Geminids: Origin of the shooting stars photographed for the first time

Saturday, December 14th, 2019
1:27 p.m.

Our sun still holds many secrets. In order to decrypt as many of them as possible, the US space agency NASA has sent the "Parker Solar Probe" probe to our central star.


The probe has flown closer to the sun than any other human-made object. So far, it has approached up to 24 million kilometers. The distance should even decrease with the further circumferences.


The first results of the "Parker Solar Probe" have been available recently. At the annual meeting of the American Geophysical Union (AGU), researchers presented another, previously unknown discovery this week: the probe's "WISPR" measuring instrument has succeeded in photographing the dust trail of the asteroid Phaethon. The results are currently being prepared for publication in the "Astrophysical Journal". "We absolutely didn't expect that. We didn't look for such dust traces at all," says Karl Battams of the U.S. Naval Research Lab in Washington.

  A photo of the dust trail of an asteroid would normally only be a message for astro gourmets. But the dust is probably responsible for the annual falling stars of the Geminids, which many people will be looking for again at the weekend.

Bahn is reminiscent of a comet


In addition to the Perseids in July and August and the Leonids in November, the Geminids in December offer a highlight in the night sky. For an observer on earth, it seems that glowing traces in the sky then shoot from the constellation Gemini – Latin Gemini.

  But it only looks like this. In fact, the falling stars of the Geminids occur when the Earth crosses the path of Phaeton on its orbit and small pieces of rock burn up in our atmosphere. Nobody has yet observed the trail directly.

  Phaeton has a diameter of six kilometers. It orbits the sun on a strongly elliptical orbit reminiscent of a comet. In any case, Phaeton comes closer to the sun on its orbit than almost all other asteroids. His name also reminds of this: In Greek mythology, Phaethon was the son of the sun god Helios.


As it approaches the sun, the celestial body heats up considerably, up to 700 degrees. Researchers suspect that the thermal load could have broken it apart. Since then, the material has been circling the sun in a ring.

  Battams and his colleagues have now observed part of the ring. The section is approximately 20 million kilometers long and 100,000 kilometers wide. In the vicinity of the sun, dust and boulders are accelerated on their way and pressed closer together in the ring. Only because of this "WISPR" could see the phenomenon at all. The measuring device is actually intended to take detailed pictures of the solar corona and the solar wind.

A billion tons of rock material

  Battams says the "Hubble" telescope has already tried unsuccessfully to photograph Phaeton's trail. That this was not possible was due to the small distance between the track and the sun. "Hubble" cannot look at this point. The "Parker Solar Probe" has now been successful by chance. The section of the trail is only visible as a faint shadow in an image published by NASA, but it is said to contain a billion tons of rock material.


The news of the observation comes at the right time: the highlight of this year's Geminids falls on the nights of the weekend. The Star Friends Association in Germany has put together a few tips:

  You can look out for it soon after dark. A clear view to the east is an advantage.
    The constellation of the twins can be found in the sky roughly where the moon is today.
    Theoretically, up to 120 shooting stars should appear in the sky per hour. However, the bright light of the moon ensures that many of them will not be visible in practice. This should lead to a shooting star being admired every three minutes.
  Will researcher Battam also be looking up at the weekend? Of course, he had admired the Geminids earlier, he says in an interview. "But this year I kind of think that I have to go out again to see it."

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