Cetus the Whale

"But see, as a swift ship with its sharp beak plows the waves, driven by stout rower's sweating arms,so does the monster come, rolling back the waterfrom either side as his breast surges through."

Ovid - Metamorphoses IV, 706

Cetus the ‘Whale’ was known to the ancient Greeks and Romans as a sea monster that was sent by Poseidon to devour the beautiful Andromeda. However, one look at the Medusa's head held by Perseus turned this beast to stone. The Arabians broke up Cetus' stars into three distinct groups: a ‘Hand’, ‘Hen Ostriches’ and a ‘Necklace’.

This constellation is one of the most extended, spanning an area of about 50° by 20°. Cetus' brightest star is beta at magnitude 2.0, half a magnitude brighter than alpha. Named Deneb Kaitos, it is derived from Al Dhanab al Kaitos al Janubiyy ‘The Tail of the Whale Toward the South’. Beta is also called Diphda from Al Difdi al Thani, the ‘Second Frog’. Fomalhaut in Piscis Austrinis is the ‘First Frog’. The Chinese called beta ‘Superintendant of Earthworks’. Lying at a distance of 60 light years, this K-type orange giant has a luminosity of about 40x that of our Sun.

Menkar or alpha Ceti, shining at magnitude 2.5, is from Al Minhar ‘The Nose’. A reddish M2 giant star 150 light years away, its luminosity lies around 175 Suns. There is a 5.6 magnitude star to the north, 93 Ceti, though it is not gravitationally bound to alpha. This blue B7 star forms a nice colour contrast with its reddish neighbour.

Gamma shines at magnitude 3.5 and lies 70 light years away. This star is not what it seems, a telescope at high power revealing an A-type main sequence star and an F-type dwarf forming a close binary system, separated by 60 astronomical units. A faint red dwarf lying to the northwest glows at 10th magnitude, orbiting this system at a distance of 18,000 astronomical units.

Omicron Ceti is one of the most famous variable stars in the sky, the first recognised as such with fluctuations in brightness between 3rd magnitude at maximum to fainter than 9th magnitude at minimum. This star sometimes attains 2nd magnitude, though rarely. Discovered by David Fabricus, a Dutch astronomer in 1596, he failed to recognise this star for what it is, thinking it was only a nova. Bayer catalogued it as a 4th magnitude star in 1603 and gave it the Greek letter Omicron. Later observers, noticing Omicron's disappearance and reappearance within a year, named it Mira the ‘Wonderful’. In 1923, R.G Aitken at the Lick Observatory noticed a blue B8 companion star close by. It also appears to be a variable star, changing from 10th to 12th magnitude, and shares the same proper motion as Mira, so they are physically bound.

Tau Ceti lies about 12 light years away and is a G-type main sequence star, similar to our Sun. It was expected that a star of this type should have a planetary system, after all, good old Sol has one. A radio search was initiated in 1959 for signs of artificial intelligence from Tau Ceti, but to date, nothing has been heard.

Cetus is devoid of bright deep sky objects, there being one faint planetary nebula and many galaxies. A dark sky will be crucial in observing the following list of objects. The brightest visual object is the galaxy M77, shining at an integrated magnitude of 9.0 and spanning an area of 2.5' x 1.7'. This galaxy is easy to find, located just 1° southeast of 4th magnitude Delta Ceti. This spiral galaxy lies around 60 million light years away and is easy in a 10cm telescope, though a 20cm makes observation of the mottling seen across its face more certain.

About 30" northeast of M77 resides a faint edge-on spiral galaxy, NGC 1055. Glowing at 10.6 magnitude and measuring 7.5' x 3.0', it is visible in a 15cm telescope as a bright central region surrounded by a faint outer envelope. Large scopes, with care, will show some mottling and possibly a dark lane of obscuring material across the nucleus.

Another spiral galaxy worth finding is NGC 247 south of beta, glowing with a combined magnitude of 9. It appears rather dim because of its large size at 18' x 5'. An elongated central region is surrounded by an elongated fainter outer halo, aligned north-south and can be seen in as little as a 15cm aperture. Close attention to detail may show an oval dark area in the northern portion of NGC 247. Lying at a distance of around 7 million light years, it is a member of a family of galaxies called the Sculptor Group that includes NGC 253, NGC 55, NGC 300, NGC 45 and NGC 7793.

Northwest of NGC 247 is the small, faint barred spiral galaxy NGC 175. This face-on galaxy needs a medium aperture to show well, a bright nucleus enclosed within a fainter halo appearing to the eye.

NGC 908 appears fairly bright in medium apertures, its elliptical shape appearing even in brightness with a very bright nucleus. The size is 4' x 1.3' and has a combined magnitude of 10. Look for it 5.4° eastward of upsilon.

Just over 1° southwest of 18 Ceti lies the large, faint, oval glow of NGC 210. This Sb type spiral galaxy has a bright nucleus and responds well to high powers. Not only will increasing the magnification bring up greater detail, it will give greater contrast between the galaxy and background sky. Within the same low-power field lies NGC 178, 20' southwest of NGC 210. A 25cm or larger scope is needed for any detail at all, showing a bright nucleus with a faint outer halo.

To the north-east lies NGC 255, forming a triangle with a pair of 5th magnitude stars, phi¹ and phi² Ceti. This face-on spiral galaxy has a bright ring-like nucleus in a 25cm scope, surrounded by a faint glow. In the same low-power field as NGC 255 lies a large, roundish ghostly glow, the planetary nebula NGC 246. Use low powers on this object as the surface brightness is low. A number of dark patches can be seen as well as the central star and a few foreground stars dotting its surface.

Finally, about 4° north of phi² Ceti lies a group of three galaxies, showing a range of sizes and brightnesses. The largest is NGC 274, right next to it is NGC 275, both slightly brighter than 13th magnitude. To the north of these two lies NGC 273, the faintest member.

Use all of your observational skills to get maximum viewing pleasure from these faint patches of light. Use a variety of powers, averted vision to bring out fainter detail, and perseverance to reward the eye.

Clear skies and good hunting. ~CosMos