Soft shells and strange star clusters

Soft shells and strange star clusters

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Public release date: 10-Oct-2013
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Contact: Nicola Guttridge
nguttrid@partner.eso.org
49-893-200-6855
ESA/Hubble Information Centre


PGC 6240 is an elliptical galaxy that resembles a pale rose in the sky, with hazy shells of stars encircling a very bright centre. Some of these shells are packed close to the centre of the galaxy, while others are flung further out into space. Several wisps of material have been thrown so far that they appear to be almost detached from the galaxy altogether.

Astronomers have studied PGC 6240 in detail due to this structure, and also because of its surrounding globular clusters dense, tightly packed groups of gravitationally bound stars that orbit galaxies. Over 150 of these clusters orbit our own galaxy, the Milky Way, all composed of old stars.

All the globular clusters around a certain galaxy form at approximately the same time, giving them all the same age. This is echoed within the clusters all the stars within a single cluster form at around the same time, too. Because of this, most galaxies have cluster populations of pretty similar ages, both in terms of overall cluster, and individual stars. However, PGC 6240 is unusual in that its clusters are varied while some do contain old stars, as expected, others contain younger stars which formed more recently.

The most likely explanation for both the galaxy’s stacked shell structure and the unexpectedly young star clusters is that PGC 6240 merged with another galaxy at some point in the recent past. Such a merger would send ripples through the galaxy and disrupt its structure, forming the concentric shells of material seen here. It would also ignite a strong burst of star formation in the galaxy, which would then trigger similar activity in nearby space leading to the creation of new, younger globular clusters around PGC 6240.

PGC 6240 is an elliptical galaxy in the southern constellation of Hydrus (The Water Snake). Also visible in this region are numerous background galaxies, speckled across the sky behind PGC 6240. Even though these bodies are at such vast distances from us, it is possible to make out the structure of many of the galaxies, especially the small spirals that stand out colourfully against the dark sky.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

###

Notes

[1] Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public. The competition is now closed, and the list of winners is available here: http://www.spacetelescope.org/announcements/ann1211.


More information

The Hubble Space Telescope is a project of international cooperation between
ESA and NASA.


Links

Images of Hubble – http://www.spacetelescope.org/images/archive/category/spacecraft/

Hubble’s Hidden Treasures – http://www.spacetelescope.org/projects/hiddentreasures/contest/


Contacts

Nicky Guttridge

Hubble/ESA

Garching, Germany

Tel: +44-75-1231-8322

Email: nguttrid@partner.eso.org



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Soft shells and strange star clusters

[ Back to EurekAlert! ]
Public release date: 10-Oct-2013
[

| E-mail

| Share Share

]

Contact: Nicola Guttridge
nguttrid@partner.eso.org
49-893-200-6855
ESA/Hubble Information Centre


PGC 6240 is an elliptical galaxy that resembles a pale rose in the sky, with hazy shells of stars encircling a very bright centre. Some of these shells are packed close to the centre of the galaxy, while others are flung further out into space. Several wisps of material have been thrown so far that they appear to be almost detached from the galaxy altogether.

Astronomers have studied PGC 6240 in detail due to this structure, and also because of its surrounding globular clusters dense, tightly packed groups of gravitationally bound stars that orbit galaxies. Over 150 of these clusters orbit our own galaxy, the Milky Way, all composed of old stars.

All the globular clusters around a certain galaxy form at approximately the same time, giving them all the same age. This is echoed within the clusters all the stars within a single cluster form at around the same time, too. Because of this, most galaxies have cluster populations of pretty similar ages, both in terms of overall cluster, and individual stars. However, PGC 6240 is unusual in that its clusters are varied while some do contain old stars, as expected, others contain younger stars which formed more recently.

The most likely explanation for both the galaxy’s stacked shell structure and the unexpectedly young star clusters is that PGC 6240 merged with another galaxy at some point in the recent past. Such a merger would send ripples through the galaxy and disrupt its structure, forming the concentric shells of material seen here. It would also ignite a strong burst of star formation in the galaxy, which would then trigger similar activity in nearby space leading to the creation of new, younger globular clusters around PGC 6240.

PGC 6240 is an elliptical galaxy in the southern constellation of Hydrus (The Water Snake). Also visible in this region are numerous background galaxies, speckled across the sky behind PGC 6240. Even though these bodies are at such vast distances from us, it is possible to make out the structure of many of the galaxies, especially the small spirals that stand out colourfully against the dark sky.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

###

Notes

[1] Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public. The competition is now closed, and the list of winners is available here: http://www.spacetelescope.org/announcements/ann1211.


More information

The Hubble Space Telescope is a project of international cooperation between
ESA and NASA.


Links

Images of Hubble – http://www.spacetelescope.org/images/archive/category/spacecraft/

Hubble’s Hidden Treasures – http://www.spacetelescope.org/projects/hiddentreasures/contest/


Contacts

Nicky Guttridge

Hubble/ESA

Garching, Germany

Tel: +44-75-1231-8322

Email: nguttrid@partner.eso.org



[ Back to EurekAlert! ]

[

| E-mail

| Share Share

]

 

AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert! system.


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