Astronomy Picture of the Day 1-01-03

Explanation: Ten thousand years ago, before the dawn of recorded human history, a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star and record the colorful expanding cloud as the Veil Nebula. Pictured above is the west end of the Veil Nebula known technically as NGC 6960 but less formally as the Witch's Broom Nebula. The rampaging gas gains its colors by impacting and exciting existing nearby gas. The supernova remnant lies about 1400 light-years away towards the constellation of Cygnus. This Witch's Broom actually spans over three times the angular size of the full Moon. The bright blue star 52 Cygnus is visible with the unaided eye from a dark location but unrelated to the ancient supernova.

Depends on where you live. If you were in the Southern Hemisphere in February 1987, you were treated to the supernova 1987A in the Large Magellanic Cloud. It reached 3rd magnitude.

Unfortunately, the last Northern Hemisphere visible supernova was seen in 1604.

Sanduleak 69-202 explodes; light reaches us in 1987.

Hubble image of the expanding shockwaves from the remnant.

Kepler's Supernova was observed in the constellation Ophiuchus on October 9th 1604, when it was already brighter than other stars (didn't anyone look up in those days?) and approaching Jupiter's brightness.

Here is a ROSAT X-ray image of the remnant:

I've researched the object mentioned in your FReepmail.

I'm of the opinion that the guy who wrote that book knows less about astrophysics than I do about the geography of Pluto.

The object in question is called 2001 KX76. It seems to be about 900 miles in diameter (this determined from estimates of distance, brightness and albedo [reflectivity]). This would make it larger than Pluto's moon Charon but smaller than Pluto itself.

A brown dwarf has to have, let's say, 20 times JUPITER'S mass. You can't compress that kind of real estate into a 900-mile-diameter sphere without some special conditions. Those conditions don't exist unless nuclear fusion is present - most definitely NOT found in a brown dwarf.

So the amount of mass in 2001 KX76 is limited. That we can observe from its orbit and perturbations. You see, the author of that book you mentioned forgot about the inverse square law. The gravitational pull of an object decreases as a square of the increasing distance. Thus if an object is twice as far away, its gravitational influence is four times weaker, three times farther is nine times weaker, etc. This is why the moon raises higher ocean tides than the sun. Moon is so much smaller but so much closer. Now, if all the moon does at its nearby location is raise tides, how is a 900-mile-wide chunk of rock whizzing by at a much greater distance going to do worse?

But then I'm just an amateur. For knowledgable details the FReeper to ask is Physicist. I'm willing to bet he's written a paper on this or knows someone who has.

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