Mysterious Bursts of Radio Waves

An international team of astronomers has found a new kind of astronomical event in the universe -- a powerful flash of radio waves, lasting only a few thousandth of a second, but coming from vast distances away.

Radio waves -- the same kind of invisible "wireless waves" that bring news of traffic jams to our car radios or wifi for our laptop computers -- come from a variety of natural events in the cosmos. If your car radio were to convert them to sound waves, they would sound like static. Radio static comes to us from the magnetic regions of the Sun and Jupiter, from remnants of exploded stars, and many other sources in the sky. But the "transmissions" usually last a long time.

A sudden burst of such waves lasting only a few thousandth of a second (and then never again) came as a surprise to astronomers. The first of these was discovered six years ago, but was classified as doubtful until others could be found. Now astronomers have found a total of five from different directions in the sky. Indications are that they come from far away -- from far beyond our Milky Way Galaxy. If so, and we can still detect them from Earth, they must be very strong bursts indeed. (In the same way, if you scan the horizon and see a flash of light from a distant city, whatever made the light must be quite bright to cross the space between cities and still be visible to your eyes.)

What could make such brief, super-strong bursts of radio waves? It must be something small and powerful. First candidates include the collapsed corpses of stars that are called neutron stars. These are what remains of stars that exploded long ago, and they can pack more than a Sun's worth of material into a ball no bigger than a suburban town (about 20 miles across!) When such densely packed star corpses collapse further or have a magnetic hiccup, they can give off a quick shot of radio energy.

But at this point, no one really knows what sorts of cosmic objects the radio bursts come from and we are eagerly searching for more. This situation is very similar to what happened in 1967 with another kind of invisible wave, called gamma rays. A secret spy satellite found a few bursts of gamma rays coming from space. At first, no one could figure our what they were and why we saw them randomly around the sky. But as decades passed, and we detected more and more of them, with better and better instruments, we learned a lot more about them and began to come up with really good explanations for these "gamma-ray bursts." We may be at the beginning of a similar era of further exploration and gradual explanation with these radio bursts. As they say on the radio, "stay tuned."

(The artistic image with this post shows the radio telescope in Australia that found the new bursts, together with a blue dot symbolizing the (invisible) burst, some distance away from a map of radio waves coming from our own Milky Way, shown with reddish colors. So only the color of the telescope is real, the other colors try to show things our eyes cannot see, using colors we can see. But how else can we have a nice picture with the story?)

Music Inspired by Astronomy

I just got back from a fascinating conference in New York on how astronomy has inspired other fields, like art, architecture, poetry, and music over the years. I was the after-dinner entertainmen...I mean...the banquet speaker and had a chance to share the results of my 30-plus years of collecting examples of astronomical music (assembled with the help of many generations of students).

Composers of both classical and popular music have long been inspired by the ideas and discoveries of astronomy. The picture with this post, for example, shows some sheet music from 1901 that was inspired by physicist (and inventor) Nikola Tesla's claim that his early radio equipment had intercepted signals from our neighbor planet Mars. Actually they turned out to be perfectly natural radio waves from the upper layers of the Earth atmosphere, but for a while the news media were touting the idea that martians might be signaling us.

If you want to see my full list of 133 "astronomy music" pieces that you can find on CD, it's at:http://aer.aas.org/resource/1/aerscz/v11/i1/p010303_s1?view=fulltext

With the growth of videos on YouTube and other web sites, you can actually watch some of these pieces being performed. Among my popular-music favorites on video are:

1) "Walking on the Moon" by the Police (comparing the feeling of being in love to being on the Moon's surface):http://www.youtube.com/watch?v=gPpvHEsC_PM

2) "Hawking" by Todd Rundgren (which tries to put the listener in the body and mind of brilliant but wheelchair-bound physicist Stephen Hawking): http://www.youtube.com/watch?v=jk7uZO1iED8

3) "Why the Sun Really Shines" by They Might Be Giants (a children's song): http://www.youtube.com/watch?v=u-KyciKHw-g

4) And, for a change of pace, the "Elements" song by 1960's humorist (and math professor) Tom Lehrer:http://www.youtube.com/watch?v=AcS3NOQnsQM

A number of brave composers have put together musical pieces that are based on the rhythms or tones of actual astronomical observations. There is music based on radio signals from galaxies, on the index of how the Sun affects the Earth's magnetic field, and on the speed with which the planets orbit the Sun. A fun recent example is "Supernova Sonata" -- music based on a catalog of newly discovered exploding stars in other galaxies:http://vimeo.com/23927216

I have enjoyed collecting these musical examples of the power of astronomy to affect our imaginations and hope you enjoy hearing some of them.

A Nearby Faint Star With 6 or 7 Planets

Big news today from astronomers studying "exoplanets" -- planets that orbit other stars in the sky. Groups of astronomers in Europe and America, working together, have found a faint nearby star which has 6 or maybe even 7 planets orbiting it, three of which are in the "habitable zone" -- where water can be a liquid.

