Sloan Digital Sky Survey 3D Map And Dark Energy

Baryon Acoustic Vibrations
Baryon Acoustic Vibrations at 5.5 Billion Light Years From SDSS Data
Image Credit: E.M. Huff, the SDSS-III team, and the South Pole Telescope team.
Graphic by Zosia Rostomian.

Dark Energy drives the accelerating expansion of the Universe, and the imprint can be found in the distribution of galaxies.

Now, researchers, including several associated with the University of Arizona in Tucson, have published a series of six papers (see below) concerning the distribution of galaxies 5.5 billion light years from Earth, using data from the Sloan Digital Sky Survey.

The papers detail how mapping the position of galaxies can measure how fast the Universe was expanding six billion years ago. The expansion is the result of Dark Energy, which makes up 72% of the universe in which we live (the remainder is Dark Matter (23%) and atoms (5%), found in intergalactic gas and stars).

The image above illustrates how variations in the cosmic microwave background (due to baryon acoustic vibrations during inflation, which followed the Big Bang) are reflected by later distribution of galaxies, and measuring the distribution of galaxies at different times reflects the accelerating expansion of the universe. The original work on the accelerating expansion came from observations of type Ia supernovae in 1998 and and 1999, and led to the Nobel Prize in 2011.

The Baryon Oscillation Spectroscopic Survey (BOSS) is one of four SDSS surveys, and the team of scientists and engineers that make up the team are the authors of these six papers.

Will Percival, a professor at the University of Portsmouth in the United Kingdom, and one of the leaders of the analysis team noted that:

We have only one-third of the data that BOSS will deliver, and that has already allowed us to measure how fast the Universe was expanding six billion years ago — to an accuracy of two percent.

This coupled with the previously released data on the distribution of galaxies at 3.8 billion light years, shows the accelerating expansion: the rate at 3.8 billion light years is more than the earlier rate at 5.5 billion light years.

Due to the original oscillations in the universe, theory predicts that the average distance between galaxies would be 500 million light years. And this is what the BOSS results have shown. They are the best measurements to date.

From the SDSS article we have the references to the arxiv papers:


Russian Progress Resupply to ISS Fails

Soyuz M-12M
Launch of Progress M-12M aboard Soyuz Rocket.
Image Credit: NASA TV

At 325 seconds into the flight, the third stage sensed a low tank pressure condition and shut down the rocket. The Progress M-12M spacecraft and the attached third and fourth stages crashed in the Altai region of the Russian Federation. The region has had its share of falling debris over the decades, but the explosion created by the spacecraft and unused fuel and liquid oxygen was the largest ever reported.

The failure was the first Progress lost since 1978. There have been 43 successful resupply missions to the International Space Station (ISS) over the past 11 years.

Nearly three tons of supplies were lost, as well as the capability that the Progress had to re-boost the orbit of the ISS. The first of which was scheduled for 31 August. There are discussions underway as to whether the Progress M-11M, which undocked just prior to the launch. could be re-docked and used for re-boost. In addition, the ISS Service Module (SM) “Zvezda” has two engines capable of performing ISS re-boosts.

ISS program manager Mike Suffredini noted that “We are in a good position logistically to withstand this loss of supplies that were going to come to ISS. In fact, I can tell you we can go several months without a resupply vehicle if that becomes necessary.”

Russia has announced the suspension of all Soyuz launches pending an investigation. Russia has lost six spacecraft in the past nine months.

Lyman Alpha Blob

Alpha Lyman Blob by the European Southern Observatory
Image Credit: ESO / M. Hayes

The European Southern Observatory‘s Very Large Telescope has returned images and data from a vast cloud of glowing gas at the edge of the observable universe. The paper appears in Nature: “Central Powering of the Largest Lyman-alpha Nebula is Revealed by Polarized Radiation”. The object is a “Lyman-alpha-blob” and has entire galaxies embedded in it.

The Object in the paper is known as LAB-1 and was discovered in 2000. It has a diameter of 300,000 light years (our Milky Way is 100,000 light years across). LAB-1 has several primordial galaxies inside, including one with an active core (quasar).

There have been two competing theories about the light emitted by these distant (11-12 billion light years) objects. One idea is that the collapsing gas clouds making up a blob creates the energy that is radiated. A second theory is that the blob is large enough to contain one or more galaxies, which provide the energy needed to shine so brightly. The paper provides evidence for this latter theory.