A home for old stars: This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the globular cluster Terzan 1. Lying around 20 000 light-years from us in the constellation of Scorpius (The Scorpion), it is one of about 150 globular clusters belonging to our galaxy, the Milky Way. Typical globular clusters are collections of around a hundred thousand stars, held together by their mutual gravitational attraction in a spherical shape a few hundred light-years across. It is thought that every galaxy has a population of globular clusters. Some, like the Milky Way, have a few hundred, while giant elliptical galaxies can have several thousand. They contain some of the oldest stars in a galaxy, hence the reddish colours of the stars in this image — the bright blue ones are foreground stars, not part of the cluster. The ages of the stars in the globular cluster tell us that they were formed during the early stages of galaxy formation! Studying them can also help us to understand how galaxies formed. Terzan 1, like many globular clusters, is a source of X-rays. It is likely that these X-rays come from binary star systems that contain a dense neutron star and a normal star. The neutron star drags material from the companion star, causing a burst of X-ray emission. The system then enters a quiescent phase in which the neutron star cools, giving off X-ray emission with different characteristics, before enough material from the companion builds up to trigger another outburst.

Name: ESO 455-23, Terzan 1
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Scorpius
Distance: 20000 light years
Release date: 14 December 2015, 06:00
Credit: NASA & ESA, Acknowledgement: Judy Schmidt (Geckzilla)

Infant star’s artistic outburst: The artistic outburst of an extremely young star, in the earliest phase of formation, is captured in this spectacular image from the NASA/ESA Hubble Space Telescope. The colourful wisps, found in the lower left of the image, are painted onto the sky by a young star cocooned in the partially illuminated cloud of obscuring dust seen to the upper right. Pictured punching through the enshrouding dust is an extremely hot, blue jet of gas released by the young star. As this jet speeds through space, it collides with cooler surrounding material. The result is the colourful object to the lower left, produced as the cooler material is heated by the jet (opo9524a, potw1307a). This wispy object is known as HH34 and it is an example of a Herbig–Haro (HH) object. It resides approximately 1400 light-years away near the Orion Nebula, a large star formation region within the Milky Way. HH objects exist for a cosmically brief time — typically thousands of years — with changes seen in observations taken only a few years apart (heic1113). Although the jet extends the entire length between the infant star and HH34, only a fraction of it appears visible. This part of the jet possesses an intricate structure of knots and ripples, thought to be caused by the different outbursts catching up and ramming into each other over time.

Name: HH 34
Type: Milky Way : Star : Evolutionary Stage : Protostar
Category: Stars
Constellation: Orion
Distance: 1400 light years
Release date: 21 December 2015, 06:00
Credit: ESA/Hubble & NASA

Two become one: This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the galaxy NGC 6052, located around 230 million light-years away in the constellation of Hercules. It would be reasonable to think of this as a single abnormal galaxy, and it was originally classified as such. However, it is in fact a “new” galaxy in the process of forming. Two separate galaxies have been gradually drawn together, attracted by gravity, and have collided. We now see them merging into a single structure. As the merging process continues, individual stars are thrown out of their original orbits and placed onto entirely new paths, some very distant from the region of the collision itself. Since the stars produce the light we see, the “galaxy” now appears to have a highly chaotic shape. Eventually, this new galaxy will settle down into a stable shape, which may not resemble either of the two original galaxies.

Name: NGC 6052
Type: Local Universe : Galaxy : Type : Interacting
Category: Galaxies
Constellation: Hercules
Distance: 230 million light years
Release date: 28 December 2015, 06:00
Credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt (Geckzilla)