting for this will be tested by this event.

M82 is also Arp 337 so I've added another supernova to my collection of Arp galaxies. A surprising number of them in my collection were caught with supernovas including M51 and M101 and about a half-dozen others. I've lost count so need to go back and look that count up. Seems peculiar galaxies that made his list are above average in the number of their supernovas by my rather unscientific survey.

I've made an annotated image showing the surrounding galaxies, galaxy clusters and quasars. I found this field particularly difficult to work with. Many of the quasars listed in NED, as well as some galaxies, had vague coordinates. Often there was nothing close to the right magnitude within the error circle or even well beyond the error circle. Rather than guess I didn't include these vague positioned objects. Even when I could identify the object it was sometimes listed as both a quasar and a galaxy yet of typical galaxy distance and sometimes showing a slight disk rather than the point source of a quasar. I listed these as both Q and G often with a question mark. NED usually preferred the quasar designation even when a small disk is seen. While NED listed about twice as many galaxy clusters as I show I only listed those with a Big Cluster Galaxy listed in NED such that I could pin down its location. Some used photographic redshift, designated with a p after the light travel time figure, for the cluster but spectroscopic redshift for the BCG. The latter is likely more accurate though in these cases they were in rather close agreement. Many time I find a wide difference but not with these.

The supernova is expected to continue to brighten for a week or maybe longer. Due to the extensive light of the galaxy around it, I was unable to get a good magnitude estimate. There are tricks for adjusting for this but I didn't take the time for them. Most estimates put it at about magnitude 11 or a bit brighter. It might reach 8th magnitude by some predictions. Time will tell if those predictions come true.

M82 was discovered by Johann Bode on December 31, 1774 the same night as he found M81. Like M81 Koehler may have seen it sometime between 1772 and 1778 but didn't record it until 1779. Pierre Méchain then saw it in August 1780 and likely reported it to Messier who observed and recorded it on February 9, 1781. William Herschel then observed it on September 30, 1802. It is in the original Herschel 400 Observing Program. My notes from April 15, 1985 on a humid night with my 10" f/5 Cave Newtonian at up to 150x reads: "Bright large streak with an even brighter central core. It can even be seen in my 8x50 finder on this rather low transparency night. Several dark lanes seen near the core. It takes high power well though this night I'm limited to 150x due to low transparency."

For more on M82 see: http://messier.seds.org/m/m082.html

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for M082

M084

M84 and M86 are two major elliptical galaxies near the core of the Virgo Cluster of galaxies. M84 is classed as an E1 galaxy and also as being a Low-Excitation Radio Galaxy (LERG), having a Low-Ionization Nuclear Emission-Line Region (LINER) and being a Seyfert 2 type galaxy. All this means it has a very actively feeding supermassive black hole at its core. A Seyfert galaxy shows this by having emission lines from the core region. A type 1 Seyfert has both narrow and broad emission lines while a type 2, like M84, has only narrow lines, an indication of less activity than a type 1. A galaxy that is only LINER is sometimes called Seyfert 3 adding to the confusion. Then there are type 1.5, 1.8 and 1.9 Seyfert's. You can read more about this at: http://spider.seds.org/spider/ScholarX/seyferts.html

Redshift puts it about 64 million light-years away while Tully Fisher measurements vary widely with a median value of about 56 million light-years. It is said to have several dust lanes but I didn't pick them up. Likely will need a lot more time to see these very low contrast features. My image shows lots of fuzzies to the southeast of the core but still in the fainter outer halo of the galaxy. I thought these might be globular clusters but most turned out to be distant galaxies without redshift data. I found no designated cluster that would cover them in NED, however. I did find a very few globular clusters, mostly to the northwest. They were so faint they are barely seen in the image so I didn't note them on the annotated image. NED also lists over 100 planetary nebulae, none of which were seen in my image that I looked for. With no magnitude listed in NED, I could only sample the listing. The Hubble image of the very core of M84 showing the dust lanes is at: http://upload.wikimedia.org/wikipedia/commons/7/7a/Messier_84_nucleus_Hubble.jpg . NED lists its diameter as about 6 minutes while I measure about 10 on my image with some really deep images showing it even larger. Using 56 million light-years and my measurement of 10 minutes puts it at about 160,000 light-years in diameter.

