Messier 90 (M90, NGC4569, a Jellyfish galaxy) and IC3583 Galaxy Pair, Virgo
Messier 90 is an intermediate spiral galaxy in the constellation of Virgo, type SAB(rs), which displays a weakly barred nucleus and a prominent but partial ring. Discovered by Charles Messier in 1781, it is observable with modest telescopes due to its apparent magnitude of 9.54 and angular size of 10.3 arcmin. Lying at a distance of 58.7 million light years, it is one of the few galaxies actually moving toward us in spite of the expansion of space. Its blueshift indicates approach velocity of 235 km/sec. Its actual diameter of 173,600 light years is about 70% larger than the Milky Way's, and its absolute magnitude of -21.74 is higher than that of the Andromeda Galaxy, and 2.37 times higher than the Milky Way's.
Containing about a trillion stars and 1,000 globular clusters, M90 is one of the largest and brightest members of the Virgo Galaxy Cluster. However it may be only a temporary, transient member. Halpha, infrared and X-ray studies show spectacular tails of super-heated ionized gas, containing Hii and star-forming regions, trailing up to 260,000 light years behind M90. These streamers are a result of "ram-pressure stripping" of the galaxy's interstellar gas as the galaxy travels at high speed through the intergalactic medium of the Virgo Cluster. Such galaxies with long trailing streamers are sometimes called "Jellyfish galaxies".
Having lost most of its gas and dust, the spiral arms of M90 are smooth and homogeneous, displaying no new star formation or flocculent features like Hii regions and large OB associations. Consequently, some authors regard it a prototype of an "anemic" or "passive" galaxy. What star formation does exist is present around the nucleus where roughly 50,000 large spectral type O and B stars formed about 5 million years ago. These are surrounded by numerous type A supergiants born during another episode of starburst activity between 10 and 25 million years earlier. M90 has an active galactic nucleus (AGN) of the Seyfert 2 type, displaying an emission line spectrum powered by X-rays generated in the accretion disk of a central supermassive black hole. Episodes of starburst activity around the nucleus may have been initiated by gas outflows from the core, and subsequently promoted by supernova explosions among the large initial generaton stars..
IC 3583 is a barred dwarf irregular galaxy, about 6 arcmin N of M90, discovered in 1892 by Isaac Roberts, a pioneer of amateur astrophotography. Large blue floccules of young and very hot spectral type O and B stars are evidence of ongoing starburst activity. High rates of new star formation and the presence of a bar structure strongly suggest the galaxy has undergone gravitational interaction with another galaxy - which is probably NOT M90. Based on its redshift of 0.003742, IC 3583 lies at a distance of 52.02 Mly, and is receding from us at 1,118 km/sec. M90 is farther away at 58.7 Mly, and is approaching us at 235 km/sec. The galaxieas are approaching each other at 1,300 km/sec, but are still some 7 Mly apart - too far for tidal interaction. Further, M90's spiral arms are very well organized, showing no evidence of recent gravitational perturbations. According to Tschoke et al., no definite tidal features have been identified in either galaxy.
As the annotated image shows, a large number of small galaxies lie in the distant background. Several are visible through the spiral arms of M90, but only two are identifiable. Most of these galaxies have a redshift around 0.094, which indicates they belong to a large, remote galaxy cluster located at a distance around 1.3 billion light years, and receding from us at 27,500 km/sec.
The most distant identifiable object is LEDA 42093 - a giant galaxy, more than twice in diameter as the Milky Way, and nearly 9 times brighter. It is receding from us at 120,000 km/sec, or 0.4 times the speed of light. When the captured photons left the galaxy 5.5 billion years ago, the Solar system, or even the Solar nebula, had not yet come into existence.
TSAPO100Q, Sigma APO 1.4x tele-extender (100 x 812 mm)
Modified Canon T3i camera, Astronomik L3 filter
IEQ30pro mount, Orion 60 mm f/4 SSAGpro autoguider
31 x 240 sec subs (5 rejected), ISO 1600, processed with 30 dark and 30 bias frames
Software: PHD2, DSS, XnView, StarNet++, and StarTools
Thank you for looking. C&C welcome.