Saturday, September 24, 2016

Gaia and a new Age of Universe

Summary: The study of astronomy is an old one, but as headlines show, it is a constantly changing field. As our instruments change, we discover that the numbers we thought we knew need some readjustment. In this case, the Gaia space craft from the esa is forcing astronomers to look about the expansion rate of the universe. Again.

This is not the first time there have been some discrepancies in the estimate for the age of the universe. But Gaia is one of the most precise telescopes we have at the moment. Just recently it published precise coordinated for one billion stars. This is leaps ahead of the last survey of this type.

Gaia's estimate of the age of the universe is based upon Cepheid variable stars. These stars pulse with a very specific brightness and rate of pulsation. This makes it easier to tell how far away they are from us and to determine the age of the stars nearby. Gaia has precisely found 212 of these Cepheid stars and with these data, Professor Reiss's team calculates a Hubble constant of 73km/Mpc. This is about the same as they calculated with Hubble data. But it is not the same number found in most textbooks as the accepted value. And it is not due to outdated textbooks. It is because of the methods used to solve for the Hubble constant. The Planck mission gives a much lower value of 66.9km/Mpc.

Why is there such a discrepancy? We aren't entirely sure, but we can probably place a lot of the blame on dark matter. Hopefully as Gaia continues forward on it's mission, we will be able to narrow down the range of possible Hubble constants, and thus the age of the universe and no longer have a few hundred million year gap. Maybe we will even be able to place stricter bounds on what dark matter actually is and what effect it has on our universe.

Source

Also, the Ig Nobel prizes were awarded this week and they are, as always, amazing.

Thursday, September 8, 2016

Juno update

Summary: After 5 years and 1.8 billion miles, the Juno spacecraft has made its first flyby of Jupiter. At only 2,500 miles above the cloud tops, this is the closest any spacecraft has come to the gas giant of our solar system.

One of the things that makes Juno exciting is the panoramic colour camera which allows for stunning images to be sent back in addition to data from its other instruments. 

Juno will make 35 further flybys in order to measure Jupiter's water content, magnetic fields, and to look for the possibility of a solid core. Will all of this new data, it is hoped that scientists will have a better idea of how the planets formed in the early solar system.

BBC News

Wednesday, June 15, 2016

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

Tuesday, June 7, 2016

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

Thursday, February 11, 2016

Double Black Hole Hails Discovery of Gravity Waves

Summary: It's the announcement of a discovery you didn't know you were waiting for. The detection of gravitational waves. It sounds weird, of course, but Einstein was onto something big when he was working on his theory of general relativity. Similar to a ball warping the surface of a rubber sheet, or a kayak being thrown into the water, large objects in outer space warp the fabric of the four dimensional spacetime that we live in.

When this happens, gravitational waves ripple through space and expand or contract the space around them. These waves have been undetectable until now. It is thanks to the LIGO interferometer that we can detect these faint waves in the universe. These waves are understandably hard to detect, the measurements are on a scale less than a width of an atom. They were able to detect this thanks to a double black hole.

Quite deservedly, the scientists involved are quite proud of their work. As this is both the first detection of gravity waves and the first direct detection of a black hole in addition to being confirmation of general relativity, they are confident that there is a Nobel Prize in their future and I am inclined to agree.

Either way, it is an exciting breakthrough in astronomy and one that I am excited to have as I enter the field.


APS Article
BBC News
Nature
SciShow

Monday, December 21, 2015

Landing a rocket

Summary: In case your Twitter feed was not just lighting up as much as mine was, Space X just made space history. In the upgrade to their Falcon 9 rocket, the booster did more than just separate, it landed itself back on earth, right where it was supposed to.

In a beautiful video, I just watched a great ball of fire slowly descend to the landing pad and then fade out to reveal a booster rocket standing as straight as you please. Absolutely incredible. The whole of mission control was throwing a party. 

The rest of the rocket went on to deploy six more satellites to complete the constellation arrangement. 

I'll update this post with a link to the video of the launch and further details as I get them.

SpaceX launch video (I suggest starting at about 21:00)
The above link will also give more mission details.

Background on the launch

Long exposure of the launch and landing of the rocket

    
The booster rocket safely on the landing pad

Monday, November 9, 2015

Strong Forces Between Antipotons

Summary: Woah, a story about antimatter on an antimatter blog! Finally.

Unlike a lot of other anitmatter and particle physics news, this does not come to us from CERN but rather from in Relativistic Heavy Ion Collider (RHIC) at Brookhaven in New York. Here physicists were able to measure the interactions between antiprotons. It seems like it is also the strong force, an attractive force, that holds the antiprotons together just as it also holds the protons together. This is just one more way in which protons and antiprotons are essentially the same, the exception of their opposite charge. Because of the similarity scientists can rule this out as a possible explanation for the matter/antimatter asymmetry in the universe today.

BBC News
Nature