Just like when you cook a big meal you often end up with some delicious leftovers, leftovers from the formation of our solar system are some of the most interesting objects to look at.
In the solar system, the main course is, of course, the sun. It contains 99.9% of all the mass in the solar system, and almost all of it is hydrogen and helium. Of the last tenth of a percent, almost three quarters of that mass is on Jupiter. Except for a small fraction that are the leftovers of the leftovers, everything else ended up on one of the other planets or moons.
Gravity from the sun and planets is doing a great job of cleaning up the rest of this debris. You can see this process at work every night whenever you see a shooting star. Each meteor is one less grain of dust wandering between the planets. After 4 ½ billion years, most of it has been removed. If all the asteroids, comets, and dust were to come together in a new body, it would be much smaller than any of the planets.
Debris that is as close to the sun as the inner planets are dense and rocky because the sun’s heat has evaporated all the lighter, more volatile components, such as water and methane. We call these denser debris asteroids. Debris that is far from the sun still has that lighter material. The term “dirty snowball” is often used to describe what we call coming. If some gravitational nudge sends one of these more distant objects toward the sun, the heat will begin to evaporate the volatiles, and the resulting gas cloud will be visible when sunlight hits it.
There are two sources of comets in our solar system, the Kuiper belt and the Oort cloud, with each location providing about half of the comets we see.
The Kuiper belt is the source of so-called short-period comets. Most of these comets lie beyond the orbit of Neptune in a wide disk that aligns with the plane of the solar system. Halley’s Comet is the best known of these short period comets. Pluto is also a Kuiper belt object and has a very wispy comet-like tail. If Pluto were somehow deflected into the inner solar system, we could probably see its tail. The elliptical orbits of Kuiper belt comets are generally well known and their trajectories are easy to predict.
The Oort cloud is a much more distant repository for comets. Instead of being a disk aligned with the rest of the solar system, the Oort cloud is a giant sphere extending perhaps a light-year from the sun. Instead of heading toward the inner solar system from near the ecliptic plane, these long-period comets come from all directions equally. The orbits of Oort cloud objects are so spread out that they appear to be nearly parabolic rather than elliptical. Without being able to accurately say the size of the orbit, it’s impossible to know 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 1. On February 11, and its closest approach to Earth will be on February 2. 1. Between those dates, your path in the sky will be between Ursa Major and Ursa Minor. Whether it will be visible to the naked eye remains to be seen.
on January 1 On the 22nd, Venus and Saturn will be separated by a third of a degree. He should be able to cover both with his little finger held at arm’s length. Venus will be by far the brightest thing in the southwestern sky at sunset, so the conjunction should be easy to see.
On the night of January 30, the moon will almost pass in front of Mars. We were cloudy during the occultation of Mars last month, and this time Durango is not quite in the path where Mars will be blocked. However, Farmington is within the path, so if you want to see the occultation, you won’t have to travel far.
Comet C/2022 E3 (ZTF)
Astronomical image of the day.
An astronomer’s forecast for Durango
Old Fort Lewis Observatory
Charles Hakes teaches in the physics and engineering department at Fort Lewis College and is the director of the Fort Lewis Observatory.