Arizona residents could see a periodic comet in its skies this month

A periodic comet known as Comet 21P/Giacobini- Zinner made its closest pass by Earth in some 72 years.

This remnant from the creation of the solar system passed by the Earth on Monday by some 36 million miles. This is still close by cometary standards, as the comet is now visible in binoculars from dark sky locations in Arizona.

Comets are thought to be remnants of the creation of the solar system, some 4.6 billion years ago.

There is a rather large cloud of comets that lie way out in the outer regions of the solar system, known as the Oort Cloud.

Comet 21P is thought to have originated from this massive cloud.

The comet orbits the sun once every 6.7 years on average and comes close to the Earth at various times in its travels.

The comet is made up of a nucleus which may be 2 kilometers in size and around this is a large region known as the coma. The coma is made up of material from the comet which is blasted off the nucleus as the comet travels around the sun.

The closer the comet gets to the heat of the sun, the more the comet develops a sizeable coma. Recent estimates place the size of the coma of Comet 21P at 180,000 miles in diameter. That makes the coma nearly as large as the distance of the Earth to the Moon!

Comet 21P, was discovered back on Dec. 21, 1900 by Michel Giacobini and later recovered, after being lost, by Ernst Zinner in 1913.

Now is the time to observe Comet 21P if you have never look for a comet!

The comet is visible in a pair of binoculars from dark location, now, until around the 20th, when bright moonlight will once again interfere with your views of the comet.

To locate the comet in real time, I suggest that you go to this important source on the web: TheSkyLive.com.

This site will not only provide you the basics in information about the comet, but it will also provide you with the actual observational coordinates to quickly locate the object with modern tracking telescopes.

The comet appears to glow green, with a small tail, pointed in the opposite direction of the sun. All comets have tails that point away from the sun and come with either a dust tail, or a plasma tail — or both!

Another important note about this comet is that it is thought to be the source of the annual Draconid meteor shower, which is known for some bright slow moving fireballs, peaking around Oct. 8.

There is a possibility of higher than average meteor rates, as Comet 21P, swings past the Earth at its closest on Sept. 10.

Comets are amazing for many reasons, as they travel with great speed as they zero in on the gravity of the Sun and whip around the other side.

Some comets are lost to interstellar space as they orbit the Sun and never return. Some simply hit the Sun and are vaporized!

This group of comets have the distinction of following regular orbits around the Sun and are thus known as periodic comets.

The most famous of the periodic comets has to be comet Halley!

Comet Halley is officially known as 1P/Halley and orbits the Sun once every 76 years on average. Last seen by many in 1986; it will return as a great comet on July 28th, 2061, to a sky near you!

So; if you are not planning on being around in 2016, why not try a spot Comet 21P, while you still can!

Listen to Dr. Sky on KTAR News 92.3 FM every Saturday at 3 a.m.

To print your very own September 2018 star chart, click here.

To view satellites/dates/times of passage, click here.