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ESA/HEIC: Snapshot of a Shedding Star (HD 94910)

[b][i]Credit: NASA, ESA, Hubble[/i][/b]

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In this new Hubble image, the strikingly luminous star AG Carinae — otherwise known as HD 94910 — takes centre stage. Found within the constellation of Carina in the southern sky, AG Carinae lies 20 000 light-years away, nestled in the Milky Way.

AG Carinae is classified as a Luminous Blue Variable. These rare objects are massive evolved stars that will one day become Wolf-Rayet Stars — a class of stars that are tens of thousands to several million times as luminous as the Sun. They have evolved from main sequence stars that were twenty times the mass of the Sun.

Stars like AG Carinae lose their mass at a phenomenal rate. This loss of mass is due to powerful stellar winds with speeds of up to 7 million km/hour. These powerful winds are also responsible for the shroud of material visible in this image. The winds exert enormous pressure on the clouds of interstellar material expelled by the star and force them into this shape.

Despite HD 94910’s intense luminosity, it is not visible with the naked eye as much of its output is in the ultraviolet.

This image was taken with the Wide Field and Planetary Camera 2 (WFPC2), that was installed on Hubble during the Shuttle mission STS-61 and was Hubble’s workhorse for many years. It is worth noting that the bright glare at the centre of the image is not the star itself. The star is tiny at this scale and hidden within the saturated region. The white cross is also not an astronomical phenomenon but rather an effect of the telescope.

In this new Hubble image, the strikingly luminous star AG Carinae — otherwise known as HD 94910 — takes centre stage. Found within the constellation of Carina in the southern sky, AG Carinae lies 20 000 light-years away, nestled in the Milky Way.

AG Carinae is classified as a Luminous Blue Variable. These rare objects are massive evolved stars that will one day become Wolf-Rayet Stars — a class of stars that are tens of thousands to several million times as luminous as the Sun. They have evolved from main sequence stars that were twenty times the mass of the Sun.

Stars like AG Carinae lose their mass at a phenomenal rate. This loss of mass is due to powerful stellar winds with speeds of up to 7 million km/hour. These powerful winds are also responsible for the shroud of material visible in this image. The winds exert enormous pressure on the clouds of interstellar material expelled by the star and force them into this shape.

Despite HD 94910’s intense luminosity, it is not visible with the naked eye as much of its output is in the ultraviolet.

This image was taken with the Wide Field and Planetary Camera 2 (WFPC2), that was installed on Hubble during the Shuttle mission STS-61 and was Hubble’s workhorse for many years. It is worth noting that the bright glare at the centre of the image is not the star itself. The star is tiny at this scale and hidden within the saturated region. The white cross is also not an astronomical phenomenon but rather an effect of the telescope.

Sitting atop Cerro Paranal high above the Atacama Desert in Chile, two of the Very Large Telescope's Unit Telescopes quietly bask in the starlight, observing the Milky Way as it arches over ESO's Paranal Observatory.

Several interesting objects can be seen in this picture. Some of the most prominent are the two Magellanic Clouds — one Small (SMC), one Large (LMC) — which appear brightly in between the two telescopes. By contrast, the dark Coalsack Nebula can be seen as an obscuring smudge across the Milky Way, resembling a giant cosmic thumbprint above the telescope on the left. ...

This new image from the NASA/ESA Hubble Space Telescope shows NGC 7793, a spiral galaxy in the constellation of Sculptor some 13 million light-years away from Earth. NGC 7793 is one of the brightest galaxies in the Sculptor Group, and one of the closest groups of galaxies to the Local Group — the group of galaxies containing our galaxy, the Milky Way and the Magellanic Clouds.

The image shows NGC 7793’s spiral arms and small central bulge. Unlike some other spirals, NGC 7793 doesn’t have a very pronounced spiral structure, and its shape is further muddled by the mottled pattern of dark dust that stretches across the frame. The occasional burst of bright pink can be seen in the galaxy, highlighting stellar nurseries containing newly-forming baby stars.

