Transit of Venus

Don’t forget to watch the transit of Venus today, when Venus will pass in front of the sun. It will be visible around sunset here in the US.

Don’t forget to use proper safety precautions. Sunglasses are not enough. If you have welding glasses, those work great. If you don’t have welding glasses or special eclipse viewing glasses, you can use a pinhole projection, but it will need to be magnified to see anything. You can use a telescope to project an image onto a piece of paper (big end towards the sun), and view it that way.

Earth-like planet a result of a gas giant getting swallowed?

Some interesting questions have been brought up by these recent Kepler discoveries. Stars like our sun usually expand to become red giants and then become compact again as helium fusion begins in their cores. Sometimes, the hydrogen is stripped off of the star (by another star for example), leaving just the helium-fusing core behind, compact and very hot. A star in this state has been observed (a hot B subdwarf), where the hydrogen was stripped off, except there is no companion star to have taken the hydrogen away. It’s a cosmic mystery: What happened to the hydrogen?

This star system has several recently-discovered small, (presumed) rocky planets orbiting it. The emerging theory is that when the star expanded to become a red giant, it consumed several gas giants with orbits close enough to be swallowed. When the star contracted again to enter the helium fusion phase, the planets reemerged as small, rocky planets, stripped of their gaseous exteriors. The disruption resulting from the planetary collisions with the star could have stripped the star of some of its hydrogen, causing it to be in the state we now find it: very hot, with several small, rocky planets locked in a tight orbit. Time will tell if this theory is correct. There is so much we don’t understand about the birth and evolution of stars and planets.

Article here.

More earth-sized planets discovered

Scientists have spotted 2 earth-sized planets in an extremely tight orbit around a star very like our own sun.

Article here.

First habitable-zone planet discovered

Observing planets outside our solar system has always been a challenge. The only way to spot one is when a planet crosses in front of its star and causes a fluctuation in the light emitted from that star. Such small fluctuations are difficult to observe from earth, where conditions have to be just right and atmospheric effects accounted for. In the past, we have been able to spot mostly large, Jupiter-sized planets. So, in 2009, NASA launched the Kepler spacecraft, whose only purpose is to observe planets outside our solar system from space, free from atmospheric troubles.

The data are flowing back fast. In fact there have been over 200 earth-sized planets spotted that are waiting to be confirmed by earth-based telescopes before announced. Forty-eight of the planetary candidates lie in the “habitable zone” of their solar systems, which means that the temperatures are right for liquid water to be sustained on the surface. That doesn’t mean they do have liquid water; it just means that it is a possibility. We are waiting on the ground telescopes to confirm these planetary candidates. And then we can get to work on determining their densities, and therefore what they’re made of.

Kepler 22-B is the first confirmed habitable-zone planet discovered outside our solar system. It is on the inside of the habitable zone. Were it in our solar system, it would be somewhere between Earth and Venus.

You may remember the discovery of a planet closely orbiting a double-sun (Kepler 16-B), confirmed by ground telescopes in Septemberish of 2011. Stay tuned for more exciting planetary discoveries from Kepler (there were several exciting ones over Christmas break).

Lunar eclipse

Don’t miss the total lunar eclipse tomorrow. The earth will pass between the sun and the moon, covering the moon with earth’s shadow and making the moon appear red. The moon normally appears white or grey in color because it reflects the light from the sun directly and encompasses the entire visible spectrum. During an eclipse, the direct sunlight will be blocked by the earth. The only light that will reach the moon will be the light redirected by the earth’s atmosphere, which will cause the moon to be sunset red in color.

This will be the last total lunar eclipse visible from North America until 2014. The eclipse will begin at about 4:45am, and be full from 6am to 7am tomorrow morning, Pacific time. Set your alarms and get up a little early. It will be worth it!

Black holes: Friend or Foe?

Too often, black holes are depicted as prowling, hungry, colossal beings that swallow everything in their path and wreak havoc on the Universe. Although that makes for good science fiction, it is pretty far from the truth. Here’s what’s up with black holes:

How they’re born:

Black holes are born when massive stars die, meaning they explode and collapse inward on themselves. Smaller stars that die turn into white dwarfs. More massive stars that collapse turn into neutron stars. Stars bigger than about three solar masses, however, are too massive to support any structure, even one as dense as a neutron star. These super massive stars turn into black holes when they die.