M86 is a far larger galaxy. NED classifies it as SO(3)/E3 by NED and simply E3 by the NGC project. The galaxies in the Virgo cluster have a wide dispersion as to radial velocity indicating it is a very dynamic cluster. M86, in fact, is blue shifted indicating redshift is meaningless for it and likely other galaxies in the cluster. For this reason, I didn't label the cluster members with a redshift distance estimate as they appeared more like a random number list than a true distance measurement. Several different measurement methods have been used on the galaxy, some based on brightness variations, some on galaxy clusters some on planetary nebula and other methods. They give distances ranging from 40 to 60 million light-years. The median value is about 55 million light-years. With 35 listed in NED, you have plenty to choose from!

It has an X-ray plume which is thought due to the stripping of gas from it by ram pressure due to its high velocity through the cluster. It has surprisingly few globular clusters for such a large galaxy. Again most were far too faint for me to show on the annotated image. It does not seem to be close to M84 except by projection as seen from our spot in space so is not considered interacting with it. There are however hydrogen traces connecting it with one of "The Eyes" galaxies, NGC 4438, Arp 120. This galaxy also is moving through the Virgo cluster and experiencing ram pressure stripping though it has a very small redshift rather than being blue shifted like M86. It lies just outside the left edge of my image.

My measurement of its diameter is at least 15 minutes. Likely larger as the north end extends beyond my frame but NED says only 9 minutes. Again deep images show it larger than I do. Again going with my estimate and the distance of 55 million light-years gives a size of nearly 240,000 light-years. Now that's big!

M84 and M86 were discovered by Johann Koehler on May 5, 1779. Charles Messier found both on March 18, 1781. SEDS coverage: M84 http://messier.seds.org/m/m084.html
M86 http://messier.seds.org/m/m086.html

NGC 4387 near the center of my image is listed as E5 by NED and simply E by the NGC Project. It seems to show hints of structure in my image those papers I saw all say it lacks structure but for its boxy nature. Redshift puts it somewhat too close to be reliable. The median value of 12 measurements in NED put it about 57 million light-years away.

Below NGC 4387 is the faint fuzzy PGC 040577. Its listing in NED is very puzzling hence the question mark in the annotated image. NED shows it as a Group Member. This would indicate it is a member of the Virgo cluster or at least some cluster. The detail says they mean the Virgo Cluster. Its classification is dE2 meaning a dwarf E2 galaxy. Problem is the redshift is z=0.295417 which puts it some 3.38 billion light-years distant. While radial velocities in the Virgo cluster show a high variability this is far beyond that! NED lists its size at 16.2" while I get a bit larger size. Going with NED's size and the 3.38 billion light-year distance it is over 260,000 light-years in diameter. That's some dwarf! For now, I'm going to assume the classification is right and it is the redshift that is in error. Assuming a distance of 60 million light years gives a diameter of about 5,000 light-years which is reasonable for its classification. Certainly, other dwarf members of the cluster fit its angular size.

NGC 4388 lies at the bottom of the image. Both NED and the NGC project classify it as SA(s)b: and a Seyfert 2 galaxy though NED also lists it as a Seyfert 1.9 as well. It too has a high velocity through the cluster but in its case, the motion is highly redshifted showing a distance about twice actual rather than it having a blue shift as with NGC 4387. The median of 13 measurements other than redshift put it about 63 million light-years away compared to 131 million for its redshift measurement. Thus it too is experiencing ram stripping. Its size on my image indicates a diameter of over 125,000 light-years which makes it a large spiral similar to ours in size.

