Doug's Darkworld

Yes, it’s true, scientists have discovered two huge gamma ray emitting bubbles emerging from the Milky Way. The above image is what they look like … if the viewer is considerably outside the galaxy and can see gamma rays. People can’t see gamma rays, so the above image is “false colour” so to speak. I know some people get upset that so many NASA images are false colour, but when talking about colours that people can’t see, what’s the problem? What’s the deal with these bubbles? Well, no one knows. The current best guess is that they are the remnants of some sort of outburst  from the black hole at the centre of our Galaxy. There are other possibilities, and scientists will be exploring them eagerly. And while this is an exciting discovery in that it gives us new insight into our galaxy, it has no practical bearing on Earth. These bubbles don’t and can’t effect Earth in any way, my histrionic headline notwithstanding.

Yes, there’s a black hole in the centre of our galaxy. It has about as much mass as thirty million Suns. No, it’s not going to swallow the galaxy, any more than the planets are going to get sucked into our Sun. For the lay people, a black hole is a region of space with so much mass that light can’t escape its gravity. So while it can’t be seen directly, this is what a black hole would look like up close and personal:

Well, technically one can’t actually see the black hole, but the astute reader should be able to discern where it is in the above image. The black hole is so dense that it warps and bends light that gets near it. Note that every star in the picture has at least two images, and the entire sky can be seen near the black hole as light from every direction is bent around the black hole. I know, hard to grasp, the original image is here, maybe they explain it better. I’m pretty sure that being this close to a back hole would be fatal, the gravity would be so strong that normal matter would be ripped apart.

Speaking of dark objects in space, the Mars Express recently captured this image of Phobos:

Phobos is the innermost and largest of Mars’ two moons, the other being Deimos. It’s an irregularly shaped lump of ice and rock, averaging about  22 km (14 miles) in diameter, covered with about a meter of dust. It’s the darkest moon in the Solar System, and is believed to be a captured asteroid. It’s also doomed, its orbit is slowly decaying and in the next 50 million years it will be torn apart and crash into Mars. It’s going to be a pretty spectacular sight, and if I’m still around then, I’ll be sure to blog about it.

And while we’re on the topic of Phobos, since it’s not a topic I visit regularly, two minor misconceptions to clear up. Yes, there is indeed a monolith on Phobos:

It’s the bright object with a shadow in the middle right, it’s about the size of a building, whatever that means. One will sometimes actually hear alien aficionados claim that the monolith on Phobos must be artificial and should be visited, apparently confused by the fact that there was a monolith in 2001, a Space Odyssey. The monolith in the fictional movie was made by aliens, the monolith on Phobos is a rock. Yes, it is upon such slender threads that belief in aliens resides.

It gets worse. Both moons of Mars were discovered in 1877. In the 1726 book Gulliver’s Travels there is a description of Mars having two moon very similar to the moons that were discovered more than a century later. Again, some have claimed that this is proof that aliens have visited Earth, or even that the author, Jonathon Swift, may have come from Mars. No, it’s proof that Jonathon Swift was reasonably well read. Astronomers of his day were very much looking for symmetry and order in the Solar System. It was speculated that since Venus had no moons, Earth had one moon, and Jupiter had four moons … might not Mars have two moons? And if Mars had two moons, they would have had to be very small to avoid detection by the telescopes of the day. Which is more likely, that Swift’s fictional moons were based on contemporary astronomical speculation … or personal knowledge gained from alien spacefarers?

No, it’s not a trick question. Have a great weekend everyone!

(The above images are all claimed as Fair Use under US copyright law. They are not being used for profit, they are central to illustrating the post, and they are properly attributed. Gamma Ray Bubble image, Credit: NASA/GSFC. Black hole image, Credit & Copyright: Alain Riazuelo. Phobos image, Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA; Acknowledgement: Peter Masek. Phobos monolith image, Credit: Mars Global Surveyor, NASA. Is there a point to this post. Yes. We are entering the greatest age of exploration ever, the exploration of the Universe around us! I mean, two of these images were taken by cameras orbiting Mars, something that would have been considered a pipe dream by many people in living memory. How cool is that?)