Starship Asterisk*

• King Henry VI, part III : Act II, scene II

• To make this shameless callet know herself.

Mtnrockdhh wrote:The north (left) tip of the Witch's Broom?

Chris Peterson wrote: Useful additional information.

APOD Robot wrote: ... Wisps like this are all that remain visible of a Milky Way star.

MarkBour wrote:

APOD Robot wrote: ... Wisps like this are all that remain visible of a Milky Way star.

When today's APOD says "visible", I think they are distinguishing this easy-to-see material from the hard-to-see central X-ray source, Cygnus X-1 ... which is widely believed to be a stellar mass black hole. https://en.wikipedia.org/wiki/Cygnus_X-1.

Ann wrote:Is there a lot of X-rays in the Veil Nebula?

bjmb wrote:splendid picture, but somewhat sloppy caption> 'Wisps like this are all that remain visible of a Milky Way star. About 7,000 years ago that star exploded in a supernova leaving the Veil Nebula. At the time, the expanding cloud was likely as bright as a crescent Moon, remaining visible for weeks to people living at the dawn of recorded history.' scientifically exact would be: 'Wisps like this are all that remain visible of a Milky Way star. About 7,000 years ago that star's explosion in a supernova became visible on earth, leaving the Veil Nebula. At the time, the expanding cloud was likely as bright as a crescent Moon, remaining visible for weeks to people living at the dawn of recorded history.' the explosion itself was of course dusted and done 7,000 years ago

Chris Peterson wrote:
We don't care when the explosion "actually" happened. What is relevant is when the light reached Earth. This is almost always true, and almost always the way things are dated astronomically. It is normal to treat the date of occurrence as the date of observation.

https://en.wikipedia.org/wiki/Spacetime wrote:
In four-dimensional spacetime, the analog to distance is the spacetime interval Δs:

---

The spacetime interval Δs between any two events is independent
of the inertial frame of reference in which they are recorded.

neufer wrote:

Chris Peterson wrote:
We don't care when the explosion "actually" happened. What is relevant is when the light reached Earth. This is almost always true, and almost always the way things are dated astronomically. It is normal to treat the date of occurrence as the date of observation.

It's not that we don't care...
it's simply that we don't know precisely when the explosion "actually" happened.

Rules For wrote:Does anybody know what's happened to Hubble Heritage? They used to put out a new image every month, but it's been awhile.

Ann wrote:

MarkBour wrote:

APOD Robot wrote: ... Wisps like this are all that remain visible of a Milky Way star.

When today's APOD says "visible", I think they are distinguishing this easy-to-see material from the hard-to-see central X-ray source, Cygnus X-1 ... which is widely believed to be a stellar mass black hole. https://en.wikipedia.org/wiki/Cygnus_X-1.

Click to view full size image

Cygnus X-1 and the Tulip Nebula.
Photo: Neil Fleming.

Please note that Cygnus X-1 is not the central source, X-ray or otherwise, of the Veil Nebula. (Is there a lot of X-rays in the Veil Nebula?)

Ann

MarkBour wrote:
If Cygnus X-1 is in the wrong location, then is there another black hole in about the right place? Cygnus X-5, perhaps?

Wikipedia wrote:

The X-ray source Cygnus X-5 coincides with SNR G074.0-08.6 (the Cygnus Loop), located at J2000 RA 20h 51.1m Dec +30° 41′, observed by Uhuru at 4U 2046+31. This source also has catalogue numbers 1E 2049.4+3050, 1H 2050+310, and 1M 2051+309, having been observed by the Einstein Observatory, HEAO 1, and OSO 7, respectively.
The Cygnus Loop is a strong source of soft X-rays.