The sun goes through the middle of buildings on 42nd Street in New York’s Manhattan branch, during a phenomenon known as Manhattanhenge, Wednesday, July 11, 2012. Manhattanhenge, sometimes referred to as the Manhattan Solstice, happens when the setting sun aligned with the east-west streets of the main street grid. The term references Stonehenge, at which the sun aligns with the stones on the solstices in England. (AP Photo/Julio Cortez)
Let’s be honest. If you live in New York City, where light pollution is probably as bad as it is there aren’t too many celestial sights you can look forward to your arrival. And yet, twice a year, New York residents and visitors from around the world are fascinated by a rare appearance that will occur in the near sunset in the giant metropolis.
It is called “Manhattanhenge.”
Around the “traditional” date of Memorial Day (30 May) and again for a day or two around July 12, the New Yorkers are intrigued by an unusual circumstance that allows the setting sun to see all the streets lead east and west at the same time, provided that you have a clear view about the New Jersey horizon. Indeed, it is not unusual, on these special nights, to see people gathered on the corners of the preferred cross streets, watching the setting sun as it aligns with Manhattan’s canyons of brick, glass and steel, creating dramatic vistas. In recent years, the term “Manhattanhenge” is become very popular in pop-culture, also is used for the title of a 2009 episode of the tv series ” CSI: new york.” [Starry Sky, May 2018: What You Can See, This Month (Cards)]
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But Manhattanhenge, the origins are not so mysterious. The phenomenon is based on a design for Manhattan described in “The Commissioners’ Plan of 1811 ‘ for a rectilinear grid, or “gridiron” of straight streets and roads that intersect each other at right angles. This design runs from the north of Houston Street in Lower Manhattan, just south of 155th Street in Manhattan. Most of the junctions in between were arranged in a regular rectangular grid that was tilted 29 degrees east of true north to approximately replicate the angle of the island of Manhattan.
And because of this 29-degree tilt in the grid, the magical moment of the setting sun align with Manhattan’s cross streets does not coincide with the June solstice, but rather with some of the dates in late May and early July.
While we say that the sun sets in the west, most times that is not quite the case. As the popular axiom ” A broken clock is correct two times a day,” the sun rises exactly in the west only twice a year on the equinox days in March and September. But between the first day of spring and the first day of fall, the position on the horizon where the sun appears to set, which is known as the azimuth, slightly north from the west. The azimuth of the sunset slowly shifts to the north up to the day of the June solstice; then reverses course and moves to the south. On 21 June, the sun is at an azimuth of 302 degrees, or 32 degrees north of west.
But for the setting sun to see all of Manhattan’s cross streets, the azimuth should be 299 degrees, or 29 degrees north of west. That happens twice, first as the sun climbs to the solstice in late May, and then for a second time after the summer solstice-when the sun migrates to the south in the beginning of July.
And that first chance in the end of May is fast approaching.
Dates and times to watch
The man who first drew attention to the Manhattanhenge phenomenon nearly 20 years ago, is a well-known astrophysicist and director of New York’s Hayden Planetarium, Neil deGrasse Tyson. He has an interesting blog post on the subject, which you can read here.
For those who will be in New York City, and the hope for a view of this year’s event — and maybe even snap a photo — here is a tip: When a cross street is sufficient, Tyson sets out specific wider, two-way cross streets that ensure the best views from the west-northwest horizon (in the direction of New Jersey): 14th, 23rd, 34th, 42nd and 57th streets. “The Empire State Building and the Chrysler Building render 34th Street and 42nd Street especially striking vistas,” he noted.
We should also note that the times below are not for the exact moment of the sunset. Sunset is defined as the top of the sun disappears under a “real” astronomical horizon, such as what one might see from a ship at sea. For the Manhattanhenge effect, the fees must be taken for the hills and all the sights along the distant New Jersey countryside, so that the sun, the height is assumed to be 1 degree (or slightly less) above the actual horizon.
In 2018, there are four possible dates to see the effect.
For the first possibility in May, the dates to circle on the calendar, May 29 and May 30. On the first day at 8:13 pm EDT, you’ll see a “half-sun” — that is, half above and half below the landscape. On the following night, at 8:12 pm EDT, you will see a “full sun”, with the entire solar disk resting above the horizon.
If you miss it in May, you will get a second chance in July, on the 12th and 13th. On the first July date, a “full sun” will appear at 8:20 pm EDT, while on the second date, we get the “half sun” effect at 8:21 pm EDT. [In 1925, Observers Lined Manhattan for the Measurement of the Total solar Eclipse]
Manhattanhenge in the morning?
Some of you may be wondering, or Manhattanhenge is visible at sunrise. The answer is yes, but you’ll have to wait until late in the year to see it. Again, there are four possibilities at this time of day, on either side of the date of the winter solstice on Dec. 21. At this point, we will be looking 180 degrees in the opposite direction, in the direction of an azimuth of 119 degrees and 29 degrees south of east. The first chance will come on Nov. 26 as the sun continues to shift to the south, with a “full sun” at 7:06 pm EST, followed by a “half-sun” on the 27th at 7:05 pm EST.
After the solstice, the sun reverses course and begins to shift back to the north. On Jan. 15, we see a “half-sun” at 7:27 pm EST, followed the next morning by a “full sun” on 7:28 pm EST.
Keep in mind, however, that in contrast to sunset, there are more likely to be local obstructions to your visibility of the rising sun. Those who live in Upper Manhattan and Harlem, must contend with buildings and structures rise up from The Bronx; those on the Upper East Side and Midtown will be looking for Queens; and in the East Village, down to Houston Street, will to Brooklyn buildings.
Of course, in an effort to see or photograph Manhattanhenge in the morning, one should also take into account that the ambient temperature of the late fall/early winter morning air temperature is likely to be somewhere between 30 and 60 degrees Fahrenheit (17 to 33 degrees Celsius) colder than the temps in the late spring/early summer evenings, and there may even be some snow (especially in January). And finally, the opportunities of a bright and sunny winter-morning, again, are significantly less favorable in comparison with having a bright and sunny summer evening.
But when you try to see Manhattanhenge, summer or winter, evening or morning, we wish you good luck and clear skies!
The Enigma of Stonehenge
Of course, there are other places on Earth where the sun is aligned with certain attractions at certain times of the year. Probably the most famous of which is Stonehenge, the Neolithic monument in Wiltshire in the Salisbury Plain of England, where, on the day of the summer solstice, as seen from the inside of the monument, the sun appears to rise above the so-called Heel Stone. It is an event that attracts thousands of people every year.
Although experts are pretty sure that the huge upright stones like Stonehenge took about 1500 years to build and that probably once served as a cemetery, many mysteries about it still abound. More than half a century ago, the British astronomer Gerald S. Hawkins and co-author John B. White published a book, “Stonehenge Decoded” (Doubleday, 1965), who claimed that Stonehenge was used to predict a large number of astronomical events. While gaining a large following, the book also drew the criticism of more than a few renowned scientific scholars, who scoffed at its findings. All these years later, the issue remains a controversial one, and the true nature of Stonehenge may always be a mystery.
Original article on Space.com.