If the sky is not cloudy tonight and the air is not too cold, it might be worth a few minutes to have a look in the southern sky for the meteoric streaks of light from the Geminid shower. Although Thursday was the predicted maximum activity, there should be plenty of sky streaks tonight from 10 p.m. well into the wee hours.

The Geminids are one of several meteor showers that occur annually, the names of which come from the region of the sky from which they appear to emanate. Others of note are the Perseids in mid-August, the Orionids in late August, the Leonids in late November and the Ursids in late December.

Of these, the Geminids are one of the slowest moving and typically produce the most meteors per hour.

Constellations are groups of stars that are an atlas of the sky as seen from Earth. Although derived from ancient names, the International Astronomical Union, a group that is better known for demoting Pluto from its status as a planet, standardizes the boundaries of the constellations. This celestial geography helps astronomers and laypersons alike to locate stars and other heavenly objects.

The Geminids are of special interest because they result from Earth passing through the junk trail in the orbit of a rocky comet called 3200 Phaethon. 3200 Phaethon itself will be only 6.4 million miles from Earth on Saturday, a rare event and a near miss by cosmic standards.

Most years during the Geminids, 3200 Phaethon is nowhere near Earth. The object’s orbit is highly elliptical and tilted slightly to the plane of the solar system.

Its orbit takes 3200 Phaethon well inside the orbit of Mercury with a perihelion (closest distance to sun) of only 12.5 million miles. At aphelion (farthest from sun), it is inside the asteroid belt between Mars and Jupiter, 21 million miles from the sun.

Even without consideration of its unusual orbit, 3200 Phaethon is an unusual object. It appears to be rocky like an asteroid, but asteroids do not typically leave a debris trail. Comets do because they are mostly ice and gas, and so degassing causes the trail. Some astronomers consider 3200 Phaethon to be a “dead” comet, from which the ice has all melted away.

Astronomers do not agree on why 3200 Phaethon leaves its dusty trail. Some think it may have originated when a crash with another space rock broke off pieces that did not come near Earth’s orbit for generations until Jupiter’s gravity slowly perturbed the dust trail enough for Earth to run into it.

Other astronomers think that when 3200 Phaethon gets too close the sun blasts particles away from the asteroid, blaming the approach to the sun for the debris trail.

NASA’s twin STEREO spacecraft imaged the asteroid between 2009 and 2012, and researchers reported that they saw a tail emerging from the comet. This occurs when Phaethon gets within 13 million miles of the sun. At that distance, its temperature rises above 1,300 degrees Fahrenheit, which is hot enough to cause the dust stream.

Earth’s next close approach of 3200 Phaethon will be on Dec. 14, 2093, when it will fly past Earth at a distance of a mere 1.8 million miles. A collision with an object this size (about 3 miles across) would be a catastrophic event, if not civilization-ending. Do not worry. It is not in the stars for a collision, unless Jupiter or some other celestial object perturbs its orbit just the right amount.

Richard Brill is a professor of science at Honolulu Community College. His column runs the first and third Friday of the month. Email questions and comments to brill@hawaii.edu.