Astronaut Matthew Dominick photographed the comet Tsuchinshan-ATLAS on September 22 when it was about 100 million miles (160 million km) from Earth. The image was made possible by Dominick's long-exposure photography aboard the International Space Station (ISS) with a camera programmed for high precision. The comet, which is thought to have come from the far reaches of our solar system, reached its closest approach to the Sun on September 27.

As a comet approaches the Sun, it heats up and this heating causes the ices on its surface to sublimate into gas. The resulting gas and dust form a bright nucleus and a tail millions of miles long. The dust tail of Tsuchinshan-ATLAS is prominently visible in this photo and extends towards the top of the frame.

A second type of tail, known as the ion tail, is also visible slightly down and to the right in the photo. The Sun affects these two different types of tails in different ways, often blowing them in different directions. The heat and pressure of sunlight pushes the particles in the dust tail away from the Sun, but the tail may show a slight tilt in the direction of the comet's arrival. At the same time, the solar wind plucks ions from the comet's surface, creating the ion tail, which can extend in a different direction.

Image description:

A comet appears to be shooting toward the center of the image, with a cross-sectional view of the Earth's horizon and the atmospheric layers below it. From top to bottom, bands of green, yellow, blue and gray stretch across the image.

 

Credit: NASA/Matthew Dominick