Friday, December 28, 2012

Curiosity Mars Rover Takes a Self-Portrait

At the beginning of November, the Curiosity rover on Mars used a camera on its big arm to take this wonderful panoramic picture of itself and its surroundings. Dozens of individual pictures were stitched together carefully to make this self-portrait. 

You can see four little trenches in the front where the arm scooped up some martian dirt for analysis.

Curiously, the way the images are taken and assembled, the arm is NOT visible in the picture. (You could imagine something similar if you held a camera out way in front of you and then took pictures from all sides. You could crop and assemble those pictures in a way so that your arm is always out of sight on the final image.)

In the background, on the upper right, you can see Mount Sharp, the mountain in the center of Gale Crater, which is the rover's ultimate destination. (See my blog post of August 19, 2012 for more on this mountain and its location.)

So far, all the instruments on board Curiosity are working fine, and the mission -- one of the most exciting astronomy events of the past year -- is continuing to send back good information from our red neighbor planet. As expected, we are already seeing clear evidence that there was lots of flowing water on Mars in the distant past.

P.S. If you are interested, you can see an animation of how this complex picture was taken and put together at:

Sunday, December 23, 2012

A Fabulous New Saturn Image

This magnificent (but artificial color) image of the ringed planet Saturn was assembled and enhanced from 60 different pictures taken with the Cassini spacecraft. You are looking up at Saturn from a perspective below its rings, at a time when the Sun happened to be directly behind Saturn. Thus we are seeing the planets and the rings back-lit, something we can never see from Earth.

The image is constructed not merely with visible light pictures, but also with some in the infra-red (commonly called heat rays). So this is not what your eyes would see if you (like Cassini) were orbiting Saturn -- this is a view only our sophisticated instruments can make available. And the details have been enhanced to show you the complex structure of Saturn's rings (made up of billions of chunks of mostly water ice, all moving around the equator of Saturn in a traffic pattern so vast it puts the Los Angeles freeway system to shame.) 

From one side to the other, Saturn's giant ring system spans 170,000 miles across.   This means that if you were to take the ring system off Saturn and put it next to the Earth, it would almost fill the space between the Earth and the Moon.

Near the top of the picture, you see the round dark shadow that Saturn casts on its own rings. Below that shadow, the greenish glow is light reflected from the rings on to the cloudtops of Saturn.

The pictures that make up this fantastic mosaic were taken from a distance of about 500,000 miles from Saturn (quite close in astronomical terms.)  Just look at all the structure you can see in the ring system, which consists of many, many ringlets.

What a beautiful holiday ornament this planet makes!  Happy Holidays.

Friday, December 21, 2012

Happy Winter Solstice (Not Doomsday)

Let me wish all my readers a happy Dec. 21, the day of the winter solstice in the northern hemisphere. Despite the hue and cry of the doomsayers, the Sun rose today and our planet continues to orbit in the usual cosmic order of things. There is no greater or lesser chance of disaster today than any other day.

Today is special, however, for being the day that the Sun makes the lowest arc in our skies and thus gives us the shortest day of the year (as beautifully illustrated on the accompanying photo by Italian astro-photographer Danilo Privato.)

For thousands of years, civilizations throughout the northern half of our planet have planned special celebrations to cheer each other up around the time the day was shortest and the night was longest. They gathered with their tribe, lit a fire, danced and sang to implore their sun-god to return, made sacrifices (like burning a valued food animal), and perhaps gave a present of something they treasured to their loved ones.

Many of our modern traditions began with such winter solstice celebrations. I encourage you to reach out to relatives and friends today in the same way, perhaps sharing the beautiful solstice photo (a composite image made of 43 different exposures during a past solstice day from Santa Severa, Italy.)

Today, as on all other days of our annual journey around the Sun, we have far more to fear from our own actions than from the cosmos. It is a sad fact that the most likely form of local or global doomsday for planet Earth will come from humanity's own prejudices, superstitions, hatreds, and persistent refusal to face facts. In our lifetimes, our planet is probably going to suffer more from our pollution and carelessness than from the actions of the universe. Now that we seem to be surviving any "Doomsday 2012" coming from the skies, maybe we can resolve to do a little better as residents of planet Earth.

(Photograph used by permission. To check out the many astronomical photographs by Danilo Privato, please see his website: )

To learn more about why the Dec. 21, 2012 doomsday fears had no basis in science, you can check out the Calendar of the Sky website from the University of California, Berkeley Space Sciences Lab -- a site to which I had the pleasure of contributing.  You might start with the essay: 
and then browse through the menu at left.)

Wednesday, December 19, 2012

POSSIBLE Planet Around a Famous Nearby Star

Today came a news story that illustrates how hard progress is at the very frontiers of science. For both science and science fiction fans, the nearby star Tau Ceti (a sun-like star just 12 lightyears away) is legendary. In science, it was one of the two stars that Frank Drake searched for intelligent signals in his first SETI project back in 1960.  In science fiction, many authors and screenwriters have used Tau Ceti as the home base of alien species.

Naturally, astronomers have searched for planets orbiting this star and no "obvious" planets (such as a big Jupiter-like planet) have been found. A key way astronomers find planets too dim to see with a telescope is to watch the effect of the planet's gravity on the much brighter star. As planets orbit a star, the star will appear to wiggle back and forth slightly, which sophisticated instruments can detect.  (For the technically minded, we can take a spectrum -- spread out the light like a rainbow of colors -- and measure the motion of the star from the Doppler Effect.)

So an international team of astronomers has been analyzing 6000 previous observations of any possible "wiggle" of Tau Ceti from the pull of smaller planets to see if they can tease out any information when they combine the information gathered by three of the largest telescopes in the world, including the giant Keck Telescope in Hawaii. The complex analysis allows scientists to get down to smaller wiggles than have ever been observed before -- down to changes in the speed of the star of 2 miles per hour!

At this level, scientists are down to speeds that are "in the noise" -- smaller than the statistical variations in the observations and the movements of the star's own surface. As the experimenters themselves quickly say, this is new territory. Yet, when they do their best to model and explain the changes in the star's speed, their work is compatible with the possibility that there are five small planets orbiting Tau Ceti. One of these appears to be in the "habitable zone" where life like us may be comfortable.

The discoverers freely admit that it may take a decade to confirm that their tiny wiggles are real. But the possibility of planets around Tau Ceti -- coming so soon after the discovery of a planet around one of the stars in our nearest neighbor star system, Alpha Centauri -- brings new excitement to the idea that planets are going to be found around the majority of stars, even the ones nearby. More than 800 planets are now confirmed out there, and we have thousands of candidates in our catalogs. It's a wonderful universe!