Gravitational Wave Astronomy is here!

Summary: For those of you not glued to your computer for the past couple hours, you may have missed the new announcement from the LIGO experiment. They have officially announced the discovery of a second gravitational wave detection. That's right, it is no longer a single event in the dark. We have two confirmed black hole mergers that created gravitational waves and another "trigger" event that may prove to be an additional gravitational wave source after a few more tests are performed. There's only an 85% chance of the signal being astrophysically significant right now and that is not good enough for the team at LIGO.

I for one am ecstatic about this announcement. Not only does it herald in a new field of astronomy, but the presentation of data so far has been very easy to understand. Great graphics and explanations.

To give a brief outline of how they conduct their science, it starts with an interferometer. Light travels down two paths of equal length before recombining at a photodetector that measures how much light is hitting the sensor. If the paths are truly equal in length, the light from the different paths will cancel each other out and it will be dark. Any little alteration in the length will cause light to be detected. The gravitational waves actually move space itself like a ripple in a still pond so as the wave flies through Earth, the different paths the light travels at will briefly be different.

The first signal in September was unexpectedly loud so it was able to be seen with human eyes, but this new one from December (Christmas in the US!) was harder to spot. They needed the computer to match the signal to a template in order to see it. It works like a child taking a circular puzzle piece and trying all of the different shaped slots until they finally are able to fit it into the corresponding circular depression on the board.

We can only imagine how much great work will still be coming out of this observatory in the future. This is not yet running at full potential and when the second run starts this autumn it will be more sensitive still. I'll be sure to keep you updated.

LIGO
Video of event

Also, if you are interested in helping LIGO look for more gravitational waves, check out GravitySpy.org

Expanding Expansion

Summary: Based on new data from the Hubble Space Telescope, the universe might actually be expanding faster than previously thought. This new data comes from an updated study of the velocities of Cepheid Variable Stars and Type Ia Supernovae to determine a value for the Hubble constant. The new data points to a slightly higher value of 73.24 km/sec/Mpc. This is only slightly higher than the value of 70 used in many textbooks.

However, this only increases the gap between the value gained from this method and the value gained from the Planck telescope. Those experiments lead to a Hubble value of 66.53 km/sec/Mpc. This means the difference of a few hundred million years when calculating the age of the universe.

At this point, astronomers can only guess at the cause of the discrepancy. Many point fingers at Dark Energy or a fourth flavor of Neutrino, but ultimately we hope that the next generation of telescopes can show us the answers.

Source:
BBC News
arXiv