Supernova in M82
Posted 22 January 2014 - 08:38 AM
last night, a new possible supernova in M82 has been observed. Currently it has already a brightness of 11.7mag.
"2014 01 22.3955
L. Elenin (Lyubertsy, Russia) and I. Molotov (Moscow, Russia) confirm an apparent supernova PSN J09554214+6940260 in M82. Object visible on 4 (BVRI) images remotely taken at ISON-NM Observatory (Mayhill, NM, USA) with 0.4-m f/3 telescope + CCD (KAF09000) on Jan. 22.3955, 2014. Object located at 09h 55m 42s.15 +/- 0".13, +69d 40' 25".8 +/- 0".11 (UCAC-4) with magnitudes 12.91B (22.3955); 11.72V (22.4101); 11.31R (22.4061); 11.33I (22.4066). Nothing is visible at this position on the archive POSS and POSSII images. Image of PSN J09554214+6940260 available at http://spaceobs.org/...60-20140122.png"
Further info as well here: PSN J09554214+6940260
P.S. I'm not sure whether this post is in the correct sub-forum. Dear Moderators, please move appropriately.
Posted 22 January 2014 - 09:39 AM
Posted 25 January 2014 - 06:41 AM
Posted 28 January 2014 - 06:05 PM
Posted 28 January 2014 - 07:28 PM
Nova - thermonuclear reaction in the outer layer of a white dwarf which is accreting material from a close binary companion. The core of the star is not affected. Much of the accreted material is blown off in the outburst but accretion continues & will eventually repeat.
So what is the difference between a nova and a Type Ia supernova?
Supernova (type 1a) - accretion raises the mass of a white dwarf above the Chandrasekhar limit, the whole core collapses, some forms a neutron star & some reacts to "heavy" elements (mostly silicon & iron group) which are ejected into interstellar space. (In fact a large part of the reaction is Si(28) fusing to Ni(56) which decays to Co(56) then to Fe(56). The half lives of the Ni->Co and Co->Fe beta decay reactions can be seen in the light curve.)
There are other types of supernova but all result in the destruction of the star's core or its conversion to nuclearly inert material (neutron star or black hole) so a SN event occurs at most once in the life of a star.
Supernovae are very much more luminous than ordinary novae. SN can be detected at huge distances - out to the edge of the observable universe, with modern observatory equipment - whereas ordinary novae can be detected only in nearby (local group) galaxies.
Posted 28 January 2014 - 09:01 PM
Posted 29 January 2014 - 06:13 AM
Posted 29 January 2014 - 06:21 AM
I'm not sure on this. I thought "magnetars" were a special class of white dwarf where the magnetic field strength is such that accreting material is funnelled down onto the magnetic poles rather than forming an accretion disk around the (spin axis) equator.
Neutron stars are just plain weird from the what I can gather, any explanation as what takes them into Magnetar territory. Is that simply a product of the mass of original star?
Neutron stars - being much smaller - have far more concentrated magnetic fields & as far as I know would all be "extreme magnetars" - the (magnetic) polar jets cause the pulsar phenomenon - a pulsar is just a neutron star which has not yet lost its angular momentum, and whose magnetic axis sweeps across our line of sight closely enough for us to observe the variation. As far as I know.
Posted 29 January 2014 - 10:52 AM
Posted 29 January 2014 - 01:47 PM
Unless the our knowledge of quantum electrodynamics is completely wrong, once a neutron star gets massive enough it has no choice other than to collapse to a singularity. There is no degeneracy pressure strong enough to halt the collapse.
a mass more than that which would form a neutron star/pulsar, but not quite big enough to form a singularity.
But please note that the outer layer of a neutron star will always consist (mostly) of iron - at the surface the pressure isn't enough to crush electrons into the atomic nuclei so atoms will exist to a depth where the pressure becomes large enough to overcome electron degeneracy. That iron shell will serve to provide the potential for huge magnetic fields, and the existing magnetic field of the progenitor star will be largely conserved during the collapse so that the magnetic fields will be much more concentrated at the surface of a neutron star (radius a few km) than they would be in a white dwarf (radius a few thousand km) or a normal main sequence star (radius of the order of a million km).
Posted 29 January 2014 - 05:45 PM
Posted 30 January 2014 - 08:16 AM
Posted 30 January 2014 - 10:35 AM
Posted 30 January 2014 - 04:22 PM
As far as I am aware it is believed that in type 1a supernova the star is completely destroyed. (As the star reaches the Chandrasekar limit, the impending collapse increases the temperature to the point where runaway C and O fusion takes place throughout the star and the star explodes leaving nothing behind)