Search found 17490 matches
- Fri Sep 12, 2008 4:57 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Planets over Perth (APOD 12 Sep 2008)
- Replies: 14
- Views: 4361
Just looked at the uncropped photo . There are two more stars at the top, and one at the extreme top right, that form an arc with Mercury and Mars. Curious about them, too. Here is a chart showing the visible stars. Forming a triangle with Mercury and Venus is Zaniah, eta Virgo. All the visible sta...
- Fri Sep 12, 2008 3:51 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Capturing meteorites in Antarctic (APOD 07 Sep 2008)
- Replies: 15
- Views: 4416
But in terms of reference there isn't a proper east or west portion of a continent that covers the south pole only the half (+/-) that lies in the eastern hemisphere and the half that lies in the western hemisphere. Exactly. And that's how the continent is divided. As noted previously, there are tw...
- Thu Sep 11, 2008 10:29 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Capturing meteorites in Antarctic (APOD 07 Sep 2008)
- Replies: 15
- Views: 4416
Yeah, It seems to me like from the South Pole all directions are North. And so they are. But there's an awful lot of the continent of Antarctica that is nowhere near the South Pole. In terms of distance to the Pole, most of Antarctica is similar to Siberia, northern Canada, or Greenland. People in ...
- Thu Sep 11, 2008 5:16 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Saturn's Anthe Arc (Background stars) (APOD 10 Sep 2008)
- Replies: 14
- Views: 3774
Re: What are hot pixel defects?
Chris, what precisely are hot pixel defects? I heared about pixel defects, single pixels, which do not work. Do hot poixel defects occur in groups of about 10 adjacent circular or square elements? Every pixel on a CCD has a slightly different dark current rate. So if you were simply to make an expo...
- Thu Sep 11, 2008 4:19 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Saturn's Anthe Arc (Background stars) (APOD 10 Sep 2008)
- Replies: 14
- Views: 3774
Some may be other arcs and it looks like some may be scratches in the film. I'm referring to the dark up and down streaks that are just barely noticeable. Nothing about this image has even remotely involved film. And data doesn't scratch <g>. There seem to be three types of background objects. The ...
- Tue Sep 09, 2008 5:03 am
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Any ideas on this one?
- Replies: 5
- Views: 2626
Re: Any ideas on this one?
I am in Cincinnati(east side) and caught this sequence early morning Labor Day... It may be something on your sensor, or on the optics close to the sensor, or it may be something floating not far above you. Whatever it is, it isn't above the atmosphere, since it is clearly a shadow against the skyg...
- Mon Sep 08, 2008 7:27 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: 2867 Steins (APOD 08 Sep 2008)
- Replies: 13
- Views: 3137
Re: 2867 Steins
Did some googling and found a light curve of March 11th 2006, in stead of August 20th 2008 in the Uwe Keller press conference . It shows the same double periodicity and the plateau, although the plateau is less striking as in the August 20th light curve. Looking more closely at the published curves...
- Mon Sep 08, 2008 6:13 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: 2867 Steins (APOD 08 Sep 2008)
- Replies: 13
- Views: 3137
Re: 2867 Steins
Thought experiment. Take a cylinder (soda can), paint it white and let it rotate around an axis, perpendicular to the symmetry axis. Let some light shine on it, e.g. from the back side of the observer. (Full moon idea). The light curve will show a double period, since the cylinder has a rotation by...
- Mon Sep 08, 2008 4:56 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: 2867 Steins (APOD 08 Sep 2008)
- Replies: 13
- Views: 3137
Re: By Toutatis!
This is probably why we don't see 2867 Šteins ROTATING . However, TUMBLING implies a more chaotic motion... In the case of asteroids, tumbling can't be taken as implying chaotic motion. Tumbling means that there is rotation about more than one axis, which is not typically chaotic. The actual motion...
- Mon Sep 08, 2008 4:50 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: 2867 Steins (APOD 08 Sep 2008)
- Replies: 13
- Views: 3137
Re: 2867 Steins
Did you see the presentation of H. Uwe keller ? On page/sheet 5 a light curve is drawn. The horizontal scale is in Modified Julian Date and the vertical scale is the "magnitude". There is a fluctuation in magnitude in length about 0.1 MJD visible, so roughly 2.5 hours, which could be inte...
- Mon Sep 08, 2008 2:44 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: 2867 Steins (APOD 08 Sep 2008)
- Replies: 13
- Views: 3137
If it is tumbling; the rate may have been too negligent for the photo to capture. :? I couldn't find much on not tumbling on google; as most sites suggested that asteroids do tumble. Most asteroids do not tumble, but simply rotate about their principal axis. Tumbling means the asteroid rotates abou...
- Sun Sep 07, 2008 8:36 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Capturing meteorites in Antarctic (APOD 07 Sep 2008)
- Replies: 15
- Views: 4416
Hey, I only said strange ... not offended, nor outraged, nor feeling the need to replace any terminology. I didn't take it wrong, but was serious if you had an alternate terminology in mind. The 2D coordinate system we find generally convenient to describe our position on the surface of a sphere do...
