So we’ve sent a spacecraft into space, put it in orbit near a comet, landed on it with a smaller probe, and listened to the comet’s song. What an amazingly human thing to do.
A Holmes Mystery
In 2007 Comet Holmes gained notoriety when it suddenly brightened from magnitude 17 to magnitude 3 in about two days. This made it visible to the naked eye under clear dark skies. The coma (the cloud-like feature surrounding the icy/rocky nucleus) expanded by a factor of four by the end of October, and this once faint object began to look like a traditional comet. We aren’t exactly sure why.
Lost Comet
This week comet Siding Spring (also known as C/2013 A1) made a close approach to Mars. It’s not a particularly bright comet, but it was close enough for the Opportunity rover to take an image of it from the martian surface. Think on that one just a bit. We have robots on Mars doing comet photography now. At closest approach, Siding Spring was about 140,000 km from the center of Mars. If it had made a similar pass by Earth it would have been about half the distance to the Moon.
Night of the Comet
The Rosetta spacecraft has successfully moved into orbit around 67P/Churyumov-Gerasimenko. We’ve been getting images of the comet as Rosetta approached, but now that it’s in orbit we are getting high resolution images such as the one above. You’ll notice the comet really looks like an asteroid, with what seems to be a rocky/dusty surface. That’s because comets and asteroids aren’t as different as often portrayed.
Mars Mission
On October 19 of this year the comet C/2013 A1 (more commonly known as Siding Spring) will make a very close approach to Mars. At its closest point, the comet could be only 120,000 km from the surface of Mars. There’s no chance it will hit the planet, but such a near miss could have an effect on both the planet and the probes orbiting it.
To Greet the Morning Sun
Comets are often pictured as cold objects, far from the Sun, but in fact there are many comets that approach quite close to the Sun, such as the one pictured above. They are known as sungrazers, and they have an interesting story to tell.
Dust in the Solar Wind
An unusual new comet has been discovered. Or perhaps it should be called an asteroid. Whatever it is, it has six tails and is called P/2013 P5. It was first observed the end of August this year, but now a new paper in Astrophysical Journal Letters gives the initial results of observations so far.
Point of Origin
Because of their gradual evaporation, periodic comets don’t last long on a geologic scale. Over time they will disappear. So it’s generally thought that periodic comets were once non-periodic ones that were perturbed by Jupiter or other planets into a short periodic orbit. Of course that raises the question: from where do the non-periodic comets come?
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