Another galaxy with a blueshift rather than redshift is IC 3303. NED classifies it as dS0,N which means it is a dwarf S0 galaxy that is non rotating. So far so good. Its size puts it at a diameter of about 20 million light-years assuming it is 60 million light-years distant. OK, a large dwarf. But then NED's morphology says it is a cD galaxy. These are defined by NED as: "supergiant galaxy with an extensive envelope in a cluster". Oops. It can't be both a dwarf and a supergiant. Another for the blooper reel it seems.

Two objects without distance data were labeled UvES which are often quasar candidates. One, down near NGC 4388 is very blue and certainly looks like it could be a quasar though it is listed simply as being a blue star. The other one isn't is on the east side of M86's halo. It is listed as a star. Both appear to have the same PSF as a star in my image though quasars often do. Without more, I'll assume they are just stars.

14" LX200R @ f/10, L=6x10' RGB 2x10'x3, STL-11000XM, Paramount ME

Related Designations for M084

M085

M85 is one of the large elliptical-like galaxies in the Virgo cluster. It is near the northern edge of the cluster in Coma Berenices. Being that the cluster is about 60 million light-years distant that is likely close to its true distance. Redshift puts it at 48 million light-years while various other methods give distances ranging from 28 to 95 million light-years. They average out to about 55 million light-years. Even though this is a much studied galaxy we still don't have a good grasp of its distance. Using the 60 million light-year figure the bright region of the galaxy is about 88 thousand light-years across with the outer halo extending about 170 thousand light years. NED classes it as SA(s)0+ pec while the NGC project says SA(s)+P. It is a shell galaxy indicating it has had a close interaction with other galaxies in the past, likely devouring a few smaller members of the cluster. While they aren't as distinct as they were in some other shell galaxies several shells and plumes are seen in my image.

M85 was discovered by Pierre Méchain on March 4, 1781 and reported to Messier who observed and recorded it on March 18, 1781.

NED lists quite a few globular star clusters around this galaxy. About half show in my image, about the same as show in the Sloan Survey image. I've marked them on the annotated image with the notation CL. The label is a couple pixels to the right of the cluster unless that wasn't possible. Things got rather tight. When too tight I used a line to the cluster.

It's companion galaxy, NGC 4394, is likely a true companion though I doubt they are interacting. It is an interesting galaxy. NED classes it as (R)SB(r)b LINER indicating it has a somewhat actively feeding black hole at its core. It's a quite photogenic galaxy in its own right.

M85 has a third companion, MGC +03-32-028 seen against its southern shell. With a similar redshift, it would appear to be a true companion. Is it destined to be M85's next dinner? NED classes it as E?

There's only one other galaxy with redshift data in the image, IC 3292 and it too is likely a companion with a similar redshift. NED calls it a dwarf S0 galaxy.

To it's left (east) is a little trio of galaxies one of which is a nice ring galaxy, SDSS J122454.57+181200.8 with what is likely its core in the upper right part of the ring. Look closely and you will see a second galaxy just to the right of the likely core region. While both appear rather red in my image the Sloan image shows it as blue. Likely it has a lot of near ultraviolet light that Sloan can see but I can't that accounts for the color. It might be the "bullet" that created the ring and is now creating new stars thanks to the collision. NED lists it as SDSS J122454.40+181159.4. The starlike object just below these two is SDSS J122454.17+181152.6. All three fit in a 10" of arc circle. Without redshift data, its difficult to say if they are related or a chance alignment but I like the idea, at least the first two may well be.

There's one asteroid in the image, 2007 GG46. It is rather faint at magnitude 20.6.

You may want to enlarge the image to see some of the details better. This was taken on a good night so can withstand some enlargement.

