Mercury has been in Gemini this month, and I got the picture above a few weeks ago. A nice conjunction of Mercury, the crescent Moon, and a comet (too dim to be seen with the other two, but there) was predicted for June 21, and my husband and I had scouted out the best view to the West in our neighborhood during one of our evening walks. Alas, the rain clouds did not cooperate. But there is always sometime to see when you look up! Which I’m looking forward to doing again once our skies clear here.
Camera Geek Info
Canon EOS 60D in manual mode set at f/4, 1 second exposure, ISO 800
Canon EF 70-300mm f/4-5.6L IS USM lens, set at 70 mm, manual focus
Friday was another day when, because we didn’t get the predicted rain, I was able to enjoy some astrophotography: in this case, a conjunction of Venus and Mercury. (A conjunction is when two objects appear near each other in the sky.) Note that, even in the picture, you can see that Venus is a crescent. Like the Moon, Venus has phases, depending upon how much of its sunlit side we can see. In fact, it is even more of a crescent than it looks in the picture – only about 5.3% illuminated – as you can see in this neat animation. If you zoom in, you can see that Mercury is also not a circle – it is 67% illuminated. The two are different because they’re in different parts of their orbits relative to the Earth. Venus is close to passing between the Earth and the Sun, so we see very little of its sunlit side. The lines between Mercury and the Sun and the Earth and the Sun are almost perpendicular, so we see a much larger percentage of its sunlit side.
I have rarely seen Mercury, so this was a real treat. It’ll be visible for a few more weeks in the evening sky, so if the clouds stay away, I’ll have another look.
Camera Geek Info
Canon EOS 60D in manual mode set at f/5.6, 1/30 second exposure, ISO 800
Canon EF 70-300mm f/4-5.6L IS USM lens, set at 300 mm, manual focus
As Murphy would have it, we’ve had heavy clouds and rain this week, so we weren’t able to look for Comet ISON. The clouds finally blew away this morning, so we braved the cold morning to see if we could spot the comet through the colors of the sunrise. We didn’t spot the comet, but we did see Saturn hovering above Mercury. It was quite striking, don’t you think?
Before this visit, I knew what meteorites were (rocks from space that actually make it to the Earth’s surface), but I had never given much thought to where they came from (other than the famous Mars meteorite).
Scientists, of course, had thought about it and have figured out the “parent” source of some meteorites.
A few meteorites have been caught on camera as they heat up falling through the Earth’s atmosphere, and their previous orbits can be determined from that data. The results show that most meteorites came from the asteroid belt.
An early example is here:
Some clever scientists set up their cameras where it would be easy to find any meteorites that made it to the Earth.
Radar data can also be used to find meteorites and figure out where they came from.
But meteorites that are caught on camera during reentry are rare.
Scientists can also measure the reflection spectra of meteorites (the amount of light reflected back at various frequencies) and compare them to the telescopic spectra of various asteroids. They found some pretty close matches:
But not all meteorites come from asteroids. Some come from planets.
Martian meteorites tend to be “young” and contain gases that match the Martian atmosphere measured by the Viking spacecraft.
Lunar meteorites are also identified by their mineralogy and chemistry.