It’s a star of ice and dust which bears the sweet name of “C/2022 E3 (ZTF)”. That cometcoming from the confines of solar system, had not pointed the tip of its tail near the Soleil for about 50,000 years. With its kilometer in diameter – half the principality of Monaco, this celestial object could be visible to the naked eye at the end of January. It will reach its perihelion, that is to say its closest point to the Sun, this Thursday, according to the calculations of astronomers.
She will be closer to the Terre next February 1, at just under 42 million kilometres. But what is so special about this comet? How best to observe it in the coming weeks? 20 Minutes looks at this star that will decorate our night sky thanks to the lighting of Léa Griton, lecturer at Sorbonne University and researcher at the Paris Observatory.
Why is this comet special?
“We do not have the opportunity to observe a comet with the naked eye every day”, notes Léa Griton from the outset, adding that this celestial object is “always very pleasant to look at, even for amateur astronomers” . With their tails, comets have fascinated mankind for a long time. Their name comes from the ancient Greek “hairy star” and they are nicknamed “star-brooms” in Japan. The specificity of “C/2022 E3 (ZTF)” is that it comes from very far away. “In the solar system, all objects are subject to the enormous attraction of the Sun. The orbit of the planets is almost round but the comets have a very crushed ellipse”, deciphers the researcher at the Paris Observatory. Farthest from its oval, the comet is therefore at the edge of the solar system.
However, “often comets provide us with information on where they come from in the solar system”, underlines Léa Griton. Astronomers watch these comets carefully to learn more about their composition and the universe. But the projectEuropean Space Agency planned pour 2029 « Comet Interceptor » (Comet interceptor) should make it possible to learn even more. “We’re going to put a small space probe in one of the equilibrium points around the Earth, that is to say where the objects can stay in place – and intercept a comet which will come from the other end of the planet. solar system for the first time”, explains the astronomer. The researchers want to catch a “primitive comet”, which has never passed close to the Sun. A rare pearl therefore, because even “C/2022 E3 (ZTF)” does not meet these criteria. “The idea is to analyze a comet before it is microwaved, near the Sun, because this can modify its composition”, simplifies Léa Griton.
What do we see when we observe a comet from Earth?
Planets, milky way, shooting stars, etc. Space is wonderful. And, with their trails of light, comets are not left out. It is specifically these tails of light that can be observed from Earth. “Comets have two tails: one of them is escaping gas, while the other is made up of plasma”, underlines Léa Griton. When approaching the sun, comets undergo its furnace but also its solar winds. A part of his body sublimates, that is to say passes from the solid state to the gaseous state, causing these beautiful streaks. “As we approach the sun, where the temperature is higher and the solar wind much stronger, the two tails become more and more intense, which allows us to see them with the naked eye”, explains the lecturer at the Sorbonne.
“It’s very moving to observe a comet, it’s a celestial object that you will never see again in your life. We have the chance to see an object millions, even billions of kilometers from us and which will continue to exist without us”, underlines Léa Griton. It will take 50,000 years for the next visit of “C/2022 E3 (ZTF)”. But even more extroverted comets rarely pass through more than once in a human lifetime. The most famous of them, Halley, only returns every 76 years and her next visit is scheduled for 2061.
How to take advantage of this opportunity?
For “C/2022 E3 (ZTF)”, the opportunity begins tonight. “Taking into account the distance between the Terre and the comet, the ideal time to observe it is around February 3. But the Moon will be full on the 5th, so it is better to try your luck around January 24 or mid-February,” explains Léa Griton. Because the brightness of the Lune can be very disabling when trying to observe celestial objects less bright than it – the vast majority. However, this comet should be “relatively easy to spot”, in particular because it will be visible from the constellation Ursa Major.
In order to best contemplate this celestial object, it is better to move away from the big cities where the light pollution erases all the details of the sky. “At the Paris Observatory, we only observe the sun because everything else is degraded by light pollution,” says Léa Griton. The specialist encourages the most motivated to invest in a pair of binoculars: “For this kind of object, it is better to have a very good pair of binoculars than a ‘cheap’ telescope. They are much more practical to reuse during the day, much more transportable and allow you to easily search for the object with your hands when a telescope must be positioned and installed. » With good binoculars, it is possible to observe several satellites of Jupiter and even “almost observe the rings of Saturn », Assures the expert. For “C/2022 E3 (ZTF)”, it will be necessary above all to pray that the weather is clear because if the sky is full of clouds, the comet will make its visit on the sly, well out of sight…