Starship Asterisk*

A spiral galaxy. It is large in the centre with a lot of detail visible. The core glows brightly and is surrounded by concentric rings of dark and light dust. The spiral arms are thick and puffy with grey dust and glowing blue areas of star formation. They wrap around the galaxy to form a ring. Part of the arm is drawn out into a dark thread above the galaxy, and dust from the arm trails off to the right.

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Image Credit: ESA/Hubble & NASA, M. Gullieuszik and the GASP team

The jellyfish galaxy JW39 hangs serenely in this image from the NASA/ESA Hubble Space Telescope. This galaxy lies over 900 million light-years away in the constellation Coma Berenices, and is one of several jellyfish galaxies that Hubble has been studying over the past two years.

Despite this jellyfish galaxy’s serene appearance, it is adrift in a ferociously hostile environment; a galaxy cluster. Compared to their more isolated counterparts, the galaxies in galaxy clusters are often distorted by the gravitational pull of larger neighbours, which can twist galaxies into a variety of weird and wonderful shapes. If that was not enough, the space between galaxies in a cluster is also pervaded with a searingly hot plasma known as the intracluster medium. While this plasma is extremely tenuous, galaxies moving through it experience it almost like swimmers fighting against a current, and this interaction can strip galaxies of their star-forming gas.

This interaction between the intracluster medium and the galaxies is called ram-pressure stripping, and is the process responsible for the trailing tendrils of this jellyfish galaxy. As JW39 has moved through the cluster the pressure of the intracluster medium has stripped away gas and dust into long trailing ribbons of star formation that now stretch away from the disc of the galaxy.

Astronomers using Hubble’s Wide Field Camera 3 studied these trailing tendrils in detail, as they are a particularly extreme environment for star formation. Surprisingly, they found that star formation in the ‘tentacles’ of jellyfish galaxies was not noticeably different from star formation in the galaxy disc.

• Astrophysical Journal 945(1):54 (2023 Mar 01) DOI: 10.3847/1538-4357/acb59b
• arXiv > astro-ph > arXiv:2301.08279 > 19 Jan 2023

• arXiv > astro-ph > arXiv:2302.10615 > 21 Feb 2023

Image Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. Chu

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Star trails blur and lasers streak across the sky in this long-exposure view from Pu‘u Poli‘ahu, the mountain peak adjacent to the Gemini North telescope of the International Gemini Observatory, operated by NSF’s NOIRLab. Gemini North can be seen slightly to the right of the center of this image, shooting its laser into the sky. A handful of other telescopes that are part of the Maunakea Observatories in Hawai‘i surround Gemini North.

Despite resembling searchlights or a battle from a sci-fi film, the lasers in this image play a vital role in correcting the vision of Gemini and the other cutting-edge telescopes. They are part of these telescopes’ adaptive optics systems, and help astronomers measure the distortions in their data caused by atmospheric turbulence. By continuously feeding these measurements into computer-controlled deformable mirrors, astronomers can compensate for almost all of the blurring caused by Earth’s atmosphere. This provides Gemini North with a crystal-clear view of the night sky, rivaling that of a space telescope above the tumultuous atmosphere.

Credit: ESO/VPHAS+ team. Acknowledgement: Cambridge Astronomical Survey Unit

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Sometimes dramatic events are needed to create something stunning. This beautiful structure of filaments and clouds in the southern constellation of Vela are all that remains of a massive star that died in a powerful explosion known as supernova. This is a small section of a larger image taken using the wide-field camera OmegaCAM at the VLT Survey Telescope (VST). Hosted at ESO’s Paranal Observatory in the Chilean desert, the VST is one of the best telescopes in the world to take large images of the sky in visible light.

Even though bright stars populate this image, it's hard to not be captivated by the pink gaseous clouds filling up the frame. Some tiny, others thicker, the filaments stretch outwards like tentacles. As they intertwine and cling together, an intricate network is formed which mixes with blurred clouds. But how did they come to be like this?

Around 11 000 years ago, a massive star exploded as a supernova, ejecting its outer layers. The explosion also generated shock waves which traveled outwards, compressing the gas around the star and creating the intricate network visible in the image. The result of such explosions are called supernova remnants. At 800 light years away from Earth, the Vela supernova remnant is one of the closest known to us.

A spiral galaxy. It is tilted diagonally, and slightly towards the viewer, making its core and disc separately visible. Its disc is speckled by small stars, has threads of dark reddish dust and bubbles of bright, glowing gas. The core shines brightly in a warmer colour. Several tiny stars and small galaxies are included in the black background. Credit: ESA/Hubble & NASA, C. Kilpatrick

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The spiral galaxy NGC 298 basks in this image from the NASA/ESA Hubble Space Telescope. NGC 298 lies around 89 million light-years away in the constellation Cetus, and appears isolated in this image — only a handful of distant galaxies and foreground stars accompany the lonely galaxy. While NGC 298 seems peaceful, in 1986 it was host to one of astronomy's most extreme events: a catastrophic stellar explosion known as a Type II supernova.

Hubble’s Advanced Camera for Surveys captured NGC 298 as part of an investigation into the origins of Type II supernovae. All Type II supernovae are produced by the collapse and subsequent explosion of young, massive stars, but they can produce a spectacular diversity of brightnesses and spectral features.

Astronomers suspect that the diversity of this cosmic firework show might be due to gas and dust being stripped from the stars that will eventually produce Type II supernovae. Observing the region surrounding supernova explosions can reveal traces of the progenitor star’s history preserved in this lost mass, as well as revealing any companion stars that survived the supernova. Hubble used the brief periods between scheduled observations to explore the aftermath of a number of Type II supernovae, hoping to piece together the relationship between Type II supernovae and the stellar systems which give rise to them.