Friday, August 26, 2011

A diamond planet? I dunno..

Artistic concept of a pulsar and its tiny companion
Image Credit: Swinburne Astronomy Productions, Swinburne University of Technology
Yesterday, the news wires were alive with excitement.  Astronomers had a confirmed discovery of a planet made out of diamond!  DeBeers better load up a rocket ship and blast off!  But before we put the cart before the horse (and the cart is already halfway across the country while the horse is still munching oats in the barn), let's look a little deeper.  The likely real story is, in my opinion, even more exotic than a planet-sized diamond.

First, let's go over what the astronomers observed.  The team, headed by Professor Matthew Bailes of Swinburne University of Technology in Australia, was looking at a millisecond pulsar.  Pulsar are the remains of very massive stars that exploded as supernovae at the end of the stars' lives.  Pulsars typically contain about 1.3 times the mass of our sun squeezed into a sphere only a dozen miles across.  This is so dense that ordinary atoms cannot exist, and most of the protons and electrons that made up the atoms in the original star merge to form neutrons.  We therefore call these very dense remains of massive stars neutron stars.

Wednesday, August 24, 2011

Y Dwarfs? Because they're cool.

Cool brown dwarf spotted by WISE
Image Credit: NASA/JPL-Caltech/UCLA
That little green dot in the center of the picture above may not look like much, but it is, in fact, one of the first absolutely definitive members of a predicted type of brown dwarf, the "spectral class Y" dwarfs.  It was discovered by astronomers using data from the Wide-field Infrared Survey Explorer, a satellite mission that scanned the entire sky in the infrared wavelengths of light during 2010.  The star above has a temperature of about 25 degrees Celcius, or roughly 80 degrees Fahrenheit -- measurably cooler than the endless summer heat here in Texas.  The discovery was announced yesterday by the WISE team, and an official journal article announcing the discovery has been accepted for publication in the Astrophysical Journal.  Even cooler than the brown dwarf is the fact that this paper was headed up by a good friend of mine, Michael Cushing (now a new faculty member at the University of Toledo).

Friday, July 08, 2011

The last shuttle launch


I just watched the space shuttle Atlantis safely launch on the final mission of the Space Shuttle program, 30 years after I watched the first launch of the program.  30 years.  Wow.


On April 10, 1981, I was a first-grader, and my parents kept me home from school to watch the launch.  I had never seen a rocket launch.  The final Apollo moon landing happened a year before I was born, the final Skylab mission was halfway over when I was born, and I was a toddler when Apollo-Soyuz was launched.  So space travel was a foreign idea to me, and I didn't understand the fascination.  I remember seeing this ungainly machine sitting on the launch pad and telling my parents that it would never work, and that I wanted to go to school.  When the countdown clock stopped 31 seconds before launch, I laughed, said, "See, I told you", and saw a pained look on my parents' face.

Two days later, the STS-1 did launch, and again, I was forced to watch.  But as soon as the engines fired and the shuttle lifted off the pad, I was hooked.  Although commander John Young had been in space as part of both Gemini and Apollo, those missions meant nothing to me, and for years I associated him solely with the space shuttle.

Over the coming years, I read everything I could about the space shuttle and astronauts, and even subscribed to a magazine and ordered a science encyclopedia without my parents' permission. (Kids, don't do that!)  Thankfully, they paid more or less willingly for my enthusiasm.

I grew up with the shuttle program, entering my turbulent teens at the same time as the Challenger disaster.  I went to Space Camp (technically Space Academy) in 1988 and saw models of the great Space Station Freedom and second-generation shuttle-like vehicles that would be operating in just the next few years. Then I watched as these programs were cancelled, reconstituted and rescoped, cancelled again, and yet again reborn.  I watched the shuttle launch and repeatedly save the Hubble Space Telescope, perhaps its finest hour.  I took my first job as a professional astronomer at the same time as the Columbia disaster.  And now, 30 years after it began, we're finishing the space station and putting the shuttle into retirement. 

Many people question whether the money we spend on space exploration is worth the cost.  Without hesitation, I say that it is.  The space program is less expensive than many people realize; out of every $100 in federal spending, 47 cents goes to NASA.  And it's not like we are launching bales of money into space; most of that costs pays American workers and American companies for labor and products, so that money goes directly back into our economy.  Our modern economy relies on space, from satellite communications, weather satellites, and through GPS navigation, space exploration impacts our everyday lives.

And space exploration serves another purpose.  It is inspiring.  How many hundreds of thousands or millions of children are like me, inspired to study and advance technology and science by watching big, lumbering rockets atop a thin spindle of smoke and flame?  Our technology-driven economy relies on that spark of interest.

Tuesday, June 14, 2011

Are sunspots going away?