- Sun Sep 07, 2008 6:53 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Capturing meteorites in Antarctic (APOD 07 Sep 2008)
- Replies: 15
- Views: 4416
But East Antarctica still seems like a strange term to me. Do you have another suggestion? Seems to me that reasonable cardinal directions for Antarctica are east, west, central/south, and coastal/north. Even though its coast is deeply dented, Antarctica surrounds the South Pole. If I pick a spot a...
- Thu Sep 04, 2008 3:03 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Earth's Shadow (APOD 20 Aug 2008)
- Replies: 65
- Views: 17161
Re: Laser reflections
It is not my intention to be rude, but the phrase "It is simple to see" is synonymous with "the author did not bother to elaborate, after three weeks of intensive calculations the result can be found". I simply meant that if you made a simple drawing of the 2D case, it should be...
- Wed Sep 03, 2008 4:31 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Earth's Shadow (APOD 20 Aug 2008)
- Replies: 65
- Views: 17161
Re: Laser reflections
In the wiki i can read that it differs from a plane mirror. It is a constellation of three perpendicular perfectly flat reflecting planes. The reason (proof or explanation) why for any incident angle the light is reflected in the same direction, is missing. I guess its a matter of repetative applic...
- Thu Aug 21, 2008 9:22 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Earth's Shadow (APOD 20 Aug 2008)
- Replies: 65
- Views: 17161
Re: Laser reflections
Why is the laser light relefected so preceisely back to earth and not somewhere near the earth? The reflectors are arrays of corner prisms, aka retroreflectors . These cannot help but to send reflected light back along the same path it entered on. How does the ever changing path (different heights ...
- Thu Aug 21, 2008 9:13 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Earth's Shadow (APOD 20 Aug 2008)
- Replies: 65
- Views: 17161
The moon probably has a liquid core of about 20% of the Moon's radius. I can only guess that they must see it wobbling or something to infer this. To be fair, this is not established. There are various well regarded theories about the Moon's core, including little iron or a small, solid iron region...
- Thu Aug 21, 2008 5:38 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Earth's Shadow (APOD 20 Aug 2008)
- Replies: 65
- Views: 17161
The terminator in this eclipse sense is the edge peak right? I think so. It's the line between night and day on the Earth. If you were standing there, with the setting (or rising) Sun at your back and the partially eclipsed Moon in front of you, your shadow would be cast on the Moon. So everything ...
- Thu Aug 21, 2008 4:59 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Earth's Shadow (APOD 20 Aug 2008)
- Replies: 65
- Views: 17161
So are you telling me there's no hope of making bunny ears appear in our moon shadow? Not even with two gigantic space elevator docking/transfer stations? Even a real bunny standing on the Earth's terminator casts its shadow on the Moon. In the case of a space elevator, the cables would cast shadow...
- Thu Aug 21, 2008 2:23 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Earth's Shadow (APOD 20 Aug 2008)
- Replies: 65
- Views: 17161
I was curious after neufer's post as to how long people believed the earth was flat and was amazed there is a Flat Earth Society in these times. In fact, it's doubtful that many people (at least, people with any hint of education) in the West believed that the Earth was flat after the Greeks demons...
- Tue Aug 19, 2008 3:02 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: The Witch's Broom Nebula (APOD 19 Aug 2008)
- Replies: 11
- Views: 4182
Re: The Witch's Broom (APOD 2008 August 19)
The wispy cloud is very intricate and colorful; I can see why it is called the veil nebula. Without reading the explanation about the sweeping action on nearby gas; It would be hard to imagine the broom name. Most of the names we have for objects like this stem from their visual appearance in the e...
- Mon Aug 18, 2008 12:14 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Io's Surface Under Construction lake-like feature? (17Aug08)
- Replies: 15
- Views: 4251
Re: Io's Surface: Under Construction
Aurora Versus Power Lines Article #506 by T. Neil Davis http://www.gi.alaska.edu/ScienceForum/ASF5/506.html Yeah, these currents are plenty large enough to cause problems. I live in ranching country, and know of anecdotal stories about people getting shocked off of fence lines during active solar p...
- Sun Aug 17, 2008 11:16 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Io's Surface Under Construction lake-like feature? (17Aug08)
- Replies: 15
- Views: 4251
If the surface is constantly changing due to volcanic activity and the throwing up of lava. Does this mean that the moon is getting larger in circumference and more hollow under the surface? A body as massive as Io can't contain much hollow space, as gravity will cause it to collapse. Because this ...
- Sun Aug 17, 2008 11:13 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Io's Surface Under Construction lake-like feature? (17Aug08)
- Replies: 15
- Views: 4251
Re: Io's Surface: Under Construction
I would say that the 1 million ampere electric current flowing between Jupiter and Io would be a much more likely suspect for Io's condition of surface agitation... A more recent article also attributes a wattage of approximately 2 terawatts (2 trillion watts) to the exchange. That's a trivial amou...
- Sun Aug 17, 2008 5:32 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Io's Surface Under Construction lake-like feature? (17Aug08)
- Replies: 15
- Views: 4251
Re: Io (8.17 APOD)
If the picture is of the side of Io that always faces away from Jupiter, and we are looking straight at it, why then does not Jupiter fill the void behind Io? The image was constructed mathematically, by taking many small field-of-view images, at different angles and resolutions, and mapping them o...