Andromeda Galaxy

Constellation              Andromeda

Right ascension            00h 42m 44.3s

Declination                +41° 16' 9"

Redshift                   −301 ± 1 km/s

Distance                   2.54 ± 0.06 Mly (778 ± 17 kpc)

Type                       SA(s)b

Apparent dimensions (V)    190' × 60'



Apparent magnitude (V)     3.4

The Andromeda Galaxy (also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda Nebula in older texts) is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. It is the nearest spiral galaxy to our own, the Milky Way. As it is visible as a faint smudge on a moonless night, it is the farthest object visible to the naked eye, and can be seen with binoculars even in urban areas.

Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, it may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping. However, recent observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars, greatly exceeding the number of stars in our own galaxy. 2006 estimates put the mass of the Milky Way to be ~80% of the mass of Andromeda, which is estimated to be 7.1×1011 solar masses.

At an apparent magnitude of 4.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects, making it easily visible to the naked eye even when viewed from areas with moderate light pollution. It appears quite small without a telescope because only the central part is bright enough to be visible, but the full angular diameter of the galaxy is seven times that of the full moon.

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Antennae Galaxies

Constellation                      Corvus

Right ascension                    12h 01m 53.0s / 12h 01m 53.6s

Declination                        -18° 52' 10" / -18° 53' 11"

Redshift                           1642 ± 12 / 1641 ± 9 km/s

Type                               SB(s)m pec / SA(s)m pec

Apparent dimensions (V)            5'.2 × 3'.1 / 3'.1 × 1'.6

Apparent magnitude (V)             11.2 / 11.1

Notable features                   Interacting galaxies

The Antennae Galaxies (also known as NGC 4038/NGC 4039) are a pair of interacting galaxies in the constellation Corvus. They were both discovered by Friedrich Wilhelm Herschel in 1785.

The Antennae are undergoing a galactic collision. Located in the NGC 4038 group with five other galaxies, these two galaxies are known as the 'Antennae' because the two long tails of stars, gas and dust thrown out of the galaxies as a result of the collision resemble the antennae of an insect. The nuclei of the two galaxies are joining to become one giant galaxy. Most galaxies probably undergo at least one significant collision in their lifetimes. This is likely the future of our Milky Way when it collides with the Andromeda Galaxy. Two supernovae have been discovered in the galaxy: SN 2004GT and SN 2007sr.

A recent study finds that these interacting galaxies are closer to the Milky Way than previously thought—at 45 million light-years instead of 65 million light-years.

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