A press conference today announced three research projects that suggest that our sun's familiar sunspot cycle might be heading toward a major change or even a pause.  You can read good summaries of the findings in this post from space.com and this article on Universe Today; I'll wait while you do that and then give you my first thoughts on this news.

Done reading?  Good.  First, let me state that I am not a solar physicist, and I do not claim to be an authority on the research being done.  So feel free to take my opinions with a grain of salt.

A new type of supernova?

Image Credit: Caltech / Robert Quimby / Nature
Last week, a group of astronomers led by Caltech astronomer Robert Quimby announced that they had learned a few crucial pieces of information about these enigmatic sources.  This new evidence suggests that we are seeing a new type of stellar explosion, though we still don't know exactly what we are seeing.


Two years ago, I attended a conference on supernovae (exploding stars), and I blogged about weird objects that we could not explain.  In apparently blank parts of the sky, a couple of "new stars" had appeared and slowly faded away, just like supernovae.  Only these new objects changed their brightness on much longer time scales than normal supernovae, they did not appear to be located inside another galaxy, and their spectra showed weird features that could not be identified with certitude.  Many different explanations were proposed, from white dwarf stars in our own Milky Way Galaxy to carbon stars being shredded by black holes halfway across the Universe.

Friday, June 10, 2011

A supernova in the Whirlpool Galaxy

Supernova 2011dh in the Whirlpool Galaxy.  Image Credit: Peter Edwards
Supernovae, the explosive end of the life of some stars, are among the most powerful and most spectacular events in the universe.  They are also very rare.  Our Milky Way galaxy, with tens of billions of stars, sees one of them explode every 100 years or so.  The last known supernova in our galaxy was seen in 1604 and was studied by the famous astronomer Johannes Kepler.  Since that time, we think that at least two stars may have exploded in the Milky Way, with the explosions veiled by some of the Milky Way's many thick, opaque clouds of dust and gas.  But none have been seen.

Thankfully, there are lots of galaxies in the universe.  So, when astronomers want to study supernovae, they look at a lot of galaxies.  Such surveys for supernovae are turning up new explosions in distant galaxies all the time.  Still, many of these galaxies are fairly far away, and it is rare to find a supernova in our neck of the woods.

Enter the Whirlpool Galaxy, also called Messier 51.  The Whirlpool is nearby, as far as galaxies go – "only" 26 million light-years away.  It is also a favorite target of amateur astronomers, because it is a beautiful face-on spiral galaxy, and its spiral arms can be glimpsed by modest-sized telescopes in dark places.  Last week, sometime before the evening of May 31, a star exploded in one of the spiral arms.  The picture at the top of this post shows a picture with the supernova (the "new star" marked by white lines on the left picture) and a picture of the galaxy taken a couple of months ago, before the star exploded.

Tuesday, May 31, 2011

Oh, deer

One of the nice things about going observing is that the trip involves visiting a secluded portion of wilderness, albeit one with hot meals, indoor plumbing, high-speed internet, and soft beds.  It's the best of both worlds!

With the short nights of summer, I have some extra time to kill in the afternoon.  Yes, I could be a good astronomer and work on papers and data analysis.  But instead, I've been taking some walks in the great outdoors.  Here are some pictures from the past few days here at McDonald Observatory.  Click on each one to see a larger view.  And, be warned, I'm not and never will be a great photographer.

The mountain is full of wildlife, including larger animals like deer and javelina.  It's a bit scary to run into the latter at night.

This is a 180-degree panorama taken near the 36-inch telescope (in the dome on the right).  The center of the view faces southeast, toward the town of Fort Davis.  I made this panorama using a demo version of some stitching software, which explains the random watermarks sprinkled liberally over the image.

On a clear day, you can see for miles, sometimes well over a hundred miles.  The last couple of evenings, there have been gorgeous views of building thunderstorms.  This picture was taken after sunset, so the base of the cloud is in shadow, but the top of the cloud is still bathed in sunlight.  This storm was off to the northeast, in the direction of Pecos, but I never checked the radar to see exactly where it was.  The distant dome on the left is the Hobby-Eberly Telescope, and the dome on the right is the Harlan J. Smith Telescope.

Friday, May 27, 2011

Finally back at the telescope

Tonight I've been observing at the McDonald Observatory.  It's been 13 months since I've last sat at the controls of a telescope to do some research.  I think this is the longest interval I've gone without using a telescope since I started graduate school in the late 1990s.  I can feel a bit of the rust.

A lot has changed since last I was sitting in front of the telescope controls.  Last April, I was negotiating terms of a new job as a university professor.  Today, I've finished that first academic year.  Or perhaps "survived" is a better term.  I was warned by many colleagues that this was going to be a busy year, and I believed them, but I was still shocked how busy the year was.  The transition from astronomy research to educator is not easy.

