Autumnal Equinox + Pluto, Pluto, Pluto!

The Mulberry Tree in Autumn, by Vincent von Gogh

This Wednesday, September 23, is the first day of fall, the Autumnal Equinox. It is one of only two days of the year that everywhere on Earth receives equal amounts of daytime and nighttime, and the Sun rises due east, and sets due west.

I'll explain more in a moment, but first, these Pluto pictures! If you haven't seen them yet - be ready to have your socks knocked off. 

All the Pluto images below can be found at the New Horizons website.

Click on the image to enlarge. Pluto's Majestic Mountains, Frozen Plains and Foggy Hazes. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

My jaw dropped to the floor when I saw this image. New Horizons snapped this gorgeous image of Pluto as it was almost behind the dwarf planet. Zoom in on the picture and you really get a sense of how tall the mountains are, and the varied terrain. Looking at this picture makes me feel like Pluto is real at last.

Just look at those mountains!

A detailed view of Sputnik Planum - Pluto's "heart".

Looking over Pluto.

Plains, mountains, and craters.

More New Horizons images will be released each week. I can't wait to see what is released next! Follow the mission on Facebook, Twitter, or by checking its website.

Now, what's going on with the Autumnal Equinox coming up?

Both spring and fall start with the equinoxes, the two days of the year when there is an equal amount of daylight and nighttime.  We have solstices and equinoxes (or in other words, seasons) because of the Earth's tilt on its axis.  As the Earth orbits the Sun, usually one hemisphere is tilted toward the Sun while the other is tilted away. When the Northern Hemisphere is tilted toward the Sun and is in summer, the Southern Hemisphere is tilted away and is in winter, and vise versa. The equinoxes occur when the Earth is at a point in its orbit where both hemispheres get equal amounts of sunlight - neither is tilted more towards the Sun than the other. On the equinox, the Sun rises due east, and sets due west, giving everyone equal amounts of day and night. 

Diagram of the Earth's seasons as seen from the North. The most opposite is the Autumnal Equinox - both hemispheres receive equal amounts of direct sunlight. (Clearly not to scale.) Image Credit: Wikipedia Commons

The Sun's path across our sky gives us longer days in the summer and shorter days in the winter. On the Equinoxes, day and night are equal! Image credit: Daniel V. Schroeder

Hourly images of the Sun were captured in Bursa, Turkey, on key days from solstice, to equinox, to solstice. The lower path is shorter and in winter, the higher path is longer and in summer. The middle path is spring or fall. Image credit: APOD and Tunc Tezel

If you observe the sky in the coming days and nights, you will notice that the Sun does not get as high as it did in the summer. After the equinox, it will start rising farther south of east, and setting farther south of west. Our nights will lengthen until the winter solstice, the shortest day and longest night of the year. You will also notice fall constellations rising earlier and earlier in the evening.

Enjoy the changes in the weather as we enter fall - and keep a look out for new images released from New Horizons! 

Join us in watching the lunar eclipse coming up!