The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) has just passed the milestone of observing 500,000 galaxies and 100,000 quasars. By the completion of the survey in 2014, BOSS will have observed 1.5 million galaxies and 250,000 quasars as it maps out the distribution of matter in the Universe and measures the properties of dark energy.

The first image, courtesy of Kyle Dawson (Utah), shows the BOSS coverage on the sky (right ascension and declination) of the current survey (red). The planned total coverage is shown in grey, and we’ve already drilled the plates for all of the tiles in blue.

The second image, courtesy of Michael Blanton (NYU), shows the redshift and right ascension coverage of the BOSS survey to date. While there are many more galaxies in the Universe beyond a redshift of 0.7, BOSS is focusing on galaxies between now and 6.5 billion years ago (redshift of 0.7, shown in white) when dark energy was just starting to have a noticeable effect. The red and yellow dots are the galaxies from the previous SDSS I/II surveys and show by contrast how much more of the Universe SDSS-III BOSS is exploring. The BOSS quasars, shown in cyan, probe the Universe out to 11.5 billion years ago to study the formation of black holes in the early Universe while also using their powerful light to explore the intervening material between those distant quasars and us. BOSS is aiming to obtain quasars between redshifts of 2 and 3 but is also taking repeat observations of lower-redshift quasars from SDSS I/II to study variability of these mysterious objects powered by massive black holes at the centers of galaxies.