Saturday, November 16, 2013
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.]
Sunday, November 10, 2013
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:
Sunday, November 3, 2013
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.
Sunday, October 27, 2013
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.
Wednesday, October 23, 2013
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)
Sunday, October 13, 2013
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?"
Wednesday, October 9, 2013
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:
An analogy for Higgs Field using everyday materials with science writer Ian Sample: