All about cosmic rendezvous with Comet ISON ... - 20minutes.fr

While turkeys rôtiront in U.S. ovens for Thanksgiving Thursday, Comet ISON has a “date” with the Sun. It will be hot, it will be brutal, so much so that this ball of ice and dust could not survive and burn out until a small cosmic death. But it could also shine brightly.

How to follow the event live?

NASA organizes a Google hangout between 19h and 20.30 (Paris time) on Thursday at that address. Via video chat, astronomers comment on the images in real time during the final approach.

ISON is it “comet of the century”?

Probably not. When it was discovered in September 2012 by two Russian astronomers ISON (an acronym for International Scientific Optical Network ) was quickly dubbed the “comet of the century”. This nickname, it owes mainly to its origins. Given its trajectory, it is a priori the Oort cloud, an icy cocoon along the area of ??gravitational influence of the Sun located at a light year away, against 4.5 for AL Proxima Centauri, our neighboring star . It is, in all likelihood, his first pass, and probably his last, before millions of years, or even forever. For comparison, Halley’s comet, a “short” orbit, returns every 75 years. From the point of view of the show, however, “we had the most brilliant comets qu’ISON well as Hyakutake and Hale-Bopp (1996 and 1997),” says 20 Minutes Phil Plait, the Bad Astronomy blog.

Its trajectory animation

How big is it?

His icy nucleus, composed of water, carbon dioxide and dust, measured in spring, between 5 and 6 kilometers in diameter. This is 10 times less than that of Hale-Bopp. Her hair, fine ionized atmosphere around the nucleus, extends over 5,000 kilometers, and dust tail dragging on nearly 90,000 kilometers, or a little more than seven times the diameter of Earth. Below its passage observed by the STEREO probe:

At what distance from the Sun Will it happen?

close. On a cosmic scale, ISON will shave our mustaches star passing a little over a million kilometers from its surface on Thursday. Mercury, the closest planet to the Sun, is 60 million miles, and the Earth, 150 million.

ISON Will it survive its passage near the Sun?

is 50/50, according to scientists. At a press briefing NASA on Tuesday astronomer Carey Lisse said that if he was in Las Vegas, it would encrypt survival of the comet to 40%. “Their behavior is very difficult to predict. So far, ISON has held up pretty well and hopefully it will stay full, “notes Phil Plait. Everything will depend on its composition and density.

The event will he visible to the naked eye?

No, because the comet will be located too close to the Sun. It was, however, visible in recent days with a pair of binoculars from the southern hemisphere.

And the potential fireworks?

If

ISON remains intact, it should be able to observe with the naked eye from the northern hemisphere between the second week of December and Christmas, circa 5am, low on the horizon, near the Big Dipper. Even if it decays, it is not excluded that residues are not consumed completely and shine in the sky of December.

What can we learn from ISON?

Scientists have pointed all their instruments on Earth and in space, on ISON. It should provide new data illuminating the formation of the solar system. Comets are indeed “frozen first day witnesses. Beyond the scientific interest, it is a fantastic show, “says Plait.

Philippe Berry