More from SEDS: http://messier.seds.org/m/m085.html

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for M085

M087

Arp 152 is one of the most famous Arp galaxies and often in the news. Here'Arp 152 is one of the most famous Arp galaxies and often in the news. Here's a link to such a current news item. http://www.universetoday.com/2009/07/02/messier-87-shows-off-for-hundreds-of-earth-bound-astronomers/ It has one of the universe's largest fireworks going off in its core, powered by a giant black hole. This creates a jet. It is the jet that put it in Arp's catalog of course. While we only think of M87 when galactic jets are mentioned Arp has 4 of them in his catalog. Two were well placed this spring and I hoped to image them along with M87 but thanks to the perpetual clouds this didn't happen. I've attached 2 different processing version of this one image; one processed normally except the core has been reduced to show the jet, the other a closeup 2x enlargement of the core and jet region processed just for the jet. I've also included an annotated image.

M87 is one of the anchor galaxies of the Virgo cluster. Its mass along with that of a couple other supermassive elliptical galaxies seem to define the center of this cluster. One of these M49 is involved with Arp 134. I've reduced the brightness of M87 considerably to allow the jet to be seen. Many of the star-like points around and within the galaxy that make it appear to be in a faint star cluster are really some of its many globular star clusters. There were just too many to try an include them in the annotated image. But virtually all fuzzy stars around and in it are listed at NED as star clusters. Unfortunately, they list both open and globular clusters the same. I think it safe to assume these are all globular clusters.

M 87 was discovered by Johann Koehler on May 5, 1779. Messier didn't hear of the discovery and found it himself on March 18, 1781.

SEDS: http://messier.seds.org/m/m087.html

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp152.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount MEs a link to such a current news item. http://www.universetoday.com/2009/07/02/messier-87-shows-off-for-hundreds-of-earth-bound-astronomers/ It has one of the universe's largest fireworks going off in its core, powered by a giant black hole. This creates a jet. It is the jet that put it in Arp's catalog of course. While we only think of M87 when galactic jets are mentioned Arp has 4 of them in his catalog. Two were well placed this spring and I hoped to image them along with M87 but thanks to the perpetual clouds this didn't happen. I've attached 2 different processing version of this one image; one processed normally except the core has been reduced to show the jet, the other a closeup 2x enlargement of the core and jet region processed just for the jet.
I've also included an annotated image.

M87 is one of the anchor galaxies of the Virgo cluster. It's mass along with that of a couple other super massive elliptical galaxies seem to define the center of this cluster. One of these M49 is involved with Arp 134 . I've reduced the brightness of M87 considerably to allow the jet to be seen. Many of the star-like points around and within the galaxy that make it appear to be in a faint star cluster are really some of its many globular star clusters. There were just too many to try an include them in the annotated image. But virtually all fuzzy stars around and in it are listed at NED as star clusters. Unfortunately they list both open and globular clusters the same. I think it safe to assume these are all globular clusters.

M 87 was discovered by Jophann Koehler on May 5, 1779. Messier didn't hear of the discovery and found it himself on March 18, 1781.

SEDS: http://messier.seds.org/m/m087.html

Arp's image:
http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp152.jpeg

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for M087

M088

M88 is one of the brighter members of the Virgo Cluster of galaxies; known to amateurs as "The Realm of the Galaxies". The cluster is located about 60 million light-years away which makes it the nearest major galaxy cluster containing thousands of galaxies. A few dozen were bright enough for Messier to see in his very small telescope. M88 is one of 8 galaxies he found in one night. He had no idea what they were or anything but they looked like fuzzy spots of light not much different than a comet looked in his scope. In fact, he listed these so he and other comet hunters wouldn't be fooled into thinking they'd found a comet. Other comet hunters would tell him of their discoveries of such objects as well. From these observations, he came up with a list now known as M objects. Rather than be famous for comet discoveries as he intended he became famous for his list instead.

M88 is a many armed spiral. Some spirals have only one arm, many have two or three but a few have many short spiral arm segments. M88 falls into this last category. You can read a bit more about it at:
http://ftp.seds.org/messier/m/m088.html

The obvious galaxy below M88 is VCC 1400. It likely is another member of the Virgo cluster and thus a dwarf galaxy. Though it isn't related to M88 as their redshifts are too different.

This is another early image taken when I couldn't deal with moon gradients all that well. As a result, it doesn't go nearly as faint as it would if processed today.

