Is Asteroid 2011 AG5 A Threat To Planet Earth

There have been internet and media reports that an asteroid whose orbit crosses Earth's orbit will be a threat to our planet in the year 2040. Like several previous stories about death-dealing asteroids, this one exaggerates the threat tremendously for its shock value. (More and more it seems, competition among the many media channels forces everyone to exaggerate the importance of all kinds of news stories!)

We only have very limited observations of this relatively small and dim piece of cosmic rock. With those limited observations, experts have put its chances of hitting us at 1 chance in 625. Already, that number doesn't make me rush out and take out extra insurance on my home. But the key here is that we will know the asteroid's orbit much better after September 2013, when it will be well placed for observing. At that time, with more of its orbit clear to us, we will be able to say far better what its chances of hitting us are. Most likely, the chances will become even slimmer, as they have for most such objects in the recent past.

That's not to say that some asteroid will not hit us again sometime in the future. We have good evidence that Earth-crossing asteroids have blasted craters on our planet in the past. But we have to examine each candidate carefully and not rush to judgment as some web sites did in the present case. Luckily we have time between now and 2040 to gather more information.

For a responsible report on Asteroid 2011AG5, see:
http://www.universetoday.com/93877/will-asteroid-2011-ag5-hit-earth-in-2040/

Asteroids that threaten Earth are rare but real.  To find out more about this intriguing topic, here are some responsible general web sites:

http://impact.arc.nasa.gov/ (Organized by astronomer David Morrison, of NASA)

http://neo.jpl.nasa.gov/  (From the Jet Propulsion Laboratories)

Find Your Favorite Composer, Painter, or Author on Mercury

The MESSENGER mission (orbiting the little planet Mercury) is taking remarkable close-up images.  One of the most intriguing features seen in these pictures was recently named after one of my favorite composers -- Sergei Rachmaninoff.  Double-ringed crater Rachmaninoff, seen on the image I have attached, is about 180 miles across and seems relatively young.  Note how the central circle is smoother (has fewer smaller impact craters in it), which indicates to the mission scientists that volcanic flows from inside the planet may have covered that inside region after the original double crater formed.

Rachmaninoff, a Russian-born early-20th-century composer, wrote some of the most romantic pieces of classical music, including his wonderfully over-the-top Second Piano Concerto.  The story is told that (after the negative reviews of his first symphony), Rachmaninoff became depressed and unable to write further music.  Friends took him to see a psychologist who used hypnotic suggestion to convince Rachmaninoff that he was a great composer and would write a great piece of music.  The interaction with Dr. Dahl gave him a new measure of confidence and he wrote the second piano concerto, which would become his most famous and beloved composition.

By international agreement, craters on Mercury are named after "deceased artists, musicians, painters, and authors who have made outstanding or fundamental contributions to their field and have been recognized as historically significant figures for more than 50 years."

To see if your favorite composer, painter, or author has been honored with a crater on the planet Mercury, you can search for his or her name in the To see if your favorite composer, painter, or author has been honored with a crater on the planet Mercury, you can search for his or her name in the Advanced Search feature in the "Gazetteer of Planetary Nomenclature":
http://planetarynames.wr.usgs.gov/nomenclature/AdvancedSearch

For target, select Mercury, for Feature Type, select "crater, craters." Then just type in your favorite composer, author, or painter into the Feature Name field. (Remember the people have to have been dead for a while, so don't look for living favorites, only for people whose reputations have become established after their deaths.)

For more on the results from the ongoing Messenger mission, see:
http://messenger.jhuapl.edu/

Thirty Billion Planets in the Milky Way

On this photo you see, from right to left, noted astronomy popularizer Donald Goldsmith, leading SETI scientist Jill Tarter, planet hunter Geoff Marcy, and Geoff's wife, chemist Susan Kegley. I took this snapshot last evening, at a banquet sponsored by the Astronomical Society of the Pacific (where I was tickled to be one of the honorees). Dr. Marcy (of the University of California, Berkeley, who is arguably the leading discoverer of planets in the world) spoke about the ongoing hunt for planets with the Kepler spacecraft. He and the mission team have more reason for optimism than ever, it appears. Based on the first two years of Kepler investigation, they think there might be some 30 billion planetary systems in the Milky Way Galaxy. He called it a "tsunami of planets" in the Kepler data. 

Many of the Kepler stars have more than one planet (just like the Sun does.) A star they call Kepler 11 has six planets and they are "co-planar" -- meaning if you pass a sheet of paper through their orbits, all six planets lie in the same sheet of paper. This indicates that the system of planets formed from a flattened doughnut of a "mother cloud", just like our own solar system did. 

And most exciting, as the Kepler teams finds and examines more and more planet candidates, they are finding that SMALLER planets are more common than bigger ones. So, while earlier techniques, that were better at finding big planets like Jupiter, found many Jupiters out there, now (with Kepler) it is becoming clear that smaller planets may make up a greater fraction of the planets in our Galaxy. Since we think smaller planets are probably better candidates for the kind of life that builds computers and does Facebook, this is good news for those who would like a universe in which we humans are not the only intelligent species.

News from Big Astronomy Meeting in Texas

Every January, the American Astronomical Society has its large national meeting and there is (for a week or so) a huge increase in astronomy news.  This year, 2500 astronomers are meeting in Texas and here are just a few of the news items (and links to give you more information):

1. Astronomers may have found an object with rings around it (like Saturn does) in another star system about 420 lightyears away:http://www.rochester.edu/news/show.php?id=3983

2. Astronomers using the Hubble Space Telescope have found the most distant grouping of galaxies seen so far.  The five galaxies are so far away, the light from them took over 13 billion years to get to us (and we are seeing them as the galaxies of stars are still forming):http://hubblesite.org/newscenter/archive/releases/2012/05/full/

3. And perhaps most exciting, astronomers announced the discovery (using the Kepler mission instrument) of the smallest planets yet discovered around a star other than the Sun.  Three small (and most likely rocky) planets orbit quite close to a small red dwarf star about 120 lightyears away.  One of the newly discovered planets is about the size of Mars, breaking the record for the smallest planet yet seen beyond our solar system:http://science.nasa.gov/science-news/science-at-nasa/2012/11jan_smallestexoplanets/

We sure live in exciting times for astronomy fans!

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: http://science.nasa.gov/science-news/science-at-nasa/2011/20dec_earthsized/

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.

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:
http://aer.aas.org/resource/1/aerscz/v10/i1.../p010302_s1

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....

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.

See: http://science.nasa.gov/science-news/science-at-nasa/2011/08dec_slamdunk/
for more on this discovery.

Also, see my short article on Mars in general at: http://www.pbs.org/seeinginthedark/astronomy-topics/mars.html

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