Wednesday, December 28, 2011

Kepler Mission Finds a Weird and Wonderful New Planetary System

Last week, work with the Kepler mission (an instrument in space designed to find planets around other stars by watching them eclipse their stars) led to a major new announcement. Astronomers reported a five-planet star system, being called Kepler 20, about 1000 light years away, which appears to contain TWO planets that are among the smallest we have ever found. One is the size of Earth and one is the size of Venus.
Artist's concept of the two small planets
compared to Earth and Venus
(no one knows what the Kepler planets really look like)

Most of the news reports have focused on these two planets in the system and their small size. And certainly, the discovery of Earth-sized planets is an important one. (The two worlds take about 6 and 20 days to go around their star, so they are both so hot your little brother would get broiled pretty quickly on their surface.)

To me, however, something else stood out in the reports from the discovery team. The five planets in the system are arranged in a surprising way. Besides the two small worlds, there are three larger planets in the same system, presumably made of gas and liquid, like the larger planets in our own solar system. But instead of being organized the way we are, with the smaller worlds closer to the star and the larger ones further out, Kepler 20 has its large and small planets ALTERNATING! We get a large, then a small, then a large, then a small, then a large planet.

That, folks, as they say, "ain't natural!" We can think of no way that such an alternating system could have had that pattern originally -- which means the planets must have rearranged themselves somehow, after the system formed.  That will be an interesting challenge for astronomers who work on the theory of how planetary systems form and settle down.

For more on this weird and wonderful system, see:

The Kepler team has over 2000 candidate planets that they are examining to confirm that they are real planets and not something else in the complex data.  In the next few years, we expect to find many new planetary systems and, if nature is kind, others will also be a challenge to our ingenuity.  This is science at its best, discoveries that force us to re-examine long-hold ideas about how nature works and what kinds of combinations she has up her sleeve.

Wednesday, December 21, 2011

The Winter Solstice and a Catalog of Astronomy Apps

Happy winter solstice everyone -- the shortest day of the year -- officially at 9:30 pm PST, on Dec. 21, 2011.  It's the beginning of winter in the Northern Hemisphere of the Earth. Because our planet is tilted (leaning to one side), the two hemispheres get different amounts and intensities of sunlight as the year goes on, and thus we have seasons. In the summer, we have long days and shorter nights, while in the winter we have long nights and shorter days. All this happens because early in its history, some cosmic accident knocked the Earth over a bit and -- like many accident victims -- it had no way of straightening out. Venus and Jupiter orbit the Sun with their axes pointed straight up, and don't have seasons like we do.
Many of our winter holiday traditions have their roots in ancient celebrations of the winter solstice.  To make sure the Sun-god increased his presence in the coming months (and to cheer everyone up when the days were short), many ancient people had festivals with music and song, sacrificed a food animal, and gathered around a fire with loved ones. So, if you are enjoying the winter holidays right now (and I hope you are), give a little thought of thanks to whatever mini-planet or planets knocked our Earth over a bit at the time our solar system was first forming.
As a little solstice present, I thought some of you might like to see a new article I published today, which is a listing of 98 astronomy apps you can get free or buy for your smartphone or tablet:

As some of you know, my hobby is making resource guides. Some people knit or shoot hoops when they need to relax; I make bibliographies and catalogs. With the help of a student volunteer, I scoured the web to find apps that can help you enjoy many aspects of astronomy. The listing includes a variety of apps for displaying and explaining the sky above you (some using the GPS function in your device); a series of astronomical clocks, calculators, and calendars; sky catalogs and observing planners; planet atlases and globes; citizens science tools and image displays; a directory of astronomy clubs in the U.S.; and even a graphic simulator for making galaxies collide. Enjoy....

Thursday, December 15, 2011

Further Evidence of Water on Mars

Even as the new Curiosity Mars Rover is making its way toward Mars for an August landing, one of the old (smaller) rovers, Opportunity, is still making discoveries after its almost 8 years on the surface of the red planet. Last week, scientists announced the discovery of a small vein of the mineral "calcium sulfate" -- most likely the form we call gypsum on Earth. Found in Endeavor Crater on Mars, this mineral deposit could not exist unless Mars had flowing water in the past.

