45th Anniversary of the Famous Earthrise Photo

It was on Dec. 24, 1968 that astronauts aboard the Apollo 8 mission orbiting the Moon took one of the most famous images in the history of photography. It's become known as "Earthrise on the Moon," and we will soon be celebrating its 45th anniversary.

Moon chronicler Andrew Chaikin has worked with NASA to make a short video of the complete story of how this image came to be taken, and wrote me about recently. I thought I would share it with all of you -- whether you are an old geezer like me (and were alive in 1968) or whether you are newer to life on Earth and saw the picture later. You can find the video at:http://www.youtube.com/watch?v=dE-vOscpiNc

I love the image and its portrayal of a small, fragile planet Earth isolated in space above the airless surface of the Moon. But since this is the AstroProf's page, I have to add, like a good teacher should, that the name creates a bit of a misimpression.

When we talk about sunrise on Earth, we mean that as the Earth turns, we can see the Sun rise above the eastern horizon. As the day goes on, we see the Sun move through our skies, until, in the evening, it sets below the western horizon. What we see as the rising and setting of the Sun is just the effect of the 24-hour rotation of our planet. The spinning of the Earth causes the whole sky to go around us in a day.

The Moon's spin is much slower than Earth's! It takes the Moon 27.3 Earth days to spin once. And in exactly the same 27.3 days, the Moon also orbits once around the Earth. This "tidal locking" of the two motions, the Moon's spin and its revolution around us, means that the Moon always keeps the same face to the Earth.

If you don't believe or see this, try the experiment with your little brother. Put him in the middle of an empty space, face him, and then go around him in the exact same time as you turn your shoulders in a circle. If you take the same time to go around him as to go around yourself, your little brother will always see the front side of your body and never the back side.

For the same reason, if you stand on the Moon, you will either see the Earth in your sky (if you are on the near side of the Moon) or you will not (if you are on the far side). But the Earth will not rise or set in the Moon's sky the way the Sun or Moon rise and set in our sky.

In the famous picture, the Earth only seemed to be "rising" to the astronauts because the Apollo spacecraft was orbiting the Moon.

But if future visitors to the Moon's surface really want to see an Earthrise, it is possible. The Moon wobbles back and forth just a bit (we call it "lunar libration") and so, if you stand in just the right place on the Moon, you could see the Earth dip very slowly below the horizon and then come up again. (Google lunar libration if you want the technical details.)

For everyone else, just enjoy the image and the video. In these times of strife and mistrust everywhere, it's good to remember that -- in the larger picture -- we are all passengers aboard spaceship Earth, sharing its limited area and limited resources.

A Beautiful New Image from the Hubble Telescope

Here is a gorgeous picture of a spiral galaxy, which is part of the Coma Cluster of galaxies, roughly 300 million light years away. This galaxy (of billions of stars), like our own, is shaped like a frisbee -- and we are looking at the disk of the frisbee face-on. Its name is just a catalog number: NGC 4921. You can see its huge encircling "arms" of countless stars, blending their light together. And notice a number of clusters of young stars glowing blue, a little distance out from the center.

But what is amazing about this image, if you look at it for a while, is how many OTHER galaxies are visible through and around NGC 4921! All those structures around the galaxy that are not precise pinpoints of light are other great islands of stars -- each containing billions of stars and planets. The cluster of galaxies which NGC 4921 is part of contains more than a thousand galaxies. And there are more galaxies beyond that cluster. Pictures like this help us remember that our problems and disagreements on Earth are such minor issues when seen from the perspective of the universe.

This image, by the way, was assembled from a number of Hubble Space Telescope images and processed by Roberto Colombari, an Italian astronomical photographer working in Brazil.

Comet ISON Ready for its Thanksgiving Date with Destiny

When it was discovered in 2012 as a new comet coming from deep space, some observers predicted Comet ISON would become so bright in our skies it would be the "Comet of the Century." Wiser heads knew, as comet hunter David Levy likes to say, "Comets are like cats. They have tails and they do precisely what they want!"

For a while, the comet seemed disappointing. But this week, on its way in to a close encounter with the Sun, Comet ISON started putting on a somewhat better show (as you can see in the image, taken by the skillful UK astro-photographer Damian Peach.) The comet now has two nice tails, one made of dust, the other of gas, pointing in the direction away from the Sun.

