New Yorkers, get ready for the latest solar spectacle.
Every year at the end of May and mid-July, residents and tourists alike flock to the streets of Manhattan to enjoy spectacular views of the sun setting in the west against the city's famous skyline. Affectionately known as Manhattanhenge, the event attracts more and more people each year, some of whom crowd together so closely that they block the streets.
“This is astronomy at its finest,” said Jackie Faherty, an astronomer at the American Museum of Natural History who calculates the date of Manhattanhenge's appearance each year. “It's like one big city-wide science party.”
The event's popularity probably goes beyond interest in science, Dr Faherty added: “People love the opportunity to take good photos, and Manhattanhenge gives them that opportunity.”
When is Manhattanhenge?
This year's Manhattanhenge will occur on Tuesday, May 28th and Wednesday, May 29th, then again on July 12th and 13th.
According to the American Museum of Natural History, the sun will set at 8:13 pm local time on Tuesday and 8:12 pm on Wednesday. In July, the sun will set at 8:21 pm on the 12th and 8:20 pm on the 13th.
The appearance of the sunset varies from day to day: on May 28th the top half of the sun is aligned with the city's grid lines, while the entire sun is visible the following day. Later in the summer, this pattern is reversed, with the entire sun visible on July 12th and the top half of the sun visible on July 13th.
Will the clouds get in the way?
Of the two opportunities this week, Tuesday's Manhattanhenge is likely to offer the best chance to get a clear view of the sunset.
The National Weather Service forecast released Monday morning predicted that New York skies would be mostly clear at 8 p.m. Tuesday. The forecast also predicted that about three-quarters of the sky would be covered in clouds at the same time on Wednesday.
Why should you see it?
Like April's solar eclipse and the dancing aurora of the sun, Manhattanhenge is another example of how our home planet's stars bring people together.
Sunsets are one of the easiest ways to experience the “wonder of the universe,” Dr Faherty said, adding that each sunset is unique: “You never know what the light will look like at sunset, what it will feel like, what the atmosphere around you will be like.”
The longer days, warmer weather and the end of the school year in New York City make Manhattanhenge “even more special,” she said. “All in all, it's a nice, relaxed summer party and celebration of astronomy.”
Why does Manhattanhenge happen?
The perfect setting of the sun amongst New York's urban canyons is the result of the geometry of the sun and the earth.
Dr Faherty said the sun sets in a different place each day because the Earth is tilted on its axis as it orbits the sun. If you look at the sun facing west from the same spot in the spring, you'll notice that the place where the sun sets moves a little further north relative to the horizon each day, she explained.
After the summer solstice on June 20 this year, the sun will slowly begin to move back south. “It's kind of like a ping-pong game between the solstices,” Dr Faherty said. “That's because it's going around the sun like we're going around a truck.”
That's why there are two chances to see Manhattanhenge – in May and July – on either side of the summer solstice. Between these dates, you'll be able to see it emerge from behind the city's skyscrapers as the sun sets, but it will appear at different heights in the sky.
“This is the season for spectacular sunsets in New York City,” Dr. Faherty said.
How did Manhattanhenge get started?
In the 1800s, city planners laid out New York City on a grid, with major streets running roughly north-south, and intersecting streets running east-west at 90-degree angles.
As long as the grid has existed, people have likely been aware of the phenomenon, Dr Faherty said.
The earliest written description of the phenomenon that Dr Faherty was able to track down was a cartoon that appeared in Natural History magazine in 1997. Neil deGrasse Tyson, director of the Hayden Planetarium, coined the name “Manhattanhenge” in 2002, inspired by the ancient ruins of Stonehenge in England.
Since then, excitement around the event has grown every year. “People noticed and it spread like wildfire,” Dr. Faherty said.
Where can I see Manhattanhenge?
One of the most popular places to watch this special sunset is the Tudor City Overpass, a pedestrian walkway above 42nd Street. This vantage point offers a great view of the Chrysler Building.
Another popular spot for photos is the Park Avenue Viaduct a few streets west, near Grand Central Terminal, but pedestrians are not allowed there and police may be present to clear any crowds that gather.
But any road running east to west through Manhattan that gives you good views of New Jersey will do, and for the best views (and photos), Dr. Faherty recommends finding a wide road surrounded by famous city landmarks.
From 34th Street you can see the Empire State Building, and another spot on 42nd Street might even bring Times Square into the frame. Wide streets like 14th, 23rd and 57th Streets are also popular, while 145th Street and Hunters Point in Uptown Queens offer unique views.
“You'd have to be standing in the middle of the road to fully appreciate it,” Dr Faherty says, so keep safety in mind when choosing a spot.
Does it work at sunrise?
A similar phenomenon occurs at sunrise in November and January, about six months after Manhattanhenge sunset. Dr Faherty calls this a “reverse Manhattanhenge.”
But calculating the date for the reverse Manhattanhenge is harder, she said, because the sun rises in the east in the other boroughs of New York.
“The Bronx, Brooklyn and Queens are big, with lots of different geographies,” Faherty says. “There's a lot of other stuff that gets in the way.”
That makes it hard to tell when you'll be able to get a clear view of the sunrise, and because the weather isn't as nice, fewer people tend to flock to Reverse Manhattanhenge.
John Keeffe Contributed report.