Just as when you cook a big meal you often end up with some tasty leftovers, leftovers from the formation of our solar system are some of the most interesting things to look at.
In the solar system, the main course is, of course, the sun. It contains 99.9% of the total mass in the solar system, almost all of which is hydrogen and helium. Of the last tenth of a hundred, nearly three-quarters of that mass is in Jupiter. Except for a small portion of leftover food, everything else ended up on one of the other planets or moons.
Gravity from the sun and planets does a great job of removing what is left of this debris. You can see this process in action every night whenever you see a shooting star. Each meteor is a smaller grain of dust that wanders between the planets. After 4 and a half billion years, most of it has been removed. If all the asteroids, comets, and dust were collected into a new body, it would be much smaller than any of the planets.
Debris close to the sun such as the inner planets are dense and rocky because the sun’s heat has vaporized all of the lighter and more volatile components, such as water and methane. We call these denser asteroids remnants. Debris farther from the Sun, still contains that lighter material. The term “dirty snowball” is often used to describe what we call comets. If some gravitational push sends one of these distant objects toward the sun, the heat will begin to vaporize the volatile components and the resulting gas cloud can be seen when sunlight hits it.
There are two sources of comets in our solar system – the Kuiper belt and the Oort cloud – and each location provides about half of the comets we see.
The Kuiper Belt is the source of so-called short-period comets. These comets are mostly located just outside the orbit of Neptune in a broad disk aligned with the plane of the solar system. Halley’s comet is the most famous of the short-period comets. Pluto is also a Kuiper belt object, and has a very faint tail like a comet. If Pluto somehow drifts further into the solar system, we’ll likely be able to see its tail. The elliptical orbits of Kuiper belt comets are generally known, and their trajectories are easy to predict.
The Oort Cloud is a much more distant repository for comets. Rather than being a disc aligned with the rest of the solar system, the Oort Cloud is a giant ball perhaps a light-year from the Sun. Instead of heading toward the inner solar system from near the plane of the ecliptic, these long-period comets come from all directions evenly. The orbits of the objects extend out from the Oort Cloud to the point where they appear almost parabolic rather than elliptical. Without the ability to accurately determine the size of the orbit, it is impossible to determine the period, other than to put an estimated lower bound on a “really long time”.
The long-period comet C/2022 E3 (ZTF) was discovered in March 2022 using instruments at the Zwicky Transit facility. Its closest approach to the Sun was on January 11, and its closest approach to Earth will be on February 1. Between those dates, its path will be in the sky between the Big Dipper and the Little Dipper. It remains to be seen if it will be visible to the naked eye.
On January 22nd, Venus and Saturn will be one-third of a degree apart. You should be able to cover them both with your pinky finger held at arm’s length. Venus will be by far the brightest object in the southwestern sky at sunset, so the conjunction should be easy to see.
On the evening of January 30, the Moon will pass almost in front of Mars. We got cloudy during Mars occultation last month, and this time Durango isn’t quite in the lane where Mars will be occluded. However, Farmington is within the path, so if you want to see the unseen, you don’t have to travel far.
Comet C / 2022 E3 (ZTF)
Astronomy picture today
Astrologist predictions for Durango
Old Fort Lewis Observatory
Charles Hicks teaches in the Department of Physics and Engineering at Fort Lewis College and is Director of the Fort Lewis Observatory.