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February 5, 2011 by Istvan

I’ve seen a good bit of traffic lately in the media and in blogs regarding the recent data from the Kepler mission.  My general reaction to Kepler previously has been rather ho-hum.  I mean, getting more exoplanet data is good, but Kepler hasn’t excited me much until now, because the starfield it’s examining is entirely made up of quite distant targets, hundreds of light-years away or more.

I’m interested in seeing humanity locate some exoplanets rather closer than hundreds or thousands of light-years away.  We humans are short-sighted as a rule. Nearby stars with planets that we might reach with near-current technologies, in the time of our grandchildren, could inspire many more people than just scientists.  Kepler isn’t finding those targets, so we must continue to await results from other research groups, such as the two at least continuing to study the Alpha Centauri system.

However, the latest Kepler results are stunning.  I’m still not excited about the six planetary detections around a single star (Kepler-11) that have been so much in the news.  Those are all small baked worlds closer to their sun than Mercury is to ours.  What is impressive to me is the sheer number of detections in the broad target starfield.

Keep in mind Kepler isn’t finding everything.  Kepler can only spot transiting planets, planets which happen to cross in front of the disc of their star as seen from the angle from which we’re viewing it.  Kepler also hasn’t been looking all that long, so it can only spot the planets that have transited at least several times, while it has been watching.  This means it’s only detecting, for now, some of the hot worlds closely hugging their parent stars, such as those six baked balls around target Kepler-11.

So what?

“What” is that Kepler has already found easily more than a thousand planet candidates.  This is with what one might call “a good first try”.

We’ve only started finding exoplanets in the last decade or so.  Our efforts thus far have been slow and halting, done by choosing specific targets and examining them closely. What we’re able to spot is still subject largely to chance and circumstance.  Kepler is the first serious effort at getting a proper statistical sample.  Kepler helps us build a real picture of just how many planets are truly out there around other stars.

In the last century, many of us, scientists and laymen alike, have simply assumed, somewhat hopefully, that our solar system is “normal”, that planets are not unusual, that there must be many, many out there.  But we did not know.

The other exoplanet surveys continue to turn up more and more candidates, becoming increasingly convincing to us that indeed there are many planets around other suns.  But perhaps we’ve been accidentally cherry-picking so far, targeting just the right stars.  Kepler’s scattergun approach to surveying a distant starfield tells us unequivocally:  planets are literally common as dirt.

If we want to find some interesting ones, perhaps some habitable ones, perhaps some already with life, perhaps some near enough that our grandkids could send a robot there, well then, knowing for sure that an awful lot of planets really are out there seems like a pretty awesome thing, in all senses of the word.

January 16, 2011 by Conway

I just read a fascinating article, http://www.nasa.gov/mission_pages/spitzer/news/spitzercepheids20110112.html.  It indicates that Cepheid Stars may be losing mass.  And this is a problem, because Cepheid Stars help us measure astronomical distances.  If these variable stars are becoming less massive, then we may need to revisit several important questions.  How large is the observable universe?  How far away are the nearest galaxies?  Do we live in an open, closed, or flat universe?  To what degree can we trust our understanding of our place in the universe?

I looked up the abstract to determine how much mass the star Delta Cephei seems to be losing:  5 × 10^–9 to 6 × 10^–8 M  yr^–1, which could be as large as two percent of the mass of Earth each year.

Let’s put this in perspective.  In 50 years, the star could lose a mass equivalent to the mass of Earth.  That’s not so bad.  Is it?  After all, it takes about 333,000 Earths to reach the mass of the Sun, and Delta Cephei is more massive than the Sun.  Who cares if the star loses up to an Earth-mass every 50 years?

The reason astronomers care is because almost all astronomical distance measurements depend on how accurately we can measure the distance to given Cepheid variable stars.  As we get better at determining the distance to these “standard candles”, we can have more confidence in our estimates of the largest distance scales.

Of course, I still would like to know exactly how big of a deal this is!

