Comet ISON passes the sun today

From 1 December, the comet could be seen in the morning sky with the naked eye

With the 60-centimeter telescope Trappist on the mountain La Silla in Chile this shot of the comet ISON succeeded on 15 November 2013. The picture was taken by three different broadband filters, whereby the telescope was tracked the movement of the comet. Therefore, the background stars appear as colorful rows of dots. © ESO / TRAPPIST / Emmanuel Jehin
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Today the time has come: The comet ISON will pass its sunniest point. He then flies only about a million kilometers past the sun's surface. It is not yet clear if he will survive, it will remain exciting. But if that is the case, the comet could be seen from Sunday in the morning sky just above the horizon with the naked eye as a bright point of light. He should then shine about as bright as Venus.

At first there was only a faint light spot, which was seen by the two amateur astronomers Vitaly Nevsky from Belarus and Artyom Nowichonok from Russia. It was formed on a shot taken on September 21, 2012 using a 40-centimeter telescope from the International Scientific Optical Network (ISON). The light spot of 21st September did not turn out to be an asteroid, as originally suspected, but as a comet. He finally received the official name C / 2012 S1 (ISON).

A "rookie" passes the sun

"ISON combines two qualities that make it a godsend for science, " says comet researcher Hermann Böhnhardt, who heads the ISON activities at the Max Planck Institute for Solar System Research in Kaltenburg-Lindau. For one thing, ISON will come very close to the sun. At surface temperatures of up to 2, 000 Kelvin, metals and other substances that remain bound in the comet material in most other cases could evaporate. There they are inaccessible for examinations with telescopes - and thus until today largely unknown.

There is also evidence that the comet may be entering the inner solar system for the first time. His orbit has been stretched so long that he seems to have been hidden in the depths and cold of space for most of his life billions of years ago. That too is a stroke of luck. "Such so-called non-periodic comets contain unadulterated information from the time of origin of our solar system, " says Böhnhardt.

ISON will be on the eastern morning sky from December 1st, just above the horizon. In the following days he always climbs a bit higher.

From 1 December in the morning sky to see

Today, on November 28th, the sunniest point of its orbit has been reached. ISON will race past the center of the sun at a distance of only 1.8 million kilometers. Since this has a radius of almost 700, 000 kilometers, this means: The comet will pass the seething surface of the star in a good million miles distance. Its core consists of ice and rock. The researchers estimate the diameter between two and five kilometers of gigantic tidal forces and heat. However, you can hardly see the comet, because ISON stands today close to the sun in the daytime sky, which shines over it. However, NASA transmits live images of its SOO Observatory SDO. display

If ISON but comes out of the Perihelpassage, he pulls steeply north and is seen from Sunday in the morning sky before sunrise just above the eastern horizon. Every day its distance from the sun increases, its tail should reach maximum size and protrude above the horizon, even before the comet's head appears. The best are the prospects from 1 to 6 December at 7 o'clock in the morning. For the days immediately after the Sun Passage, the scientists expect a broad tailed tail, which should be clearly visible.

Gas environment of the comet ISON with two wing-like structures that look like a long drawn U (arrow). The core is shown for orientation as a bright dot in the middle. Wendelstein Observatory / MPS

Breaking the comet possible

"However, it is a prerequisite that ISON survives the flyby, " B hnhardt points out. Because the body could break under the influence of the heat and gravity of our star. A few days ago, astronomers had already discovered signs that the comet had lost first fragments. For many amateur astronomers, who are eagerly awaiting the visitors, who for the first time have been celebrated as "century comets" for months, this would be a disappointment, but by far not the worst for many researchers Variant. Especially the solar probes STEREO and SOHO, which in the hours and days before and after the passage enjoy a particularly good view of the happenings, would allow ISON even deeper insights into its interior and so on to another Case of luck for comet research.

From mid-December, the comet will also show itself in the evening sky after sunset deep in the west. However, the tail runs very flat, almost parallel to the horizon. In addition, the brightness now goes back further and further. Probably there will not be an impressive poinsettia on Christmas Eve. ISON will probably once again become a binocular object - despite the fact that the comet reaches its shortest distance to Earth on December 27th and passes by in 64 million kilometers. Just in time for the end of the year, the appearance of the curly vagabond from space is more or less history.

(Max Planck Institute for Solar System Research, 28.11.2013 - NPO)