May 3

Comet C2/2017 T2 Panstarrs

Comete de Hale-Bopp

Comets: the origins of the world

Comets have always fascinated humanity with their mystery and splendor. They generally heralded tragic events, such as the death of King Harold II of England in 1451 and the advent of William the Conqueror, and we find many observations of them over the centuries; the most famous in Europe is from the Halley comet which is present in the Bayeux tapestry. I was able to film one and I am happy to introduce it to you.

What's a comet ?

Les comètes

These are relatively medium-sized objects (a few hundred meters to kilometers), composed of a hard core made of solidified gas ice and dust. They are in orbit around a star.

They follow an elliptical trajectory (in the shape of an egg) around this star and as they get closer, the ice sublimes by passing to the state of gas and a halo is formed around the comet.

Behind, two tails form in the opposite direction of the star; a blue ionized gas, and a longer containing dust, which spanning millions of kilometers.

Where are they from ?

Kuiper belt and Oort Cloud

Comets come from two differentiated regions in our system: the Kuiper belt and the Oort cloud.

The Kuiper belt is a distance between the orbit of Neptune and the depths of our solar system, or 33 to 55 times the distance Earth-Sun (named 1AU or Astronomical Unit or 150,000 million kms). The Oort cloud is located much further and also includes our system but over a distance of 20,000 times to 100,000 times the Earth-Sun distance. It's a huge field with billions of objects that can become comets.

We currently know more than 3800 of these comets around our Sun; the famest is Halley comet that I had the chance to observe in 1986 when I was only 11 years old and that I hope to see again in 2061: it comes back close sun every 76 years. They are listed through to the PANSTARRS project (acronym for Panoramic Survey Telescope And Rapid Response System) based on several terrestrial telescopes around the world.

What comet can we observe ?

C/2019 Y4 (ATLAS)

During the last two months, the comet Atlas C / 2019 Y4 discovered in 2019 from the Oort cloud, was about to show up and illuminate our sky by getting very close to the sun, and therefore to us. Scientists even predicted that we could see it in broad daylight.

It finally disintegrated in flight as the sun approached, and we could only observe its debris.

Astronomy magazine wrote a very nice article on this subject.


Our subject : Comet C2-2017/T2

Position of C2-2017/T2

This comet evolves on an elliptical plane perpendicular to ours, and also comes from the Oort cloud  - and so far from our solar system that it is almost impossible to imagine the distance traveled-. It makes it literally an object from outside our solar system.

This month, it is easily observable during our nights. A photo on the left to show you its current position; do not hesitate to go watch this animation which gives an idea of ​​where the object comes from.

The emotion is great for an astronomer to be able to capture these objects in photo. And I got there this week: 160 photos of one minute each or two hours of time. I let you appreciate the result.

To read more about comet C2-2017/T2 :


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