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Four natural divisions in weather and daylight throughout the year resulting from Earth’s yearly revolution around the Sun and the tilt of Earth’s axis. The seasons are Spring, Summer, Fall, and Winter.


Aries, the ram

Aries, the Ram October 4, 2011

Radio Programs

Canicular Star Starting the Canicular Days of summer July 2, 2023

Summer Moon The evening sky on the first day of summer June 21, 2023

Moon, Venus, El Nath A planet without seasons April 23, 2023

Vernal Equinox Springing into a new season March 20, 2023

Lingering Summer The stars of summer hang around October 18, 2022

Hunter’s Moon The second-most-popular full Moon October 8, 2022

Autumn Marking the dates of the equinox September 22, 2022

Neptune at Opposition Lots of sunrises and sunsets September 14, 2022

Harvest Moon Timing up the Harvest Moon September 9, 2022

Moon and Mars An old milestone and a new season July 20, 2022

Far from the Sun Our “eccentric” orbit around the Sun July 3, 2022

Moon and Mars Uneven seasons on the Red Planet June 21, 2022

Summer Solstice Heading into summer’s “oven” June 20, 2022

Vernal Equinox A new season and a new beginning March 20, 2022

Planetary Seasons “Seasoning” some bright planets February 25, 2022

Perihelion Snuggling close to the Sun January 3, 2022

Hanging Triangle A holdover from summer skies December 11, 2021

Earliest Sunsets Early sunsets for much of America December 5, 2021

September Equinox II Changes in the changing seasons September 23, 2021

Autumn Equinox Marking the start of a season September 22, 2021

Moon and Saturn Stretching out the summer September 16, 2021

Moon and Antares Shifting stars across the night sky September 12, 2021

Martian Summer Heading into a long, moderate summer August 25, 2021

Far From the Sun The changing rhythms of the Sun July 3, 2021

Summer Solstice The land of the midnight Sun June 20, 2021

Equinox Myth Cracking a myth about the equinox March 20, 2021

Vernal Equinox Calibrating the seasons March 19, 2021

Groundhog Day Thinking about the seasons February 2, 2021

Close to the Sun Rounding out Earth’s orbit January 1, 2021

Blue Hunter’s Moon A Blue Hunter’s Halloween Moon October 30, 2020

Autumn The Sun changes directions September 22, 2020

Short-Night Moon A short excursion for the full Moon July 4, 2020

Mars Equinox A new season for the Red Planet April 7, 2020

Spring Equinox An egg-xacting test of balance March 19, 2020

Celebrating Spring “Springing” a seasonal tradition February 1, 2020

Close to the Sun Snuggling up to the Sun January 5, 2020

Winter Solstice The shortest day, but not the coldest December 20, 2019

Earliest Sunset Messing with the sunset December 3, 2019

Uranus at Opposition Lining up a sideways giant October 28, 2019

Summer Solstice Time for the swimsuits — on Mars October 8, 2019

Winter Preview Taking a sneak peek at winter September 29, 2019

Autumnal Equinox Stretching out the daylight September 22, 2019

Dog Days The Dog Days of summer August 17, 2019

Lahaina Noon The Sun stands high July 14, 2019

More Solstice Different dates for summer June 21, 2019

Summer Solstice Springing into summer June 20, 2019

Martian Spring Springing into a long season March 23, 2019

More Vernal Equinox The start of a cosmic journey March 20, 2019

Groundhog Day Celebrating Groundhog Day February 2, 2019

Spring Stars Leaping into next spring October 7, 2018

Autumn Falling into autumn September 20, 2018

Summer Solstice Standing still for summer June 21, 2018

Martian Autumn A new season for the Red Planet May 22, 2018

Groundhog Day Lighting the coming spring February 2, 2018

Winter Astronomy and the changing seasons December 20, 2017

Harvest Moon Sliding back the Harvest Moon October 5, 2017

Cahokia Aligning the rising Sun September 23, 2017

Autumn Ushering in the shorter days of autumn September 22, 2017

The Dog Days Sweating through the Dog Days of summer August 6, 2017

Far from the Sun Circling far from the Sun July 3, 2017

Summer Solstice Marking time by the motions of the Sun June 20, 2017

Twilight Dark, darker, and darkest skies June 18, 2017

Martian Spring Springing into a new season May 5, 2017

Last Glance A last good look at the hunter April 23, 2017

Vernal Equinox Springing into a new season March 19, 2017

Climbing Dipper Following the Big Dipper February 11, 2017

Groundhog Day Shadow or sunlight for a famous rodent February 2, 2017

Earth at Perihelion Soaking up some extra sunlight January 4, 2017

Featured Images

Dog Days August 7, 2022

Saturn and its rings viewed shortly before the start of northern summer

A New Season September 16, 2021

The Sun above Earth from the ISS

Close to the Sun January 2, 2021

Moon over Arches National Park

Plenty of Moonlight December 11, 2019

Animation of our changing view of Uranus

Planetary Bullseye October 28, 2019

Summertime! October 8, 2019

Moonrise over Yellowstone National Park

Moon Over Yellowstone September 23, 2018