RAS Meeting Friday 10th October 10:30
John Murrell
The next RAS meeting ‘Celebrating Ten Years of Cassini-Huygens in the Saturnian System’ looks quite intersting and not too technical see https://www.ras.org.uk/component/gem/?id=297 .
There is an entry fee of £15 for non-RAS members reduced to £5 if you have a valid student card.
RAS meetings are held on the second Friday of most months starting around 10:00 or 10:30 they are followed by the RAS general meeting that finishes around 18:00.
Regards
John Murrell FRAS
John Murrell
The talk by Professor Andreas Burkert (Munich) (Presidant of the German Astronomical Society) was very interesting. I did not realise there were so many mysteries about the centre of our Galaxy and the gas cloud (G2) that is being shredded by the Black Hole. Amongst the unsolved points are:
1. To get the X-Ray Emission & Radio emission from Sag A* requires 30 to 50 Supernova to explode in the local area in the last few 10’s of million years. It is not clear where they came from or why they exploded at the ‘same’ time.
2. The density of stars close to the center is very high I think he said 1 million in a cubic parsec.
3. The inner stars that are orbiting the Black Hole ( numbered S1 upwards) are all O type stars
4. These stars cannot have formed where the stars are now as the radiation from the SN in 1 above and the tidal forces would have disrupted the gas clouds before the stars formed.
5. Outside the central area where the O stars orbit ( I can’t remember the size) there is a torus or disc of B stars that cannot have formed there due to the tidal forces.
6. The Gas cloud that is at present being torn apart by the Black Hole has an orbital period of 391 years and was therefore at the furthest from the BH in about 1820. It cannot have formed there and even if it had it cannot have got to where it is now without the tidal forces destroying it
7. Another gas cloud has now been observed following G2 ( I think it is G2a). It is not clear where that has come from or if it is going to follow G2 into orbit around the Black Hole.
8. While a lot of people are watching for flaring from the black hole due to Gas influx the speakers view is that we may have to wait several years until the gas losses some of it’s angular momentum.
In all a very confusing picture.
The RAS were filming the talk so it might be published online in due course.
Regards
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John Murrell
There is an article on the S&T website (published 16/10/14) which makes many of the same points on gas cloud G2 see http://www.skyandtelescope.com/astronomy-news/g2-survives-black-hole-pass-10162014/?et_mid=698485&rid=246424110
Remember the news was here first !
John Murrell
There is an interesting update on the trip of the gas cloud G2 around the Super massive black hole in the centre of the Milky Way.
It appears that the gas cloud G2 is not a gas cloud after all but is a very much more massive proto star. This partly explains why the gas cloud was not shredded on it’s close pass to the black hole. The press release from the ESO is here http://www.eso.org/public/news/eso1512/ , there is a link to the full paper here http://www.eso.org/public/archives/releases/sciencepapers/eso1512/eso1512a.pdf.
In some ways this leaves even more unexplained principally why it was seen to be shredding in the earlier observations and why the earlier mass estimate was around 3 solar masses – it has now grown. It must be quite massive to be seen as the other ‘S’ stars are all ‘O’ type stars.
Any comments ?