Summer solstice 2021: When to see it in the UK © Getty Images

Summer solstice 2021: When to see it in the UK

Astronomy lecturer Dr Darren Baskill tells us everything we need to know about the longest day of the year.

Did you get up at the crack of dawn this morning to watch the sunrise on the summer solstice? No, us neither. But that’s okay – there’s still time to enjoy the rest of the day.

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But what precisely is a summer solstice, and why do we have it at all? And why do people visit Stonehenge?

We’ve answered all of these questions, with the the help of Dr Darren Baskill, an astrophotographer and astronomy lecturer at the University of Sussex.

There are plenty of other astronomical wonders you can see in the sky later this year. Check out our full Moon UK and meteor shower UK calendars, and our astronomy for beginners guide.

When is the summer solstice in 2021?

In the northern hemisphere, the summer solstice lands on Monday 21 June 2021.

People in the southern hemisphere have half a year to wait for their longest day: for them, the summer solstice will fall on Tuesday 21 December 2021.

What is the summer solstice?

The summer solstice is the longest day of the year. This happens on the day when the Sun reaches its highest point in the sky.

“The summer solstice occurs for the northern hemisphere when the Earth moves into such a position that its North Pole is pointing in the direction of the Sun, making the Sun high in the sky,” says Baskill.

“At the same time, the South Pole of the Earth is pointing away from the Sun, and so the southern hemisphere have their winter solstice on the same day.”

What time does the Sun rise and set in the UK on the summer solstice?

The exact times of sunrise and sunset will depend on where you are in the UK. Though the British Isles are quite small, they’re big enough to make a sizeable difference to the amount of daylight we’ll get.

“For myself here at the University of Sussex in Brighton, the longest day of the year will last 16 hours and 31 minutes,” says Baskill. “London is 50km to the north, and so the Sun will be above the London horizon for an extra 8 minutes.

“Sheffield will have a minute over 17 hours of daylight on the solstice, Edinburgh will enjoy 17 hours and 36 minutes of having the Sun overhead, while Aberdeen will have the Sun above the horizon for just a few minutes short of 18 hours!”

If you’re in London, you’ll be able to see the sunrise at 04:43am, and the sunset at 9:21pm, and the Sun will rise over Edinburgh at 04:26am and set at 10:02pm.

Counterintuitively, even though 21 June is the longest day of the year, it’s not the day with the earliest sunrise, says Baskill. “The earliest sunrise actually occurs 4 days earlier, and the latest sunset occurs 3 days later,” he says. “This slight difference is caused by the Earth orbiting the Sun not in a circle, but in a slight ellipse.”

Can I photograph the sunrise on the summer solstice?

Okay, the weather in the UK isn’t fantastic today. But there’s a chance that it might be clear where you are – and in that case, what better day of the year to try to capture the majestic sunrise?

However, Baskill suggests not trying to take a photo of the Sun itself.

“Looking at the Sun rise can be dangerous, because the Sun is so bright – it could damage your eyes or your camera,” he says. “But just before the Sun rises in the east, you can see the shadow of the Earth set in the west, revealing a beautiful pink glow that is known as the Belt of Venus.

“So I’d suggest that it’s actually best to look away from the Sun to photograph the colourful Belt of Venus in the opposite direction, rather than the sunrise itself.”

Why is the Earth tilted?

We get a summer solstice because the Earth’s North Pole is tilted at around 23.5° from the vertical, compared with its orbit around the Sun. For the same reason, the Arctic Circle gets the Midnight Sun: on the summer solstice, and for longer further north, the Sun is visible above the horizon all night long.

But where does the Earth get its tilt?

“Go back 4.5 billion years, and our infant Solar System was a violent place, with vast numbers of large asteroids hitting the young planets,” says Baskill. “One particularly large collision between the Earth and an object half its size, lead to the creation of the Moon – that’s the only way we know for such a relatively large moon to end up in such an orbit around the Earth.

“Today’s tilt of the Earth is caused by the sum of all of the impacts that were big enough to affect the tilt, including the impact that formed the Moon.”

What happens at Stonehenge at the summer solstice?

Each year, hundreds of people flock to Salisbury to see in the summer solstice at Stonehenge.

It’s believed that Stonehenge was carefully built to align with the Sun’s movements on the summer and winter solstices. On the summer solstice, the Sun rises to the left of the rock known as the Heel Stone – and archaeologists suggest that there may have been a partner stone next to it that would have framed the Sun.

Similarly, on the winter solstice, you can watch the Sun set between the upright stones of the Stonehenge’s tallest trilithon (the iconic arrangement of two upright stones with a third on top).

Is the summer solstice the first day of summer?

There are a few different definitions of summer. The astronomical seasons are defined as starting on the spring and autumn equinoxes and the summer and winter solstices. So, today, 21 June, is the first day of the astronomical summer.

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However, the meteorological seasons are defined slightly differently. The meteorological calendar splits the year into four parts of exactly three months each. By this definition, summer starts on 1 June and finishes on 31 August every year. September to November makes up autumn, winter is from December to February, and March to May is spring.

About our expert, Dr Darren Baskill

Darren is an outreach officer and lecturer in the department of physics and astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich, where he also initiated the annual Astronomy Photographer of the Year competition.

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