14" LX200R @ f/10, L=4x10' RGB=2x10x3, STL-11000XM, Paramount ME

Related Designations for M088

M089

M 89/NGC 4552 is a large elliptical galaxy in Virgo. As a member of the Virgo Cluster, it is likely about 60 million light-years away. NED classes it as E; LINER;HII Sy2 while the NGC project says simply that it is E. Though a paper I read insists this is wrong and it is an S0 galaxy.

I'd ignored most elliptical galaxies as boring. But since it was an M object decided I had to add it to my digital library. I'd not paid it any attention until I went to process this image. At first, I thought my flats were bad as there was a faint halo around the galaxy, mostly to the south as well as a large smudge to the southwest. I was debating whether I could salvage the mess when I found that these were real. It has a large but very faint halo few seem to have picked up except on a very deep image such as one by David Malin. Turns out I didn't pick up but part of it. The large elongated smudge is thought to be the remains of M89's last meal that it is still digesting. Malin's image is at http://messier.seds.org/more/m089_aat.html . It needs far more time than I gave it to pull out these features as more than a hint. I've included a highly stretched version that's quite noisy but better shows the extent of the shell and remains of its last meal. Doesn't help that my L filter had loosened in the filter wheel and rotated slightly so the dust mots didn't line up perfectly limiting how far I could stretch the image without that showing up.

The annotated image shows the globular clusters NED listed that were visible in my image. They are noted by *CL in the annotated image. I found that just by looking at them I couldn't tell a faint star from a distant galaxy from a globular cluster. A plate solve however made it easy to separate one from the other. I noted the galaxies (even though there's no distance known) with a G?. Stars were left unlabeled. One NED lists as a globular is rather orange which bothers me. Seems an odd color for a globular cluster. Looking at it in the Sloan image it looked perfectly star-like. It is on the southeast side of M89 with an anonymous galaxy (not in NED) beyond it.

One of the smaller smudges in the halo turns out to be VCC 1613 which NED shows as a dE2 galaxy (dwarf elliptical). The other smudge to the north wasn't listed in NED but I do see it in the second image at: http://cseligman.com/text/atlas/ngc45a.htm#4552 . Note the orange "globular" looks like an ordinary star in this image. I really question NED's identification of it as a globular.

For a bit more see: http://messier.seds.org/more/m089_aat.html

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for M089

M090

Arp 76 is better known as M 90 and IC 3583. Arp put it in his category for spiral galaxies with small, high surface brightness companions. The redshift of M 90 is actually a blue shift indicating it is moving toward us. Still, there's good reason to put the galaxy about the middle of the Virgo Cluster and thus about 60 million light-years distant. IC 3583, the "companion" on the other hand has a redshift that puts it about 67 million light-years distant. It does appear somewhat distorted. While it was considered a possible companion of M 90 at the time of Arp's atlas most today doubt that due to the very different redshifts meaning any interaction would have happened at such high speed neither would have noticed the passage. M90 is classified by NED as SAB(rs)ab;LINER;Sy. The NGC project says simply Sb. Seligman agrees with NED but adds a question mark, SAB(rs)ab?. It was discovered by Charles Messier on March 18, 1781 along with many others. IC 3583 was found by Isaac Roberts on April 29, 1892. Seligman classifies it as SBm? pec. One interesting note at NED discussing if it is a companion of M90 or not reads: "Non-interacting pair with dwarf IC 3583 at 6.0 arcmin north. Possibly interacting." Now that's covering your backside!

This image dates back to 2007 when my imaging knowledge was weak and I didn't realize I was losing faint details to read noise. Processing was so poor I completely reprocessed it from the original data. In doing so I saw one asteroid (38582) 1999 XE37 at magnitude 17.8 southwest of M90. At the time I wasn't doing annotated images and didn't take the time for on for this image.

