Search found 66 matches

by RJ Emery
Tue Jun 14, 2016 3:56 am
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: APOD: NGC 6888: The Crescent Nebula (2016 Jun 10)
Replies: 15
Views: 7712

Re: APOD: NGC 6888: The Crescent Nebula (2016 Jun 10)

... ultimately go out with a bang in a spectacular supernova explosion.
Since this object has been studied, what type of supernova will be its end game?
by RJ Emery
Mon May 30, 2016 10:02 pm
Forum: Open Space: Discuss Anything
Topic: Moon's Positioin During Interplanetary Spacecraft Launches
Replies: 2
Views: 1271

Moon's Positioin During Interplanetary Spacecraft Launches

When rockets are launched from Cape Canaveral for destinations beyond earth's orbit, I am curious to know the position of the moon at such times. The moon has a gravitational sphere of influence, and so I would expect launches are scheduled when the moon is opposite the space center to minimize the ...
by RJ Emery
Mon May 30, 2016 9:51 pm
Forum: The Library: Information Desk and Educational Resources
Topic: Book Recommendations for Spaceflight
Replies: 0
Views: 40247

Book Recommendations for Spaceflight

I seek book recommendations that would quantitatively cover spaceflight, i.e., with equations and data tables. Of particular interest is interplanetary transfers and time of flight.
by RJ Emery
Mon May 30, 2016 9:43 pm
Forum: Open Space: Discuss Anything
Topic: Timing of Mars Space Probe Launches
Replies: 21
Views: 4069

Re: Timing of Mars Space Probe Launches

When the Mars Global Surveyor reached it's destination it was traveling approximately 5KPS faster than Mars' relative velocity. To achieve orbit insertion and be successfully captured by Mars' Gravity Well the orbiter needed to shed about 1KPS of speed which required sufficient fuel for a 20 to 25 ...
by RJ Emery
Sat May 28, 2016 3:00 am
Forum: Open Space: Discuss Anything
Topic: Timing of Mars Space Probe Launches
Replies: 21
Views: 4069

Re: Timing of Mars Space Probe Launches

geckzilla, Yes, physics IS physics, but I have no way of validating and verifying the accuracy of the Kerbal program. With the programs used by NASA and/or JPL, they are of course very well vetted, certainly not cartoonish and probably applicable for all the planets including return voyages. Neverth...
by RJ Emery
Sat May 28, 2016 2:31 am
Forum: Open Space: Discuss Anything
Topic: Timing of Mars Space Probe Launches
Replies: 21
Views: 4069

Re: Timing of Mars Space Probe Launches

geckzilla,

Thanks, but I would be more interested in the programs NASA or JPL use for interplanetary exploration.
by RJ Emery
Sat May 28, 2016 1:36 am
Forum: Open Space: Discuss Anything
Topic: Timing of Mars Space Probe Launches
Replies: 21
Views: 4069

Re: Timing of Mars Space Probe Launches

Chris, I appreciate your response, but it still does not make sense to me. It should take the same amount of energy to lift the spacecraft and put it on its trajectory to Mars, whether it coasts for 7 months and 300 million miles or much longer. The time spent coasting to its Mars rendezvous is pres...
by RJ Emery
Fri May 27, 2016 11:50 pm
Forum: Open Space: Discuss Anything
Topic: Timing of Mars Space Probe Launches
Replies: 21
Views: 4069

Timing of Mars Space Probe Launches

It has been reported that the window of opportunity to launch a space probe from Earth to Mars occurs every 26 months, owing to the amount of rocket fuel able to propel a spacecraft to Mars. I do not understand why. Once a spacecraft is sent on its way to rendezvous with Mars, I presume there will b...
by RJ Emery
Wed Jan 20, 2016 1:44 am
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: APOD: 2005 October 25 - Supernova Remnant N132D
Replies: 6
Views: 1552

APOD: 2005 October 25 - Supernova Remnant N132D

APOD: 2005 October 25 - Supernova Remnant N132D in Optical and X Rays http://apod.nasa.gov/apod/ap051025.html In the description for the referenced APOD, it was written "The expanding shell from this explosion now spans 80 light-years and has swept up about 600 Suns worth of mass." I do no...
by RJ Emery
Tue Sep 02, 2014 2:09 pm
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: APOD: Airglow Ripples over Tibet (2014 Sep 01)
Replies: 26
Views: 42630

Re: APOD: Airglow Ripples over Tibet (2014 Sep 01)

What are the colorful objects in the foreground?
by RJ Emery
Tue Jun 22, 2010 8:54 pm
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Where New Horizons is
Replies: 606
Views: 545696

New Horizons Mission

Is the New Horizons mission just a flyby of Pluto, or will the probe attempt some kind of orbit? If it just a flyby, what will New Horizons do, if anything, for its remaining life in space?
by RJ Emery
Sun Oct 25, 2009 6:00 am
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Galactic Capture by Milky Way
Replies: 4
Views: 691

Re: Galactic Capture by Milky Way

I believe the Canis Major Dwarf Galaxy is the one. Its discovery is more recent, and I do recall the galaxy I have in mind is on the other side of the galactic plane. Thank you for the pointer.
by RJ Emery
Sun Oct 25, 2009 5:04 am
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Galactic Capture by Milky Way
Replies: 4
Views: 691

