Starship Asterisk*

Jean-Loup Bertaux wrote:
it seems that the link activated when clicking on "what heavy elements formed, " is not appropriate. (identify an obsject in the sky). You may rectify it. There was an APOD image some days ago about the origin of gold element, I assume that it should rather be this one.

• Blame it on the kilonova with its magic spell
  Blame it on the kilonova that they did so well
  Oh, it all began with just one little dance
  But then it ended up a big romance
  Blame it on the kilonova
  The dance of love
  
  (Now was it the moon?)
  No, no, the kilonova
  (Or the stars above?)
  No, no, the kilonova
  (Now was it the tune?)
  Yeah, yeah, the kilonova
  (The dance of love)

sillyworm2 wrote:
Would the Explosion have been as easily noticed had this Lenticular Galaxy NOT appear to us FACE on?

neufer wrote:

Chris Peterson wrote:

Guest wrote: I thought the propagation speed (velocity) of both, esp light, were the same regardless of circumstances.

Theory tells us that they should have the same propagation speed. This is the first time it's been tested, and the two speeds were "similar", as in yielding values that are very close and have overlapping error bars. This supports, but obviously does not prove that the propagation speeds are the same.

One could argue that the first indirect observation of gravitational radiation by Hulse & Taylor in 1974
was also a crude indirect measurement of the propagation speed of gravitational waves (c_g)
since the radiation loss itself depends on (c_g)^-6.

Chris Peterson wrote:

Guest wrote:
I thought the propagation speed (velocity) of both, esp light, were the same regardless of circumstances.

Theory tells us that they should have the same propagation speed. This is the first time it's been tested, and the two speeds were "similar", as in yielding values that are very close and have overlapping error bars. This supports, but obviously does not prove that the propagation speeds are the same.

https://en.wikipedia.org/wiki/Hulse%E2%80%93Taylor_binary wrote:

[b][color=#0000FF]Orbital decay of PSR B1913+16[/color][/b]

---

<<PSR B1913+16 (also known as PSR J1915+1606, PSR 1913+16, and the Hulse–Taylor binary after its discoverers) is a pulsar (a radiating neutron star) which together with another neutron star is in orbit around a common center of mass, thus forming a binary star system. PSR 1913+16 was the first binary pulsar to be discovered. It was discovered by Russell Alan Hulse and Joseph Hooton Taylor, Jr., of the University of Massachusetts Amherst in 1974.

Using the Arecibo 305m antenna, Hulse and Taylor detected pulsed radio emissions and thus identified the source as a pulsar, a rapidly rotating, highly magnetized neutron star. The neutron star rotates on its axis 17 times per second; thus the pulse period is 59 milliseconds. After timing the radio pulses for some time, Hulse and Taylor noticed that there was a systematic variation in the arrival time of the pulses. Sometimes, the pulses were received a little sooner than expected; sometimes, later than expected. These variations changed in a smooth and repetitive manner, with a period of 7.75 hours. They realized that such behavior is predicted if the pulsar were in a binary orbit with another star, later confirmed to be another neutron star. Pulses from the companion neutron star have not been detected, but this might only be the result of an unfavorable viewing angle.

The pulses from the pulsar arrive 3 seconds earlier at some times relative to others, showing that the pulsar’s orbit is 3 light-seconds across, approximately two-thirds of the diameter of the Sun. Since this is a binary system, the masses of the two neutron stars can be determined, and they are each around 1.4 times the mass of the Sun. Observations have shown that the pulsar’s orbit is gradually contracting, which is generally understood to be evidence for the emission of energy in the form of gravitational waves, as described by Einstein’s theory of general relativity, causing the pulsar to reach periastron slightly early. Also, periastron advances 4° per year in longitude due to the gravitational field (thus the pulsar’s periastron moves as far in a day as Mercury’s moves in a century).>>

Guest wrote:

the similarity of the speeds of gravitational radiation and light

I thought the propagation speed (velocity) of both, esp light, were the same regardless of circumstances. Is the speed of light not a constant?

