Longest Day of the Year

The longest day of the year in the Northern Hemisphere is this upcoming Sunday, June 21st (and the shortest day in the Southern Hemisphere)! The Summer Solstice marks the official beginning of Summer. It also happens to be Father's Day, so all you dads out there get extra sunlight on your day. 

Bright filaments connect solar storms in this Solar Dynamics Observatory image from May 14, 2015.

So why is June 21st the longest day of the year?

We have solstices and equinoxes (and seasons) because of the Earth's tilt and orbit around the Sun. While the Earth orbits the Sun, one hemisphere is tilted toward the Sun while the other is tilted away. The hemisphere that is tilted toward the sun gets more direct sunlight than the opposite hemisphere, and so is in summer. 

Image Credit: Wikipeda Commons.

The June Solstice is the day that we are most tilted toward the Sun in the Northern Hemisphere, so the Sun takes the longest time to go from sunup to sundown. In Peoria, we have 15 hours of sunlight on the Solstice.

Check out the video below to see the light of the Sun on the Earth change over a full year.  A satellite orbiting Earth took a picture of our planet at the same time each day, starting at the Fall Equinox. You can watch the Northern Hemisphere go into winter, to spring when the shadow is vertical, to summer, and back to the Fall Equinox in just 13 seconds!  





Solstices and equinoxes are nice ways to mark the passage of time. Click here to read about the Winter Solstice, Spring Equinox, and Autumnal Equinox. 

South Pole star trails at Gemini South observatory. Image Credit: Gemini Observatory.

This year, I will be in the Southern Hemisphere on the solstice! I will celebrate two Winter Solstices this year, and entirely miss out on having a longest day. I won't be too sad however, since on June 21st I will be starting my ACEAP program in Santiago, Chile. Click here to read more about the trip, and watch this blog to see updates while I am there. You can follow me and the planetarium on Facebook and Twitter too. 

Also, this Thursday, June 18, from 2-3 PM, you can join us in the Giant Screen Theater at the Peoria Riverfront Museum while we Skype with NASA astronaut Col. Mike Hopkins! The program is free, but you might want to call 309-686-7000 to reserve seats. Mike spent 6 months in space on the International Space Station, and conducted two spacewalks. Click here for more information.  

As always, if you are interested in learning more about space, science and what's up in the night sky, visit us at the Dome Planetarium.