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Imaging Vesta and Ceres
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Determining a Light Curve
Finding Ceres
Finding Vesta
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Imaging Vesta and Ceres
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In order to locate objects in the sky, we must have a reference frame. On land, we most commonly use streets and addresses. On the ocean or in the air there are no streets so we must use imaginary lines called latitude and longitude. These are the lines you see on maps and globes. Cities, islands, and other “stationary” objects have the same latitude and longitude all the time. Animals, such as humans, are often moving and their latitudes and longitudes change with time.
To find things in space, we use celestial latitudes and longitudes. If you could put a light bulb at the center of a transparent Earth and project the imaginary latitude, longitude lines into space, you would have a coordinate system that would work for objects in space. If we view the universe as a huge sphere the celestial equator would be a projection of the earth’s equator. For a reference frame, we take the position of the sun on the first day of spring (vernal equinox) to be on the 0 hour celestial longitude line. Using that as a zero line, we can divide the sphere into equal celestial longitude lines from zero to 24 hours. Any position along this plane could be given as so many hours, minutes, and seconds. The hours, minutes, and seconds assigned to an object is called its Right Ascension (RA).
Projecting the earth’s equator provides a celestial equator. An object in space would be either north or south of the celestial equator. Its position would be in degrees, minutes, and seconds. The degrees, minutes, and seconds of an object with respect to the celestial equator is called the Declination (Dec). Using the celestial longitude and latitude, we can give any object in our universe a set of coordinates.
This system allows us to locate any object in our universe. An object could be found at 3hr 42min 3sec RA and 34deg 15min 17sec N dec; a fixed point in space. This would be the “address” of a star or another stationary object in space. A planet (from the Greek word for wonderer) does not have a fixed address since it is always on the move with respect to the background of the stars and our reference frame. It does, however, have coordinates for a given time.
The same is true for Asteroids. Asteroids are small bodies that are orbiting the sun. Most asteroids reside in the asteroid belt between Mars and Jupiter (see vignette). Some have collided with objects or been affected by gravitational forces in such a way that they have orbits around the sun but are not located in the asteroid belts. Some of these objects can come near earth. These objects are often called Near Earth Asteroids.
In this activity, you will use a remote telescope in Chile, Australia, or the United States to view Vesta and/or Ceres. You will need to work through time zones and use the latitude, longitude of the telescope you will be using to determine when Vesta and Ceres are available for viewing. Information about time zones, latitude, longitude and scheduling for the various TIE telescopes is available at: http://telescopesineducation.com. Have a backup plan ready in case of bad weather or equipment failures.
Here is an Asteroid finder. This site also prints out a star chart for you to compare and look for your asteroid. Make sure that you use the latitude, longitude, and time zone of the telescope you will be using.
Once you have connected to the telescope, you can slew the telescope to point to either Vesta or Ceres. You should check with the forum for discussions on how long of an exposure to take. Vesta is quite bright, and exposures of less than a second may be necessary. The time for the exposure is set by you when you request an image to be taken and downloaded. If you let us know via the discussion board when you will be using a telescope for the first time, we can be on-line to walk you through the experience.
The question now becomes, which spot of light is the asteroid? To find the asteroid, we are going to take an image of the same spot in the sky every 5 minutes for approximately 1 hour. Once you have those images, you can do a comparison of the “stars” to see which one (or more) is moving. The one moving is not a star. But, it may not be an asteroid either. You will need to be careful about noise. Sometimes the CCD cameras used by the telescopes pick up random electronic signals that get registered as a photon of light. These random, faint, dots may appear and disappear, but there will be no smooth motion that marks a distinct path. An asteroid will normally make a smooth path along the ecliptic.
Vesta will be very bright in relation to the other stars in the telescope’s star field. You will have no trouble identifying it and plotting its path.
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