Hubble views lenticular galaxies PGC 10922 and NGC 524

Lenticular Galaxy
This great image was made by Judy Schmidt for the Hubble’s Hidden Treasures image processing competition:

Seen face-on, the image shows the disc and tightly-wound spiral structures of dark dust encircling the bright centre of the galaxy. There is also a remarkable outer halo of faint wide arcs or shells extending outwards, covering much of the picture. These are likely to have been formed by a gravitational encounter or even a merger with another galaxy. Some dust also appears to have escaped from the central structure and has spread out across the inner shells.

Lenticular galaxies are rare objects and there is a chance that they represent some particular stage on the way from a spiral galaxy – which always contain star-forming material – to an old, red elliptical galaxy, which contains mostly red giants and has literally ran out of gas. Or, as suggested above, they are indeed some kind of stable state reached after the interaction of maybe two spirals or a spiral and an elliptical. In the case of a merger, as readers know well, somewhere down the line the gas content of the galaxy will be compressed and star formation will be triggered. One day, I’ll write more about how the Universe might evolve and how spiral galaxies will become increasingly rare, as on mighty timescales all the material for star formation is slowly consumed into condensed stellar remnants and black holes, as what is becoming known as the “stelliferous era” draws to a close. The only galaxies existing then will likely be irregular swarms of trillion year old red dwarfs surrounding black holes and neutron stars undergoing increasingly frantic dynamical and tidal interactions and mergers, if the timescales involved can possibly be described as frantic…

For now I prefer to perform my more familiar condensation of brown dwarf and planet-related matters. There has been much of the possible “water world” GJ 1214 b and some difference in academic opinion in which both sides are represented over at Astrobiology magazine. In the first, a new theory might indicate the planet has a deep H/He-rich atmosphere after all, while at the same time, there is new observational evidence for a thin (relatively to the depth of a gas giant atmosphere) water-rich layer. Elsewhere, in a highly impressive synthesis of knowledge made possible by a homogeneous mid-infrared astrometry dataset, Trent J. Dupuy and Adam L. Kraus have done the job on the first batch of sixteen Y dwarfs, where the effects of age and metallicity on spectral type start to become nearly as noticeable as those of temperature (paper in Science). At the same time, a seventeenth Y dwarf has been discovered, and it is of remarkably low mass and extremely red. Its apparent magnitude in the J-band (1.2 microns) is 22.7. This is maybe 7 or 8 magnitudes fainter than a regular field mid-L dwarf which is substellar regardless of age. To finish, the A8 star planet host HD 95086 looks like it has a disk as well (arXiv) and the GJ 504 b discovery paper is published in ApJ.

To more miscellaneous matters – just to remind us how weird were the aerial refractors of Hevelius and the like in the late 1600s, J. Lozi et al., have analyzed Cassini’s still extant lenses and established that he would have indeed been able to see his famous division. I have observed this feature of Saturn’s rings with a very good antique (1883) 4 inch refractor of 1500 mm focal length in good seeing, but never with a more commercial 3 inch refractor of the 1980s. Finally, we have to have some loop quantum gravity, and I also want to recommend Nautilus, a new and exciting looking online science magazine. One article there is a great introduction to the quantum graininess thought to describe the Planck length, a concept of “stochastic space-time“.

Lenticular Galaxy


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