January 9, 2011 by Conway

While growing up, I dreamed of the possibility of discovering planets outside our Solar System.  I especially wanted to know if any of these potential planets could be habitable by humans.  We already knew that our Sun was not very unique among stars in our galaxy.  I wondered how unique the planet Earth might be.  I wanted to know if conditions around other stars could allow Earth-like planets to exist.

Now, I want to know more about the planetary systems that we’ve actually found beyond our Solar System.  And I still want to know about the possibility of finding another Earth-like planet.  Here is a quick survey of our progress so far.

http://planetquest.jpl.nasa.gov keeps track of the number of exoplanets that we’ve discovered, currently just over 500, and the number of Earth-like exoplanets that we’ve discovered, currently ZERO.  Most of these discoveries are very recent.

Before 1990, only eight planets were known to exist, given that poor Pluto has been demoted to the status of Dwarf Planet.  In 1992, the first two exoplanets were found.  By 2000, about 50 exoplanets had been discovered.  This number jumped to over 100 in 2003, over 200 in 2006, and over 300 in 2008.

To make these discoveries, we have used a variety of techniques.  Each large, massive planet tugs at the star it orbits.  This causes the star to “wobble” as the planet goes around.  We can measure this motion by observing the Doppler shift seen in the star’s spectrum over time.  As the star approaches us, we see a slight blue-shift, and as the star recedes from us, we see a slight red-shift.  We can also measure a star’s slight displacement directly using interferometry.  Another approach that works for large planets is to observe a dip in the brightness of a star due to a planet blocking some of its light as it gets between the star and us.  We can also notice a change in the apparent position of a star due to gravitational microlensing, when a massive planet literally bends the light from the star it orbits.

The problem with these approaches is that they work best for large planets with a high orbital speed.  If a planet is too small, the signs we look for are too insignificant to detect.  If a planet takes over a hundred years to orbit a star (like Neptune), it’s not easy to notice the slight changes we could detect over time.

Two exciting missions are planned to improve our chances of detecting Earth-like exoplanets.  Gaia, developed by the European Space Agency, is scheduled to launch this year.  The James Webb Space Telescope is scheduled to launch in 2013.  Both have advanced instrumentation that can help us find exoplanets, and both are going to be much farther from Earth than the Hubble.

I look forward to the day when we detect an Earth-like exoplanet!

January 7, 2011 by Conway

According to NASA, the following movies are the most absurd with regard to the validity of the science presented: 2012, The Core, and Armageddon. While I love a good story, I am even more impressed with a good story that also features good science.

I am reminded of the movie 2010. Now that the year 2010 is in the past, we might be tempted to laugh at everything the movie got wrong. We have not sent a manned mission to the Jovian system, and as far as I know, we have not discovered a monolith on our Moon. (Never mind what the next Transformer’s movie suggests we may have found there.) It’s easy to disregard the predictions science fiction makes after the fact.

However, a more useful exercise is to consider what the movie 2010 (for example) got right. Could manned space flight happen in a manner similar to what Arther C. Clarke postulated? What constraints does physics impose? What political and economic forces may shape a different vision of space exploration?

NASA’s list of more plausible science fiction movies includes Gattaca and Contact. While I have enjoyed both, I look forward to seeing even more movies that portray science and space exploration with an awareness of what may be possible.

Deceber 21, 2010 by Istvan

I admit it. From time to time I lose track of robotic missions. Especially to the outer system, they take long enough to get places that after I watch their launches with excitement and anticipation, I let them drop off my radar for years at a time, only checking now and then to see how much longer we have before an encounter.

Thus it was with some excitement I realized yesterday that Dawn reaches Vesta in 2011. And of course, it’s New Year’s, so 2011 isn’t far-off anymore: it’s now.