The name of the star is Gliese 667C (part of a system of three stars that orbit around each other). Only the faintest of the three stars has been found to have planets, but that faint one has quite a family of them. You can see the planets and the star on our diagram.

The way astronomers name these things is by giving each object a letter in order of discovery. So in this Gliese 667 system, capital A, B, and C are the letters for the three stars. Then the planets around star C are given lower-case letters, starting with b. (Planet "h" is not fully confirmed, so it has a question mark next to it.) The green zone is where the planets are that have the right temperature for life as we know it.

The three planets in the green zone of this star are what we call "super-Earths" -- they are bigger than Earth, but smaller than Uranus and Neptune. The method we use to discover these planets only gives us an estimate of their mass, but given how crowded the habitable zone seems to be, scientists are feeling reasonably sure that these planets are no bigger than about 10 Earth masses.

This is the largest number of planets ever found in the habitable zone of another star. (Planet h, the one that is not yet confirmed, is just tantalizingly at the edge of that zone.)

All the planets and the three stars are about 22 light years away in the constellation of Scorpius. (The closest star is 4 light years away, so, in the cosmic scheme of things, Gliese 667 is one of our closest neighbors!)

What's especially interesting about this discovery is that the faint star that has all the planets is what astronomers call an M-type star -- it has only 1/3 the mass of our Sun and shines with only about 2% of our Sun's light output. So the habitable zone is much closer to the cool star than our Sun's is. The planets in the habitable zone take between 28 and 62 days to orbit the star. (Recall that the Earth takes 365 days to go around our much hotter Sun!)

The interesting part is that M type stars are much more common in the universe than stars like our Sun. So if an M type star like Gliese 667C can have 6 or 7 planets crowded around it, that means that perhaps other such M type stars also have families of planets and the number of sites we can look for life in the universe has just gone up.

For more technical details, more pictures, and even short videos, see: http://www.eso.org/public/news/eso1328/

(By the way, Gliese comes from the name Wilhelm Gliese, a German astronomer, who constructed one of the most important catalogs of nearby stars. Many faint stars near us have Gliese numbers from his catalog.)

Summer Science Fiction

With the summer vacation and the season of science fiction blockbuster movies now upon us, it's a good time to think about reading a science fiction book in the coming months. If you like science, but all you know about science fiction is what you see on TV or in the movies, you might be pleasantly surprised by how much more scientifically realistic and how much more filled with real human emotion some written works of science fiction can be.

But it can be hard for the beginner to find the best science-oriented science fiction.  There are so many books available, many of them more devoted to fantasy than real science fiction.

On my Facebook page: www.facebook.com/Fraknoi I keep a set of images and captions that may be useful if you are on the lookout for some science fiction authors to get to know.  When you get to the Facebook page (which is called "The AstroProf"), clic on the small "Photos" link in the header box. That takes you to a new page and then you can click on "Albums" to see collections of some of my favorite astronomy photos, bumper stickers, and more. 

One of the albums consists of photos and brief discussions of some of my favorite science fiction writers. For each author, I list a little about why I like him and suggest a book you may want to start with.

In addition to the recommendations in this album, I also keep an annotated web list of science fiction stories with good astronomy in them. If you want to see good portrayals of the planets, black holes, or time travel in science fiction, you might check out my list at:http://www.astrosociety.org/edu/resources/scifiprint.html

Here's wishing you a summer of starlit skies and good reading.

Galaxy with a Tail Shows How Some Galaxies Run Out of Gas

In a galaxy with lots of raw material (like our own Milky Way), baby stars are forming all the time.  But some galaxies have run out of the gas (and dust) for making new stars, leaving them barren, with no further opportunities for "childbirth."  Now a new observation of a small galaxy shows how the raw material for stars can be stripped out of a galaxy by outside circumstances.

This is not the first time astronomers have been intrigued by the appearance of the little galaxy known by its catalog number IC3418.  In 2010, the GALEX satellite observed ultraviolet light from the galaxy and first revealed that it had a "tail" -- streamers of gas that had been removed from IC3418 and were following behind it.  Now, new research gives us a better understanding of just how the little galaxy got stripped of its life-giving gas.

IC3418 is falling through a giant collection of galaxies called the Virgo Cluster.  Consisting of some 1,500 galaxies and lots of superhot gas, the Virgo Cluster is our nearest big cluster of galaxies.  Because the Virgo Cluster is full of hot gas, when little IC3418 falls through it, its own gas is stripped out.  (The cluster's hot gas can't affect the stars of a galaxy, which are heavy, but can strip away the lighter gas.)  It is this stripped away gas you are seeing as a tail in our picture.  The removed gas makes some new stars as it gets compressed and it's their glow we see.  But by leaving its parent galaxy, the gas in the tail deprives IC3418 of the fresh gas it needs to make new stars.

