Starship Asterisk*

neufer wrote: ↑Thu Oct 31, 2019 8:20 pm

• "Yesterday, upon the stair,
  I met a man who wasn't there!
  He wasn't there again today,
  Oh how I wish he'd go away!"

Wikipedia wrote:

Geminga /ɡəˈmɪŋɡə/ is a neutron star approximately 250 parsecs[1] (around 800 light years) from the Sun in the constellation Gemini. Its name, attributed by its discoverer Giovanni Bignami, is both a contraction of Gemini gamma-ray source, and a transcription of the words gh'è minga (pronounced [ɡɛ ˈmĩːɡa]), meaning "it's not there" in the Milanese dialect of Lombard.

Dark Matters wrote: ↑Thu Oct 31, 2019 6:48 pm
So was anything left behind where the star used to be?
A neutron star or black hole? Would they be visible?

https://en.wikipedia.org/wiki/Veil_Nebula wrote:
<<The Veil Nebula constitutes the visible portions of the Cygnus Loop, a supernova remnant.

The Cygnus Loop source supernova was a star 20 times more massive than the Sun, which exploded around 8,000 years ago.>>

https://en.wikipedia.org/wiki/Sanduleak_-69_202 wrote:
<<Sanduleak -69 202 (Sk -69 202, also known as GSC 09162-00821) was a magnitude 12 blue supergiant star [~20 times more massive than the Sun], located on the outskirts of the Tarantula Nebula in the Large Magellanic Cloud. It is notable as the progenitor of supernova 1987A.>>

https://en.wikipedia.org/wiki/SN_1987A wrote:
<<SN 1987A appears to be a core-collapse supernova, which should result in a neutron star given the size of the original star. The neutrino data indicate that a compact object did form at the star's core. However, since the supernova first became visible, astronomers have been searching for the collapsed core but have not detected it. The Hubble Space Telescope has taken images of the supernova regularly since August 1990, but, so far, the images have shown no evidence of a neutron star. A number of possibilities for the 'missing' neutron star are being considered. The first is that the neutron star is enshrouded in dense dust clouds so that it cannot be seen. Another is that a pulsar was formed, but with either an unusually large or small magnetic field. It is also possible that large amounts of material fell back on the neutron star, so that it further collapsed into a black hole. Neutron stars and black holes often give off light as material falls onto them. If there is a compact object in the supernova remnant, but no material to fall onto it, it would be very dim and could therefore avoid detection. Other scenarios have also been considered, such as whether the collapsed core became a quark star.>>

• "Yesterday, upon the stair,
  I met a man who wasn't there!
  He wasn't there again today,
  Oh how I wish he'd go away!"

GeoX wrote: ↑Thu Oct 31, 2019 11:15 am

golfgod65 wrote: ↑Thu Oct 31, 2019 10:24 am If the nebula is 1,500 light years away, how could the light from the supernova get here 5,000 years ago?

The light from the supernova reached us 5,000 years in the past. Thus that would make the explosion 6500 years old. We are seeing it now as it was 1,500 years in our past or 5,000 years after the original star went supernova.

golfgod65 wrote: ↑Thu Oct 31, 2019 10:24 am
If the nebula is 1,500 light years away, how could the light from the supernova get here 5,000 years ago?

golfgod65 wrote: ↑Thu Oct 31, 2019 10:24 am If the nebula is 1,500 light years away, how could the light from the supernova get here 5,000 years ago?