A Whale (and Dolphin) of a Show Light Up the Night Sky

A tiny constellation can be found soaring high in the southern part of the sky, almost directly overhead for skywatchers in the Northern Hemisphere this week. It's Delphinus the dolphin and this cosmic marine mammal is not alone.

The constellation Delphinus is a star pattern composed only of faint stars, yet the stars are so close to each other that they can easily be seen on clear, dark nights. A variety of different descriptions have been used in various astronomy guidebooks for Delphinus; everything from charming to just plain cute. 

This sky map shows where to find the constellation Delphinus in the night sky. It makes its appearance  around 8 p.m. local time, weather permitting.

Although Delphinus possesses no star brighter than fourth magnitude, it has several as bright as that. Magnitude is a measure of brightness for night sky objects. The lower the number, the brighter the object.

As such, Delphinus forms a distinctive diamond-with-a-tail pattern that gives this group a prominence greater than you might otherwise expect from so faint a constellation. 

Mysterious Stellar Monikers

Some reference books refer to the Delphinus diamond as "Job?s Coffin," though the origin of this name is unknown.

Two stars in Delphinus have rather odd names: Sualocin and Rotanev. They first appeared in the Palermo Star Catalogue in 1814, but nobody seemed to have a clue as to their origin.

The English astronomer Thomas Webb finally solved the mystery by reversing their letters, revealing the name of Nicolaus Venator, the Latinized form of Niccolo Cacciatore, the valued assistant and eventual successor of Palermo Observatory?s director Giuseppe Piazzi.

But to this day nobody knows whether it was Piazzi or Cacciatore himself who ultimately christened these two stars.     

Dolphin to the rescue!

The tale of Delphinus comes from ancient legend.

It goes something like this: Arion, a Greek musician, was sailing to Corinth, carrying a substantial cache of money and jewels. Unfortunately, the ship?s crew planned to throw Arion overboard and abscond with his treasure. 

When confronted by the pirates, Arion requested that he be allowed to play his harp one final time.  The music attracted the dolphin Delphinus. Upon seeing the dolphin, Arion jumped overboard and was carried safely to shore. When the ship docked at Corinth, the crewmen were arrested and hanged. Arion recovered his treasure and the dolphin was given a place of honor in the sky.

Another Whale

On Earth, dolphins are marine mammals ? a group that also includes whales. There are whales in the night sky, too. As the constellation Delphinus happily swims high in our south-southern sky during early evening hours, its cosmic whale cousin Cetus will be emerging into view, sprawling above the southeast horizon. 

This Cetus constellation sky map shows where to look for the whale constellation.

Known by the ancient Greeks as the whale that was about to attack Andromeda when Perseus destroyed it, Cetus was later thought to represent the whale that consumed Jonah. However, if one were to look at some of the allegorical star atlases of the past few hundred years, the portrayals are hardly what we know whales to be. 

In fact, not a few astronomy guides refer to Cetus as a sea monster even though, ironically, the scientific name for the whale order is Cetacea. Some star atlases, in fact, depicted Cetus looking more like Godzilla with a fish tail.

Cetus consists chiefly of faint stars, but it occupies a relatively large part of the sky. His head is a group of stars not far from Taurus and Aries, and his body and tail lie toward Aquarius.

The ?Wonderful Star?

Over the next week, the long-period variable star Mira ? actually the first-ever variable star to be discovered ? is forecast to reach its predicted peak brightness. In the 2010 Observer?s Handbook of the Royal Astronomical Society of Canada, Mira should be at peak brightness on Oct. 14.

In 1596, David Fabricus (1564-1617) an amateur astronomer and native of Friesland, the Netherlands, saw a third magnitude star in the constellation of Cetus. As the intruder faded in the following days and weeks, it was logical to suppose that it was a nova.

Then, Johann Fokkens Holwarda (1618-1651),also of Friesland, watched this ruddy star brighten and grow dim again over an 11-month interval during the year 1638. While a nova would not be expected to reappear, this was apparently flashing on and off again. Its existence with variable brightness contradicted the Aristotelian dogma that the heavens were both perfect and constant.

As astronomers became aware of the unusual fluctuations they honored the star with the name Mira, the "Wonderful Star." Mira grows brighter, then fainter, then brighter again in regular, predictable cycles of approximately 332 days, and it rises to its greatest splendor twice as fast as it fades to obscurity again. 

At its faintest, Mira is about 15 times dimmer than the faintest star that you can see without a telescope.  At maximum, it usually reaches third magnitude, or about 250 times brighter. The star is estimated to be a 6 billion-year-old red giant. Currently, Mira rises above the eastern horizon shortly after sunset and is well up in the southern sky by around midnight. Try looking for it the first clear night this week.  

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Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.