The Rosette Nebula

• The Rosette Nebula is a star-forming region about 5,000 light years from Earth.

• X-rays from Chandra reveal about 160 stars in the cluster known as NGC 2237 (right side of the image).

• Combining X-ray and optical data, astronomers determined that the central cluster formed first, followed by neighboring ones including NGC 2237.

This composite image shows the Rosette star formation region, located about 5,000 light years from Earth. Data from the Chandra X-ray Observatory are colored red and outlined by a white line (roll your mouse over the image above). The X-rays reveal hundreds of young stars clustered in the center of the image and additional fainter clusters on either side. These clusters are labeled in the X-ray only image, where they are more obvious to the eye. Optical data from the Digitized Sky Survey and the Kitt Peak National Observatory (purple, orange, green and blue) show large areas of gas and dust, including giant pillars that remain behind after intense radiation from massive stars has eroded the more diffuse gas.

A recent Chandra study of the cluster on the right side of the image, named NGC 2237, provides the first probe of the low-mass stars in this satellite cluster. Previously only 36 young stars had been discovered in NGC 2237, but the Chandra work has increased this sample to about 160 stars. The presence of several X-ray emitting stars around the pillars and the detection of an outflow -- commonly associated with very young stars -- originating from a dark area of the optical image indicates that star formation is continuing in NGC 2237 (the outflow and some of the pillars are labeled in a close-up view). By combining these results with earlier studies, the scientists conclude that the central cluster formed first, followed by expansion of the nebula, which triggered the formation of the neighboring clusters, including NGC 2237.

Image Credit: X-ray (NASA/CXC/SAO/J. Wang et al), Optical (DSS & NOAO/AURA/NSF/KPNO 0.9-m/T. Rector et al)
Explanation from: http://chandra.si.edu/photo/2010/rosette/

Globular Cluster Messier 56

The NASA/ESA Hubble Space Telescope has produced this beautiful image of the globular cluster Messier 56 (also known as M 56 or NGC 6779), which is located about 33 000 light years away from the Earth in the constellation of Lyra (The Lyre). The cluster is composed of a large number of stars, tightly bound to each other by gravity.

However, this was not known when Charles Messier first observed it in January 1779. He described Messier 56 as “a nebula without stars”, like most globular clusters that he discovered — his telescope was not powerful enough to individually resolve any of the stars visible here, making it look like a fuzzy ball through his telescope’s eyepiece. We clearly see from Hubble’s image how the development of technology over the years has helped our understanding of astronomical objects.

Astronomers typically infer important properties of globular clusters by looking at the light of their constituent stars. But they have to be very careful when they observe objects like Messier 56, which is located close to the Galactic plane. This region is crowded by “field-stars”, in other words, stars in the Milky Way that happen to lie in the same direction but do not belong to the cluster. These objects can contaminate the light, and hence undermine the conclusions reached by astronomers.

A tool often used by scientists for studying stellar clusters is the colour-magnitude (or Hertzsprung-Russell) diagram. This chart compares the brightness and colour of stars – which in turn, tells scientists what the surface temperature of a star is.

By comparing high quality observations taken with the Hubble Space Telescope with results from the standard theory of stellar evolution, astronomers can characterise the properties of a cluster. In the case of Messier 56, this includes its age, which at 13 billion years is approximately three times the age of the Sun. Furthermore, they have also been able to study the chemical composition of Messier 56. The cluster has relatively few elements heavier than hydrogen and helium, typically a sign of stars that were born early in the Universe’s history, before many of the elements in existence today were formed in significant quantities.

Astronomers have found that the majority of clusters with this type of chemical makeup lie along a plane in the Milky Way’s halo. This suggests that such clusters were captured from a satellite galaxy, rather than being the oldest members of the Milky Way's globular cluster system as had been previously thought.

This image consists of visible and near-infrared exposures from Hubble’s Advanced Camera for Surveys. The field of view is approximately 3.3 by 3.3 arcminutes.

Image Credit: NASA, ESA, Gilles Chapdelaine
Explanation from: https://www.spacetelescope.org/images/potw1234a/

Total Solar Eclipse seen from plane above Turkana

Plane above Turkana, Kenya

November 3, 2013

Image Credit & Copyright: Catalin Beldea