Mon Jul 3, 2023 EARTH AT APHELION
Our planet is now coming to a place in its orbit called aphelion. Because the earth’s orbit is slightly elliptical, we are sometimes a little closer to the sun than at other times. The near point is called perihelion, and the far point is known as aphelion - that’s where we are right now. So how come we're having summer? Well, it’s summer now where we are, but winter has just begun for folks south of the equator. Temperature changes occur because our planet is tilted over a little, about 23 and a half degrees, from straight up and down. Right now, our hemisphere is leaning inward, which puts the sun higher in our sky, and causes summer; in the winter the top half of earth leans away from the sun, putting it lower in our sky, which cools things down. Over the next few nights, you may see the waxing gibbous moon in the evening sky, adding its light to the fireworks displays.
Tue Jul 4, 2023 4TH OF JULY COSMIC FIREWORKS
On the 4th of July in the year AD 1054, a bright star appeared in the eastern predawn sky. It was near the star Al Hecka, the forward horn tip of the constellation Taurus the Bull. For the next month this new star, this “nova,” was so bright that it could even be seen in the daytime! As summer drew to a close, the star faded out of sight and was seen no more. In Europe there is no written record of this star’s appearance: either no one was looking up then, or more likely, the skies were overcast throughout its appearance. But Chinese astronomers made note of this “guest star,” as they called it, and that’s how we know about it today. If you’re out before sunrise this month, aim your telescope at that part of space behind the forward horn tip of Taurus, and you’ll find the Crab nebula, the exploded remains of a supernova - cosmic fireworks from nearly a thousand years ago.
Wed Jul 5, 2023 JULY FULL MOON
The moon is full today. Because thunderstorms are common in July, this full moon is often called the Thunder moon. According to the Sioux Indians, this is the Moon When the Wild Cherries Are Ripe. To the Winnebago, it is the Corn-Ripening Moon, and to the Kiowas, it is the Moon of Deer Horns Dropping Off. To the Omaha Indians, however, this is the Moon When the Buffalo Bellow. In ancient China, this was the Hungry Ghost Moon, named for departed souls who had left no descendants. In medieval times this was the Hay Moon or the Mead Moon, named for the elixir from the meadows of Briton and Europe. After this full moon came the first harvests from the fields and the pagan festival of Lughnasaid, which was later adopted by early Christians and became the celebration of Lammas, or “loaf mass,” in thanksgiving for the first fruits of the farmer’s labor.
Thu Jul 6, 2023 HENRIETTA LEAVITT
On July 6, 1868, the American astronomer Henrietta Leavitt was born. She worked at Harvard Observatory, and while cataloging a class of stars known as Cepheid variables - named for the fourth-brightest star in the constellation Cepheus the King - Leavitt analyzed the light curves of various Cepheids. Variable stars change their brightnesses over time; this is caused by the star’s expanding and contracting as it reaches the end stages of its life. When the star expands, it becomes brighter, when it contracts, it dims a bit. Henrietta Leavitt discovered that there was a relationship: Cepheid variable stars that were intrinsically brighter, or larger, than others, took longer to go from bright to dim to bright again. This made it possible to figure out how far away distant galaxies were, and gave us a much larger measuring stick to determine how far away things are in the Universe.
Fri Jul 7, 2023 TANABATA DAY: VEGA AND ALTAIR
Today is Tanabata Day in Japan, marking the reunion of the weaver princess and the cowherd. In this ancient story, the Sky Emperor’s daughter, Orihime, loved a herdsman, Hikoboshi. The emperor separated them by the great celestial river Amanogawa, so that they would not neglect their work. Orihime became the star Vega, and Hikoboshi is the star Altair - both these stars are well-placed in the eastern sky after sunset tonight. The river Amanogawa is the Milky Way, which when the skies are dark, you can see runs between these two stars. But on the seventh day of the seventh month, if skies are clear, magpies gather and with their wings form a living bridge across the Milky Way, so Orihime and Hikoboshi can be together once more. Part of a traditional poem recited at this time goes, “the stars twinkle on the gold and silver grains of sand... The stars twinkle, and there they will watch us.”