This makes IC3418 an old barren galaxy long before its time. It's as if the interaction with the big Virgo Cluster made it age right before our eyes.  The stripping of gas works so well because the speed with which the little galaxy moves through the cluster is 2 million miles per hour!  (Don't try speeds like this at home without adult supervision.)

For a beautiful picture of some of the thousands of galaxies that make up the Virgo Cluster, check out: http://apod.nasa.gov/apod/ap110422.html

The new observations were reported by a team led by astronomer Jeff Kenney of Yale, and were reported at the meeting of the American Astronomical Society going on this week in Indianapolis.

Black Hole at Center of the Milky Way is Found to be Cooking its Dinner

Astronomers working with the European Herschel Space Observatory have discovered really hot gas in the vicinity of the monster black hole at the center of our Galaxy. Over the years, many lines of evidence have shown us that there is a black hole with enough material to make 4 million Suns at the heart of the Milky Way. The new observations, made using infrared (or heat) rays, show that gases such as water vapor and carbon monoxide have been heated to about 1000 degrees Centigrade within a lightyear of the black hole.

While energy from nearby stars may also be heating this inner gas, the astronomers can't account for so much heat from stars alone. They think that great streamers of gas heading toward the black hole may be colliding and the shock waves from the collisions may be significant contributors to the heating. Some of the streamers of gas will someday be "eaten" by the black hole. In other words, like many a hungry diner, the black hole appears to be "cooking" its dinner in anticipation of eating it.

In fact, other observations have recently shown a cloud of gas weighing as much as several Earths, falling to its doom much closer to the black hole. This cloud may be consumed by the black hole as soon as the end of 2013. When such clouds actually spiral inward to their doom, they heat up a lot at the end. The last thing we observe from them before they fall into the black hole (and are no longer visible) is a "burp" of x-rays. Several x-ray telescopes in space are prepared to record such burps when they happen.

If you are cooking a barbecue this Memorial Day Weekend (a holiday in the U.S.), you can enjoy the idea that some serious cooking may also be going on at the center of our Galaxy. The center region is 26,000 lightyears away from us, so none of this poses the least danger to planet Earth and its cooks.

(By the way, to see one of the lines of evidence for the existence of the monster black hole, we recommend a great new movie made from observations by astronomer Andrea Ghez' group at UCLA. The movie shows the whirling orbits of stars very close to the black hole, being pulled around by the enormous gravity of the black hole. Check it out at:

http://www.astro.ucla.edu/~ghezgroup/gc/images/media/ghezGC_comp3-18_H264_864.mov

Note that each second of the movie shows two years of star motion. It's enough to make you dizzy.)

Giant Hurricane at Saturn's North Pole

Astronomers working with the Cassini spacecraft orbiting Saturn have taken a wonderful close-up picture in visible light of a giant storm at the exact North Pole of Saturn. On the FALSE COLOR image here, you can see the hurricane in red color right in the center. This giant storm is about 1250 miles wide (roughly 20 times the size of the eye of a typical earthly hurricane). Like sodas in the movie theaters, weather on the giant planets like Jupiter and Saturn comes only in super sizes .

(To be fair, this is not the first time we are seeing this storm. But now that summer sunlight is reaching the north pole of Saturn, we can actually see the storm in greater detail in visible light.)

Wind speeds at the edge of the storm are being measured at 330 miles per hour, so hold on to your hat if you intend to go windsurfing there.

Also on the current picture, in pale greenish color, you can see the mysterious hexagon of flowing gas that surrounds Saturn's north pole. This hexagon is about twice the size of planet Earth in diameter! The strange shape of this "jet-stream-like" feature is thought to be the result of complicated waves colliding in the upper atmosphere of the ringed planet.

Another storm is visible in teal color at the lower right, and -- in this false color view -- the rings of Saturn are an intense blue color in the upper right. (You can see the many ringlets that make up the rings. Bear in mind that each ringlet is composed of millions of chunks of ice, all staying in a regular traffic pattern around the equator of Saturn.)

Why is the image presented in false color? I think the Cassini astronomers themselves will be the first to tell you they make such images in part because they are beautiful. But also, in this case, color gives a sense of how high in the atmosphere you are looking. The reddish features are deeper down and the greenish ones float higher up.

Want to see the hurricane move? There is a wonderful short movie with good narration by astronomer Andrew Ingersoll that has been assembled at:http://photojournal.jpl.nasa.gov/archive/PIA14944_640.mov
(You will need the free Quicktime player on your computer to see it and a little time for it to load.)

For readers who are more technically oriented, a nice discussion of a possible explanation for why the jet stream takes the shape of a hexagon can be found in one of Emily Lakdawalla's columns at: http://www.planetary.org/blogs/emily-lakdawalla/2010/2471.html