The image below is just breathtaking. I found it at the Astronomy Picture of the Day site and just gaped at it for a few moments. Pictures like this are what draws us all to astronomy — if for nothing else than the sheer loveliness of such distant, alien visions. This was actually released a couple of years ago as a part of a story about looking for what we thought might have been the heaviest (most massive) star in the Milky Way Galaxy. When astronomers first studied this region, they speculated that there was a single star here that could be as much as 200 solar masses, which would make it the most massive known.
It turns out that what they thought was a single massive star was, in fact, three stars with about 100 solar masses divided between them. If you’re interested, they’re the central bright stars above the cloud in this image. Even three stars having a hundred solar masses is … well… massive. These stars will become insanely bright and stupendous supernovae when they die. And, below them is a huge stellar nursery, cranking out more hot, young stars for future astronomers to study!
Yesterday the MESSENGER mission did a close flyby of Mercury and began returning high-resolution images. I’ll start with the last one first — it was was taken about 90 minutes after the spacecraft’s closest approach to the planet, while Messenger was on the way “out”.
The bright crater in the center is called “Kuiper” — named after Gerard Kuiper, a well-known planetary scientist. This crater was first spotted in Mariner 10 images in the 1970s, but the real news is that this image shows terrain we haven’t seen before. Everything east of Kuiper (toward the limb (right edge) is new to our eyes. Notice the rays extending out across the whole right side of the image, emanating from a relatively fresh crater that had only been seen at low resolution from Earth using radar scanning techniques. This gives planetary scientists a whole new side of Mercury to interpret as they work to understand Mercury’s formation and cratering history.
A close-up of Mercury a few minutes after close approach.
Only a few minutes after closest approach, the spacecraft snapped this image of Mercury’s cratered, pitted surface. The last time anybody saw an image of this part of Mercury was from Mariner 10 in the 1970s. The largest impact feature at the top of the image is about 133 kilometers (83 miles) across and is named Polygnotus (who was a Greek painter who lived in the 5th century B.C.). It has a central peak ring and is surrounded by smooth plains material (which probably was molten rock that flowed and hardened after the impact). Another large crater at the top left of the image is called Boethius (after a 6th century Roman philosopher). It also appears to be almost filled with smooth plains (probably formed the same way). Sometime well after the impact which created the crater, the whole area was deformed during the formation of a prominent scarp (a cliff).
Never-before-seen terrain on Mercury
Finally, from a time about 58 minutes before closest approach, Messenger snapped this dynamic image, which I think gives a nifty 3D “feel” for those of us watching on flat screens. The features in the foreground, near the right side of the image, are close to the terminator, the line between the sunlit dayside and dark night side of the planet, so shadows are long and prominent. You can make out two very long scarps that appear to cut across each other. One occurred first, and then sometime later, tectonic forces created the other one. The easternmost scarp also cuts through a crater, which means that it formed after the impact that created the crater. Other neighboring impact craters, such as in the upper left of this image, appear to be filled with smooth plains material (again, probably from molten rock that flowed after the impact and then cooled and hardened).
There will undoubtedly be more images coming from the MESSENGER mission. If you want to follow the action and get larger versions of all the images, point your browser to the MESSENGER website gallery. Mission scientists are examining images and putting them up as they do — so check frequently!