Jim Leff wrote:

alcor wrote:You can argue about when a star is truly a star, but I define them as stars so long they emit electromagnetic radiation themselves without any help from the outside.

By that strict definition, I believe you'd need to consider Jupiter a star.....

alcor wrote:You can argue about when a star is truly a star, but I define them as stars so long they emit electromagnetic radiation themselves without any help from the outside.

Guest3 wrote:The Galactic Home of a Historic Explosion. NOT AN HISTORIC! An is only used when preceding a word that begins with a vowel sound.

dirt farmer wrote:
Information about the system under observation indicates it is 130 million light years away. Are we just now seeing something that happened that long ago?

Wadsworth wrote:

Guest3 wrote:
The Galactic Home of a Historic Explosion. NOT AN HISTORIC! An is only used when preceding a word that begins with a vowel sound. For example: An abuse of the English language.

Funny, I read it as 'a' when I read the title, but noticed the author used 'an' shortly thereafter. 'A' is probably best, but either will work.

See: http://www.betterwritingskills.com/tip-w005.html

http://www.pearsonlongman.com/ae/azar/grammar_ex/message_board/archive/articles/00053.htm wrote:
<<Historically speaking, according to The American Heritage Dictionary of the English Language (Houghton Mifflin, 1996), "an was once a common variant before words beginning with h in which the first syllable was unstressed; thus, 18th-century authors wrote either a historical or an historical but a history, not an history." By 1926, H. W. Fowler (Modern English Usage) regarded the continued use of an before such words as pedantic. Nowadays it survives primarily before the word "historical"; one rarely encounters a reference to "an hysterectomy" or "an hereditary trait."

Apparently using a or an before the h- of the unstressed syllable of a few words is at the discretion of the speaker or writer. Some people say a historic time, others say an historic time; some say a hotel, others say an hotel; some say a hysterical child, others an hysterical child.>>

http://grammartips.homestead.com/historical.html wrote:
A Historical? An Historical?
by Tina Blue

<<The problem is that the h is a bit of a wuss as a consonant. When it occurs in an unaccented syllable and is followed by a vowel, it tends to soften to a vowel-like mushiness.

[N]ow say these words out loud: historian, historical, hysterical, heredity, habitual.

Do you notice how much less, well, pronounced the h is in these words? Now, put a or an before each one (the adjectives should be paired with nouns so you can get the full effect):

• a historian / an historian
  a historical reference / an historical reference
  a historic occasion / an historic occasion
  a hysterical display / an hysterical display
  a hereditary disease / an hereditary disease
  a habitual liar / an habitual liar

Notice that when you use a before the words, you fully aspirate the h, but when you use an, you do not--and the h sound very nearly disappears into the following vowel.

So here's the general rule.

If you speak and write British English, you can probably keep using an before historical, hysterical, habitual, etc. I doubt that you will be challenged by your own countrymen, and if Americans challenge you, just point out that British usage and American usage often differ.

If you are American, you probably should use a rather than an, even in a historic occasion or a historical reference. Most of us are comfortable with a historic occasion, because the word historic has fewer syllables than historical, so the h is more fully pronounced. But if, like me, you are old enough to find a historical reference a tad uncomfortable, then go ahead and say an historical reference. >>

Guest3 wrote:The Galactic Home of a Historic Explosion. NOT AN HISTORIC! An is only used when preceding a word that begins with a vowel sound. For example: An abuse of the English language.

heehaw wrote:

Guest wrote:

the similarity of the speeds of gravitational radiation and light

I thought the propagation speed (velocity) of both, esp light, were the same regardless of circumstances.
Is the speed of light not a constant?

I sure think so, but you never know, and it is good to test, and make sure! Some have doubts about c : http://backreaction.blogspot.com

Guest wrote:

the similarity of the speeds of gravitational radiation and light

I thought the propagation speed (velocity) of both, esp light, were the same regardless of circumstances. Is the speed of light not a constant?

the similarity of the speeds of gravitational radiation and light

Ann wrote:
The kilonova was blue when it exploded, like many supernovas, and then faded to red.