Mon Jan 6, 2025 PERIHELION
The earth's distance from the sun changes. On Saturday January 4th at 8:28 am EST, our planet reached perihelion, a point in its orbit where we’re closest to the sun. On average, we're about 93 million miles from the sun, but right now, we are just a little under 91 and a half million miles from it. So if we're a million and a half miles closer to the sun, how come we're having winter? Well, not everyone on earth is having winter; summer has just begun for folks who live below the equator. Our seasons are caused not by distance, but by the earth’s 23 and a half degree tilt as it orbits. Like a gyroscope, the earth‘s north pole points toward the North Star. Now our north hemisphere is tipped away from the sun; this puts the sun lower in our sky, and with less direct sunlight we get cooler temperatures
Tue Jan 7, 2025 GALILEO'S MOONS
On January 7th in the year 1610 Galileo wrote: "…at the first hour of night, Jupiter presented itself to me. Beside the planet there were three starlets, small indeed, but very bright. Returning on January eighth I found a very different arrangement. On the thirteenth of January four stars were seen by me for the first time." Galileo concluded that the four star-like objects were moons going around Jupiter. To see what Galileo saw, look for Jupiter well up in the eastern sky this evening; to the unaided eye it will look like a very bright star. But a telescope will let you see Jupiter as a small, round disc, and its moons will appear as tiny stars, lined up on either side of the giant planet’s equator.
Wed Jan 8, 2025 CALENDAR ORIGINS
Our calendar is based on repeating patterns in the heavens – the earth’s rotation, the phases of the moon, the earth’s orbit about the sun. The calendar has its origins thousands of years ago, from Egypt. By observing the sun’s progress through the sky, ancient Egyptians were able to accurately measure the length of the year, and knew it was about 365 and a quarter days long. Their calendar had 12 months of 30 days each, which worked out to 360 days total. Then they had five extra days or “empty” days, known as heiru renpet, which they used as a holiday at the end of the year. The new year began with the predawn rising of a star they named Sothis, which appeared in the east just before sunrise. Sothis is still shining up there; we call it Sirius, the brightest star in the night, which appears below and to the left of the constellation Orion.
Thu Jan 9, 2025 RIDDLES IN THE DARK
J.R.R. Tolkien was born on January 3rd, 1892. In his fantasy story, “The Hobbit,” the hero Bilbo meets a strange creature named Smeagol down in a deep cave, and they ask each other riddles. One goes like this: “It cannot be seen, cannot be felt Cannot be heard, cannot be smelt. It lies behind stars and under hills And empty holes it fills.” And the answer is, “darkness.” Now, here’s an astronomy riddle I made up: “At weddings they appear; and at front doors it’s them we hear. They’re found on Elven hands and soda cans; ‘Round Saturn they appear.” And the answer is, “rings.” Let’s try another astronomy riddle. “It’s always on, and never off. It’s more when nearby, and less when far off; It keeps the sun from spilling out. And in the end, it stops us going up and about.” The answer is “gravity.”
Fri Jan 10, 2025 MOON AND JUPITER IN CONJUNCTION
The moon is now nearly full in our sky. It has that lopsided, egg-shape that’s called a gibbous moon. This evening you’ll find it well-placed in the east after sunset; and immediately to the south of it, you should find two bright stars. The star that is closest to the moon is really bright, and it’s actually the planet Jupiter. The next star over is a real star, Aldebaran, which is a red giant star that marks the eye of the constellation Taurus the Bull. Whenever we see two celestial objects that appear next to each other, we call it a conjunction. Jupiter and the moon are separated by a distance of hundreds of millions of miles, and the distance to Aldebaran is trillions of miles – but to our eyes, they seem to be right next to each other!