In the dark night, lightning flashed in the distance, revealing a hidden landscape. In the middle, a single giant tree stands alone, and above it float two sky icons. On the left is the Andromeda Galaxy, on the right is a sprite. The U.S. National Aeronautics and Space Administration (NASA) released the photo on the 16th (local time) as the "Astronomy Picture of the Day."
The Andromeda Galaxy is a barred spiral galaxy similar in size and shape to the Milky Way, located about 2.5 million light-years (light-year: the distance light travels in one year, about 946 billion km) from Earth. It is also called Messier 31 (M31) or NGC 224. The Andromeda Galaxy had been predicted to collide and merge with the Milky Way in billions of years, but a recent study found that the likelihood may be lower than thought.
A research team at the University of Helsinki in Finland said in June in the international journal Nature Astronomy that, contrary to the prevailing view that the Milky Way and the Andromeda Galaxy will continue to approach and collide in 5 billion years, the probability that the two galaxies will not collide within 10 billion years is as high as 50%. Compared with earlier findings that made a collision almost certain, that probability has dropped significantly.
On the right is a sprite, a lightning phenomenon that occurs above a thunderstorm in less than a second. Ordinary lightning forms in clouds several kilometers above the ground, but sprites occur in the mesosphere at an altitude of 50–80 km. Reports of sightings date back to the 19th century, but it was only 36 years ago that they were confirmed as an actual atmospheric phenomenon. On July 6, 1989, Robert Franz at the University of Minnesota, while testing a TV camera to film a scientific rocket launch, accidentally recorded flashes above a cumulonimbus with thunder and lightning. It was the first time a sprite was filmed.
The tree in the center is a baobab, which can live up to 1,000 years. Baobabs grow naturally in Australia and Africa and are known to store up to 100,000 L of water. This photo was taken near Derby, Western Australia, on the 15th.
The baobab is famous as the tree in the novel The Little Prince by French writer Saint-Exupéry. In the book, the Little Prince said baobabs bore holes in the star with their roots and must be pulled out as soon as you see them. In reality, it is the exact opposite. The baobab is a tree that gives generously to people and animals.
Bats, bees, and birds nest in baobabs, and elephants strip and eat the moisture-rich bark to survive the dry season. People make juice and bread from baobab fruit, and water boiled with the leaves is used as medicine. In the past, a large hollow space in the middle of a tree was used as a grain storehouse or a jail.
References
Nature Astronomy (2025), DOI: https://doi.org/10.1038/s41550-025-02563-1