For November, I thought I would talk about asteroids since the Earth had a close encounter, astronomically speaking, at the beginning of the month. Before talking about asteroids, I should remind you of the difference between meteoroids, meteors, meteorites, comets, and asteroids. As you might guess from the object names, meteoroids, meteors, and meteorites are all related. A meteoroid is a small pebble sized object, typically a small piece of an asteroid or comet. When a meteoroid enters the Earth's atmosphere, it burns up creating a streak of light across the sky. When this happens, we call them meteors or "shooting stars". As you have learned from reading my blog, we have many meteor showers throughout the year. These showers are caused by the Earth passing through the debris left by a comet as it approaches the Sun, then accelerates back to the outer solar system. A meteorite is what we call a meteor that does not completely burn up in the atmosphere and makes it to the surface of the planet. Many meteorites are made up of large quantities of iron, such as a small one that I have that came from the Sikhote-Alin Mountains in Russia. This meteorite fragment is from a much larger meteorite which fell to the Earth in 1947.
Comets come from the outer solar system and are typically made up of rock and ice. They have earned the name of "dirty snowballs" for this reason. As the comet approaches the Sun, the heat and solar wind cause a tail to form, such as the tail that can be seen in my pictures of NEOWISE from earlier this year. This tail, called a dust tail, is usually the brightest tail that can be seen on a comet. A dimmer tail, called the ion tail, usually has a blue color and is formed by the ultraviolet light from the Sun interacting with gas from the comet. The gas is not exhaust fumes! The gas can be formed when the ice sublimates (solid form to gas form) as the solar wind and heat from the Sun warms the comet. The ion tail points straight out from the Sun, while the dust tail can sometimes curve as the comet moves around the Sun.
Asteroids are large chunks of iron and rock. They come in all shapes and sizes like a potato. In fact, sometimes asteroids are referred to as "space potatoes!" When an asteroid impacts the Earth, it leaves a large crater, which you can see using Google Earth or other satellite images. A famous one that is located close to Utah, is Meteor Crater in Arizona. This was caused by a 150 foot asteroid exploding just before impacting the Earth. Meteor Crater is one of the most well preserved impact craters on Earth, mostly due to its young age of only 50,000 years, and the dry climate in Arizona.
While on the topic of impact craters, Meteor Crater is fairly small in size, but may seem large if you were to visit it. The diameter of this crater is less than a mile and can be difficult to see from the International Space Station which orbits at about 250 miles above the Earth. From Earth, an observer can easily see the craters on the Moon. Perhaps the easiest one to see is Tycho Crater at the "bottom" of the Moon. Tycho Crater is about 53 miles in diameter, which is still small compared to the largest crater on the Moon, known as South Pole-Aitken basin. This crater has a diameter of roughly 1,600 miles! This is currently the largest known crater in the solar system and is, unfortunately, located on the far side of the Moon. Below are a couple of images taken through my telescope with my phone. The first shows the entire illuminated Moon from the particular night it was taken. On the left you can see Tycho Crater, the bright, white crater. The second image is using a higher power eyepiece just to show the many craters on this particular area of the Moon. This was also taken on the same night.
Some day in the future, the Earth will be impacted (again) by an asteroid. Hopefully it will be a small impact over an unpopulated area of the Earth. NASA and other space agencies around the world are on the lookout for asteroids that have the potential to cause harm to those of us on Earth. These and other teams are working on ways to help divert these potentially hazardous objects so it will completely miss the Earth. Perhaps some of my young readers will grow up and join the team that helps find these objects and keep them safely away from Earth!
I want to remind you to look for Comet Howell. Beginning on the 15th, this comet can be found below Jupiter. Each passing night, the comet will move eastward so if looking for the comet later in the month, you will want to scan the sky southeast of Jupiter. Don't forget to watch for the Leonid Meteor Shower which peaks on the 17th. Hopefully my readers outside of Utah will have a better chance of seeing this shower as meteorologists are predicting cloudy skies in Utah. More notably, there is the lunar eclipse on the 30th which will peak at 2:45 AM Utah time. Hopefully the clouds won't interfere!! Remember that this is not a total lunar eclipse so that only part of the Moon will pass through the shadow of the Earth.
Check back in a couple of weeks for my next monthly sky report!
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