The comet is currently visible in the pre-dawn sky, but only barely and only when it's really dark. It's better with binoculars or telescopes. The excitement, however, is just beginning. Comet ISON is what astronomers call a "sungrazer" -- a comet that comes indecently close to our Sun. It just so happens, the closest encounter -- only about 3/4 of a million miles from the Sun's surface -- will be on Thanksgiving Day 2013.

The solid "nucleus" of this comet -- a chunk of frozen ices and rock -- is now estimated to be somewhere between 1/4 and 3/4 of a mile across. The Sun's heat could vaporize much of its ice and rock and the Sun's gravity could tear it apart into smaller chunks. Past sungrazing comets have had one or both of these things happen. So it could emerge from its date with the Sun one smaller but strongly evaporating comet, or as several comets spread out over a wider area, or as nothing more than a subtle trail of gas and dust.

If Comet ISON survives Thanksgiving, it will swing away from the Sun and emerge into our dark skies going northward from the plane of our solar system. Should there be enough of it left to make a show, that show will be visible to us in December and January. Around January 8th, for example, it will be near the north star, remaining in our view all night long. (But by then it will likely be much fainter.)

As we say on the radio, "Stay Tuned!" I will give you more updates on this interesting new visitor to our cosmic neighborhood in future posts.

If your want bulletins on Comet ISON between my posts, or need more technical information, see the "Current Status" page at NASA’s Comet ISON Campaign: http://isoncampaign.org/Present and then look around on that site.

[If you search the web for Comet ISON information, beware of the nutty websites predicting a collision with Earth or some other reason for the end of the world. The closest the comet will get to Earth is about 40 million miles on Dec. 26th. That's far enough that we can all sleep soundly at night.]

Billions of Earth-like Planets

This week, the University of California, Berkeley and NASA's Kepler Telescope project jointly announced that the ongoing discovery of planets around other stars had yielded some exciting statistics: It now appears that one out of five Sun-like stars has an Earth-like planet!

One out of five! This means there are likely to be BILLIONS of earth-sized planets orbiting at comfortable distances from BILLIONS of stars in our Milky Way Galaxy. All of us involved with SETI -- the Search for Extra-Terrestrial Intelligence -- are, of course, thrilled to hear this news. Our hope is that among all those planets, there are some where intelligent creatures with an interest in astronomy have developed and perhaps enjoy their own blogs with astronomy news like we do.

The latest stats about known planets around other stars are also record-breaking.  As of early November 2013, we have found 1039 planets around 787 stars beyond our solar system! (There are 173 stars so far where we have discovered more than one planet in the same system.)  In addition, the Kepler mission (which is searching for such planets from space) already has over 3000 candidate planets which are still being checked out!  And they still have a whole year's worth of data to go through.

I was interviewed on KQED, the San Francisco Bay Area public radio station, by Michael Krasny, the host of the Forum program, about all this -- and we were joined by the Berkeley graduate student who had done the basic work of making the estimates. If you want to hear the interview, it is available at:
http://www.kqed.org/a/forum/R201311060930 

Earth-like Planet Discovered in a Ridiculous Orbit

 Astronomers from two continents made a startling announcement last week. They had found a world similar in size and composition to the Earth that orbited its star in only eight and a half hours.... Just think about that for a minute. Our planet takes 365 and a quarter days to complete its orbit. The innermost planet in our system, Mercury, takes 88 days to circle the Sun. The new planet, designated Kepler 78b, takes only about a third of one of our days to orbit its star. In other words, a year on Kepler 78b is only 8.5 hours long -- a two-Earth-year-old toddler on this alien world would already be 2,063 years old in local time!

The planet is a bit larger in size than our Earth, but made of dense rock like our inner planets (and not gas and liquid, like our outer planets.) Since it circles so close to its star, it must be torridly hot, so we imagine its surface is molten rock and not solid like our own crust.  Some are calling it a lava planet.

How can astronomers know so much about a distant world like Kepler 78b? As its name implies, the planet was discovered around a faint star in the constellation of Orion by the Kepler telescope in space. Kepler's camera measures the size of a planet when the planet is seen going across the face of its star and diminishing the star's light briefly. But that can only tell us how big the planet is across, and not what kind of material it's made of.

But once Kepler found the planet, astronomers in the U.S. and Europe used giant telescopes on the ground to find the tiny wiggle the pull of the planet causes in the motion of its star. This "wiggle method" tells us how much pull (gravity or mass) the planet has.