This discovery cements (pardon the pun *) our understanding that billions of years ago, when Mars had not yet lost its thick atmosphere, there were streams, lakes, and underground flows of water on the planet. A number of other minerals that require water have been found by earlier rovers and probes. We also see large-scale areas that look like former river channels, flood plains, and lakes.

Today, Mars is drier than the worst desert on Earth and its air is horribly thin, because little Mars -- with its weaker gravity -- could not hold on to its air. But ancient Mars could have been much more Earth-like than Mars today. This is why astronomers continue to hold out hope that some sort of primitive life might have gotten started there long ago and that our exploring machines might find fossils or chemical indications of such a "second genesis" on another planet.

for more on this discovery.

Also, see my short article on Mars in general at:

(* The pun: gypsum is used in plaster of Paris and as a form of cement)

Saturday, December 10, 2011

Record-Breaking Monster Black Holes Found

Record-Breaking Monster Black Holes Found

A team of astronomers from several universities recently reported the discovery of two black holes that are SO BIG that they have each eaten as much material as 10 billion Suns -- the largest black holes ever found. Each is located in the center of a big galaxy and the two galaxies are both over 300 million light years away.

A black hole is a place where one or more stars have collapsed completely and their gravity overwhelms every other force in the universe. Nothing, not even light, can escape from a black hole -- making falling into one of them a "once-in-a-lifetime experience!" Many black holes exist in splendid isolation, but if a black hole forms in the crowded center of a big galaxy, then watch out!  When there are stars (and gas and dust) close enough to the black hole, it can cosume them for lunch -- and thus grow a bit. Like the Blob in the old horror movie, the more a black hole eats, the bigger it gets, the bigger it gets, the more it can eat. As long as there is food available, a black hole can grow.

Astronomers had expected that in the biggest, most crowded galaxies, black holes would grow really, really big. Now, in these two galaxies, which have only catalog numbers for names (NGC 3842 and NGC4889), we see clear evidence of just how "overfed" such black hole monsters can be. (Astronomers measure the mass of such black holes by watching stars close to the black hole whirl around at fast speed due to its enormous gravity.)

What is also interesting about this discovery is its connection to "quasars" -- which were mysterious when first discovered, but are now known to be the energetic (bright) centers of distant galaxies.  They are tiny regions at the cores of their galaxies which can outshine the entire galaxy of stars in which they live.  Their energy output is truly staggering. 

Astronomers have established that these quasars were supermassive black holes that had so much "food" (material to eat) around them, that the swirling ingestion of this material produced fantastic energies -- large amounts of light and other radiation.  (The energy had to come from a region outside the black hole -- once anything falls INTO the black hole, no energy can come back out.)   But to produce such huge amounts of energy, the quasar black hole must have been very massive indeed. 

We believe that we see quasars only in the early days of the universe -- when the giant black holes were supplied with plentiful food, espeially when smaller galaxies fell into bigger ones and were eaten in an act of galaxy cannibalism.  Nowadays, such really big black holes will have eaten all the material in their neighborhood and have little left to eat.  Thus they are no longer shining as quasars.  As one of the discoverers of the monster black holes said, these are black holes "in retirement." 

The more quiet black holes of our present epoch are harder to find.  So astronomers have been actively searching for really huge "retired" black holes, which once were quasars but now are quiet.  It looks like the two we found are candidates for just this kind of status.  When, long ago, they acted like quasars, their gigantic mass ensured that the feeding process was a very energetic one.

Saturday, December 3, 2011

The Second Largest Mountain in the Solar System

We have found the second largest known mountain in the solar system, on the battered asteroid Vesta (which is currently being orbited and examined by the DAWN spacecraft). The mountain, not yet named, is 13 miles high and 112 miles across its base. It rises from the center of a giant impact crater; the hit that produced that crater is probably also responsible, in part, for Vesta becoming the largest body in the solar system that is NOT round. See an image of the mountain, on a map drawn from the DAWN photographs, here:

(The largest known mountain is Mount Olympus on Mars, by the way. It is 16 miles high and larger at its base than the entire state of Arizona.)

You can see an interesting modeled image of the Vesta mountain here:
but please note that the height of everything on this picture has been exaggerated by a factor of 1.5 to make the huge mountain look more mountain-like, as it was posing for the media and the public.

We expect many more discoveries about asteroid Vesta as the DAWN mission continues.