Dawn is exciting for three reasons. Number one, it’s yet another ion-drive propulsion mission. That’s awesome because chemical rockets are fine for getting to LEO, but beyond that, well, we need better.  Lots better.  I grew up reading stories about “space rangers” with “ion ultradrive” on their cruisers. So with every robotic mission that uses ion propulsion, we practice, refine, and improve that technology for future missions, making them faster and more reliable.

Number two, Dawn is going to Ceres and Vesta. We’ve had a few asteroid flyby missions in the past decades, and a few rendezvous missions, such as NEAR Shoemaker and Hayabusa, which were great successes. Dawn isn’t a flyby – it will visit both rocks for extended periods (hurray for that ion engine again, for making this possible), with cutting-edge instruments. The targets are interesting. Ceres is a dwarf planet – something we’ve never visited before. Planetary scientists should be on the edges of their seats, because surprises are guaranteed. Vesta, on the other hand, is also one of the largest asteroids, but it is expected to have an unusual composition. It is understood to have melted entirely in the distant past, and also been subject to a serious impact much more recently. That recent impact is how we know about the melting – pieces have reached Earth as meteorites, and spectroscopic comparisons with observations of the asteroids have matched that rubble to Vesta! Vesta’s the brightest asteroid, meaning high surface albedo. Should we hope for some water ice, which is a high-albedo material, or something more interesting? Water ice itself would be pretty interesting! So the data from these rocks will increase our knowledge of asteroid formation and evolution, and teach us about a class of objects we’ve never really scrutinized before.

This is great stuff, so what’s reason number three to care about Dawn? I’ll rant about this over and over: Ceres and Vesta aside, asteroids are possibly the Most Important target for any of our space programs, unmanned, manned, whatever. Even more so than Mars (barely). Why?

Even perfect planets like our own are hard to work with. It takes serious energy to move anything to space from the surface, and it takes some care to get anything safely down. Landing something on another planet like Mars incurs these costs and risks twice. The biggest handicap to all our space efforts is launch energy, represented by the launch cost per kilogram. The biggest risk to our probes, after launching them, is landing them somewhere else. With debris like asteroids and comets, this energy cost is hardly an issue, because of their tiny gravity. Just getting our equipment there is the real challenge for us today.

Getting to asteroids and comets is worthwhile, because our direct mineral studies of meteorites (and our spectroscopic examinations of comets) indicate these objects have materials we’re going to want, now and in the future. The abundance of platinum group metals and rare earth elements in asteroids (as compared with Earth’s crust) makes them potentially quite valuable, if we could just move the ores back here (or refine them in situ and then move the results here). We expect these ores would be even easier to get to on an asteroid a few hundred meters across, as opposed to digging through a similar distance (or more) of Earth’s crust (which is also likely denser). Furthermore, one of our best means of beating that launch cost problem I mentioned is to avoid sending all the fuel our equipment needs along with it. If a mission is manned, air and water are requirements too, which is even more mass you have to send along. If we get these things from a comet or asteroid, especially an asteroid that has other minerals we need…suddenly we’re talking about a cheaper, more sustainable space program that can actually return value to Earth industries. Therefore, we really need to know about asteroids, to learn whether these ideas are pie-in-the-sky, or whether there really is pie waiting for us, in the sky.

But the real deal on asteroids is this: we have no reason to believe habitable worlds are common around other stars. Earth is still likely to be a rare gem. Even near-habitable worlds like Mars, where landing and living there takes serious effort, are not yet known to be commonplace either. Asteroids and comets, however, are expected to be practically everywhere, in any planetary system around any star and even around stars that lack real planets. If we can learn to live off asteroids and comets, getting the materials and metals we need for shelter and industry, getting the volatiles like air and water we need to live and travel, then our species can go anywhere, live anywhere, around any star, no matter what else we find there.  Forever.

Habitable worlds we may yet find, and that will be all to the good. Other life we may find, and that will teach us something also. But asteroids are the real diamonds. Asteroids are the Future.

December 25, 2010 by Istvan

I’ve seen lunar eclipses before.  They’re much more common, safer to view, and longer-lasting than solar eclipses.  This week’s was particularly special to me, though.