When astronomer combine the size of the planet from Kepler and the mass of the planet from the wiggle method, they can calculate the planet's "density" (mass per unit volume). In this case, all the measurements made it clear this was a dense world, made of rock, just like our Earth.

The mystery is: how did an Earth get SO outrageously close to its star. If it was falling in, what made it stop? We know it couldn't have been born so close to the star, because the star was larger when it was young, and the planet would have been inside the star, where no planet can exist. Kepler 78b is part of a group of strange planets Kepler has been discovering -- all of them too close to their stars for their own good and for our peace of mind.

Where Are All the Aliens?

Saturday, at the request of Jill Tarter (for many years, the leader of the major program to search for radio signals from alien civilizations), I spoke to a group at the California Academy of Sciences about what we call the Fermi Paradox. Perhaps you will agree with me that it's one of the most interesting dilemmas in astronomy.

In the 1950's, physicist Enrico Fermi posed a question to some lunch-time companions, which we can sum up in modern terms this way: There are more than 200 billion stars in our Galaxy and Kepler mission results show that many of them have planets.  The Sun and its family are relatively young compared to the Galaxy (5 billion years old versus 13 billion years old).  So there must have been many stars and planets that developed long before ours did.

If so, life (and intelligent life) should have evolved on some of these worlds long before it did on Earth.  There must therefore be many civilizations out there whose technology is far in advance of ours.  In that case, Fermi and others have asked, where are they?  Why have we not found any signals, artifacts, or visitors from these extra-terrestrial civilizations?

The answer most scientists would give is that the stars are far away, travel among them is slow or expensive, and we have just begun to search for complex signals the aliens might be putting out.  Therefore it's much too soon to ask Fermi's question.

But scientists and science fiction author have delighted in finding other answers as well. Maybe the aliens (like your crotchety uncle) don't like to travel or write letters. Maybe they are so happy playing with their equivalent to Facebook, they don't need to find neighbors among the stars. Maybe they communicate in ways we have yet to dream of.

Or maybe they are here, but are too smart to let us see them watching us (sometimes this is called the "zoo hypothesis.")  Another answer is that while planets are common, perhaps the evolution of technology is very rare, making communication rare too.  What if alien species are more like the dolphins, swimming in a planetary ocean and reciting complex poems to one another?  But they don't mine metals or build telescopes and radio transmitters.

A really depressing proposal is that once aliens develop intelligence and technology, they also develop the ability to destroy their planetary environment through pollution or nuclear war.  A clever science fiction story that develops this further, "The Fermi Paradox is our Business Model" by Charlie Jane Anders, can be found free on the web at: http://www.tor.com/stories/2010/08/the-fermi-paradox-is-our-business-model

Many articles and books have been devoted to the Fermi Paradox.  Scientists enjoy such speculations, but eventually we come back to the notion that in science, the ultimate way to judge what is true is doing an experiment or making an observation.  Those scientists who continue the patient, long-term search for signals or other evidence of extraterrestrial intelligence do so in part because the discovery of another intelligent species in the universe might be the best answer we can give to Fermi's question.

Triple Asteroid Seen More Clearly

I remember the excitement in 1993, when a photo from the Galileo spacecraft, going through the asteroid belt on its way to Jupiter, unexpectedly showed that the asteroid Ida had a tiny moon orbiting it. Twenty years later, we now know more than 160 moons orbiting different asteroids. (Asteroids are chunks of rock orbiting the Sun -- pieces of cosmic garbage left over from the messy period when the planets first formed.)

At least five asteroids are now known to have two moons each, making them triple systems. Perhaps the most famous of these is the asteroid Sylvia, named after Rhea Silvia, the mother of Romulus and Remus, founders of the city of Rome in ancient mythology. Sylvia is one of the larger objects in the main asteroid belt, which lies between Mars and Jupiter.

Recently, a team of professional and amateur astronomers, led by Franck Marchis of the SETI Institute (where I have the pleasure of serving on the Board of Trustees) has made the most accurate measurement so far of Sylvia and its two moons (which got named Romulus and Remus). Our painting shows you what the system may look like if you could get up close and personal with it.

This past January, European observers could see the triple asteroid pass in front of a faint star, hiding its light as each object moved in formation. From this, the astronomers could make estimates and models of the size and shape of each member of the triple system, even though it orbits some 325 million miles from the Sun.