Galactic Capture by Milky Way

At some point in the last few years, I remember reading of evidence that our Milky Way galaxy is currently in the process of capturing and assimilating a satellite galaxy, the task almost completed. Can anyone provide a reference to same?
by RJ Emery
Wed May 16, 2007 8:39 pm
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: Dark Matter Ring (APOD 16 May 2007)
Replies: 26
Views: 10182

sacolton wrote:So, is this kinda like a black hole? Aren't black holes and dark matter the same?
No.
by RJ Emery
Wed May 16, 2007 2:25 pm
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: Dark Matter Ring (APOD 16 May 2007)
Replies: 26
Views: 10182

Dark Matter Ring (APOD 16 May 2007)

APOD for 5/16/07 ( http://antwrp.gsfc.nasa.gov/apod/ap070516.html ) shows a simulated dark matter ring around Galaxy Cluster CL0024+17. The work is the product of Jee and Ford, et al, of Johns Hopkins University. In a separate NY Times article at http://www.nytimes.com/2007/05/16/science/space/16hub...
by RJ Emery
Fri Mar 16, 2007 10:08 pm
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Black Holes From Assimilated Galaxies
Replies: 9
Views: 3968

Is it a given that every galaxy has a black hole? I hadn't thought that to be generally agreed upon. I think the consensus is that all galaxies have a black hole at their center. Recently, a supermassive black hole was discovered in a dwarf galaxy. See Even Dwarf Galaxies Have Supermassive Black Ho...
by RJ Emery
Fri Mar 16, 2007 8:13 pm
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Black Holes From Assimilated Galaxies
Replies: 9
Views: 3968

Black Holes From Assimilated Galaxies

The April, 2007, issue of Scientific American contains an interesting article on dwarf galaxy assimilation by the Milky Way (MW) Galaxy. The article is entitled "The Ghosts of Galaxies Past" by Ibata and Gibson, pp. 40-45. The article documents streams of stars in and around our home galax...
by RJ Emery
Mon Feb 26, 2007 9:31 am
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: Observational Effects - Exploding Russian Rocket (26 Feb 07)
Replies: 3
Views: 2323

Observational Effects - Exploding Russian Rocket (26 Feb 07)

By now, most Australians who wondered what had happened in the skies above them know it was an exploding Russian rocket stage. The debris field seems to include a gas cloud of spent fuel, no doubt expanding as it disperses. I wonder how such a field affects astronomical observations, especially spec...
by RJ Emery
Mon Feb 19, 2007 11:58 pm
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Mini-Black Holes and Stars Winking Out
Replies: 91
Views: 23590

So suppose an astronomy professor has a grad student he doesn't particularly enjoy spending time with...give him this as a straightforward project to make a dissertation out of, using existing data. If no other researchers are interested in the results, no major loss. If they are, the prof gets som...
by RJ Emery
Sun Feb 18, 2007 1:57 pm
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Mini-Black Holes and Stars Winking Out
Replies: 91
Views: 23590

I see you're pretty familiar with much of this ... My knowledge base is very incomplete. Also, Woosley's work of which I wrote is more than ten years old. I have not had an update since, and I am sure he and the field has not stood idly by. I just read what I can when I can. By no means, do I claim...
by RJ Emery
Sat Feb 17, 2007 10:12 pm
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Mini-Black Holes and Stars Winking Out
Replies: 91
Views: 23590

* Some people maintain rather fantastically that the 1908 Tunguska blast over Siberia was actually a mini-black hole passing clean through the earth. It's generally believed to have been a comet disintegrating rapidly in midair. Yes, I read that, too. I accept the more prosaic explanation until pro...
by RJ Emery
Sat Feb 17, 2007 3:24 pm
Forum: The Asterisk Café: Discuss Anything Astronomy Related
Topic: Mini-Black Holes and Stars Winking Out
Replies: 91
Views: 23590

Mini-Black Holes and Stars Winking Out

Isaac Asimov, in his 1979 book A Choice of Catastrosphes: The Disasters That Threaten Our World , raised the possibility that mini-black holes created with the Big Bang may burrow into stars and cause them to wink out (pp. 92-96). Stephen Hawking in 1974 suggested that (to quote Asimov) "... in...
by RJ Emery
Mon Feb 12, 2007 5:37 pm
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: Comet McNaught Over New Zealand (APOD 12 Feb 2007)
Replies: 14
Views: 8092

bystander wrote:We can't see all of the one at the upper edge of the photo. I believe that one is the LMC. The one in full view is the SMC. IMHO
I think you have it nailed.
by RJ Emery
Mon Feb 12, 2007 4:21 pm
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: Comet McNaught Over New Zealand (APOD 12 Feb 2007)
Replies: 14
Views: 8092

... My bet is that we have no only the Milky Way; Comet McNaught; and a meteor: but also the LMC and SMC. :) Orin Ah, but which is which? Would not the larger (and lower one) of the two smudges be the LMC? FWIW, according to Wikipedia, the LMC is 168,000 ly away, and the SMC is 197,000 ly away. I s...
by RJ Emery
Mon Feb 12, 2007 7:53 am
Forum: The Bridge: Discuss an Astronomy Picture of the Day
Topic: Comet McNaught Over New Zealand (APOD 12 Feb 2007)
Replies: 14
Views: 8092

I, too, would be interested in the answer to Orin's question, but I would also ask about the slightly more diffused patch at the photo's top edge directly above Orin's unidentified feature.