Where could you see the Milky Way glowing softly above you in a big city? A planetarium possibly, or perhaps during a major power blackout. But if you're in New York City, you can see it on the ceiling of Grand Central Terminal. A beautiful mural of the night sky has graced this elegant Beaux-Arts building since its opening over a century ago. It has been seen by millions, but also generated controversy and confusion.

Two murals
The mural we can see today dates from the 1940s. It was painted on a set of panels and bolted onto the ceiling, covering the original 1913 mural. Although less ornate than the earlier one, it's faithful to the design.

When the terminal was built, the architect Whitney Warren asked French artist Paul César Helleu to design a night sky for the ceiling. Helleu chose cerulean blue tempera to present a bright daytime Mediterranean sky. On this background, stars and outlines of constellations would be in gold leaf. The brighter stars would also have small incandescent light bulbs in their centers. For classical representations of the constellations – as in old star atlases – Helleu asked for guidance from a prominent astronomer, Dr. Harold Jacoby at Columbia University. Australian-born artist Charles Basing and a team of painters carried out the work.

When Grand Central opened for business, it was no surprise that the passengers were bowled over by this beautiful ceiling 125 feet above them in a concourse 275 feet long and 120 feet wide.

Sadly, over the years the mural deteriorated and also became discolored. In the 1940s, rather than repair it, they replaced it. And in its turn the newer one gradually got grimy. People assumed it was due to diesel smoke, but it eventually turned out that it was tar from passengers' cigarette smoke.

The mural on the ceiling was one of the matters to resolve in the nineties when the terminal was to be redeveloped. Some experts argued that the original ceiling should be restored. Others said that it was in such poor condition that wasn't a viable option. The newer tableau also had its fans who said it was a work of art in its own right.

The decider was asbestos. The ceiling was full of it, but it was contained as it was. However if they tried dismantling the panels to expose the old mural, it could become hazardous. The newer mural was in good condition except that it needed cleaning.

The sky of Grand Central Terminal
The mural contains nearly 2500 stars. It depicts the zodiac constellations visible in autumn/winter in the Mediterranean region: Cancer, Gemini, Taurus, Aries, Pisces and Aquarius. There are also some non-zodiac constellations, most prominently, Orion and Pegasus. The Milky Way, made up of a multitude of tiny stars, seems to flow from the southwest to the northeast corners.

There are also two bands stretching across the mural in an east-west direction. A broken line represents the ecliptic, the path the Sun seems to take during a year. The zodiac constellations all lie on the ecliptic. The solid line is the celestial equator. That's a projection of Earth's equator into the sky as part of a celestial coordinate system that functions much as the grid system of latitude and longitude does on Earth.

All of these sky features are in gold leaf, and the lights of the brightest stars are enhanced by the LED lighting installed in 2010.

Three surprises
A dark square
Modern conservation and restoration protocol includes leaving evidence of different stages of the past. Therefore when the ceiling was cleaned, a small square was left to show what the whole ceiling had looked like before.

A hole in the ceiling
Not far from “Pisces” there's a small hole. In July 1957 a Redstone missile was to be displayed in the concourse. (This type of missile was the first intercontinental ballistic missile armed with a nuclear warhead.) The hole was needed for a cable to stabilize the missile, not because it was the only way to fit the missile in the concourse.

Many people seem to think that the Redstone display was in response to the Soviet launch of Sputnik. In the days of the Cold War, a nuclear missile might well have been a not-so-subtle message to the Russians, but Sputnik wasn't launched until October of that year. The Redstone did take part in the space race several years later. A Redstone rocket launched the first American into space in 1961 – Alan Shepard in his Mercury capsule.

The constellations are backwards
The starscape was supposedly so accurate that children could come to Grand Central to learn astronomy. Nonetheless a month after Grand Central Terminal opened, a commuter pointed out that the constellations were backwards.

Is this true? You will be able find out more in a few weeks in “The Sky of Grand Central Station – It's Backward”.