Starship Asterisk*

by **neufer** » Tue Nov 08, 2011 5:11 pm

1yioi87 wrote:
Now can you tell me how fast they are moving to complete an orbit in 172,523.78 seconds.

http://adsabs.harvard.edu/abs/1986ApJ...300..788C wrote:
The orbit of GK Persei
Crampton, D.; Fisher, W. A.; Cowley, A. P.
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 300, Jan. 15, 1986, p. 788-793.

<<New spectroscopic observations of the old nova GK Per reveal the orbital period to be 1.996803 + or - 0.000007 days. The orbit is circular and the late-type component has a semiamplitude of 124 + or - 2 km/s. The hydrogen emission lines show a velocity variation in antiphase with the absorption lines with a semiamplitude of 34 + or - 5 km/s. The most probable masses are 0.25 solar mass for the K star and 0.9 solar mass for the white dwarf. The K star has obviously lost a lot of mass and is continuing to do so. An effort should be made to obtain photometry at the predicted times of occultation to see whether the system is eclipsing in order to further define the parameters of the system.>>

by **1yioi87** » Tue Nov 08, 2011 4:38 pm

Thank you for the definition of a day. Now can you tell me how fast they are moving to complete an orbit in 172,523.78 seconds.

by **Chris Peterson** » Mon Nov 07, 2011 4:35 am

1yioi87 wrote:I find it hard to believe that this binary system has a 2 day orbital period. What does that mean? Not to sound Clintonian but seems that depends on what the meaning of DAY is. As a novice I am confused.

A day is 24 hours, so a two day orbital period means 48 hours. More precisely, the orbital period of this binary is 1.996803 days, or 47.923272 hours, or 172,523.78 seconds.

by **1yioi87** » Mon Nov 07, 2011 2:37 am

I find it hard to believe that this binary system has a 2 day orbital period. What does that mean? Not to sound Clintonian but seems that depends on what the meaning of DAY is. As a novice I am confused.

by **NoelC** » Sun Nov 06, 2011 5:16 pm

Thanks for that. I must have uncovered a glitch in the software I'm using (Cartes du Ciel), because a search for PGC 13065 led me to a field where I can see the stars shown in the APOD - a different spot from what entering the coordinates takes me to. There's a possibility one of many, many settings is wrong (i.e., my fault).

In general I found CDC version 2 to be more stable than this newer version - though to be fair it's a beta and I haven't looked for an update in a long time... Off to the intertubes...

-Noel

by **Ann** » Sun Nov 06, 2011 5:25 am

NoelC wrote:

Does the charting program you have show anything at this object's position? Assuming not much, it really makes Adam's capture of this field, in which several of the stars seem absolutely brilliant, all the more impressive!

Yes, my software, Guide, shows the position and magnitude of GK Per. Its magnitude is given as 12.7, and its position as 3 hours, 31 minutes and 12.019 seconds in right ascension and +43 54' 15.76" in declination. Some mostly 13th magnitude stars are seen close to it.

My software also says that something extended is seen around GK Per, and it gives the extended object around GK Per the designation PGC 13065. I question that designation. To me, a galaxy fan, PGC means Principal Galaxy Catalog.

Ann

EDIT: OK, I googled PGC 13065, and I got this page. Check it out. Members of Galaxy Zoo discuss the nebula around GK Per (which at least one of them calls GH Persei). The nebula itself shows up as all green in the Galaxy Zoo image, to nobody's surprise, since Ha emission always looks green through the filters used by the Sloan Digital Sky Survey, which provides the images for Galaxy Zoo.

Anyway, one of the members of Galaxy Zoo, Karma, posted this comment about the nebula:

A really interesting nova. Also, the nebula is erronously registered as a galaxy in the Principal Galaxy Catalog (as PGC 13065). Beautiful picture.

by **S_S** » Sun Nov 06, 2011 5:07 am

orin stepanek wrote:Wow; I'm glad Nov. 5 APOD came up; people were getting excited and worried! I can't say I blame them; we love our APOD!

But what happened today ? Its already 10:05 pm San Jose, CA time and today's APOD hasn't come up.
As your signature aptly said yesterday, tomorrow (which is today) is another day. APOD came up last night, not yet today .. I'll keep refreshing the page ..

by **Chris Peterson** » Sat Nov 05, 2011 11:59 pm

NoelC wrote:Does the charting program you have show anything at this object's position? Assuming not much, it really makes Adam's capture of this field, in which several of the stars seem absolutely brilliant, all the more impressive!

