Illuminating Reality

Have you heard that the Universe is expanding? Edwin Hubble changed astronomy in the 1920s by discovering this, but did you also know that the expansion of the Universe is actually accelerating?  This was one of the biggest surprises in Cosmology back in 1998, leading to the discovery of the mysterious Dark Energy that makes up the vast majority of the energy density of the Universe.  Now to measure the expansion of the Universe, astronomers needed a way to accurately determine extreme distances.

One of the most effective ways to do this is to look at the apparent brightness of lights of a known magnitude.  Because light energy fades in a very predictable way (inverse square falloff), you can determine the distance accurately as long as you know the absolute brightness.  So try this thought experiment: if you went out on a deserted road at night and placed 100 watt light bulbs along the road every hundred meters, the closest lights would be the brightest and the farthest would be the dimmest - yet in reality they are all of the same absolute brightness.  If you stand next to each of them, they put out 100 watts of energy, but the light traveling from the farther ones loses energy, so it appears dimmer.  So by measuring the brightness of each light you could determine the distance because you know how bright it actually is and how bright it appears; essentially just by measuring the loss of energy over distance.

So how do we do this to measure the distance to stars?  As you can see in the image to the right, stars come in a wide variety of sizes and brightness (click to enlarge).  From the relatively cool, tiny Red Dwarf to the hottest, most massive blue Hypergiants, the brightness of stars varies considerably even amongst the same type.  With so much variation, it would be impossible to accurately use brightness to measure distance.  If only there was a class of bright object scattered throughout the Universe that always had the same brightness?  It turns out there is!

Read more…

What the hell is that?  It looks like a comet, doesn’t it?  But it’s not.  Spectral analysis of the tail shows that it’s not gas and orbital analysis says it’s connected to the Flora family of near Earth asteroids.  What you’re looking at here is most likely a very recent asteroid impact with the debris trailing off, driven by the solar wind.  Initially the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey discovered the unusual site and then Hubble was pointed at it to reveal the detail you see above.

This is pretty amazing and the very first time we have witnessed an asteroid collision!

Read more at the Hubble website…

Did you know that gravity is a bit of a mystery to scientists?  Given that we have space probes orbiting Saturn and Mars right now, you’d think it would be well understood, but the reality is it’s the most mysterious of the Four Fundamental Forces of Nature.   Mathematically it’s well understood and can be calculated with great precision, yet it’s so weak compared to the other forces, all of which are roughly comparable to each other.  How weak? Try – 10⁴⁰ weaker than the electromagnetic force, in other words:

0.00000000000000000000000000000000000000001 times as strong

Don’t believe me? Ever notice that you can pick up a paper clip with a refrigerator magnet, which is pretty weak, with relative ease?  The gravity from the entire mass of the Earth is being defeated by that little magnet, which seems so unintuitive and bizarre, doesn’t it?

The Four Fundamental Forces of Nature, according to the Standard Model, are Electromagnetism,  Strong Nuclear Force, Weak Nuclear Force and Gravity.  This isn’t speculation either – the Standard Model is one of the greatest achievements in Science, forming the backbone of modern physics and it works exceptionally well.

These forces interact with matter via carrier particles (aka bosons) and have a finite range to their interaction – except gravity.  To this day there is no known force carrier particle for gravity (they’ve been theoretically dubbed “gravitons”); it can’t be absorbed or shielded like the other forces; it has an unlimited range and it’s behavior is always attractive in nature; it’s somehow tied to the mass of objects in that it interacts with every particle that has mass.

Understanding gravity has been a long and storied endeavor, but it was Sir Issac Newton who made the first significant breakthrough when he published his Principa Mathematica in the 17th Century, wherein he described his universal law of gravitation.  His simple equation was highly accurate at calculating the motion of everything from objects falling out of a tree to the orbit of planets.  His work survived for two hundred years as the dominant theory of gravity until Einstein came along in 1905 and fundamentally changed the way we think of gravity.

Part of the problem was that there was no known mechanism for gravity.  It’s effects could be calculated, but it wasn’t clear how, for example, the Sun reach out to the Earth, across 93 million miles of empty space and tugged on it.  Einstein wondered if the Sun disappeared, how would the Earth know?  In other words, how did the force actually work to travel that distance?  Part of the problem it turns out was that we were thinking of Gravity in the same way we thought of the other known force at the time: electromagnetism.  Einstein radically overturned Newton by defining gravity not as a typical force but as curvature of space itself.  When Einstein published his Theory of Relativity ushered in a new age of physics, solving many of the outstanding problems of Newton’s theory – mainly that because gravity distorts space, the Sun reaches out to the Earth through that distortion to pull the Earth inward.

