X-ray view of the perseus cluster

The Perseus galaxy cluster is filled with a hot X- ray emitting gas, as seen in this image from NASA's Chandra X-ray Observatory. Astronomers using the Soft X-ray Spectrometer aboard the Hitomi satellite have, for the first time, mapped the motion of this gas and determined its velocity structure across a large part of the cluster.

The square overlay shows the area observed by Hitomi.
The X-ray spectrum is also shown with emission from helium-like iron (that is iron with only 2 electrons) on the left and hydrogen-like iron (iron with only one electron) on the right. The narrowness of the emission lines shows that random motions in the 50 million K hot gas in the Perseus cluster core are only 164±10 km/s along the line-of-sight. This represents a dramatic improvement in the measurement precision of the velocities which are crucial for determining the total masses of clusters and the energy flow from the accreting black hole at the cluster center.

Source:http://sci.esa.int/hitomi/58045-galaxy-cluster-keeps-calm-and-carries-on-radiating-x-rays/

Credits: NASA/CXO; Spectrum: Hitomi
Collaboration/JAXA, NASA, ESA, SRON, CSA

Mercury on the Horizon

Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun, it never wanders far from the Sun in Earth's sky. If trailing the Sun, Mercury will be visible low on the horizon for only a short while after sunset. If leading the Sun, Mercury will be visible only shortly before sunrise. So at certain times of the year, informed skygazers with a little determination can usually pick Mercury out from a site with an unobscured horizon.

Below, a lot of determination has been combined with a little digital manipulation to show Mercury's successive positions during March of 2000. Each picture was taken from the same location in Spain when the Sun itself was 10 degrees below the horizon and superposed on the single most photogenic sunset. Currently, Mercury is rising higher above the horizon with each passing sunset, and just now is angularly very close to the brighter planet Venus.

Image and info via APODhttp://apod.nasa.gov/apod/astropix.html
Image Credit & Copyright: Juan Carlos Casado