by Kim Malville
The magnificent constellation of Orion the Hunter rises at evening twilight and will be visible throughout the night. The brightest star of the northern hemisphere, Sirius rises a few hours later. Further north along the horizon is Gemini.
December 13-14: The Geminids meteors are visible for most of the month, from December 4-16, but they peak on the night of December 13/14. With the moon only a slender crescent, it should be a good show. The meteors radiate out of the star Castor, in the constellation of Gemini, which rises above the eastern horizon at dusk. The Geminids produce a number of Earth-grazing meteors, which hit the earth’s atmosphere at a low angle, sometimes producing brilliant fireballs. The Geminid meteor shower is nearly 200 years old, according to known records—the first recorded observation was in 1833 from a riverboat on the Mississippi River—and is still going strong. In fact, it’s growing stronger. That’s because Jupiter’s gravity has tugged the stream of particles closer to Earth over the centuries. The Geminids are associated with the near-Earth object 3200 Phaethon, an asteroid that may have undergone a collision with another object in the distant past to produce the stream of particles that Earth runs into.
December 21: December solstice at 9:28am MST. The longest night of the year, but around the solstice the sun changes its position in the sky imperceptibly, and night stays longest for a number of days. It has been a troubling time for many cultures, when it was not certain the sun would return north again and begin warming the earth. Among the Rio Grande Pueblos, winter solstice dances have been held to remind the sun of his duty to humans and not to tarry too long in his winter abode.
The Great American Eclipse
For those who drove up to the eclipse line, the sun and moon put on a great show for us. The most magnificent photograph of our great eclipse, to my knowledge, was taken by a Czech Republic professor of mathematics, Miloslav Druckmüller, who used two automatic cameras, which took a series of exposures from 1/500 sec. to 16 sec. This image is a combination of 161 eclipse images pasted together. The beautiful detail you can see in the photograph is due to the structure of the sun’s magnetic field. For millennia, the total eclipse has been the rare opportunity for humans to view this incredibly beautiful but still largely unexplained aspect of the sun.
Is Encedalus teeming with life?
Encedalus is the sixth-largest of Saturn’s 63 moons. It is 310 miles in diameter, 1/7 the size of our moon, which is dead and cold. Enceladus is even colder but may be teeming with life. It is the brightest moon in the solar system, because it is mostly covered by fresh, clean snow produced by geysers of water coming from its under-ice global ocean. Deep under its ocean, there appears to be a core made of wet sand. Water may heat up while flowing through the core, becoming a promising environment for life.
Observations from NASA’s Cassini spacecraft indicate that gravitational flexing of the core is generating heat and fueling hotspots where plumes of liquid water squirt out of Enceladus’s crust. The hot water is produced by hydrothermal vents probably as hot as 190°F, compared to -330°F on its surface.
Like a baker lovingly kneading dough, Saturn changes the shape of Enceladus every 33 hours as its orbits the planet. This kneading heats the core, a process which has probably been going on for millions if not billions of years, giving any life lots of time to evolve in the warm water around the vents. When Cassini flew through the geysers it detected silica particles that could form mineral towers growing near hydrothermal vents, like in our ocean, around which fish could swarm.
I’m sure it has happened before, but this the first time we have photographic proof of a visitor from another solar system. On October 19, this strange torpedo-shaped asteroid passed through our neighborhood, travelling much too fast to be a member of the solar system. At the earth the escape velocity from the solar system is 42 km/sec while this object was moving past us at nearly 50 km/sec, meaning it will be able to escape completely from the gravity of the sun. It was discovered by a team of astronomers at the University of Hawaii and they gave it the equally strange Hawaiian name Oumuamua which means “messenger from afar, arriving first.” Its shape is clearly unusual, with a radius of nearly 330 feet and length about a quarter-mile long. Its shape is revealed by its strange brightness variations when it rotates every 7.3 hours. When the asteroid’s long side faces the Earth, more of its surface area could reflect sunlight, making it more visible to us. And when the tip of the rock faces us, it is a very dim point of light.
The rock has a reddish hue, perhaps from metallic iron and carbon-rich matter, similar to some asteroids in the solar system and some very distant dwarf planets. Preliminary orbital calculations suggested that the object came from the approximate direction of the bright star Vega, in the northern constellation of Lyra. However, even travelling at its breakneck speed, it took so long to reach us that Vega was not near that position when the asteroid was there about 300,000 years ago. It seems likely that Oumuamua has been wandering, lonely, lost, and cold, through the Milky Way, unattached to any star system, for hundreds of millions of years before reaching us. An interstellar asteroid similar to Oumuamua probably passes through the inner Solar System about once every year, but it would have been too faint to spot. It is only recently that survey telescopes are powerful enough to have a chance to discover such an object. Oumaumaua will pass Neptune’s orbit in 2022 and leave the Solar System in roughly 20,000 years.