A Lonely Dwarf


Wolf – Lundmark – Melotte (WLM) is a lonely dwarf galaxy named for the three astronomers who discovered it. It’s about 3 million light-years from the Milky Way in the constellation Cetus, and it’s one of the most remote members of our local galaxy group. It’s so isolated that it may never have interacted with any other local group galaxy.

Image Credit: ESO

Stellar Explosions in Orion


Stellar explosions are usually associated with supernovae, the spectacular deaths of stars. New ALMA observations of the Orion Nebula provide insights into explosions at the other end of the stellar life cycle, star birth. This image shows the remains of a 500-year-old explosion from the birth of a group of massive stars; star formation can be a violent and explosive process too.

The colors in the ALMA data represent the relative Doppler shifting of the millimetre-wavelength light emitted by carbon monoxide gas. Blue data represents gas approaching at the highest speeds; the red data is from gas moving toward us more slowly.

The millimetre wave data is superimposed over optical and near-infrared images from the Gemini South and the ESO Very Large Telescope. The famous Trapezium Cluster of hot young stars appears towards the bottom of this image. The ALMA data only covers the central portion of the picture.

Image Credit: ESO

A Hole in the Cosmic Microwave Background


The Cosmic Microwave Background (CMB) in the afterglow of the Big Bang. Why would this cluster of galaxies punch a hole in it? The CMB flows right through most of the gas and dust in the universe. It is all around us. However, large clusters of galaxies have enough gravity to contain gas hot enough to up-scatter the CMB photons into light of significantly higher energy, creating “holes” in the CMB. This is known as the Sunyaev–Zel’dovich (SZ) effect, and it’s used for decades to study the hot gas in clusters. This picture combines CMB data from ESO’s ALMA with imagery from the Hubble Space Telescope to measure the galaxies in the massive galaxy cluster RX J1347.5-1145. False-color blue shows light from the CMB; almost every yellow object is a galaxy. The shape of the SZ hole indicates not only that hot gas is present in this galaxy cluster, but also that it is distributed in a surprisingly uneven manner.

Image Credit: ESO / ESA / NASA