First of all, despite light cloud cover as it began, my customary meteorological ill-fortune didn’t materialize and the event was easily viewable from my back porch. Second of all, the weather that evening was unseasonably warm, so stepping out to observe wasn’t unpleasant, even without a coat.  Third of all, the eclipse was just north of the middle of the Great Hexagon – making the view utterly spectacular.

The Great Hexagon is an asterism – not a constellation – made up of some of the brightest stars in the sky.  It’s centered on Betelgeuse, meaning Orion (well-known as one of the brightest and most recognizable constellations) stands surrounded by the Hexagon.  The six vertex stars of the Hexagon are Aldebaran, Rigel, Sirius, Procyon, Pollux, and Capella.  Ordinarily an awesome winter spectacle at any time, but particularly awe-inspiring with the dim reddish eclipsed Moon just a degree or so above Betelgeuse!

Another element making the evening special was noticing various neighbors, whom I had no reason to suspect of having any interest in astronomy or space, quietly stepping out of doors to also partake of the view at various moments as the eclipse progressed. Eclipses allow the excitement of the celestial to reach many, without teachers or instruments, who ordinarily don’t give the sky much daily thought, beyond the possibility of rain.

For those of us who love space, though, even without an eclipse, just gazing at the familiar moon is enough to set our hearts beating faster.  We look at the moon as familiar, but not familiar enough.  Even with the shadow of Earth sliding across it, we cannot help but ask, “What’s the view like – from there?”  How soon will our children stand there in pressure suits, and watch from outside a quonset hut buried in regolith, as our Earth transits across the Sun?  For us, not soon enough.

January 5, 2011 by Conway

What an exciting time for Kathryn Aurora Gray, a ten-year-old Canadian girl!  On January 2, 2011, she noticed a bright spot on an image containing the galaxy UGC 3378 … a bright spot that was not there previously.  It turns out that she is now the youngest amateur astronomer to have discovered a supernova!

I am thrilled that amateur astronomers can make such significant discoveries.  Anyone with a decent telescope can look up at the night sky to view interesting phenomena.  Almost anyone can join in the cosmic treasure hunt.  And every so often, with a little discipline and more than a little luck, one of the participants may be rewarded by noticing something that no one else has seen yet.

If you don’t have a telescope and would like to participate in real astronomical research, check out www.galaxyzoo.org, an interactive project to classify millions of galaxies.

December 22, 2010 by Conway

Last night, we gazed up at the sky to watch as the full Moon wandered into Earth’s shadow.  Our excitement surged as darkness crept across the surface of the Moon.  As my eyes adjusted, I noticed the ruddy color that had been predicted.

Astronomical events bring great questions to mind.  Why is this particular time so special?  How often does a Lunar Eclipse occur on the date of the northern winter solstice?  How many people have looked up at the sky during a Lunar Eclipse without the benefit of knowing what to expect?  Why do words and photographs fail to convey the depth of what it means to experience such events in person?  When will be the next time that I look up at the sky with great expectations?

December 15, 2010 by Conway

When I was young, I read an essay by Isaac Asimov that still remains fascinating to me.  He told the story of a mathematician who predicted the perihelion precession of the planet Mercury in the 1800′s.  When observations were made, the prediction was off by a small amount.  The mathematician figured that a small planet closer to the Sun than Mercury might be causing the difference.  Vulcan is the name he gave to this proposed planet.

The search was on, but the planet was never found.  Instead, Newton’s theory of gravitation was found to be lacking.  Einstein’s general theory of relativity predicted a value for Mercury’s perihelion precession that was very close to the actual measurements.  So, the planet Vulcan was no longer needed.

This is the heart of scientific progress.  When theories make predictions that can be tested through experimentation, and when odd experimental results propel new theories forward, we gain a deeper appreciation of the mysteries that surround us.

For more information, you can look up Vulcan (hypothetical planet) on Wikipedia.