What they are:

A black hole is a region of space where the gravitational force is so large that the escape velocity is greater than the speed of light, meaning that even light cannot escape the region. It contains a singularity inside that region of space, or a point of infinite density. The matter from the core of the star collapses so far that there is no longer any force to stop it from collapsing and it collapses to a point of zero radius and infinite density, meaning that the surface gravity is infinite at that point as well. There is some debate as to whether the point at the center of a black hole is actually a singularity of zero radius. Some say that there cannot be singularities in nature and that the collapse must halt at some extremely small radius (like way, way smaller than a proton). But in practice, it doesn’t really matter either way. You still have your crazy-dense point surrounded by a region that light cannot escape from.

To understand black holes a little better, let’s step back for a minute and talk space-time. Einstein is the one that discovered the link between space and time. Space and time are cut from the same cloth: the fabric of the Universe, a material that we now call space-time. Gravity exists because objects with mass warp space-time, and cause other objects with mass to fall towards them because of that warping. It would be as if you had a sheet pulled tight at all edges and put two heavy balls near each other on the sheet. The balls would roll towards one another because of the dents they put in the sheet. This is the same phenomenon that causes gravity, except in two dimensions. Black hole singularities warp space-time so much that it wraps around upon itself again, and nothing can escape this region of super-warped space-time. This is known as the event horizon.

How they live:

There are many different kinds of black holes, mainly the differences are size (which is proportional to how much matter the black hole has consumed), rotation, and electrical charge. Black holes with rotation and charge have very large, complex magnetic fields surrounding them that actually spew out a stream of matter along the magnetic poles (not matter from inside the black hole, just some of the stuff that approached it). The stuff being spewed out of the black holes are called jets. See photo above. There is a visible accretion disk of matter surrounding the black hole, and long jet streams coming out of the magnetic poles.

Why you don’t have to lock your doors at night because of them:

So far, so good. It is true that nothing can escape from inside a black hole and that as far as we know, they can continue swallowing matter indefinitely. The misconceptions begin when people start talking about black holes like we are in danger of being swallowed by a black hole at any second. The truth is that the force you feel from a black hole is the same as the force you’d feel from any form of matter with an equivalent mass, unless you get up really close. In fact, if you were to replace our sun with a black hole of equivalent mass, we would not feel the difference gravitationally. The earth would continue to orbit around the black hole the same way that we do now around our sun. Of course the lack of light would be a bit noticeable after a couple of minutes, but you get the idea. It is true that our galaxy might collide with another galaxy someday, and there’s a chance that we’d end up at the center of that galaxy’s black hole in the process, but it is extremely unlikely, and it’d be so far into the future that odds are none of us’d be around to witness it anyways.

Semi-recent discoveries have indicated that there are black holes at the center of every galaxy,  including our own Milky Way Galaxy. The truth is that black holes are really a natural, benign part of our Universe, holding galaxies together and intriguing scientists on this insignificant little planet called earth. So where’s the love?

Here’s a shoutout to the reader that asked an awesome question about black holes and inspired this post. There’s some good black hole reading here if you’re interested in learning more.

Oldest recorded supernova

This picture was recently released by NASA. It was made by combining data from 4 different space telescopes at different wavelengths. RCW 86 is the oldest documented example of a supernova, and was observed by the Chinese in 185 A.D. They called it a “guest star” and documented that it stayed in the sky for 8 months.

Data from the X-ray spectra (shown in blue and green) show that the interstellar gas has been heated to millions of degrees by the passing shock wave caused by the supernova. The infrared data (in yellow and red) show dust that is radiating at several hundred degrees below zero, which is warm compared to our galaxy’s dust. This thing was a class 1A supernova that was caused when a dead star (a white dwarf) sucked a bunch of material off of a companion star. RCW 86 has gotten large quicker than it should have. It is postulated that the star released gasses and blew out a region of low-density prior to going supernova, allowing the explosion to reach a large area very quickly. It is pretty neat that we know all of this partly thanks to the work of scientists 2000 years ago. Imagine what we will know about the universe a couple thousand years from now.

