Magellanic Cloud galaxies and the Milky Way seen above the Salar de Atacama salt flat (and reflected in the Laguna Cejar) in northern Chile (12-image mosaic panorama by Alex Tudorica) [2320x2000]

There is a road that connects the Northern to the Southern Cross but you have to be at the right place and time to see it. The road, as pictured above, is actually the central band of our Milky Way Galaxy; the right place, in this case, is dark Laguna Cejar in Salar de Atacama of Northern Chile; and the right time was in early October, just after sunset. Many sky wonders were captured then, including the bright Moon, inside the Milky Way arch; Venus, just above the Moon; Saturn and Mercury, just below the Moon; the Large and Small Magellanic Clouds satellite galaxies, on the far left; red airglow near the horizon on the image left; and the lights of small towns at several locations across the horizon. One might guess that composing this 30-image panorama would have been a serene experience, but for that one would have required earplugs to ignore the continued brays of wild donkeys.

Image Credit & Copyright: Nicholas Buer

Galaxy explorers

At the beginning of dawn the southern Milky Way is photographed over the Cerro Paranal Observatory in the barren Atacama Desert. Bright stars Alpha and Beta Centauri are near the horizon and the Southern Cross (Crux) appear above them. Higher in the sky is the large red emission Carina Nebula. The Large Magellanic Clouds is on the right. With its dark, steady, and transparent sky, Paranal is home to some of the world’s leading telescopes. Operated by the European Southern Observatory (ESO) the Very Large Telescope (VLT) is located on Paranal, composed of four 8-meter telescopes and smaller auxiliary telescopes, each 1.8 m in aperture (appear in this image), which are important elements of the VLT interferometer.

Image credit & copyright: Babak Tafreshi

The Seahorse of the Large Magellanic Cloud

It may look like a grazing seahorse, but the dark object toward the image right is actually a pillar of smoky dust about 20 light years long. The curiously-shaped dust structure occurs in our neighboring Large Magellanic Cloud, in a star forming region very near the expansive Tarantula Nebula. The energetic nebula is creating a star cluster, NGC 2074, whose center is visible just off the top of the image in the direction of the neck of the seahorse. As young stars in the cluster form, their light and winds will slowly erode the dust pillars away over the next million years.

Image credit: NASA, ESA, and M. Livio (STScI)

Henrietta Swan Leavitt

Henrietta Leavitt joined the Harvard College Observatory as a volunteer in 1895. She was appointed to the permanent staff in 1902, and eventually became chief of the photometry department. She worked there for the rest of her life.

Leavitt discovered 2,400 variable stars, about half of the known total in her day. Through these discoveries came her most important contribution to the field: the study of cepheid variable stars in the Magellenic Clouds — the Milky Way’s two companion galaxies. By intense observation and mathematical calculation, Leavitt realized that with cepheid variable stars (which change brightness with great regularity), there is a direct correlation between a star’s magnitude (degree of brightness) and the length of time it is most luminous. The brighter the star is overall, the longer the period of luminosity. Since the cepheids in the Magellanic Clouds were all about the same distance from Earth, Leavitt concluded that the period, or time it took to complete one cycle of dimming and brightening, was related to the star’s magnitude, not distance. Yet magnitude itself allowed you to calculate distance.

Leavitt published her findings in 1912 — in a chart of 25 cepheid periods and their apparent brightness. Using this, astronomers only needed to know the period of a cepheid variable to figure out how bright, and therefore how far away it was. Until then, methods for measuring distances in space only worked within about 100 light years. With Leavitt’s findings, distances of cepheids could be determined up to 10 million light years. This became the “yardstick to the universe” used by Edwin Hubble and others to make discoveries that changed our view of our galaxy and the universe.

Cygnus OB2

Cygnus OB2 is an OB association that is home to some of the most massive and most luminous stars known, including Cyg OB2 #8 and Cyg OB2 #12. It also includes one of the largest known stars, NML Cygni.The region is embedded within a wider region of star formation known as Cygnus X, which is one of the most luminous objects in the sky at radio wavelengths. The region is approximately 1,400 parsecs from Earth in the constellation of Cygnus.

The young cluster is one of the largest known, and the largest in the northern hemisphere with some authors classifying it as a young globular cluster similar to those present in the Large Magellanic Cloud. Although it is over ten times more massive than the famous Orion Nebula, Cygnus OB2 is much less well known due to its location behind a massive dust cloud known as the Cygnus Rift, which obscures many of the stars in it; this means that, despite the consensus of its large size, it’s hard to determine its actual properties with its estimated number of massive stars ranging, according to different scientists, for example, from 50 to 100 of spectral type O and its total mass having been calculated as 3*104 solar masses.

Credit: NASA/Chandra