Einstein’s theory was confirmed  in many areas such as resolving the long standing anomaly with Mercury’s orbit that Newton’s theory couldn’t account for as well as the observed phenomenon of light being refracted by the mass of the Sun during a total eclipse.  Like any good theory, Einstein’s work makes lots of testable predictions that have been observed over the years, but around the same time he was getting lots of attention in the world, the world of atoms was slowly being revealed and it required a new kind of physics to describe.

Quantum Mechanics is to sub-atomic particles what General Relativity is to the orbit of planets.  It’s the physics that accurately models the way atoms and sub-atomic particles interact and has been tested to a high degree of accuracy as well.  There is a really big problem though: Quantum Mechanics does not jibe well with General Relativity.  Physicists tried using Einstein’s equations to model the interactions of molecules and atoms to find that as you get down to those very small scales, everything starts to fall apart and you get gravitational values of infinity (psst, that’s a sign there’s a problem with your theory).

So General Relativity is shown repeatedly to be correct on large scales and Quantum Mechanics is shown to be accurate the same way at the sub-atomic scale – what gives?  Gravity is messing things up in a big way or should I say our incomplete understanding of gravity is messing things up.  Finding an accurate quantum-scale model of gravity has been an elusive quest for physicists.  Some of the ongoing attempts include Loop Quantum Gravity*and String Theory, both of which are so theoretical that they currently can’t be tested in the first place.

This is why the Large Hadron Collider (LHC)  is particularly exciting to physicists.  It’s hoped that when it’s operating at full power, the LHC will be able to expose the innards of the sub-atomic world at an energy scale never before witnessed.  This could be the very device that detects gravitons, the theoretical force carrier for gravity or the Higgs boson which is theorized to give particles mass (remember, gravity is related to mass).  Exciting stuff!

So gravity remains a mystery for now; something we understand well enough to calculate its behavior extremely accurately, but mysterious enough that its mechanism remains elusive.

* Read Lee Smolin’s “Three Roads to Quantum Gravity” for an introduction to the theory…have aspirin handy.

Galaxy Zoo,  just kicked off a new project: mergers!  For those unfamiliar with Galaxy Zoo, it’s a project started a couple years ago that takes data from the robotic Sloan Digital Sky Survey and distributes it online.  Using an applet, users can look at a galaxy and use tools to identify its features and classify it.  For a detailed explanation of Galaxy Zoo, read The Story So Far.

Earlier this year the Galaxy Zoo team attempted to start a new project to identify supernovae, but it had a few hiccups and was put back in development.  However, today they rolled out a new project that allows us to help them identify and classify galactic mergers.  These are some of the most beautiful objects in the Universe, when two or more galaxies are drawn together and fling apart and then together as their constituents are ripped by tidal forces.  It looks violent, but there’s literally so much space between stars in a galaxy that few if any ever actually collide as a result.  What I find really cool about this new project is that the applet identifies a merger, then runs a series of quick 2D simulations of galactic mergers with different parameters.  We look at the results and see if any of these match the look of the actual galaxy.  If a match is found, then it helps explain the initial conditions that lead to the merger.

Neat stuff! Join in and help out!

In the wee hours of Friday morning, NASA’s LCROSS probe will impact the moon.  The impact will occur at 7:31 a.m. EDT/4:31 a.m. PDT for any of you really wanting to wake up and stare at the impact points with your binoculars – you might actually see a flash!  For the rest of us who’ll be catching up on our much earned sleep, we can just see the info online.   While I’m going to assume we’ll able to see images when we log onto news sites or turn on CNN in the morning, NASA’s pulling out all the stops on the LCROSS website, simulcasting the following info leading up to the impact:

The 1.5 hour broadcast includes:

• Live footage from spacecraft camera
• Real-time telemetry based animation
• Views of LCROSS Mission and Science Operations
• Broadcast commentary with expert guests
• Prepared video segments
• Views of the public impact viewing event at NASA Ames
• Possible live footage from the University of Hawaii, 88-inch telescope on Mauna Kea.

The live LCROSS Post-Impact News Conference will be 10 a.m. EDT/7 a.m. PDT on NASA TV and www.nasa.gov/ntv.

Have you ever heard of Apophis? Chances are you haven’t unless you pay attention to astronomy or occasionally watch science shows.  Apophis is the name given to a 250 meter wide asteroid whose orbital path crosses the Earth’s over and over again.  These kinds of asteroids more or less follow us around the Sun and often cross our path, however space is really big  so they don’t hit us very often (in fact, they hit very rarely).

