The picture is where a "Gamma Ray Burst" was detected by a satellite on March 17, 2002.
This image covers an area near Regulus, the brightest star in the constellation Leo, with dimensions 33 x 22 'arc (about the size of the first quarter moon). The range of star brightnesses is from magnitude 11 to 20.3 (magnitude 19.5 stars are easy to see). Four galaxies can be seen in this picture: at the bottom is the brightest one (cut-off by the border), two others are to its upper-left, and a spherical galxy is the brightest object in the upper-center. The 16-bit original image shows all stars "unsaturated" with FWHM (full-width half-maximum) values of 6 "arc, corresponding to 2.2 pixels. Asteroids are visible in this image, as shown by the following movie. [Meade LX-200 10-inch f/6.3 Schmidt-Cassegrain telescope, Meade 416ETX CCD, 3x focal reducer, sum of 7 exposure, each 3 minutes long; Santa Barbara residence]
The movie, below, is a sequence of 7 images taken over a 1-hour interval on the evening of March 18, 2002. It covers about 1/4th the area of the first image (left side).
Movie (7-frames) showing the motion of faint asteroids. How many can you see?
There are three asteroids, and they're all moving in the same direction - toward the upper-right. (Sorry for their faintness in this rendition; the desire to keep files sizes small for web pages really degrades what can be shown. The three asteroids are more easily seen with my full quality originals that fill my screen.)
This is the last frame of the movie, showing the location of the three asteroids.
According to JPL's Near-Earth Objects Program (Object Identification web pages) there should be three asteroids brighter than magnitude 20 within this image. The coordinates of the predicted asteroids differ from those I detect by 0.9, 1.3 and 1.8 "arc - which is amazingly good, considering that my pixel size is 2.66 "arc! Thus, it is posssible to "idenftify" these asteroids:
Asteroid
Name
JPL Ephem. Bruce's
Magnitude Coordinate
Location
Magnitude Magnitude
Difference Difference
Top of image 1999 NL4
19.2
18.9
-0.3
0.9 "arc
Middle
1999 RW167 17.8
18.1
+0.3
1.3 "arc
Lower
2002 BV18 19.3
18.9
-0.4
1.8 "arc
This region is near the ecliptic, or path of the planets and many asteroids that orbit between Mars and Jupiter. It is not uncommon to encounter this many asteroids when imaging near the ecliptic with a sensitive CCD having a wide field of view.
About the "gamma ray burst" search, I've blinked this image with another taken before the burst (provided by the AAVSO) and I don't see anything new. The satellite coordinates for the GRB have an error region that is slightly larger than this image (36 'arc, compared with the image size of 33x22 'arc). If the GRB is within my imaged area, it would have to be fainter than magnitude 19.3, at the time of the exposure (1.56 days after the burst was detected). So far, no one else has detected the optical "afterglow" of this GRB event (that I know of). GRBs decay fast, and it's important to observe within hours of the time they're detected by the gamma ray satellite instrument.
I really didn't expect to detect the optical afterglow of the GRB, but the asteroids were a serendipitous bonus!
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This site opened: March 19, 2002. Last Update: March 20, 2002