Mercury, Elongation, Earth, Sky, Sun, Star Talk January 17, 2021
We have a first quarter, moon on january 20th, a full moon on january 28th and a last quarter moon on february 4th this week. The sun is rising around 7 15 a.m and setting around 5 00 p.m. Isn’T it great that the sun is setting just a little bit later. I feel, like we’ve, crossed a major threshold now that the sun sets after 5 pm. So what will we see after sunset? Well, go outside at sunset, just after sunset and look in the southwestern sky, you may see the elusive planet. Mercury, it’s shining at about magnitude, zero. If you can observe at 5 30 pm each night this week, you’ll see mercury a little higher than it was the day before next saturday january 23rd. Mercury will be at its greatest elongation 19 degrees east of the sun, so that’s when it will be highest in our sky. Mercury is the smallest planet in our solar system, only slightly larger than our moon. Have we sent spacecraft to mercury? Why? Yes, we have, in 1974, mariner 10 performed three flybys of mercury and got the first close up images of this planet. It only saw about 45 of the planet, though. In august 2004 the messenger spacecraft was launched by nasa. Its goal was to gain a better understanding of the topography and composition of mercury. To do this, it would need to put itself into mercury’s orbit, and that was a difficult challenge. When you send a spacecraft from earth in towards the inner solar system, it picks up speed.
The only way to do an orbiter was to take a long time and have multiple flybys of venus and mercury, each one of which was used to change the orbit of the craft and tune it to be closer to mercury in 2011. Messenger finally entered mercury’s orbit. After seven years traveling to get there over the course of its mission, messenger orbited mercury over 4 000 times took more than 200 000 images and mapped the topography of the entire planet. It taught us that the surface is the product of ancient volcanic eruptions. We see evidence of huge lava flows and see explosive volcanic vents. We see huge fault systems. The kind of faults that on earth would generate very large earthquakes during their active phase. Another goal of messenger was to confirm that there are ice deposits within permanently shadowed craters near the north pole. Earth based radar systems had found signs of water ice deposits at the poles 20 years earlier. In addition to confirming the presence of ice, messenger revealed that the ice deposits are covered by a dark layer of something that is likely to be organic material that may be 20 centimeters thick. The ideas we had for how mercury was formed had to be redone. After this mission, we’re still working on the question of how the solar system was assembled to give us a planet like mercury, so close to the sun, well that’s our sky for this week, thanks for joining me in our virtual planetarium, please subscribe to our channel, like Our video and share it with your friends, i look forward to seeing you in our real planetarium in the future.