So now that the summer is here, I'll be working hard on my research projects, and hopefully getting to write a lot more here than I have over the past several months.

Friday, April 08, 2011

New discoveries on odd stellar explosions

Image Credit: NASA/Swift/Penn State/J. Kennea
Over the last week and a half, there have been a couple of news releases about stellar explosions.  In the first story, astronomers have spotted a puzzling blast of gamma ray and X-ray emission that could be a star being ripped apart by a massive black hole.  In the other story, astronomers have made substantial progress in understanding the brightest supernovae ever observed.

First, the puzzling gamma rays.  For decades, astronomers have seen sudden, short bursts of gamma rays coming from all over the sky.  About ten years ago, after a lot of hard work (and a little luck) by many different researchers, most astronomers came to believe that many of these "gamma-ray bursts" are the birthing cry of new black holes formed at the centers of massive, exploding stars. 

Wednesday, March 16, 2011

The nuclear crisis in Japan

Like many of you, I've spent a lot of time this week watching and reading coverage of the earthquake, tsunami, and subsequent nuclear crisis in Japan.  The news coverage I've seen of the earthquake and tsunami has been heart-wrenching, and I strongly encourage all of you to give generously to reputable relief charities.

However, the news coverage of the unfolding crisis at Japan's Fukushima Daiichi nuclear power plant has been, through most of what I've seen, poorly done.  Two days ago I spent an agonizing 15 minutes watching a national news anchor and a meteorologist discussing what impact the wind might have on radiation levels in Japan.  Both people freely admitted to not understanding why the wind would have an impact, or even where nuclear radiation comes from.  Yet rather than bring on an expert who could explain these important issues, they admitted their ignorance and threw it to commercial.

News coverage like this leads to fear and panic, and fails to provide that one crucial item that the field of journalism is built upon: correct information.  So today there are reports of panic purchasing of radiation-related health products on the West Coast of the U.S. when, to the best I've heard, there has not yet been a catastrophic release of radiation from the Fukushima Daiichi plant, and if there were, it would be many days before any radiation could reach the U.S. 

Radiation leaks are scary.  We need special equipment to detect radiation, so unlike many threats, the public can't see it coming.  We have to rely on people "in the know" to be honest with us.  And, in the worst radiation accident that we know of, the explosion at Chernobyl, those people tried to cover up the accident.

What we as the public need is sound journalism with expert scientific reporting to help us to understand what is happening at nuclear plants in Japan.  We don't need anchors wildly speculating about radiation and constant reports on fear and panic.  Perhaps major news organizations will rethink their attitudes toward science journalism – there should be more effort involved than incorrectly regurgitating a story from a marginally-reputable news outlet.

Thankfully, some expert sources of information are finally starting to be heard.  This morning, the American Astronomical Society provided links to some detailed sources of information.  As far as I can tell, these links are providing some of the most thorough reporting, including detailed explanations about what we do and do not know about the ongoing situation.  So, without further ado, here they are for your consumption:
  • http://ansnuclearcafe.org/ - A blog from the American Nuclear Society, compiling information from several different sources.
  • http://www.world-nuclear-news.org/ - The World Nuclear News is provided by the World Nuclear Association; this content is produced by in-house journalists who have access to nuclear experts around the globe
  • http://mitnse.com/ - the MIT Nuclear Science and Engineering Nuclear Information Hub, maintained by students at MIT's department of nuclear science and engineering.
As in any crisis, the situation is fluid, could change rapidly, and is subject to interpretation.  From all that I can tell right now, there is no need for panic.  Fear is a natural response, but those of us outside of the immediate area surrounding the reactor are not in immediate danger. 

Be concerned.  Stay informed.  Don't panic.

Friday, March 04, 2011

a visit from a famous scientist

Professor S Jocelyn Bell Burnell
Image Credit: Department of Physics, University of Oxford
This week, our department was honored to host a visit by Professor Jocelyn Bell Burnell.  Dr. Burnell is most famous as having discovered pulsars while a graduate student at Cambridge University.  Her thesis work involved building a radio telescope (radio astronomy was still a young field at the time) and searching the sky for radio sources.  She discovered multiple sources that emitted strong pulses of radio waves every second or so.  These sources turned out to be neutron stars, or stars with the mass of the sun squeezed in to a ball about 10 miles across.  Neutron stars are the remnants of many stars that end their lives as supernova explosions. The discovery of neutron stars revolutionized our understanding of how stars live and die.  You can read her own description of her discovery here.  Dr. Burnell's thesis advisor was awarded a share of the Nobel prize for this discovery, but Dr. Burnell did not receive that recognition.  Her contributions to this discovery have been well-recognized and rewarded since, and Dr. Burnell has had a long and fruitful career in astrophysics.