For more details, you can see the announcement at:http://www.seti.org/seti-institute/press-release/telescopes-large-and-small-team-study-triple-asteroid

The very first moon discovered around an asteroid was soon named Dactyl, a term that can mean finger, or a small finger-like creature in Greek mythology, or a small unit of poetic verse.  To keep up with all the moons of asteroids, you can check the website: http://www.johnstonsarchive.net/astro/asteroidmoons.html

Ida and Dactyl (NASA)

A Matter of "Gravity"

The new space-disaster movie "Gravity" is very much in the spotlight these days. Astronomer Neil deGrasse Tyson, whose articulate and good-humored commentary is justly earning him the title of America's public astronomer (a title Carl Sagan used to hold,) recently found some problems with the science in the film and it caused a stir. But two other astronomer-writers have done an even more detailed analysis of what is right and what is wrong with the film.

Before I send you to the web pages where the analysis can be found, let me urge you to see and enjoy the movie first. Those of you with some science background, see if you can spot what is so well done and what is not quite right with the science. Everyone else, please go and enjoy the 3-D spectacle. Then you can come back and read about the issues with the science.

Phil Plait, the "Bad Astronomy" webmaster, gives his articulate analysis at:http://www.slate.com/blogs/bad_astronomy/2013/10/04/ba_movie_review_gravity.html

Jeffrey Kluger discusses the film's pluses and minuses for Time Magazine at: http://science.time.com/2013/10/01/what-gravity-gets-right-and-wrong-about-space/

Neil Tyson's tweets and a response from astronomer Kevin Grazier, the science advisor for the film (and a number of TV shows) can be found summarized at:http://www.theatlanticwire.com/technology/2013/10/neil-degrasse-tyson-fact-checks-gravity/70234/

As for me, I am always happy when film blockbusters get kids and the public thinking about things beyond the Earth. Some of my favorite films that have good science ideas to recommend them include "2001," "Contact (where Jodi Foster's character was based in part on one of my favorite astronomers, Jill Tarter), and the older (and more philosophical) "Five Millions Years to Earth." 

And I heard it from astronomer Fred Hoyle that the old British horror movie "Dead of Night" was one of the contributing inspirations to the steady-state theory of the universe that he and Hermann Bondi came up with (together with Thomas Gold.)  Hoyle and Bondi saw the film (which has no real beginning or ending -- watch it to see what I mean) and asked themselves, "Could the universe be like this?"

The Nobel Prize and the Higgs Boson

As you may have read or heard, the Nobel Prize in physics was just announced, and it went to two of the physicists who came up with the idea of the Higgs boson (and the Higgs field). I wrote a post explaining this subject when the experiments were announced last year. Since we have many new readers on this page, I thought it might be useful to review what this Higgs business is about:

Scientists working with the atom smasher called the Large Hadron Collider in Europe announced in July of 2012 the 99% likelihood of the discovery of the Higgs boson. It was big news in the realm of the fundamental particles, forces, and energies that govern the universe (although it has few immediate practical applications.)

Physicist Leon Lederman, some years ago, was writing a popular book about the ideas behind the Higgs boson and he wanted to call it the "goddamn" particle (because it was so complex and abstract). The decencies of publishing required that he and his publisher change the name to the "God Particle" -- which became the name of his book and the name that stuck to the Higgs boson, somewhat to the regret of scientists.

The important idea behind the particle is the Higgs field, which is a kind of low-level universal energy that gives particles their property of MASS. Mass, in turn, is what then allows particles to attract each other, clump together, and make stars, planets, and Facebook readers. The Higgs boson is evidence that the Higgs Field is real. (The term boson by the way is not a reference to a 1950's TV clown, but to Satyendra Nath Bose, an Indian-born mathematical physicist, after whom a whole class of particles is named.)

The Higgs boson shows itself only under very energetic conditions -- it existed when the universe was extremely young and hot, soon after the Big Bang. This is why it takes very energetic collisions in a large atom smashers to produce the particle today and why it took so long for us to gather evidence of its existence. If the Higgs boson can be observed in our atom smashers, it's pretty good proof that there is a Higgs field in the universe. That, in turn, is one more powerful supporting "pier" for the "standard model" of particles and forces that underlies our understanding of the natural world.

Professor Peter Higgs -- after whom the field and particle are named -- is 84 years old and so there was a lot of (appropriate) pressure in physics to make sure he receives the Nobel Prize now. (The Nobel committee cannot, by the rules of the prize, give it to anyone posthumously.)