14" LX200R @ f/10, L=9x5' RGB=3x5', STL-11000XM, Paramount ME

Related Designations for M090

M091

M91 is a spiral galaxy in the Virgo Cluster. NED's non-redshift distance is about 54 million light-years though most sources say 60 million light-years. A 1999 paper using the HST to study its few cepheid variable stars came up with a distance of 52 million light-years plus or minus 6.5 million light-years. http://iopscience.iop.org/article/10.1086/307151/fulltext/39340.text.html

Redshift for the Virgo Cluster is highly unreliable as the cluster members are orbiting rapidly about it some even having blue shifts. M91 is a very obvious barred spiral whose core has Seyfert activity. It is often considered the faintest of the Messier objects. While discovered by Charles Messier on March 18, 1871 there was nothing ever found at his position. Now it is thought he referenced it from M58 when he thought he was using M89. But this wasn't discovered until 1969. Thus many older sources credit William Herschel as its discoverer on April 8, 1784. You can read more on this at: http://messier.seds.org/m/m091.html

This put it in the original Herschel 400 observing program. My notes from April 23, 1985 with my trusty Cave 10" f/5 on a fair but moonlit night at up to 150x reads: "Large, knotty galaxy. Spiral structure seems on the verge of coming through. Seems to be a detached piece to the south. Is this a small galaxy or a knot in an out arm. Most probably a knot as at times of best seeing a faint curving arch is seen from it to the west end of the main halo. Very interesting." Apparently, I wasn't as hurt by the moon as my notes might indicate.

I recently prepared an annotated image for this field including two asteroids and two galaxy cluster, one seen along the right edge. Normally the position of the cluster matches that of the BrClG (Bright Cluster Galaxy) so I point both with one entry as I did with the group to the southeast of M91. But in this case, there was a few seconds of arc difference between the two so both are noted. A "p" after a distance indicates a photometric redshift was used rather than the more accurate spectroscopic one I normally use. This may explain why the BrClG has a slightly different distance than the cluster itself. VPC stands for the Virgo Photometry Catalogue. ASK stands for Automatic Spectroscopic K-means-based classification. I use this when only positional catalog names are available. They are so long as to make annotation difficult. If I don't have any non-positional name I use G, GC or Q for galaxy, galaxy cluster or Quasar.

This was taken in my very early days of digital imaging when I was poor at retaining star color and let read noise limit my ability to see faint detail clearly. I also underexposed it adding to the noise issue. I do need to retake this one to get better detail in the faint outer arms.

14" LX200R @ f/10, L=6x5' RGB=3x5' STL-11000XM, Paramount ME

Related Designations for M091

M092

M92 is the "other" Hercules globular cluster besides its more famous M13 to make Messier's list. It was discovered by Johanne Bode on December 27, 1777. Charles Messier made an apparent independent discovery of it on March 18, 1781 and recorded it in his catalog.

This globular cluster is thought to be about 26,000 light-years away though there's a problem. Using that distance its age is a bit older than the universe at an estimated 14 billion years. The error bar does allow it to be slightly younger than the universe but considering our galaxy is about 10 billion years old, at least that's the age of most of its globular clusters (some are younger) this age is a problem. Is it a captured globular from a galaxy we merged with? Seems unlikely as this is a very large globular, I measure its diameter at about 125,000 light-years assuming the 26,000 light-year distance is right. It could be further away which would result in a younger age calculation and smaller size. You can read more about this problem at http://messier.seds.org/m/m092.html

While I had great seeing for this image transparency was awful. The thick haze created nasty halos around the brighter stars that were beyond my processing abilities back in 2007 when this was taken. Unfortunately, I didn't save the original data so I had to try and kill the halos in the TIFF image I did save. I was only somewhat successful. But at least the seeing allowed good resolution of its stars right to the center. I took it three different nights but on the first two, only the color frames were usable. This resulted in 3 times my usual color data. But considering the haze on two of those nights that probably wasn't a bad thing. Only the luminance data from the third night was usable.

14" LX200R @ f/10, L=4x10' RGB=6x10', STL-11000XM, Paramount ME

Related Designations for M092