Dr. Burnell visited our department through the efforts of one of our postdoctoral researchers, Will Newton.  Dr. Newton came to know Dr. Burnell while he was studying at Oxford.  When Dr. Newton learned that Dr. Burnell would be in the United States this spring, he was able to convince our department to invite and host Dr. Burnell for a week.

During this week, Dr. Burnell delivered several talks, including a talk on poetry and astronomy, a talk on the astronomical evidence against various "end of the world in 2012" hype, and a research talk on neutron stars.  She also spoke with many of our classes, including a question-and-answer session with my introductory astrophysics class.  The students seemed really enthusiastic to have her visit, and they asked some great questions.  I was very happy.

I hope that some of the benefits of Dr. Burnell's visit will be more than memories of a visit by a great astronomer.  First, I hope that many of the students saw, consciously or unconsciously, that women scientists arre absolute equals in research and teaching ability.  Our department is male-dominated, and a very large fraction of our regular visitors to the department are male.  I and many of my colleagues and I would like to see this change, and I think that having a visitor with the stature of Dr. Burnell is a big step in the right direction.

Second, I was glad that my students heard Dr. Burnell talk at length about the discovery of pulsars.  While the end result, a new class of star, was tremendously important and transformative to the science, this discovery was much more involved than simply seeing a repeating blip on a piece of paper and then dancing around while popping champagne.  The efforts that Dr. Burnell and her advisor, Dr. Anthony Hewish. went through to prove that they were seeing some new class of astronomical object are a classic example of how new discoveries should be made.  They tested their equipment, they considered every possible existing explanation, they made multiple observations, and they finally found a second (and then third and fourth) radio source that was similar, but different enough to prove that these must be different sources of radio waves.  Then they considered the most likely sources of those radio waves and wrote a journal article announcing their discovery, observations, and possible explanations.  Other scientists were then able to duplicate their observations and expand upon them.

We all-too-often present scientific discoveries as a "Eureka!" moment, where finally there is understanding and it all makes sense.  But good science doesn't work that way.  Certainly, there are flashes of inspiration, and luck plays an important role.  Yet the discovery of pulsars was a months-long process involving multiple people tracking down multiple possibilities, not an instant of seeing a blip on a radio telescope.  Seeing some odd blips on radio data started the process of discovery.

We are very grateful that Dr. Burnell took the time to visit our university.  I was pleased to have a good talk about white dwarfs and my research with her, as well as to learn a lot about neutron stars and the present state of various radio and gravitational wave observatories.  I even heard some inside anecdotes about the International Astronomical Union's decision on the status of Pluto (maybe I'll write about that another day).

Thursday, February 03, 2011

Watching the world change

World-changing events come in many guises.  Sometimes they are highly visible, like the launch of Sputnik, the fall of the Berlin Wall, or the current political upheaval in the Arab world. We rarely know what the eventual outcome and import of such events will be, but there is little doubt that what has happened is Important and will impact us all.

Other world-changing events are more subtle, with impacts that take a long time manifest themselves, but are no less dramatic.  The invention of the telegraph and the creation of the Internet were not trumpeted by the forebears of Anderson Cooper swooping in with live reports, but events like these inexorably led to a changed world.  (The first public demonstration of the telegraph by Samuel Morse was in 1838; his famous "What Hath God Wrought" message was not sent until 1844.  Seven years later, Western Union was founded, and the rest is history.)

Yesterday, NASA and its Kepler Mission team announced a small landslide of new planets and planet candidates.  In one announcement, the number of known/suspected planets went from just over 500 to over triple that number, at around 1700.  Not only that, but the number of known Earth-sized planets went from a zero or a few (depending on your definition) to nearly 70.  And this is certainly just the tip of the iceberg.  In two years, Kepler has discovered more planets than all of humanity had discovered in all of history.  Think about that for a second.  Granted, we've been getting better at finding planets recently, but Kepler's pace is still far beyond all other efforts combined.

In many regards, yesterday's data avalanche was expected.  We knew Kepler was working well, and there had been many hints and insider slips that the team was finding planets everywhere in Kepler's sight.  But the fact remains that, before the Kepler Mission, we did not know how common Earth-sized planets are.  And now we are starting to get the answer.  They are very common.

One of the questions humans have been asking for ages is, are we alone in the Universe?   We don't have an answer to that yet, but Kepler has taken a giant step along the path to answering that question.  There are profound implications in the Kepler team's work, not just for understanding how the Universe works, but for understanding our place within this Universe.  There are potentially huge philosophical implications that extend far beyond the science of astronomy.

The Kepler Mission still has work to do.  Its primary goal is to count how common Earth-sized planets are at distances from their parent stars where life similar to that on Earth might be possible.   Yesterday we got some initial hints, but the final answer is still years away.