For further non-technical introductions to Higgs bosons, I recommend:

A cartoon animation: Higgs Boson Explained:

http://www.phdcomics.com/comics/archive.php?comicid=1489

An analogy for Higgs Field using everyday materials with science writer Ian Sample:

http://www.guardian.co.uk/science/video/2012/jul/03/what-is-a-higgs-boson-video

Galaxy Cluster Abell 1689 Breaks Two World Records

A huge cluster of galaxies so far away that light from it takes 2.2 billion years to reach us has revealed itself to be a record-breaker. It has the largest number of star clusters ever seen in one place and it is farthest place in the universe where we have seen star clusters.

To appreciate this story, you have to distinguish between the two kinds of clusters we're discussing. Stars are often born in groups called "star clusters" and the largest and most impressive of these are called "globular clusters" (because their stars are organized into a big globe-shaped collection of 100,000 stars or more.) Our Milky Way Galaxy has about 150 of these globular clusters and they are among the oldest and most crowded places in our home galaxy.

Galaxies -- the great islands of billions of stars -- also turn out to be organized into clusters. Each cluster might contain hundreds or even thousands of galaxies. (And each galaxy contains billions of stars -- it makes you dizzy if you think too hard about it!)

The late George Abell (an astronomer at UCLA and the author of a famous textbook from which astronomers in my generation first learned astronomy) made a catalog of these galaxy clusters, and the one we are discussing is entry 1689 in his catalog.

A new study of the central region of Abell 1689, made with the Hubble Space Telescope, reveals 10,000 globular clusters of stars in a small region of the galaxy cluster. The astronomers who carried out the work estimate the throughout the entire galaxy cluster, there may be as many 160,000 of these giant old star clusters -- a record unequaled anywhere else we have looked so far.

At a distance of 2.2 billion lightyears, Abell 1689 is also the farthest location in the universe where we have seen a globular cluster.

In the attached picture, you can see part of the cluster of galaxies on the left and then a close-up where the globular clusters look like little yellow dots among the bigger galaxies.

For a scan through the galaxy cluster, you can check out this YouTube video: http://www.youtube.com/watch?v=bumxssc9Cdo
(On this scan, you can also see faint rounded arcs of light -- those are direct proof of one of Einstein's ideas -- that the huge gravity of the galaxy cluster acts like a "gravitational lens" and bends the light of other galaxies behind it into arc like shapes.

We have seen other rich clusters bend light from objects behind them, but the effect is especially clear on this beautifully detailed image. 

An Alien Sea on a Moon of Saturn's

I want to introduce you today to Ligeia Mare (the Ligeian Sea), the second largest known body of liquid outside the Earth. It's on the surface of Saturn's moon Titan, the only moon in the solar system to have a thick atmosphere and, therefore, to have air pressure. It's air pressure that keeps liquids from evaporating and makes rivers, lakes, and seas possible.

And to our delight, Titan, despite the freezing cold temperatures in the Saturn System, has rivers, lakes, and seas. At Titan temperatures, water is frozen until it's harder than rock on Earth. So the bodies of liquid on Titan are not water, but methane and ethane, which can be liquid under Titan conditions. Methane is natural gas (and also what comes out of both ends of the cow after it has been digesting its food for a while.) Ethane is a chemical that is often found in natural gas and is also a product of refining oil.

Take a look at the picture. This is not a photograph, but an image that comes from bouncing radar beams off Titan, something we equipped our clever little Cassini spacecraft to do. On radar pictures, rough things show up light, smooth things (like bodies of liquid) show up dark. The colors are added artificially to make the picture more interesting.

The name Ligeia comes from one of the sirens of Greek mythology, beautiful creatures who lured sailors toward rocky shores and their certain death. Look at Ligeia on the image -- ain't she beautiful? Some people see the shape of a sleeping dog, with its head toward the bottom. But its size is what astounds. The sea is about the size of the Earth's Caspian sea and if you walked completely around it on the shore, you'd walk a total of 1,240 miles.

Where the radar picture is black, the sea is deep; where you see grey, the sea is more shallow, so the radar beam can hit the sea bottom and some of it bounces back. Already scientists have proposed a mission (not approved yet) to splash down a capsule in Ligeia Mare and either drift or purposely navigate around the sea, sending back images to Earth.

