Standing on Pluto looking at the Sun

At the TAU meeting in 2006, Pluto was removed from the list of planets in the solar system by a vote of astronomers and classified as a "dwarf planet" because it was too small! The removal of Pluto from the list of planets once caused discontent among the American public.

The discovery of Pluto was in the 1930s, when the United States was in economic crisis, when the level of technology in the United States, has not yet reached the world's first, the discovery of Pluto can be said to be a great discovery of the scientific community, when the Americans were hungry, listening to the advanced technology of "spiritual food", has become a generation of memories.

No matter how mankind classifies Pluto, it is there, not at the will of mankind. In the solar system, Pluto is very far from the Sun, where the closest distance to the Sun is 30 astronomical units, and the farthest distance is 50 astronomical units. Some may wonder, if standing on Pluto, can still see the sun?

In fact, in the wide solar system, this distance is not particularly far, if there is no obstruction in the middle to block the line of sight, standing on Pluto can see the sun. So the sun seen on Pluto, and the sun seen on Earth, what will be different? Have you heard of the apparent magnitude, which refers to the brightness of the stars seen by the human eye, if the value is smaller, the brighter, and vice versa. For example, during the full moon, the apparent magnitude of the moon we observe on Earth is about -12.7, while the apparent magnitude of the sun is -26.74.

As the eccentricity of Pluto's orbit around the Sun is too large, the difference between perihelion and aphelion is almost half, so the brightness of the Sun is different when we look at different positions of Pluto, we can see that the brightness of the Sun at perihelion is -19.35, and at aphelion is -18.24. The brightness of the Sun is 457.23 times brighter than the Moon we see on Earth, and the aphelion is 164.54 times brighter, so it should not be a problem to read a book on Pluto.

Our vision is not only to perceive the brightness, but also the size of the volume. So how big is the Sun seen on Pluto? The diameter of the Sun is about 1.4 million kilometres, and Pluto's orbital perihelion and aphelion are 30 and 50 astronomical units, respectively. According to the simple trigonometric calculation, the perspective of the Sun's perihelion is 0.018 degrees, which is about 1.08 arc minutes, and the perspective of the aphelion is 0.01069 degrees, which is about 0.64 arc minutes. Compared with the viewpoint of the Sun on Earth is about 0.5 degrees, perihelion is almost 1 in 771, and aphelion is 1 in 2187, the difference is still a bit large, the limit of our naked eye is 1 arc minute, in Pluto's perihelion to see the Sun just can be distinguished is a round point, while in the aphelion only very good eyes can barely see a little. So the sun we see in Pluto is like a very bright and big star we see on Earth.

Scientists studying Pluto also found an interesting phenomenon, Pluto's size is not large, but there are many satellites, there are five known satellites, including the Cajun satellites almost half the diameter of Pluto, so they have been tidally locked to each other, always face to face rotation!

In addition, Pluto's moons are relatively large and close together, so the eclipse seen on Pluto will be exaggerated, and if it starts to happen, then a total solar eclipse will be seen on Pluto 5-6 days apart for a variable amount of time, while the next one will be hundreds of years away!