This is a bright target, easy to image with just a few minutes of exposure time. The brightest stars in the field are a bit dimmer than magnitude 13. By constructing most of the image from Ha data, the contribution of the stars is considerably reduced, allowing for a much longer exposure of the comparatively dimmer nebula.

Both charting programs I have installed, TheSky 6 and Cartes du Ciel, show GK Per (GCVS), as a variable star (not a nebula). So pointing a telescope at this field is straightforward enough.

by **NoelC** » Sat Nov 05, 2011 11:18 pm

You're welcome, Ann. I was hoping you'd see it.

Does the charting program you have show anything at this object's position? Assuming not much, it really makes Adam's capture of this field, in which several of the stars seem absolutely brilliant, all the more impressive!

-Noel

by **Ann** » Sat Nov 05, 2011 10:03 pm

I'm very glad to see a new image by Adam Block as the new APOD!

I agree with Noel that this is really an object which looks like an explosion in space. As for the color of the central star, it is perhaps not so surprising. The dominant contributor to the star color may well be the cool swollen companion star, but the white dwarf may also contribute. And isn't it possible that there are some gas clouds very close to the white dwarf which are strongly ionized and made to glow pink?

Thanks, Noel, for your visual assessment of the star colors. I found them very interesting and pleasing.

All in all, today's APOD is beautiful, dramatic and striking. Thanks, Adam!

Ann

by **katy** » Sat Nov 05, 2011 6:08 pm

I think it looks like a firework in the universe!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

by **NoelC** » Sat Nov 05, 2011 4:12 pm

Interesting. One of the few exploded things in space that really looks like an explosion.

The central star appears pretty reddish-orange in this image. I wonder... Is it the reflected starlight that's making the explosion fragments shine red, or are they glowing on their own, or both?

Using software to assess the colors and brightnesses of the stars in the image visually...

: Star Color Assessment

Wow, this object must be super dim! I tried to locate it on Cartes du Ciel and there's almost nothing shown there. Did I assess the position correctly?

(RA, Dec) center (H:M:S, D:M:S): (03:31:11.523, +43:54:15.416)
Field size : 6.56 x 6.56 arcminutes

-Noel

by **orin stepanek** » Sat Nov 05, 2011 4:05 pm

Wow; I'm glad Nov. 5 APOD came up; people were getting excited and worried! I can't say I blame them; we love our APOD!

by **starstruck** » Sat Nov 05, 2011 3:52 pm

Light the blue touch-paper and stand well back! . . . now, that is some squib!

by **neufer** » Sat Nov 05, 2011 3:20 pm

APOD Robot wrote:
GK Per: Nova of 1901 : Early in the 20th century, GK Persei briefly became one of the brightest stars in planet Earth's sky, an event known as Nova Persei 1901. Documented in this modern day composite of two images from 2003 and 2011 the ejecta from the explosion, popularly called the Firework Nebula, continues to expand into space.

http://asterisk.apod.com/viewtopic.php?f=9&t=25783#p161741 wrote:
<<In Britain, 5 November has variously been called Guy Fawkes Night, Guy Fawkes Day, Plot Night and Bonfire Night; the latter can be traced directly back to the original celebration of 5 November 1605. Bonfires were accompanied by fireworks from the 1650s onwards.>>

by **APOD Robot** » Sat Nov 05, 2011 3:05 pm

GK Per: Nova of 1901

Explanation: Early in the 20th century, GK Persei briefly became one of the brightest stars in planet Earth's sky, an event known as Nova Persei 1901. Documented in this modern day composite of two images from 2003 and 2011 the ejecta from the explosion, popularly called the Firework Nebula, continues to expand into space. These images are part of a time lapse video tracking the nebula's expansion over the last 17 years. About 1500 light-years away, the nebula is still just under a light-year in diameter. GK Per and similar cataclysmic variable stars known as classical novae are understood to be binary systems consisting of a compact white dwarf star and swollen cool giant star in a close orbit. The build up of mass transferred to the surface of the white dwarf from the giant star through an accretion disk eventually triggers a thermonuclear outburst, blasting the stellar material into space without destroying the white dwarf star. With a 2 day orbital period, the GK Per system has produced much smaller outbursts in recent years.

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the Firework Nebula (Fawkes?) up.

APOD: GK Per: Nova of 1901 (2011 Nov 05)