Undoubtedly, yesterday's Kepler data release will fundamentally transform our study of planets around other stars, in our understanding, our future observing programs, in the challenges to our ideas about planet formation, and even in the basic questions we astronomers are asking.   But I also feel that there will be a societal impact extending far beyond the astronomy of planets.  It may take years or decades for that impact to be felt, and this impact will be driven not just by the Kepler mission, but also by the hard work and discoveries of astronomers who will work (and have been working for nearly two decades)  on planets around other stars.

The universe of astronomy has changed, even if that change was mostly anticipated.  And I think these discoveries will change the rest of the world.  How long we have to wait, and where will this change lead society I do not know.  But I do know that this is Important.

Wednesday, February 02, 2011

Planets everywhere

Image Credit: NASA/Wendy Stenzel



Today, NASA and the Kepler Mission team announced the most up-to-date results of the Kepler mission's search for planets around other stars.  Today's haul was nothing short of astounding (though, dare I say, mostly expected): 1235 candidates, 68 of which are Earth-sized.  54 planet candidates (not necessarily the same ones that are Earth-sized) are the right distance from their parent star that they could have liquid water.  170 of these 1200 candidates also show some evidence of being in multiple-planet systems, and one has at least six planets!


Friday, January 28, 2011

In Remembrance

25 years ago today, the space shuttle Challenger was lost 73 seconds into her flight.  Seven souls were lost.  At the time, I was at home -- school had been canceled due to snow.  Though a was a space nerd even then, I wasn't watching the launch.  I was out sledding, and came inside for a break when my mom called to say she'd heard something on the radio about the space shuttle landing in the Atlantic Ocean.  I was glued to CNN for the rest of the day.

Like many people, I felt that combination of shock, sadness, disbelief, even occasional hope that someone may have survived.  At the time, I was angry that the majority of the coverage seemed to focus only on Christa McAuliffe, the "teacher in space" astronaut.  As a kid, I didn't fully appreciate what it meant to have a civilian astronaut, and I felt that the rest of the crew was being shortchanged.  I had never appreciated just how dangerous space travel is, and how much each of our astronauts risks every time they journey into the heavens.

This week always contains a day of remembrance at NASA.  Yesterday was the 44th anniversary of the Apollo 1 fire, in which three souls were lost, and February 1 will be the 8th anniversary of the loss of the Space Shuttle Columbia and her crew of seven.  Each of these tragedies was the result of cultural and technical failures that, in retrospect, probably should have been caught.  But each also led to crucial improvements in safety, technology, and bureaucracy.  Perhaps the Apollo 1 fire is the most obvious example, as improvements made to Apollo capsules following the fire likely saved the Apollo 13 crew.

It appears that our country's space program may be beginning a transition to one dominated by the private sector.  When one of the many competing firms has a failure resulting in a loss of life, how will we respond?  Will we ground all private space missions until the exact cause is identified?  Will we end private investments in space travel?  I fear these reactions.  Instead, I hope we may be able to respond similar to how we have in the past -- be saddened, learn lessons and make necessary improvements, and then continue to push out bravely into the stars.

Friday, January 21, 2011

Two suns next year?

Will the Earth have two suns in 2012?  Will the star Betelgeuse explode and make the nighttime as bright as midday?

No and no.

Why not? See these posts by Ian O'Neill and Phil Plait.

And national news outlets that pride themselves on being reliable (I'm looking squarely at you, Time and CNN), shame on you for just copying someone else's story rather than checking it out first.  Fox News managed to get it right.

And if you have no clue what I'm talking about, read here if you dare.  (In all fairness, the original story, the one I linked to, is only moderately inaccurate -- more hype than wrong, and the astronomer who is quoted doesn't say anything that looks out of line.  But like a game of telephone, things went downhill as the story got repeated.)

Monday, January 17, 2011

Astro101: The Signs of the Zodiac

Astro101 is an occasional series touching on the very basics of astronomy.

Ophiuchus, the Serpent Bearer
 Image copyright © T. Credner & S. Kohle, AlltheSky.com

Last week, there was a surprisingly big flurry of astronomical news.  Not over all of the exciting science coming out of the annual meeting of the American Astronomical Society, despite all of the exciting results.  Rather, the kerfuffle erupted over comments that astronomer Parke Kunkle made in an interview with the Minneapolis-St.Paul Star Tribune regarding astrology: namely, that the sun passes through thirteen constellations, not just the twelve, and that the signs of the zodiac don't align with astrological signs.