Not too long ago Apophis, before it had a cool name, was calculated to come so close to the Earth in 2029, that it would dip below the orbits of some of our highest flying satellites.  In astronomy, that’s damned close!  Because the mass of the Earth warps the space around it (ie gravity),  such a close fly-by of the asteroid will perturb its orbit a bit and give it the potential of coming back and smacking us pretty hard in 2036.  So astronomers dubbed this potentially deadly asteroid Apophis – after a demon in Egyptian lore.  Sounds cooler than 2004 MN₄, doesn’t it?

We’re talking about a rock the size of a football stadium traveling at +/- 20 miles per second which results in a very scary number when you plug the values into the very simple Force = Mass * Acceleration physics equation.  No, it wouldn’t be an extinction event, but it would definitely challenge our civilization.  Some calculations have it smacking about 500 miles off the coast of southern California if indeed it came around and struck us in 2036.  If that happened you can pretty much write off any civilization in the Pacific Rim – Hawaii and many of the islands in the Pacific like Fiji, Polynesia – gone! Wiped out by a mile-high tsunami.  It would be quite a spectacularly lethal event.

But there’s good news today! New observations show that Apophis may miss us by a larger margin than expected in 2029.  How is that possible when scientists were harping gloom and doom over the last couple years?  Well, not exactly – usually the media is the one to exaggerate such things.  It all stems from the difficulty of determining velocity (speed + direction) from a single snapshot.  Think about every picture you’ve seen in Sports Illustrated of a ball flying through the air.  Can you tell by that one picture how fast it’s moving or in what direction?  Not really, so what astronomers have to do is take lots of snapshots over time to determine the object’s trajectory or path through space.More observations over a longer period of time will refine the data to produce a more accurate representation of the object’s trajectory, almost like connecting the dots.  Today NASA refined the trajectory of Aphophis and “he refined path indicates a significantly reduced likelihood of a hazardous encounter with Earth in 2036.”  It’s going to swing by us a record setting close in 2029, but the chance of it coming around in 2036 and smacking us is now so low there’s no reason to worry.

Party on!

I recently read an Op-Ed in the New York Times by Lawrence Krauss, director of the Origins Initiative at Arizona State University, about how we should start considering the option of sending astronauts to Mars on a one way ticket, without the intent or means to return them to Earth.  This is naturally controversial and goes very much against the spirit of human space exploration.  Who, you might wonder, would be willing to ride a rocket to Mars and know they would not be coming home?  Surprisingly, quite a few if you ask scientists.

The reason Krauss thinks we should consider this option is that the hurdles of sending humans on a return trip are nearly insurmountable at this point and even if we apply concerted effort and resources, it may take twenty to thirty years before it’s a viable option.  However, today we have the means to send astronauts on a one-way trip.  Such a trip would require far fewer resources and very much simplify the mission.  One of the biggest hurdles to getting to Mars is how you bring everything you need to survive on the planet as well as all of the fuel and material to get home.  The most realistic mission plan at this point has astronauts staying on the surface for over a year so that the transits take place when Mars and the Earth are close together in orbit.

It’s a complicated issue, but I happen to agree with Krauss – but that may have something to do with my military “sacrificial lamb” complex.  Humans are drawn to adventure, both as individuals and as a society.  We see this over and over in history, from people in Britain following Burton & Speke through journals as they explored Central Africa in the Victorian era to random people sitting glued to the television as the Pathfinder rover landed on Mars in 1997.  Perhaps a sacrificial effort to jump start exploration and move our species forward will inspire us to collectively do the same and better us as a whole?  At this point planetary exploration is limited to robotic probes and it seems like there’s no momentum to send humans out into the void.  Krauss makes a good point in that explorers of centuries past often set out on their voyages knowing their chances of returning alive were quite slim and even with a return mission in place, the task is so daunting and the risks so great that it still may turn out to be a one-way trip anyway.

For more info, you can listen to Krauss’ interview on KPCC…

If you’ve ever worn glasses, used a camera or burned ants with a magnifying glass – you’ve used a lens.  All a lens really does is refract light, warping its path and focusing it so that we’re able to see things a bit differently.  Telescopes focus light onto receptors that capture photons that have traveled across the Universe while eyeglasses are built specifically to match just the right amount of distortion necessary to give one “correct” vision.

These physical lenses work because they are made with specific materials in mind and shaped in such a way that they focus the light.  But there’s something else that can focus light: gravity.  Einstein showed us this almost a hundred years ago and a prediction of General Relativity is that sufficiently large masses should be able to act as a lens.  These Gravitational Lenses were sought after for decades but not discovered until 1979, yet have become a very important tool for astronomers.

