NGC 4449 - Dwarf Galaxy
The galaxy NGC 4449, also known as Caldwell 21, is an exciting irregular dwarf galaxy located in the constellation Canes Venatici
(the Hunting Dogs). It was discovered in 1788 by the famous astronomer Friedrich Wilhelm Herschel. He described it as “very brilliant,
considerable and large, with three or four bright nuclei”. Its visual brightness is approximately 9.4 mag, which makes it visible even in
smaller telescopes.
NGC 4449 is relatively close to our Milky Way and is located at a distance of about 12 to 13 million light-years. It is part of the Messier 94
group (also known as the Canes Venatici I group), which is relatively close to our Local Group.
The galaxy has an apparent diameter of about 5.5 x 3.6 arcminutes, which corresponds to a true diameter of about 20,000 to 22,000
light-years. This makes it about 5 times smaller than our Milky Way. Despite its small size, NGC 4449 is one of the most massive galaxies
of its type, with an estimated total mass of about 30 billion solar masses.
NGC 4449 is characterized by an exceptionally high star formation rate, which is twice as high as that of the Large Magellanic Cloud.
This is evident in numerous bright, bluish regions of young, massive stars and luminous areas of ionized hydrogen gas. The irregular
shape of the galaxy and the distribution of star formation regions are likely due to interactions and mergers with smaller satellite galaxies.
NGC 4449 is surrounded by a huge shell of neutral hydrogen that extends over 200,000 light-years and shows distortions that indicate a
past collision with the dwarf galaxy UGC 7577.
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In my 20" f/3 telescope, NGC 4449 offers a stunning view under a dark sky – especially at higher magnifications of 270x.
The goal of the observation was to closely observe the many HII regions in the galaxy. To do this, I marked the nine brightest regions on a
DSS printout and then approached them at a magnification of 270...380x. Here are the observations in detail:
#1: very bright, elongated with 2-3 separate cores (difficult to separate)
#2: bright and roundish
#3: faint, diffuse
#4: bright, roundish with condensation inside
#5: extremely faint, diffuse with low FH
#6: not seen :((
#7: extremely faint, homogeneous
#8: faint, roundish with a slightly brighter center
#9: bright, roundish
The galaxy itself is not particularly exciting. An extended halo with an irregular shape can be seen, crossed by a brighter bar near the center.
A star can be seen directly in the center (brightest area), and a second one east of the core (still within the halo).