Kunkle didn't say anything astronomers haven't known since the second century B.C., and astrologers have been making excuses for just as long.  But I'm not here to talk about why astrology is a load of bunk. (If you want to argue otherwise, do a few things before trying to tear me a new one: First, devise and execute a precise scientific study proving astrology and your explanation for how it works, and get your study published in a peer-review journal.  This is something I require of even my best friends before I believe their claims.  Second, go pick up your million dollar prize.  Lastly, come back and laugh in my face.  But not before.)

Instead, let's focus on reality and learn something about the constellations and the zodiac, making use of what some might call a "teachable moment".


1. Constellations
Let's start with the definition of a constellation.  In ancient days, constellations were specific patterns of stars in the sky that made a more-or-less recognizable picture.  Today, these patterns are often called asterisms. A well-known asterism in the northern hemisphere is the Big Dipper (or Plow).  Ancient astronomers defined many different asterisms, but most of these varied from culture to culture.  Also, not every star in the sky was part of a constellation, nor did anyone seem to think that every star had to be.  Many of the patterns we call "constellations" today were used by the ancient Greeks.

The Scientific Revolution, which started in the mid-16th century, began the modern science of astronomy.  One important thing that modern astronomers learned early on was that there are interesting objects all over the sky, and in order to study these objects, astronomers need to make catalogs detailing where each interesting thing is.  The most commonly-used method of cataloging involves a coordinate system on the sky, known as Right Ascension and Declination (akin to longitude and latitude on the Earth).

However, many astronomers also referred to stars as being in constellations.  This didn't mean that a star was part of the pattern, but merely that it was in the same region of the sky as the better-known constellation.  Since the boundaries of constellations were not well-defined, this led to lots of confusion.  So, in the late 19th century and early 20th century, astronomers defined official boundaries to every constellation.  The result is that every portion of the sky belongs to one and only one constellation, even if there are no bright stars in that part of the sky corresponding to some recognizable pattern!  This is analogous to the United States, where every square inch of land belongs to a state, even if nobody lives there.

2. The Ecliptic 
As you hopefully know, the Earth orbits around the sun, completing one circuit every year.  Because we are moving, we have a different viewpoint of the sun and sky every day.  In particular, the sun appears to move against the background stars, completing one full trip around our sky in a year.

If you don't believe me, go to the SOHO solar observatory movie page and watch the most recent  LASCO C3 movie.  The SOHO satellite constantly takes pictures of the Sun, and the LASCO is a camera that blocks the sun's bright disk so its faint outer atmosphere can be seen.  In addition to the sun's atmosphere, you'll see tiny white dots moving from left to right across the image.  These are the stars.  Once in a great while, you may even see a pattern of stars that you recognize, like the Pleiades star cluster.  A few months later, you can go out in the early morning and see these same stars high in the sky.

The sun always appears to go past the same stars around the sky every year.  This is because the Earth repeats its orbit every year, and so at the same time every year we have the exact same view of the sun and the stars.  This path is called the ecliptic.    If you could see the sun's path drawn on the night sky, you would see that the ecliptic appears to be a complete circle around the sky, and that this circle goes near or through some familiar star patterns, like Scorpius, Leo, and Gemini.

Although ancient astronomers could not make pictures like the SOHO spacecraft takes, through careful observation they were able to deduce the path of the sun through the stars, and, by definition, the ecliptic.

3. The Zodiac
The zodiac is the group of constellations through with the ecliptic passes.  In other words, over the course of a year, the sun passes through all of these constellations.   Traditionally, the zodiac contained twelve constellations.  In Europe, these constellations correspond to the twelve signs of the zodiac that astrologers often quote.  The number of constellations is not an accident -- since many cultures have 12 months in a year (corresponding to the roughly 12 cycles of the moon that fit into a single year), ancient astronomers thought it made a nice balance if the number of constellations equalled the number of months in a year.  But different cultures had different constellations and so different "signs" of the zodiac.

More importantly, the sun's path doesn't depend on how we humans define constellations -- the ecliptic is the same whether there are no constellations, 12 constellations, or a billion constellations.

4. Ophiuchus
The constellation Ophiuchus, the serpent bearer, is an old constellation, but one that most people have not heard of.  It lies north of the constellations Scorpius and Sagittarius.  But one star of the pattern sticks down between the two constellations: theta Ophiuchus.  This star is the right foot of the serpent wrangler.  And the ecliptic (the sun's path through the sky) passes right past this star. 

So, the sun's path takes it through part of the constellation Ophiuchus.  Even though astronomers arbitrarily defined constellation boundaries, by any Greek's definition of the boundaries of Ophiuchus, the sun's path must go through the constellation.  Whether or not ancient astronomers realized this, I don't know and don't have time to research.  But having a thirteenth sign of the zodiac would ruin that nice balance between the 12 months of the year and the (roughly) 12 lunar cycles a year, so it's not surprising that Ophiuchus is not considered a sign of the zodiac.

