Masquerading as a double star: The  object in this image is Jonckheere 900 or J 900, a planetary nebula —  glowing shells of ionised gas pushed out by a dying star. Discovered in  the early 1900s by astronomer Robert Jonckheere, the dusty nebula is  small but fairly bright, with a relatively evenly spread central region  surrounded by soft wispy edges. Despite  the clarity of this Hubble image, the two objects in the picture above  can be confusing for observers. J 900’s nearby companion, a faint star in  the constellation of Gemini, often causes problems for observers  because it is so close to the nebula — when seeing conditions are bad,  this star seems to merge into J 900, giving it an elongated appearance.  Hubble’s position above the Earth’s atmosphere means that this is not an  issue for the space telescope. Astronomers  have also mistakenly reported observations of a double star in place of  these two objects, as the planetary nebula is quite small and compact. J 900’s  central star is only just visible in this image, and is very faint —  fainter than the nebula’s neighbour. The nebula appears to display a  bipolar structure, where there are two distinct lobes of material  emanating from its centre, enclosed by a bright oval disc. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Josh Barrington.

Name: Jonckheere 900, PN G194.2+02.5
Type: Milky Way : Nebula : Type : Planetary
Category: Nebulae
Constellation: Gemini
Release date: 25 March 2013, 10:00
Credit: ESA/Hubble & NASAAcknowledgement: Josh Barrington

Light and dust in a nearby starburst galaxy: Visible  as a small, sparkling hook in the dark sky, this beautiful object is  known as J082354.96+280621.6, or J082354.96 for short. It is a starburst  galaxy, so named because of the incredibly (and unusually) high rate of  star formation occurring within it. One  way in which astronomers probe the nature and structure of galaxies  like this is by observing the behaviour of their dust and gas  components; in particular, the Lyman-alpha emission.  This occurs when electrons within a hydrogen atom fall from a higher  energy level to a lower one, emitting light as they do so. This emission  is interesting because this light leaves its host galaxy only after  extensive scattering in the nearby gas — meaning that this light can be  used as a pretty direct probe of what a galaxy is made up of. The study of this Lyman-alpha emission is common in very distant galaxies, but now a study named LARS (Lyman Alpha Reference Sample) [1] is investigating the same effect in galaxies that are closer by.  Astronomers chose fourteen galaxies, including this one, and used  spectroscopy and imaging to see what was happening within them. They  found that these Lyman-alpha photons can travel much further if a galaxy  has less dust — meaning that we can use this emission to infer how dusty the source galaxy is. The  LARS study relies heavily on the high resolving power of Hubble. When  Hubble is decommissioned, no telescope will be able to make observations  like this in the far ultraviolet part of the spectrum — meaning that  small, glittering galaxies imaged and probed by studies like LARS may  give us some of the most detailed data we have to work with for some  time to come. Credit: ESA/Hubble & NASA, M. Hayes [1] Hayes, Östlin et al., The Lyman Alpha Reference Sample: extended Lyman alpha halos produced at low dust content, The Astrophysical Journal, 2013.

Name: SDSS J082354.96+280621.6
Type: Local Universe : Galaxy : Activity : Starburst
Category: Galaxies
Constellation: Cancer
Distance: z=0.047 (redshift)
Release date: 1 April 2013, 10:00
Credit: ESA/Hubble & NASA, M. Hayes