Massive dust cloud spotted NASA’s Spitzer telescope could give insights into planet formation

A group of astronomers made over 100 routine observations of a dant ten-million-year-old star called HD166191 using NASA’s Spitzer Space Telescope and combined that with knowledge about the star’s brightness and size to arrive at information that will help scients test theories about how planets are formed and how they grow. Their findings are published in The Astrophysical Journal.
The Spitzer Space Telescope was an infrared space telescope that was launched NASA in 2003 and continued operating for sixteen years before it was finally decommissioned in 2019.
Most rocky planets, satellites and other celestial objects in the solar system, including the Moon and the Earth, were formed massive collisions early in the early hory of the solar system. Terrestrial bodies accumulate more material and increase in size with these collisions. They can also break apart into many smaller bodies this way.

The astronomers, led Kate Su of the University of Arizona, began making observations for HD 166191 in 2015. Around the star’s early life, dust left over from its formation has clumped together to form small rocky bodies called ‘planetesimals’, which are potentially seeds for future planets.
After the gas that had previously filled the space between these objects dispersed, catastrophic collisions between them became more frequent. The scients began makings these observations using Spitzer between 2015 and 2019, anticipating that they might be able to gather evidence of such collisions.
Even though the planetesimals themselves were too small to be captured the telescope, their smashups produce large amounts of dust. As an infrared light telescope, Spitzer was uniquely suited to detecting the dust and debris created these collisions.
Astronomers are able to record these observations detecting when the debris cloud from one of these bodies passes in front of a star and briefly block light. This is called a transit.
In mid-2018, the HD 166191 system became significantly brighter for the Spitzer telescope, which suggests an increase in debris production. During the time, the telescope also detected a transit, or a debris cloud blocking the star.

The astronomers’ work suggests that this cloud is highly elongated with a minimum area estimated to be at least three times that of the star. However, the amount of infrared brightening detected probably means that only a small portion of the cloud passed in front of the star and that the debris from this event could even cover an area hundred times larger than that of the star.
To produce a debris cloud that big, the objects in the collision must be the size of dwarf planets — like Ceres in the asteroid belt between Mars and Jupiter, which is about 473 km wide. The initial clash would have generated enough energy and heat to vaporise some of the material and set off a chain reaction of impacts between fragments from the collision and other small bodies in the system. This could be the reason for the significant amount of dust captured Spitzer.
Over the next few months, the dust cloud began growing in size and became more translucent until 2019, when the part of the cloud that passed in front of the star was no longer visible. But, then, the system contained twice as much dust as it had before the cloud was spotted. According to the astronomers, this information can help scients test theories about how terrestrial planets form and grow.