But the fact remains, both by official definitions and by classical definitions of constellation boundaries, the ecliptic passes through 13 constellations.  So, if your astrological sign is "supposed" to be the constellation in which the sun is present when you are born, some people who should be Ophiuchans are left out in the cold.  But astrologers have many (and differing!) "explanations" for why this doesn't matter.

Which brings us to our last point:
5. Precession of the equinoxes 
Remember, the sun's path through the sky repeats year after year, so the ecliptic remains the same.  But Earth's axis of rotation, the direction in which the North Pole points, changes over very long time scales.  Every 26,000 years, the Earth's axis makes a big circle in the sky; this motion is called precession of the equinoxes.  If you've ever seen a toy top or gyroscope, you'll have noticed that it wobbles, with its spin axis making circles.  This is basically the same effect as the Earth's precession!

Precession has two major impacts over that long time span.  First, the star we identify as the "north star" changes every thousand years or so.  But more importantly, since Earth's seasons are caused by the Earth's tilt, the seasons slowly change.

If we defined our calendar by the sun's position against the stars, our seasons would slowly get out of sync.  After 13,000 years, our "summer" months would be cold, and the "winter" months would be hot.  This would be confusing.  Therefore, the definition of a "year" that we use for our calendars takes this slow change into account.  Therefore, June will always remain the start of the northern summer, and December the start of the winter.  The effect of Earth's wobble will therefore be seen in the stars.  In 13,000 years, the stars we now see in December will be up in June, and the stars now up in June will be visible in December.  This change is gradual, but noticeable with careful observations.  The first recorded observation of precession was by the ancient Greek astronomer Hipparchus in the 2nd century BC.

The signs of the zodiac that most modern astrologers use were defined by the ancient Greeks, as I've said.  That was about 2200 years ago.  One full circle of the precession of the equinoxes takes 26,000 years.  Take 2200 divided by 26,000, and you get 1/12.  In other words, since the ancient Greeks defined the zodiac, the Earth has completed 1/12 of a precession cycle.  This means that the constellations are about 1/12 of the way through their yearly changes, or that they appear about 1 month out of sync with what the ancient Greeks saw.

But astrologers use definitions of zodiac birth times set by the ancient Greeks, so although a person born in early August may be called a Leo, the sun is actually in the constellation Cancer at the time.  If this bothers you, just stick around another 24,000 years, and things will be back to "normal".

Now you have the full, lengthy story about what Parke Kunkle said in that interview last week. Hopefully you've learned something along the way!

But none of this is news to astronomers.  And, as I've said, astrologers have a wide variety of excuses for why this doesn't matter, and have used these excuses for centuries.  So, perhaps the bigger question is, why did this one news story (not the first to talk about Ophiuchus and the precession of the equinoxes) make such a big impact in the news?  Is it an indictment of how little our society knows about the science of astronomy?  Or should I be optimistic and take it as a sign that society is actually starting to pay attention to what is really happening in the sky?  Given that Americans spend at least as much money on astrology every year as the National Science Foundation spends on astronomy research, I'm not feeling very optimistic.

Thursday, January 13, 2011

American Astronomical Society meeting, days 2 and 3

It's been a busy couple of days here at the 217th meeting of the American Astronomical Society.  I've spent a lot of time in meetings and talks the last two days, so I haven't had much time to sit down and blog. Here are a few little tidbits, not meant to be comprehensive.  Just nuggets that I found interesting.  Click on the links for more info.
  • The biggest picture yet made: The Sloan Digital Sky Survey, which is taking pictures large portions of the sky, released what they are calling the largest picture ever made, over 1 trillion pixels.  I'd suggest against downloading the full-resolution picture (which actually isn't available as a single file), unless you have a roughly 10 Terabyte (10 trillion byte) hard drive.  However, you can go to their website and look up portions of the picture corresponding to your favorite objects, if that object is in the portion of the sky looked at by Sloan.
  • New, amazing pictures in wavelengths of light invisible to the human eye were released.  Planck, a satellite studying the entire sky in microwaves, released their early science data.  Lots of cool stuff there.  Fermi, a gamma-ray satellite, also talked about some amazing discoveries, including anti-matter made in thunderstorms on Earth.  The Herschel Space Observatory, which looks at the sky in long-wavelength infrared ("heat" from very cold objects) released lots of science results, including this picture of the Andromeda Galaxy, a nearby sibling of the Milky Way.
  • Lots of talks on planets around other stars. That's great, because there is a ton of great data streaming in from numerous missions and planets.  I did think there were too many plenary talks (talks designed for everyone to attend) about planets.  There are other topics in astronomy, too.
  • Anyone who still holds the stereotype of the astronomer as an old male hermit should have been at this meeting.  There are a lot of young, motivated researchers, socially well-adjusted, and of all genders and ethnicities.  This is not to say that astronomy does not still have issues with genders and minorities -- it does!  But the science results are not dominated by an old man's club anymore.
All in all, I had a great time and have some inspiration for more research work.  But for now, it's time to go home and prepare to teach the spring semester.