It's been winter in the North polar region of Titan since Cassini arrived in the neighborhood. Some scientists think that once the weather starts to warm up on Titan (it will still be outrageously cold compared to Earth,) the Titan winds might blow hard enough to make waves on this alien sea, and our radar might just pick up those waves. (Somebody should tell the Beach Boys that surf might soon be up another world!)

For more details about weather on Titan, see:
http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20130522.html#.UjEPocYqh8E

Crescent Moon and Venus Get Close Sunday Night Sept. 8

A minor, but cute, pairing is visible in the sky tomorrow. It happens soon after sunset and you can only see it if you have an unobstructed view of the west-southwest horizon. (For many of us that means we will have to get high -- only in the geographical sense, mind you!! Typically, our view is blocked by buildings, trees, hills, etc. and we can't see the western horizon.) But if you get to a place where you can see low in the west Sunday evening, you will see a very thin crescent Moon and the bright planet Venus just to the right of it.

You can start looking about a half hour after the Sun sets on Sunday and you'll see it best about 45 minutes after sunset. But don't wait too long to catch it; soon both objects will set in the West, and disappear from your view.

When Venus is visible just after sunset, people call it the evening star. But it's not a star at all, but a planet -- our neighbor planet just sunward of the Earth. It reflects quite a bit of sunlight both because it's close to the Sun and because it's covered with clouds that are quite reflective. (In fact Venus is so cloudy, there hasn't been a clear day there in 3 billion years. I like to cheer up my friends in Seattle by telling them that.)

As you can see in the nice diagram, which I borrowed from the good people at Sky & Telescope magazine, if you look further up and to the left, you will also see the planet Saturn in the same part of the sky. The distance in the sky between the Moon and Saturn should be about the width of your clenched fist, if you hold out your hand at arm's length. If you have binoculars or a telescope, you can enhance your view, but if you don't have an instrument, it's still fun to look. If you have kids, bring them outside and show them the sight too. It couldn't hurt to impress them with your knowledge of the universe while they are young.

For more information, you can see the full story at the Sky & Telescope web site: http://www.skyandtelescope.com/observing/highlights/Crescent-Moon-and-Venus-Put-on-a-Show-222505621.html

Hints of Water on a Super-Earth

A Japanese team of astronomers, using the giant Subaru telescope, atop an extinct volcano in Hawaii, have found further hints of the presence of water on a planet orbiting the star Gliese 1214, about 40 lightyears away.

The planet orbits its star in only 38 HOURS (not days, folks, but hours!) You might think that a planet this close to a star will soon be french fried, but, in this case, the star itself is much dimmer and cooler than the Sun -- it is what astronomers call a "red dwarf."

The planet circling the red dwarf is one of the few planets outside our own solar system which we have been able to find in two independent ways. We know it's there because its gravity makes the star wiggle a bit, and we also know it's there because we can see the planet move across the face of the star and cause a mini-eclipse (or transit).

This double identification is very helpful, since it lets us measure both the size of the planet and how much stuff (mass) it contains. That's how we know it's a "super-Earth" -- a kind of planet we don't have in the Sun's family. This super-Earth is about three times the size of Earth, and more than 6 times its mass. These characteristics make this alien world denser than Jupiter but less dense than Earth. It could be a little rocky planet with a giant atmosphere, or a planet with some rock and a lot of liquid water surrounding it.

The new Japanese study examined the planet's atmosphere and concluded that the way light of different colors scattered from it was consistent with either the presence of water vapor or with some kind of extensive cloud cover. Combining this work with other studies makes astronomers a bit more sure that this is a water-rich environment. That still doesn't help us pin down exactly what this super-Earth looks like, and it's probably too warm overall for life as we know it. Nevertheless, isn't it amazing that we can now discover not only planets out there in other parts of the Galaxy, but even something about the kind of air they have surrounding them?

(NOTE: The image above is an artist's conception of what the star might look like through a blue filter.  The star itself would look red to your eye.  The planet is the smaller black sphere on the left side of the star.)

Astronomy Versus Astrology

If I had a dollar for every time someone in casual conversation had called me an astrologer or astrologist (instead of an astronomer), my retirement funding would be a lot more secure. Often, it's an honest mistake, where the speaker really does understand that astronomy is a science and simply isn't sure of the science's proper name. What's much worse is when I run into a "true believer" in astrology, who thinks that our personality, our character, and our destiny is shaped by the arrangement of stars and the position of celestial objects at the moment of our birth.

