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.)