NASA's Galaxy Evolution Explorer captured this ultraviolet image of the nearby planetary nebula NGC 3242, also called "Jupiter's Ghost" (blue and white region at centre). It may sit as little as 1400 light years away in the constellation Hydra. As sun-like stars run out of fuel, they swell into red giants. These bloated stars jettison their outer layers of gas, eventually exposing a dense core of carbon and oxygen called a white dwarf. The ultraviolet light released by the white dwarfs lights up the surrounding gas, creating planetary nebulae. Although sun-like stars live for billions of years, planetary nebulae only last some 10,000 years. Astronomers are not sure whether the wispy white cloud that curves around the blue nebula is a chance passerby or gas that was ejected while the star was still a red giant. (Image: NASA/JPL-Caltech)

Organic molecules mixed with dust glow green in this infrared image of M33 captured by the Spitzer Space Telescope. M33, also called the Triangulum Galaxy, sits some 2.9 million light years away from Earth. The spiral is a member of the Milky Way's Local Group, a band of dozens of galaxies that travel as an ensemble because they are gravitationally bound. Star-forming regions appear orange-red in this image. Cool material, possibly carried outwards by winds from giant stars or supernovae, glows at infrared wavelengths beyond what optical telescopes detect as the galaxy's edge. (Image: NASA/JPL-Caltech/University of Arizona)

The ultra-dense remains of a massive star light up surrounding gas and dust to create what appears to be a cosmic hand. This pulsar, seen in bright blue at the base of the "palm", is called B1509. The star is so dense that the electrons and protons in its atoms have combined to form neutrons. B1509 spins some 7 times a second and measures just 19 kilometres in diameter. The magnetic field at its surface is 15 trillion times stronger than the Earth's magnetic field. The field drives a wind of electrons and charged atoms that illuminates finger-like structures that extend north.



The pulsar's reach extends to a neighbouring gas cloud called RCW 89, where the wind lights up knots of gas, making them glow brightly in X-rays (visible in orange and red in the upper-right). The temperature in the cloud seems to vary in a circular pattern, which could mean the pulsar is precessing like a spinning top. B1509 sits some 17,000 light years away from Earth, and is estimated to be about 1700 years old. This image was captured by the orbiting Chandra X-ray Observatory. (Image: NASA/CXC/SAO/P Slane et al) Advertisement

This trio of galaxies, which together form a system called Arp 274, seem to be heading toward a cosmic collision. In fact, the two large spirals (middle and right) already seem to be entangled. But their proximity is just an illusion – the galaxies lie at different distances from Earth and are far enough from one another that astronomers do not think they interact. Two foreground stars in the Milky Way can also be seen on the right.



All three galaxies show colourful evidence of new star formation. The energised gas of stellar nurseries (pink) and clusters of young, massive stars (blue) dot the arms of the two spiral galaxies and encircle their compact companion (left). Older stars appear yellow.



Arp 274 sits 400 million light years away in the constellation Virgo. The Hubble Space Telescope snapped the ensemble in early April, after it was chosen by the public from six candidate targets. (Image: NASA/ESA/M. Livio/Hubble Heritage Team/STScI/AURA)

A stellar nursery is not uniformly bright, a fact highlighted by this image of NGC 3582, a nebula that sits some 10,000 light years away in the constellation Carina. Here, dark dust clouds share space with glowing gas that is energised by the ultraviolet light of young stars. Wispy structures in the clouds are created by radiation from these young stars, as well as by the explosions of short-lived, massive neighbours. This image was taken by the Gemini South telescope on Cerro Pachon in the Chilean Andes. (Image: Gemini Observatory Legacy Image)

A nascent bar sits at the centre of NGC 3359, a delicate spiral galaxy that sits some 49 million light years away in the constellation Ursa Major. Bars are elongated, rectangular bodies of stars, gas and dust that are often seen in spiral galaxies, though it is not yet clear how they fit into galaxies' evolution. Although NGC 3359 is several billion years old, this bar seems to be just 500 million years old.



The galaxy's arms are dotted with light-red patches, hydrogen-rich regions that are sites of intense star formation, similar to those seen in the Orion Nebula in the Milky Way. This image was taken by the Gemini North telescope on Mauna Kea in Hawaii. NGC 3359 can be seen with amateur telescopes. (Image: Gemini Observatory Legacy Image)

The chaotic structure of the spiral galaxy NGC 7793 makes it difficult to identify individual spiral arms, though it is possible to discern some rotation. NGC 7793 sits some 12.5 million light years away from Earth. It is one of the brightest members of the Sculptor Group, a cluster of galaxies that is one of the closest neighbours to our Local Group of galaxies. The Very Large Telescope in the Atacama Desert in Chile snapped this image. (Image: ESO)