A mere 12.5 million light-years from Earth, irregular
dwarf galaxy NGC 4449
lies within the confines of
Canes
Venatici, the constellation of the Hunting Dogs.

About the size of our Milky Way's satellite galaxy the Large Magellanic
Cloud, NGC 4449 is undergoing an intense episode of star formation,
evidenced by its wealth of young blue star clusters, pinkish star forming
regions, and obscuring dust clouds in
this
deep color portrait.

It's also holds the distinction of being the first
dwarf
galaxy with
an identified tidal star stream, faintly seen at the lower right.

Placing your cursor over the image reveals an inset of the
stream resolved into red giant stars.

The star stream represents
the remains of a still smaller
infalling satellite galaxy, disrupted by gravitational forces and
destined to merge with NGC 4449.

With relatively few stars, small galaxies
are thought to posses extensive dark matter halos.

But since dark matter interacts gravitationally,
these observations offer a chance to examine
the significant
role of dark matter
in galactic merger events.

The interaction is likely responsible for NGC 4449's burst of star
formation and offers a tantalizing insight into how even
small galaxies are assembled over time.

Read the full story:
NGC 4449: Star Stream for a Dwarf Galaxy

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The star near the top is so bright that it is sometimes hard to
notice the galaxy toward the bottom.

Pictured above, both the star,
Regulus, and the galaxy,
Leo I,
can be found within one degree of each other toward the constellation of the Lion (Leo).

Regulus is part of a multiple star system, with a close companion
double star
visible to the lower left of the young main sequence star.

Leo I is a
dwarf spheroidal galaxy in the
Local Group of galaxies dominated by our
Milky Way Galaxy and
M31.

Leo I is thought to be the most distant of
the several known small satellite galaxies orbiting our
Milky Way Galaxy.

Regulus is located about 75 light years away, in contrast to Leo 1 which is located about 800,000 light years away.

Read the full story:
Bright Star Regulus near the Leo I Dwarf Galaxy

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Spiral galaxy NGC 4651 is a mere 35 million light-years distant,
toward the well-groomed constellation
Coma Berenices.

About 50 thousand light-years across, this galaxy is seen to have
a faint umbrella-shaped structure (right) that
seems to extend some 50 thousand light-years farther,
beyond the bright galactic disk.

The
giant cosmic umbrella is now known to be composed of
tidal star streams.

The streams themselves are
extensive trails of stars
gravitationally
stripped
from a smaller satellite galaxy that was eventually
torn apart.

Placing your cursor over the image will superimpose a simulation of
the satellite galaxy's path as it was disrupted and
absorbed into NGC 4651.

Recent work by a remarkable collaboration of amateur and professional
astronomers to image faint structures around bright galaxies
suggests that
even in nearby galaxies,
such tidal star streams
are common.

The result is
predicted by models
of galaxy formation,
including
the formation of our Milky Way.

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A satellite galaxy of our own Milky Way, the Large Magellanic Cloud
(LMC) is an alluring sight
in dark southern skies and the constellation
Dorado.

A mere 180,000 light-years distant,
the LMC is seen in amazing detail in this
very
deep 4 frame mosaic of telescopic images,
a view that reveals the
Milky Way's
satellite to have the appearance
of a fledgling barred spiral galaxy.

The mosaic includes image data taken through a narrow filter
that transmits only the red light of hydrogen atoms.

Ionized
by energetic starlight, a hydrogen atom emits the
characteristic red
H-alpha light
as its single electron is
recaptured and transitions to lower energy states.

As a result, this mosaic seems spattered with
pinkish clouds of hydrogen gas surrounding massive, young stars.

Sculpted by the strong stellar winds and ultraviolet radiation,
the glowing hydrogen clouds are known as
H II
(ionized hydrogen) regions.

Composed of many overlapping clouds,
the sprawling Tarantula Nebula
left of center, is by far the LMC's largest star forming region.

The Large Magellanic Cloud is about 15,000 light-years across.

Read the full story:
Hydrogen in the LMC

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Andromeda

Abbreviation: And

Genitive: Andromedae

Translation: Princess of Ethiopia or the Chained Lady

Position in the Sky

Right Ascension: 1 hour
Declination: 40 degrees
Visible between latitudes 90 and -40 degrees
Best seen in November (at 9:00 PM)

Named Stars

ALPHERATZ (Alpha And)
MIRACH (Beta And)
ALMAAK (Gamma 1 And)
Adhil (Xi And)

Messier Objects

M31 The Andromeda Galaxy (spiral galaxy)
M32 Satellite galaxy of Andromeda (elliptical galaxy)
M110 Satellite galaxy of Andromeda (elliptical galaxy)

alpheratz, adhil the star, 88 constellations stars andromeda, right ascension of stars, genitive andromede, astronomy the princess sky, andromedas position in the sky

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