Some years ago, I wrote an article for Sky & Telescope magazine setting out an astronomer's reaction to astrology. A much revised and updated version is now on-line, thanks to the Astronomical Society of the Pacific. If you have wondered about astrology and what to say to those who believe in it, this short article may assist you. At the very least, you might find it amusing. In it, I also describe a new field for predicting things called "jetology" (where your future is determined by the position of all the jumbo jets at the moment of your birth.) The article is in PDF file format at:http://www.astrosociety.org/astrology.pdf

As the World Turns

It's a dizzying thought, but the solid ground beneath our feet is moving at great speeds through space. For example, our planet turns once a day. Every 24 hours, the place where you live on the surface of the Earth goes in a big circle around the center of our planet. In the San Francisco Bay Area, this motion happens at a speed of about 818 mph. (Children, you can do this without adult supervision, because gravity holds all of us firmly to the Earth's surface.)

Our planet turns around an imaginary stick that goes from the Earth's north pole through its south pole. We call the line of that imaginary stick the Earth's "axis." As our planet turns around its axis, the Sun appears to rise in the East and set in the West and we have day and night. At night, as we turn, we see everything in space slowly turning around us. But we know the Sun during the day and the stars at night are not really turning. They sit in space and mind their own business. The motions we see in the sky hour by hour just reflect the turning of planet Earth. Do you want to see this motion displayed?

On the magnificent photo I have attached to this little posting, you can actually see the turning of the stars (around the still point of the north pole of the sky). Master photographer Phil McGrew captured the turning of the sky above the Golden Gate Bridge. I was so enchanted with this photo, I asked him to give me permission to share it with all of you. You can see more of his photos at his web site: http://www.philmcgrew.com/

The photo is actually made up of more than 180 20-second exposures, skillfully added together. Instead of being a point, each star becomes a curved line as the Earth turns with the camera and photographer attached to it. Astronomers call the curved lines "star trails."

Can you think of other ways that you are moving even while sitting still in your favorite armchair? We'll discuss these other motions in future posts.

Astronomy Talks Have a YouTube Channel

The Silicon Valley Astronomy Lectures, which I have the pleasure of moderating, feature noted scientists giving nontechnical illustrated talks on recent developments in astronomy. I am happy to announce that they are now available on their own YouTube Channel, at:
http://www.youtube.com/SVAstronomyLectures/

The talks include:

* Frank Drake (the father of the search for radio signals from civilizations in space) discussing his modern view of the Drake Equation,

* Michael Brown explaining how his discovery of the dwarf planet Eris led to Pluto being kicked out of the planet club,

* Alex Filippenko (selected as the U.S. Professor of the Year, a few years ago) talking about the latest ideas and observations of black holes,

* Natalie Batalha (mission scientist for the Kepler Project) sharing the latest planet discoveries from outside the solar system, and

* Chris McKay updating the Cassini discoveries about Saturn's moon Titan (the only moon known to have an atmosphere thicker than Earths).

The lectures are taped at Foothill College near San Francisco (where I teach), and co-sponsored by NASA's Ames Research Center, the SETI Institute, and the Astronomical Society of the Pacific.

Note that the top page of the YouTube channel shows the lectures in the order they happened to be uploaded to YouTube. If you want to see them in chronological order, select the Playlist option.

Both new and older talks in the series will be added to the channel as time goes by. Many well-known astronomers have given talks in this series since its founding in 1999; recent lectures are being recorded so that people around the world can "tune in."

(About the picture: This is a false color image of the Helix Nebula, the last gasp of a dying star located about 650 lightyears away.  A relatively low-mass star is collapsing and losing its outer layer in a final internal adjustment before it dies as a white dwarf.  The material the star loses is excited by the energy of the shrinking star and set to glow.  In this image, infrared radiation (as measured from the Spitzer telescope in space) is shown in green and red, ultraviolet radiation (as measured by the GALEX telescope in space) is shown in blue.)

Good Meteor Shower Starts This Weekend

Whenever small chunks of cosmic dust or dirt hit the Earth's atmosphere at high speed and heat up, they make a flash of light that's visible from the ground. We call these meteors or "shooting stars." When the Earth encounters an organized swarm of cosmic material, we call it a meteor shower.

The Perseids (one of our most reliable meteor showers) is best this year the night and morning of Sunday Aug. 11 to Monday Aug. 12, and the night and morning of Monday Aug. 12 to Tuesday Aug. 13th.