A gravitational lens occurs when so much mass is located between an observer and a distant object, that the light from the object gets distorted and focused along the way to the observer.  This results in all kinds of weird things like repeating patterns such as Einstein’s Cross and warping arcs, but also it tends to allow astronomers to observe objects behind other objects or help to magnify extremely faint objects.

The photons from those distant objects have often traveled for billions of years across the expanding Universe and arrive on Earth in such few numbers, but when they travel through a gravitational lens they become focused and arrive more tightly packed.  And because the physics of gravitational lensing is well understood, astronomers can measure the lensing effect to determine the mass of the cluster bending the light.  This last bit has become very useful in hunting for the elusive “Dark Matter” that appears to make up a much larger quantity of the Universe than normal matter – but that is another story.

image: Robert Gendler 2005 - click to see me HUGE

This is the Andromeda galaxy, our nearest neighbor in the Local Group that our own galaxy inhabits.  There are so many remarkable things to note about Andromeda, such as that it’s on a collision course with the Milky Way, rushing towards us at 300km per second, making it one of the only blue shifted galaxies we see (for a quick refresher on Red/Blue Shift, see the post about searching for planets orbiting other stars).  And because it’s so close, it’s one of the most studied galaxies in the sky.  For this reason it has played an important historical role in Astronomy.

Prior to the 1920s, astronomers didn’t know there were other galaxies and stars beyond the Milky Way, instead just called galaxies such as Andromeda “spiral nebula.”  It wasn’t until Edwin Hubble came around and used observations of Cephid Variable stars in Andromeda to determine that the Universe was MUCH larger than known at the time and that Andromeda was in fact a separate galaxy like our own, out there 2.5 million light years away. This eventually led to Hubble’s monumental discovery that the Universe was expanding.

Something a lot of people don’t realize with Astronomy is that scientists look at the sky in a much wider spectrum than what we can see – not just visible light but everything from microwaves to gamma rays.  By looking at Andromeda with just visible light, bright stars and opaque dust obscures much of the detail, though it may be pretty to our eyes.

By looking at infrared light, Astronomers can “see heat” and therefore pierce through clouds of dust to resolve interior details of the galaxy that weren’t apparent in visible light.  Click the image to see it REALLY BIG!

Today NASA released a new image of Andromeda by the Swift satellite, this time in Ultra Violet.  By studying the galaxy in UV light, astronomers are able to see details in very hot stars, particularly young ones just forming.  Click the image to see it REALLY BIG too.

One last little thing about Andromeda is the super massive black hole at it’s center.  It’s over 140 million solar masses (ie over 140 million times more massive than our own sun) compacted into a relatively small space.  Astronomers have tracked stars orbiting the void at the galactic nuclear at incredible velocities: 2.2 million miles per hour.  Stars in the Milky Way’s galactic nucleus are doing a similar race around a super massive black hole.

Remember when you were a kid and you had a favorite dinosaur or favorite animal?  I had a favorite star: Eta Carinae, that always dazzled me when I saw pictures of it in books.  It’s a HUGE star with roughly 100 times the mass of our sun and it’s not that far away (about 8,000 light years).  What’s amazing about it is that it’s in its final death throes, belching out huge amounts of material full of heavy elements fused in its core.  While it may look like a diseased brain, the star itself is at the center glowing over a million times brighter than our sun.  This sucker is about to go any minute now; well it may have actually died but it’ll take 8,000 years for us to see it; regardless when this star’s fuel runs out, the core will collapse under intense gravity to form a black hole…and here’s the kicker, it may also produce a Gamma Ray burst!  This is a little scary having a GRB so close to Earth because if one of the two insanely intense beams of energy shooting out along the poles were to hit us, Earth and all life dies.  Don’t freak out – see how Eta Car’s orientation is tilted a bit? It ain’t pointing at us.

I bring up Eta Carinae today because Hubble is fully operational again and it snapped a picture of it using it’s advanced Spectrascope, which breaks up the light to reveal elemental compositions, and the results are pretty spectacular…

By analyzing the light with the  Spectrascope, Hubble is showing us all of the heavy elements spewing from the star.  This is important because massive stars heat up and fuse elements to create heavier elements.  We can see from this image that it’s kicking out Helium, Argon, Nitrogen and…Iron!  Iron is really important here because as a star runs out of one fuel it compresses and heats up which often leads to the fusing of heavier elements which releases lots of energy.  But Iron is a problem for massive stars because it takes more energy to fuse Iron than is actually released.  So Eta Carinae is really damned close to hitting the limit and when it does it’s going to go kablammo!

Iron…it’s bad for stars, but good for us.  Yep, the iron in your blood came from a star like Eta Carinae billions of years ago.