Nobel prize in physics

Dark matter is something we need to get our models of the universe to work (this is something we should talk about some other time), but it is well supported with physical evidence and we have a fairly good guess as to what it is made of. Dark energy, however, is more of an unknown. We’re pretty sure it exists in large quantities (over 70% of the universe), but that comes from only one type of observation. We have no other data. We have no idea what it is… and that makes it pretty tough to make testable predictions about it. Nevertheless, it has changed the way we think about the universe, and the Nobel prize in physics has gone to the cosmologists that first made a case for dark energy.

When Einstein developed the theory of relativity, the universe was thought to be constant, neither expanding nor contracting. The math came out that it would be possible for the universe to expand or contract, so Einstein put a cosmological constant in, representing the energy of free space, and set the value so that the universe remains constant. A few years later, astronomers (with the help of Hubble) discovered that distant objects were moving away from us faster than closer ones (as measured by the redshift of the light of those objects), indicating that the universe is expanding. Einstein removed his constant, saying that it was a mistake. The Big Bang model of the universe was eventually developed, and it explained the expanding of the universe, but predicted that it would be expanding and a slightly decreasing rate due to gravitational forces. When scientists (the folks that received the Nobel prize this year) went to look for this phenomenon by looking at the red shift of class 1A supernovae, they discovered that the opposite is happening: the universe is expanding at an increasing rate. The explanation for this became dark matter: a mysterious energy that is causing our universe to expand. There are many theories as to what it could be (such as vacuum fluctuation energy), but nothing seems to get anywhere close to the numbers. And until we have more data and more of an idea of what to look for, it will remain a mystery. But scientists are hopeful, and I’m sure that whoever makes the next dark energy discovery will receive a Nobel prize as well.

Read more or check out a cool representation of the universe’s expansion here.

Where do the elements come from?

We are all made up of dust. Atoms in bound states create molecules. The right molecules in bound states creates proteins and amino acids. Keep binding and combining and you eventually make your way up to cells, organs, people. Every miraculous bit of us is formed from atoms. But even those atoms are formed from smaller stuff. Atoms are made up of electrons, protons and neutrons. Electrons, protons, and neutrons are made up of quarks. We think quarks might be made up of strings.

Have you ever wondered how all the elements got put together? Well, I won’t tell the whole story (mostly because we don’t know it), but part of the answer is in the stars. Hydrogen (H) and helium (He) are the only two elements that are just floating around the universe on their own. Hydrogen: a proton and an electron (usually). Helium: 2 protons, 2 neutrons and 2 electrons (usually). All the other elements had to be made from these. The elements heavier than helium, up through iron (Li to Fe) were created in the fusion that occurs inside stars. The intense heat and pressure inside a star causes the atoms to bang into one another and fuse into heavier elements. All the elements heavier than iron need even more heat and pressure than the star can provide to form, and all of these elements were created inside supernovae, the explosive death of large stars.

All the elements heavier than H and He were created inside either the life or the death of a star, meaning that you and I are literally made of stardust. There’s some perspective for you.

Diamond the size of Jupiter

Now that we’ve established how awesome neutron stars are, I’m going to tell you about another crazy happening of the neutron star world. Once the neutron star is formed from the remnants of the supernova, it will generally cool and its spin will slow. Often, however, there is something else nearby that will get sucked in by the neutron star’s strong gravitational pull, causing the neutron star to speed up and heat up again. A rotating, highly magnetized neutron star is called a pulsar. The pulsing is caused by flashes of electromagnetic radiation emitted from the magnetic poles as the neutron star rapidly rotates.

Our astronomer friends in Australia have discovered one of these systems, a millisecond pulsar binary. The binary bit tells us that the pulsar is rotating around another body, and the millisecond bit tells us that the neutron star is rotating very fast due to having been fed by its binary companion. In this case, the companion was a carbon-rich white dwarf, a type of star. But a large part of the star has been sucked off by the neutron star’s strong gravitational force. And, deprived of its mass, the star became a planet. Here’s the kicker. What was left of the companion mass was mostly carbon, which then crystallized under the intense heat and pressure to form a diamond the size of Jupiter.

This discovery was debuted in a paper that was published in Science online in August, and I have to say it really makes me laugh. The diamond part isn’t even mentioned in the abstract, and doesn’t show up until almost the end of the paper, where it says, “The chemical composition, pressure and dimensions of the companion make it certain to be crystallized (i.e., diamond).” Were I to discover a diamond the size of Jupiter, I think I would put that in the title of the paper!