Monday, January 10, 2011

American Astronomical Society, Day 1

This week I am at the 217th meeting of the American Astronomical Society in Seattle, Washington.  There are nearly 3000 astronomers registered for the meeting and swarming all over downtown Seattle.  There should be lots of exciting astronomy news coming out of this conference; keep an eye on your newspaper or sites like Universe Today for the full complement of news; I only get to see a small portion of all the excitement!

Today's news included a Kepler discovery of a planet only a little larger than the Earth and a cool Hubble picture of Hanny's Voorwerp, a cloud of ghostly, greenish glowing gas discovered by a Dutch school teacher.  The planet is about 40% larger in diameter than the Earth and has a mass about 4 or 5 times that of the Earth, which means it almost certainly has a core of iron and nickel surrounded by some rock.  It would not be a great place to live -- it circles its parent star every 20 hours and likely has a surface temperature of 2500 degrees Celsius.  As one astronomer said about another, even hotter Jupiter-sized planet, "It's not very hospitable."

Over lunch, I went to a town hall meeting led by the National Science Foundation (NSF).  The NSF is trying to balance an ambitious plan for astronomy research in the new decade with extreme pessimism regarding future budgets.   Even with optimistic budgets, the NSF and the astronomy community would have to make some tough choices regarding priorities, but it is the uncertainty about the budget that seems most concerning.   Many of the planned projects may not need money until 2017 or 2020, but require concrete investments today.  Given that we don't yet have a federal budget for the fiscal year that started last fall, plans for a 2020 budget are just pipe dreams.  At least we are far better off than our British colleagues (for now).

The quote of the day came during the National Science Foundation town hall meeting during an answer to a question about Advanced Technology Solar Telescope (ATST, a new, advanced telescope to study at the sun): "We have an extragalactic astronomer [an astronomer who studies distant galaxies] in charge of ATST because there's nobody in astronomy who knows anything about the Sun."

Thursday, January 06, 2011

Happy 100th birthday to the AAVSO!

Welcome back to a new year (and technically a new decade, though I celebrated that a year early)!  All of us on this celestial ball have just started a new revolution about the Sun (technically the center of mass of the Solar System, which is close to the Sun, but that's not important for most people), so we tend to look forward to a new year full of possibilities and discoveries yet unwritten (or half-written, in my case, but that's another column).

I've blogged many times about the important contributions that non-career astronomers have made and continue to make to the science of astronomy.  Just earlier this week a 10-year old Canadian student, Kathryn Gray, became the youngest known person to help discover a supernova (exploding star). 

One of the largest organizations of citizen astronomers is the American Association of Variable Star Observers, or AAVSO.  The AAVSO was organized in 1911, which makes this year their (let's see, subtract 1911 from 2011, borrow 1 from the thousands column....) centennial!  100 years!  That's no small accomplishment, and the organization is only continuing to grow in membership and impact.

Members of the AAVSO participate in science by monitoring the brightnesses of stars.  Many stars change their brightness, hence the term "variable".  The reasons for these variations are many.  Some stars are really close pairs of stars that periodically eclipse each other.  Some stars grow and shrink in radius due to an unstable structure.  Some stars are pulling material off their companions.  And some stars have planets that occasionally block a tiny amount of light of their parent star. 

The most important tool needed to study variable stars is time.  While many variable stars change their brightnesses in predictable fashion, many others are unpredictable.  And professional telescopes have too many varied research projects to sit and stare at a star that may do nothing for months, years, or even decades before it does something interesting.  The total membership of the AAVSO does have the time and telescope power to watch these stars and notify the big telescopes when something unexpected happens.

But the AAVSO does much, much more than simply act as night watchmen for professional astronomers.  Their measurements of star brightness are often just as accurate, and in some cases better, than those obtained by professional astronomers.  AAVSO members and their data regularly appear in scientific papers.  They are discovering hitherto unknown planets around other stars.  They are discovering changes in variable stars that professionals would never have noticed.  This is all cutting edge science.

You do not need to have a degree in astrophysics to participate in the AAVSO.  You don't even need to have thousands of dollars worth of equipment.  You just need an interest in astronomy, a willingness to learn how to make astronomical measurements, and dedication to looking up at the sky.  Why not stop by the AAVSO website, read about their centennial celebration and their history, and see if any of their ongoing projects tickles your fancy.  There's no reason you can't discover a supernova or a planet yourself!