The star HBC 672 casts a gigantic shadow that is reminiscent of wings. Now astronomers have discovered: the shadow is moving. There is only one plausible explanation for this.
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The phenomenon is nicknamed “Bat Shadow”
Photo: NASA, ESA, K. Pontoppidan
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Sometimes discoveries need a catchy name, whether it fits or not. This is the case with the star HBC 672 in the Serpens nebula.
The still quite young star, which is around 1300 light years away, is surrounded by a protoplanetary disk made of dust particles and gas, which in turn casts gigantic shadows. They are about 200 times the size of our solar system. The images that astronomers use Hubble Space Telescope taken up by this phenomenon are impressive. The protoplanetary disk of the star is aligned with our earthly perspective. This results in an effect that we know from tubular lampshades: the light only penetrates up and down, but a shadow is cast along rings.
Stern casts huge “fluttering” shadows
The shadow, which appears to be to the right and left of the star, is reminiscent of huge wings. “Bat Shadow”, so-called “bat shadows”, scientists have lovingly christened the phenomenon. Now the team at the Hubble telescope has noticed: The bat shadow flutters! “The shadow is moving. It flutters like a bird’s wings, ”says Klaus Pontoppidan, an astronomer at the Space Telescope Science Institute (STScI) in Baltimore.
The team was able to observe the “fluttering” of the shadow over 404 days. When they overlaid old and newer shots, they found that the shadow had moved. Behind the phenomenon could be a planet that pulls on the protoplanetary disk due to its gravity and distorts it. The circular disk of gas, dust and rock is not a ring like Saturn, but could be saddle-shaped, as the scientists suspect. “The disc is not like the Saturn rings – it is not flat. It is inflated. So that means that when the star is going straight up, the light can continue straight up – nothing blocks it. However, it does not come out along the plane of the pane and cast a shadow, ”says Pontoppidan.
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Planet could be as close to the star as Earth is from the Sun.
The time it takes for the light to get from the star to the edge of the shadow is around 40 to 45 days. Pontoppidan and his team have calculated that the planet, which may distort the disk, orbits the star in no less than 180 days. They estimate that the planet is approximately as far from its star as the earth is from the sun.
Foto: NASA, ESA und A. James und G. Bacon (STScI)” width=”980″ height=”680″ srcset=”https://www.ingenieur.de//srv/htdocs/wp-content/uploads/2020/06/Schatten-980×680.jpg 980w, https://www.ingenieur.de//srv/htdocs/wp-content/uploads/2020/06/Schatten-520×361.jpg 520w, https://www.ingenieur.de//srv/htdocs/wp-content/uploads/2020/06/Schatten-768×533.jpg 768w, https://www.ingenieur.de//srv/htdocs/wp-content/uploads/2020/06/Schatten-313×217.jpg 313w, https://www.ingenieur.de//srv/htdocs/wp-content/uploads/2020/06/Schatten-150×104.jpg 150w, https://www.ingenieur.de//srv/htdocs/wp-content/uploads/2020/06/Schatten.jpg 1501w” sizes=”(min-width: 768px) 980px, 520px”/>
The graphic shows a young star surrounded by a saddle-shaped disk. When the disk rotates around the young star, the light from the star is blocked in different places and not evenly. So there is a “fluttering” shadow.
Photo: NASA, ESA and A. James and G. Bacon (STScI)
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A second explanation given by the researchers: A second star with lower mass orbiting HBC 672 outside the plane of the disk could also be the cause of the “flutter”. Pontoppidan and his team doubt that.
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Protoplanetary disks: always interesting for astronomers
The few million year old star HBC 672 is too far away for astronomers to study its protoplanetary disk directly. In this respect, the shadow that the disc casts is a stroke of luck: it allows certain conclusions to be drawn about the composition of the disc. The researchers can use color differences at the edges of the shadow to determine what type of particles the disc is made of.
Protoplanetary disks of young stars are also of particular interest to researchers because they allow us to look at the beginnings of our own solar system and to draw conclusions about how planets are formed. A protoplanetary disk made of gas and dust also revolved around our sun 4.5 billion years ago, from which the solar system developed over time.
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