A spiral of the water snake

NGC 5042

A spiral galaxy. It’s noticeably bright around the central region of its disc, then dims somewhat out to the edge where there are fewer stars. Two spiral arms circle through the disc and emerge beyond its edge, around the galaxy’s sides. Many pink spots of new star formation, as well as dark reddish strands of dust, cover the galaxy. The arms contain some speckled, blue patches containing hot stars. Credit: ESA/Hubble & NASA, D. Thilker

This vibrant spiral galaxy and the subject of today’s NASA/ESA Hubble Space Telescope Picture of the Week is NGC 5042, which resides about 48 million light-years from Earth in the constellation Hydra (the water snake). The galaxy nicely fills the frame of this Hubble image, with a single Milky Way star marked by cross-shaped diffraction spikes attempting to blend in with the bright stars along the galaxy’s edge.

Hubble observed NGC 5042 in six wavelength bands from the ultraviolet to the infrared to create this multicoloured portrait. The galaxy’s cream-coloured centre is packed with ancient stars, and the galaxy’s spiral arms are decorated with patches of young blue stars. The elongated yellow-orange objects that are scattered around the image are background galaxies far more distant than NGC 5042.

Perhaps NGC 5042’s most striking feature is its collection of brilliant pink gas clouds that are studded throughout its spiral arms. These flashy clouds are called H II (pronounced “H-two”) regions, and they get their distinctive colour from hydrogen atoms that have been ionised by ultraviolet light. If you look closely at this image, you’ll see that many of these reddish clouds are associated with clumps of blue stars, often appearing to form a shell around the stars.

H II regions arise in expansive clouds of hydrogen gas, and only hot and massive stars produce enough high-energy light to create an H II region. Because the stars capable of creating H II regions only live for a few million years — just a blink of an eye in galactic terms — this image represents a fleeting snapshot of life in this galaxy.

Source: ESA/Hubble/potw

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The Penguin and the Egg Galaxies (Arp 142)

NGC 2936/NGC 2937 (Arp 142)
High Res.（10.8 MB)

In the vast cosmic images captured through the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), a large-scale survey spanning 330 nights of Subaru Telescope operations starting in 2014 and lasting over seven years, many interacting or colliding galaxies are captured, affecting each other’s shapes through mutual gravitation. Interacting galaxies have a wide variety of shapes; one galaxy pair looks like a jellyfish, and the other looks like a penguin holding an egg.

This image shows a pair of interacting galaxies in the Hydra constellation. The galaxy resembling a penguin is NGC 2936, which is thought to be distorted by the strong gravity of NGC 2937, an elliptical galaxy in the lower left of the penguin that looks like an egg. The pair are jointly known as Arp 142.

NGC 2936 is a distorted spiral galaxy. The brightest part, resembling a penguin's eye, is the center of the galaxy. The blueish areas of the galaxy, looking like the penguin's beak and outline, contain many newly formed stars induced by gravity interactions, and newborn stars emit blue light. In contrast, the elliptical, egg-like galaxy looks red or orangish due to the dominance of old stars.

The fuzzy features surrounding the penguin show gravitational interaction events between the two galaxies. A small-aperture telescope cannot capture these faint features, but the Subaru Telescope, with its 8.2-meter primary mirror, successfully detected them. Additionally, Hyper Suprime-Cam (HSC), the ultra-wide field of view camera, captured a faint feature apart from the penguin in the upper-left direction. Credit: NAOJ)

Distance from Earth: About 330 million light-years
Instrument: Hyper Suprime-Cam (HSC)

Source: Subaru Telescope/Press Release

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Hubble Spies a Stately Spiral Galaxy

NGC 5495
Credit: ESA/Hubble & NASA, J. Greene / Acknowledgement: R. Colombari

The stately sweeping spiral arms of the spiral galaxy NGC 5495 are revealed by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 in this image. NGC 5495, which lies around 300 million light-years from Earth in the constellation Hydra, is a Seyfert galaxy, a type of galaxy with a particularly bright central region. These luminous cores — known to astronomers as active galactic nuclei — are dominated by the light emitted by dust and gas falling into a supermassive black hole.

This image is drawn from a series of observations captured by astronomers studying supermassive black holes lurking in the hearts of other galaxies. Studying the central regions of galaxies can be challenging: as well as the light created by matter falling into supermassive black holes, areas of star formation and the light from existing stars all contribute to the brightness of galactic cores. Hubble’s crystal-clear vision helped astronomers disentangle the various sources of light at the core of NGC 5495, allowing them to precisely weigh its supermassive black hole.

As well as NGC 5495, two stellar interlopers are visible in this image. One is just outside the centre of NGC 5495, and the other is very prominent alongside the galaxy. While they share the same location on the sky, these objects are much closer to home than NGC 5495: they are stars from our own Milky Way. The bright stars are surrounded by criss-cross diffraction spikes, optical artefacts created by the internal structure of Hubble interacting with starlight.

Source: ESA/Hubble/potw

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Hubble Spies a Tenuous Diffuse Galaxy

ultra-diffuse galaxy GAMA 526784
Credit: ESA/Hubble & NASA, R. van der Burg
Acknowledgement: L. Shatz

The ultra-diffuse galaxy GAMA 526784 appears as a tenuous patch of light in this image from the NASA/ESA Hubble Space Telescope. This wispy object resides in the constellation Hydra, roughly four billion light-years from Earth. Ultra-diffuse galaxies such as GAMA 526784 have a number of peculiarities. For example, their dark matter content can be either extremely low or extremely high — ultra-diffuse galaxies have been observed with an almost complete lack of dark matter, whereas others consist of almost nothing but dark matter. Another oddity of this class of galaxies is their anomalous abundance of bright globular clusters, something not observed in other types of galaxies.

Hubble captured GAMA 526784 with the Advanced Camera for Surveys (ACS), which was installed in 2002 by astronauts during Hubble Servicing Mission 3B. Since then, the instrument has played a pivotal role in some of Hubble’s most impressive scientific results, including capturing the Hubble Ultra Deep Field. The ACS has also photographed Pluto in advance of the New Horizon mission, observed gargantuan gravitational lenses and found fully formed galaxies in the early Universe.

This image comes from a set of Hubble observations designed to shed light on the properties of ultra-diffuse galaxies. Hubble’s keen vision allowed astronomers to study GAMA 526784 in high resolution at ultraviolet wavelengths, helping to gauge the sizes and ages of the compact star-forming regions studding the galaxy.

Source: ESA/Hubble/potw

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