Daystar is Venus, it is the closest planet to the earth, and it is the inner planet, so its distance and orientation change is relatively large, sometimes can be seen at night, this time is Chang Gung Star, sometimes in the morning can see, this time for the Daystar! But sometimes you can't see Venus! To determine if we can see Venus now, we must first understand the direction of Venus!
1. The relative position of Venus and the Earth
The picture above is the position of Venus at 4:39:21 on July 1, 2019, that is, the position of Venus in the early morning of tomorrow! Because Venus is about to travel to the farthest point from Earth! That is, about to hide behind the sun, about 1.682 auronic units from the earth, and at the same time as the earth is at both ends of the sun!
At this point, we have passed the western distance of Venus (the western distance is visible before the sun comes out) and will be close to the position of the upper conjunction! Let's start with a few concepts!
East Distance: The East Distance refers to the point where the inner planet appears to be the farthest away from the Sun on Earth, and when it appears on the east side of the Sun, it is the East Distance! Planets can be seen in the evening at the Eastern Distance!
West Distance: The West Great Distance refers to the point where the inner planet appears to be the farthest from the Sun on Earth, and when it appears on the west side of the Sun, it is the West Great Distance! Planets can be seen in the early hours of the morning at the Western Distance!
2. Transit of Venus
Convergence and union: When the Earth is in the same straight line as the sun and the inner planet, it is called the upper union when the inner planet is on the back of the sun, and vice versa!
Transit of Venus: Because there is a relatively large angle between the orbital plane of Venus and the ecliptic plane (the plane of the Earth's orbital orbit), it is not necessarily possible to transit the sun when it is combined! The nearest transit time for Venus is:
June 8, 2004; June 6, 2012;
December 11, 2117; December 8, 2125;
Have you found that the interval between the two sets of transits is the shortest interval of 8 years, and the longest interval is about 105 years! That's right, Venus's transit cycle is more or less like that, which is formed by a special law between it and the Earth's orbit! On June 6, 2012, it is a pity that there were no friends who watched the transit of Venus, and it is estimated that I will not see the transit of Venus in this life!
Third, the phase of Venus
Venus is the only planet where phase changes can be easily seen with binoculars! And, of course, the moon we see almost every day! But the moon is a satellite of the earth! Consistent with the principle of lunar phase formation, the phase formation of Venus is caused by the change in position between the Earth and Venus and the Sun!
Principle of formation of moon phase changes! The reason for the formation is the change in the position between the Sun and the Earth and the Moon!
The phase change of Venus, of course, with the change of position between Venus and the earth will also lead to a change in distance, so the size of Venus in each phase is not the same, the largest at the time of the conjunction, but it will be submerged in the dazzling sunlight of the day, and the western distance is visible in the early morning, and once the sun rises, it cannot be seen! It is visible almost all night at the Eastern Distance, so we believe that the Eastern Distance is the most suitable for Venus observation!
Comparison of the maximum and minimum viewing angles of Venus with the lunar perspective! Phase changes in Venus require at least one binoculars to see!