Category Archives: astronomy

astronomy, black holes, Sagittarius A*

A Snake on a Galactic Plane

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Action at the Heart of the Milky Way

The center of the Milky Way galaxy is a busy place. While we can’t see everything that’s there using optical light due to intervening clouds of gas and dust, astronomers do look at it using infrared-enabled telescopes as well as x-ray telescopes. The wavelengths of light they see reveal some interesting details about the stars and masses of gas and dust that lie at the core. Astronomers using radio telescopes are studying the supermassive black hole at the galaxy’s heart and have found clouds of hot gas and a gas streamer there. In the not-too-distant future, we’ll see the first “image” of that object, called Sagittarius A*.

Stars at the Galaxy’s Heart

stars near SGR A*
Stars and gas at the heart of the Milky Way, as seen through repeated observations by telescopes at the European Southern Observatory

One of my favorite images of the stars at the Milky Way’s heart was made over a period of 16 years by astronomers at the European Southern Observatory in Chile. What they wanted to do was track the motions of stars in the region of Sag A*. As they watched the motions of 30 stars near the black hole and tracked their orbits. Knowing the orbits of the stars also reveals information about the mass of the black hole, plus knowledge about other stellar motions and formation. There is a great deal of star-forming material in the region, and it’s useful to know if stars can form in such a busy environment.

Sag A* in Radio Emissions

snake in the galaxy
A radio image from the Karl G. Jansky Very Large Array showing the center of our galaxy and a curious radio filament (the curved red line). It is located near the center of the image, & the supermassive black hole Sagittarius A* (Sgr A*, the bright source near the bottom).
NSF/VLA/UCLA/M. Morris et al.

Radio emissions from the center of the galaxy also tell an interesting tale. Those come from superheated material near the black hole. In 2016, a researcher named Farhad Yushuf-Zaden spotted a very odd-looking filament—a gas streamer—near the region of the black hole. The data came from the Karl G. Jansky Very Large Array in New Mexico, and it showed a 2.3 light-year-long “snake” of gas. New observations show that the hot gas originated from the area of the accretion disk around the black hole. It’s not possible for something to actually escape FROM the black hole itself because its gravity is too strong. However, activity in the accretion disk kicks stuff away before it gets swallowed up. This generally happens through energetic jets of hot material escaping the region of the black hole. In the case of this stream, astronomers are still speculating on its cause.

Building a Snake of Hot Gas

So, how would such a lengthy hot gas streamer make its way across space from the region of Sag A*? Nobody’s quite sure, but astronomers have some good ideas. In an accretion disk environment, particles can get kicked away at very high speed by the spinning of the accretion disk. These particles get sped up as they circle around lines of magnetic force generated by actions in the disk. That could cause them to be ejected from the disk at very high speeds. If there are enough of them, they would form a constant, fast-moving stream and that could be what the VLA “saw”.

The gas streamer might be something called a cosmic string. It’s a bit more farfetched, but not entirely out of the question. Nobody’s actually SEEN a cosmic string, so they remain theoretical until one is detected. Scientists think of them as very long, thin objects with some amount of mass and carry an electric current. If they do exist, astronomers suspect they might gravitate to the centers of galaxies, and they could be “captured” if they get too close to any lurking supermassive black holes. It’s an “out there” kind of idea. If it’s true, finding it at the heart of our galaxy would prove a great deal of theoretical work. To prove it, however, is going to take more observations.

The gas streamer might just be superimposed over the region and not connected to the black hole at all. It just “looks” like it’s connected to Sag A* because of our point of view. However, there’s one kink in the snake that implies something in the region is affecting it. What that could be remains to be figured out. The jury’s still out on all three ideas.

astronomy

History of Space Exploration is a History of Our Culture

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Creating a Space-bound Civilization

Hubble Space Telescope, although decades old, is part of the space age, delivering visions across the universe. NASA

For much of the past year and a half, I worked on a book about space exploration called Space Exploration: Past, Present, Future (it’s actually due out in mid-November in the UK, and April in the U.S. for some reason). When the publishers came to me with the idea, they were interested in having a slightly different “take” on the subject. First, they wanted it to be written for the folks who aren’t space junkies but are interested in what humanity has done to accomplish space flight and travel. Second, they wanted me to look not just at the space race of the ’60s, but all the elements that contributed to the achievements people have made so far in orbit and at other planets.

That was kind of a tall order. Certainly, there are a lot of people who don’t really know the history of space exploration, particularly the younger generations. For them, it’s always been there. In fact, for ME it’s always been there!

So, I thought about it for a while. Yes, I was a kid during the height of the first space race in the 1960s, so I had little to compare with it in my own experience. My parents, on the other hand, came of age during the end of World War II, a time when rockets were mainly used not for exploration, but for destruction. Exploration came later. Their parents saw the age of flight begin. And, before that, flight was by balloon, if it existed at all. Yet, the dreams of flight have been with humans for centuries. It turns out, however, that spaceflight and exploration have their roots going back at least two thousand years.

Thus it is with each generation growing up in an age of expanding technology—what the youngest take for granted, the elders see as a marvelous advance.  That is the way history works: new technologies and ways of doing things define a culture, even as they change it.

Space Exploration Grows A New Society

Today, as a space-faring society, we don’t always see that “newness” anymore, compared to the thousands of years of history that preceded our time. We take for granted so many things once “new” and are now part of our lives. We take instant access to information for granted and easily recognize space-age technology that exists across all endeavors. I’m writing this on a computer that is many, many times more powerful than anything used in the Apollo capsules. My phone probably has more storage capacity than the early missions’ computers did. People in hospitals are routinely diagnosed and treated with technology that had its birth in the space age. We are now seeing a new age of laws and rules come about as companies and countries seek to expand to space.

Could a future mission to Mars be mounted by a private company and government support? Who will fly it? What will they do? All questions our society needs to answer. Image courtesy SpaceX.

As we move outward towards colonies and work environments on the Moon and Mars, the tenets of our spacefaring civilization will continue to change. New technologies will flourish, languages will change to accommodate the outward push, and the people who “do” space will also change.  Our descendants, the future Martians and Loonies, will be very different people from us. Their children may well never be able to visit Earth since their bodies will be so different. That is, if the humans who go to those places are able to reproduce successfully (a big question).

Space Exploration: Outbound

In my book, I look at what a future civilization will look like as it goes to Mars. It’s hard to say how different those people will be from us today. We’re not sending them to another place just like Earth where the air and water are abundant. The trip isn’t a quickie flight across an ocean between continents. The worlds they head to are dry, barren, but fascinating. Their trip will take days (in the case of the Moon) and months (in the case of Mars). Unless there’s a substantial change in the way we build spaceships, they’ll be headed into months of weightlessness. That condition will affect their bodies. We already know what some of those changes are, based on the long-duration flights made by various astronauts and cosmonauts.

The project was a fascinating one to do. Over the next few weeks, I’ll write more about the book, and share a few excerpts to tantalize you. It certainly taught ME a lot about civilizations and technologies. I look forward to the next steps on a new world, by people who will continue our rocket rise to the cosmos.