Although it may look serene and beautiful from our perspective, this galaxy is actually a very dramatic and violent place. Astronomers have discovered a powerful microquasar within NGC 7793 — a system containing a black hole actively feeding on material from a companion star. While many full-sized quasars are known at the cores of other galaxies, it is unusual to find a quasar in a galaxy’s disc rather than at its centre.

Micro-quasars are almost like scale models — they allow astronomers to study quasars in detail. As material falls inwards towards this black hole, it creates a swirling disc around it. Some of the infalling gas is propelled violently outwards at extremely high speeds, creating jets streaking out into space in opposite directions. In the case of NGC 7793, these jets are incredibly powerful, and are in the process of creating an expanding bubble of hot gas some 1000 light-years across.

The 15-metre diameter Swedish–ESO Submillimetre Telescope (SEST) was built in 1987, and was operated at ESO's La Silla Observatory in Chile until it was decommissioned in 2003.

At the time of construction, SEST was the only radio telescope in the southern hemisphere that was designed to observe the submillimetre Universe, and it paved the way for later telescopes such as the Atacama Pathfinder Experiment telescope (APEX), and the Atacama Large Millimeter/submillimeter Array (ALMA), both located at Chajnantor.

In this image, we see a crowded night sky filled with star trails, a result of the camera's long exposure time. The starlight is reflected back at numerous different angles towards the camera from the giant parabolic dish. In the background, the ESO 3.6-metre telescope stands in its dome, silently surveying the cosmos.

This picture, taken by the NASA/ESA Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC2), shows a galaxy known as NGC 6872 in the constellation of Pavo (The Peacock). Its unusual shape is caused by its interactions with the smaller galaxy that can be seen just above NGC 6872, called IC 4970. They both lie roughly 300 million light-years away from Earth.

From tip to tip, NGC 6872 measures over 500 000 light-years across, making it the second largest spiral galaxy discovered to date. In terms of size it is beaten only by NGC 262, a galaxy that measures a mind-boggling 1.3 million light-years in diameter! To put that into perspective, our own galaxy, the Milky Way, measures between 100 000 and 120 000 light-years across, making NGC 6872 about five times its size.

The upper left spiral arm of NGC 6872 is visibly distorted and is populated by star-forming regions, which appear blue on this image. This may have been be caused by IC 4970 recently passing through this arm — although here, recent means 130 million years ago! Astronomers have noted that NGC 6872 seems to be relatively sparse in terms of free hydrogen, which is the basis material for new stars, meaning that if it weren’t for its interactions with IC 4970, NGC 6872 might not have been able to produce new bursts of star formation.

Here we see ESO's La Silla Observatory with a backdrop of the Milky Way. Established in the 1960s, La Silla was ESO's first observatory to be built in Chile.

Visible on the hill in the centre of this image is the rectangular New Technology Telescope (NTT) on the left, and the domed ESO 3.6-metre telescope to the right. The 3.58-metre NTT was inaugurated in 1989, and was the first in the world to have a computer-controlled main mirror. The main mirror is flexible, and its shape is actively adjusted during observations to preserve the optimal image quality. This technology, known as active optics, is now applied to all major modern telescopes — including the Very Large Telescope at Cerro Paranal, and the future European Extremely Large Telescope.

La Silla is home to several other telescopes, including the Swedish–ESO Submillimetre Telescope (SEST), and the robotic TAROT, which is used to monitor rapidly occurring events such as gamma-ray bursts.

This picture was taken by ESO Photo Ambassador José Joaquín Pérez. When José is not taking stunning photos of the night sky, he works as an agricultural engineer where he devotes his time to the protection of crops in central Chile.

starsurfer wrote:NGC 7252
https://www.flickr.com/photos/geckzilla/12527192305/
Copyright: Hubble Legacy Archive/NASA/ESA
Processing: Judy Schmidt

Click to view full size image

This peculiar galaxy is also catalogued as Arp 226. It seems to consist of a spiral core surrounded by multiple tidal shells. It also has many tidal tails and loops that aren't included in the narrow HST field of view. These also give it the popular name of Atoms for Peace Galaxy. Recently, an OIII ionization echo was discovered near its core: http://arxiv.org/abs/1307.2233