Watching for meteors is easiest for most people’s schedules in the evenings (before midnight). However, the meteor display is generally better after midnight (making night owls and early risers happy.)

The Perseids are better after midnight for two reasons this year:

a. The Earth turns after midnight to face the shower (so that the meteors are coming more directly at us)
b. The crescent Moon will set by then, so its light will not bother meteor shower fans. (On Aug. 11, the Moon sets at 10:32 pm, while on Aug. 12th the Moon sets at 11:10 pm.)

Whenever during those two nights you decide you want to watch, here are Fraknoi’s Friendly Meteor Shower Tips for best viewing:

1. It’s more important to decide WHERE to watch them, than WHEN to watch them. The crucial issue is that meteors are faint, so you need a location where the sky is DARK. That means getting away from city and car lights as much as possible. The darker your site, the more you will see.

2. Of course, if it’s foggy or cloudy, you won’t see a thing. So make sure you get to a place where the sky is not only dark but CLEAR.

3. Don’t use a telescope or binoculars. (Meteor showers are one of the most democratic of sky shows; those of us in the 99% can enjoy them as much as those in the 1%!).) Your eyes are the best tool, because the flash can be anywhere in the sky. So restricting your view to a small part of the sky makes it more likely you will miss many of the meteor flashes.

4. Dress warm for night-time temperatures and be patient. Meteor showers are far more subtle than fireworks. You will need to relax and wait for time to pass. First, it takes a while for your eyes to get adapted to the dark (I recommend at least 15 minutes) and, second, a minute or several minutes might pass without a single flash. Eventually, though, you should see significantly more shooting stars than on a regular night.

5. So (perhaps most important) try to take someone with you with whom you like to spend time in the dark.

The Perseid meteors are cosmic “garbage” (dust and dirt clumps) left over from a regularly returning comet, called Swift-Tuttle (after the two astronomers who first discovered it). When comets get near the Sun, their ice evaporates, leaving behind some of the dirt that was frozen inside them. Since comets are "left-overs" from the early days of our solar system, you can tell yourself that each flash you see is the “last gasp” of cosmic material that formed about 5 billion years ago.

(Our photo, by ESO Photo Ambassador Stéphane Guisard, shows a bright Perseid meteor in 2010 over the grouping called the Very Large Telescope at the European Southern Observatory in Chile.)

Stunning Wide-Field Image of a Star Nursery

Every once in a while, I see a new astronomical picture that leaves me with my mouth open, saying "Wow!" The above image, assembled by a talented amateur astronomer, from information taken by a number of different telescopes, is one of those.

This wide-angle view is centered on a cluster of recently-born stars that is known by its catalog number of NGC 2264. Surrounding the adolescent stars is a whole region of cosmic gas and dust -- the raw material from which stars are born. The nearby gas glows with the characteristic red color of its most common constituent -- hydrogen.

At left center is the Cone Nebula, a region of gas and dust in the shape of a sideways dark cone; the energy of bright stars to the right of the cone is eating away at the sides of this thick dusty region, leaving only a cone of thicker material behind.

To the right of the Cone Nebula, you can see an opposite (larger) cone pattern of bright stars stretching rightward. Some people see the lights of a sideways holiday tree in the pattern of bright stars.

At the bottom center of the image, pointing upward into the bluish emptier region (where the energy of freshly made stars is clearing things out), you can see an odd region of gas and dust that is sometimes called "The Fox Fur Nebula." Click on the picture and take a good look -- can you see the head of a furry red fox pointing upward into the bluish region?

The entire complex of stars and gas and dust is about 2,600 lightyears away, which means the light we see tonight left this region about 2,600 years ago -- a time when humans on Earth lived a much more challenging existence and lifespans were less than half of what we enjoy today.

This remarkable picture was assembled by Dr. Robert Gendler, a physician and amateur astronomer, who is a master at working with photographic information using his computer. The image was constructed from information provided by the Subaru Telescope in Japan and the Digitized Sky Survey, put together by astronomers at the Space Telescope Science Institute from a number of earlier surveys of the sky. To see more information about the photo, see:
http://www.robgendlerastropics.com/Cone-Subaru-DSS.html

You can go to Dr. Gendler's home page at that site and then browse his many other wonderful images. But take a minute and just enjoy a full-screen version of the picture -- you are seeing the same process of star birth that gave rise to our Sun some five billion years ago.

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