An interstellar butterfly: They say the flap of a butterfly's wings can set off a tornado on the other side of the world. But what happens when a butterfly flaps its wings in the depths of space? This cosmic butterfly is a nebula known as AFGL 4104, or Roberts 22. Caused by a star that is nearing the end of its life and has shrugged off its outer layers, the nebula emerges as a cosmic chrysalis to produce this striking sight. Studies of the lobes of Roberts 22 have shown an amazingly complex structure, with countless intersecting loops and filaments. A butterfly's life span is counted in weeks; although on a much longer timescale, this stage of life for Roberts 22 is also transient. It is currently a preplanetary nebula, a short-lived phase that begins once a dying star has pushed much of the material in its outer layers into space, and ends once this stellar remnant becomes hot enough to ionise the surrounding gas clouds and make them glow. About 400 years ago, the star at the centre of Roberts 22 shed its outer shells, which raced outwards to form this butterfly. The central star will soon be hot enough to ionise the surrounding gas, and it will evolve into a fully fledged planetary nebula. Information about the nature, age, and structure of Roberts 22 was presented in a paper using Hubble data back in 1999, published in The Astronomical Journal.

Name: AFGL 4104
Type: Milky Way : Nebula : Type : Planetary
Category: Nebulae
Constellation: Carina
Release date: 10 March 2014, 10:00
Credit: NASA, ESA, and R. Sahai (Jet Propulsion Laboratory)

Secrets at the heart of NGC 5793: This new Hubble image is centred on NGC 5793, a spiral galaxy over 150 million light-years away in the constellation of Libra. This galaxy has two particularly striking features: a beautiful dust lane and an intensely bright centre — much brighter than that of our own galaxy, or indeed those of most spiral galaxies we observe. NGC 5793 is a Seyfert galaxy. These galaxies have incredibly luminous centres that are thought to be caused by hungry supermassive black holes — black holes that can be billions of times the size of the Sun — that pull in and devour gas and dust from their surroundings. This galaxy is of great interest to astronomers for many reasons. For one, it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation [1]. Naturally occurring masers, like those observed in NGC 5793, can tell us a lot about their environment; we see these kinds of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, which are thousands of times more luminous than the Sun. A version of this image was submitted to the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt. [1]  This name originates from the acronym Microwave Amplification by Stimulated Emission of Radiation. Maser emission is caused by particles that absorb energy from their surroundings and then re-emit this in the microwave part of the spectrum.

Name: NGC 5793
Type: Local Universe : Galaxy : Type : SpiralLocal Universe : Galaxy : Activity : AGN : SeyfertLocal Universe : Galaxy : Component : Central Black Hole
Category: GalaxiesQuasars and Black Holes
Constellation: Libra
Release date: 17 March 2014, 09:50
Credit: NASA, ESA, and E. Perlman (Florida Institute of Technology) Acknowledgement: Judy Schmidt

Magnifying the distant Universe: Galaxy clusters are some of the most massive structures that can be found in the Universe — large groups of galaxies bound together by gravity. This image from the NASA/ESA Hubble Space Telescope reveals one of these clusters, known as MACS J0454.1-0300. Each of the bright spots seen here is a galaxy, and each is home to many millions, or even billions, of stars. Astronomers have determined the mass of MACS J0454.1-0300 to be around 180 trillion times the mass of the Sun. Clusters like this are so massive that their gravity can even change the behaviour of space around them, bending the path of light as it travels through them, sometimes amplifying it and acting like a cosmic magnifying glass. Thanks to this effect, it is possible to see objects that are so far away from us that they would otherwise be too faint to be detected. In this case, several objects appear to be dramatically elongated and are seen as sweeping arcs to the left of this image. These are galaxies located at vast distances behind the cluster — their image has been amplified, but also distorted, as their light passes through MACS J0454.1-0300. This process, known as gravitational lensing, is an extremely valuable tool for astronomers as they peer at very distant objects. This effect will be put to good use with the start of Hubble's Frontier Fields program over the next few years, which aims to explore very distant objects located behind lensing clusters, similar to MACS J0454.1-0300, to investigate how stars and galaxies formed and evolved in the early Universe. A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nick Rose.

Name: MACS J0454.1-0300
Type: Local Universe : Galaxy : Type : Gravitationally LensedEarly Universe : Star : Grouping : Cluster
Category: Galaxies
Constellation: Orion
Release date: 24 March 2014, 10:00
Credit: ESA/Hubble & NASA Acknowledgement: Nick Rose

A spiral home to exploding stars: In this new Hubble image, we can see an almost face-on view of the galaxy NGC 1084. At first glance, this galaxy is pretty unoriginal. Like the majority of galaxies that we observe it is a spiral galaxy, and, as with about half of all spirals, it has no bar running through its loosely wound arms. However, although it may seem unremarkable on paper, NGC 1084 is actually a near-perfect example of this type of galaxy — and Hubble has a near-perfect view of it. NGC 1084 has hosted several violent events known as supernovae — explosions that occur when massive stars, many times more massive than the Sun, approach their twilight years. As the fusion processes in their cores run out of fuel and come to an end, these stellar giants collapse, blowing off their outer layers in a violent explosion. Supernovae can often briefly outshine an entire galaxy, before then fading away over several weeks or months. Although directly observing one of these explosions is hard to do, in galaxies like NGC 1084 astronomers can find and study the remnants left behind. Astronomers have noted five supernova explosions within NGC 1084 over the past half century. These remnants are named after the year in which they took place — 1963P, 1996an, 1998dl, 2009H, and 2012ec. The most recent explosion, 2012ec, was detected at the end of NGC 1084’s top right arm in August 2012. It is not visible here as these images were taken in 2001, some eleven years before this supernova exploded. Astronomers at Queen's University Belfast have managed to use these "before" images to directly identify the star that exploded. It appears to be a red supergiant some 10 to 20 times more massive than the Sun, and quite similar to the well-known star Betelguese in Orion. A version of this image was entered into the Hubble's Hidden Treasures image processing competition by Flickr user Brian Campbell (Sinickel).

Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Eridanus
Distance: 70 million light years
Release date: 31 March 2014, 10:00
Credit: NASA, ESA, and S. Smartt (Queen's University Belfast)Acknowledgement: Brian Campbell