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 And it is not due to outdated textbooks.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.

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

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

A Peek at the Earliest Stars

Summary: At the beginning of our universe, stars were not made of the same elements that they are today. Everything in the early universe was composed of completely hydrogen and helium. It is the very first stars that created the heavier elements like carbon, oxygen, and iron. The supernovae from these stars are what spread these elements throughout the rest of our universe. But what about these first stars that were formed before these heavy elements were common? Scientists have just maybe found some hints of these that confirm this theory. A team of astronomers has found one of these low-metallicity stars.

Using spectroscopy to look at the elements in the star with the Japanese Subaru telescope, the scientists noticed that some colors, visual representations of elements, were missing. It had very low levels of heavy metals.

With the available telescopes on earth, we cannot get much more than the barest hints of these early stars. We wait, instead, for the future and the James Webb Space Telescope to look back far into the past and help cement our current observations and find stars from even earlier times.


BBC News
Science Mag

The Secret of the Super Bright Supernova

Summary, almost four years ago, astronomers found a supernova, PS1-10afx, that was 30 times brighter than any other of it's class. They didn't see any abnormalities that would account of this huge magnitude difference and were confused. However, this mystery has now been solved. Then Dr Robert Quimby and his team had an idea that proved fruitful. They looked to see if we were seeing this supernova through a gravitational lens. As it turns out, there was an entire galaxy directly in from of the supernova that was bending the light around it and magnifying it. PS1-10afx is just a normal Type 1A supernova. 

This is will be useful knowledge for measuring cosmic distances since objects of known brightness like Type 1A supernovae are a good constant against which we can measure other objects in the night sky.


BBC News
Science

Cosmic Waves of Discovery

Summary: Scientists at the BICEP2 collaboration at the South Pole have detected signal that confirm theories of the rapid expansion of the universe immediately after the big bang. If validated by other experiments (which is likely to happen as the signal found is actually stronger than predicted) this confirms a super-rapid expansion within the first instants of the universe before "slowing down" to rapid expansion. What they found were twists in Cosmic Radiation Background that could have only been produced by gravitational waves.

So what does this mean? These signals tell astronomers that gravity was present during this time in which quantum effects dominated the, then very tiny, universe. This gives us greater hope that the Four Fundamental Forces can be one day combined into a unified Theory of Everything which could better describe conditions at the big bang.


BBC News
Minute Physics video explaining the discovery
Discussion on background and implications
Video of the founding scientists hearing the news
SciShow

BOSS Data

Summary: The BOSS (Baryon Oscillation Spectroscopic Survey) collaboration has released a new report with record precision of 1% and a more accurate measure of w, Dark Energy's pressure to density ratio. If this number is simply Einstein's cosmological constant, then w=-1. The new data seems to provide solid proof for this theory as their results yielded w= -1.03±0.06.

The overall purpose of the collaboration is to more precisely determine the redshift of galaxies so that astronomers can connect this measurement with other measurements of cosmological distance. This correlation can then be applied to galaxies that are too far to measure distance by anything other than redshift.


Physics Today

New 1% Accuracy of Universe

Summary:  Set by the Baryon Oscillation Spectroscopic Survey (BOSS), astronomers now have a new standard for measuring distances in the universe. Using baryon acoustic oscillations (BAOs), they have created a standard ruler of half a billion light years long which they can use to measure distances in the universe to a 1% accuracy.
With incredibly accurate measurements, astronomers can calibrate fundamental cosmological properties that were wishy-washy at best before. The most exciting one for me, is being able to pin down how dark energy accelerates the expansion of the universe. It also can help provide a better estimate of the curvature of the universe. The latest estimates of which, seem to indicate that the universe is flatter than we previously thought. If it gets much flatter, we may find out we are living in an infinite universe.


BBC News

Source for Dark Matter and Antimatter News

I stumbled upon a link on the APS website to an archive of all their cosmology news which includes lots of articles on Dark Matter and antimatter and the beginnings of the universe. If any of that interests you, don't hesitate to check it out.


APS-Cosmology

The Universe's Violent Youth

Summary: Scientists at the Kavli Institute for Particle Astrophysics and Cosmology found new evidence to support the prevalent theory of the universe having a violent stage mare than 10 billion years ago that was responsible for the initial creation of heavy elements. Using the Suzaku satellite they saw an even spread of iron between the galaxies. This means that iron was present in the intergalactic gas even before the Perseus cluster was formed; an observation which they speculate holds true for more than just this cluster. This would put the creation of these elements between 10 to 12 billion years ago, during a time of intense star formation and energetic black holes. Most of this iron was created by Type Ia supernovae that then rocketed out their material into space.

Symmetry

Nature