The World’s Largest Telescope
Published on Feb 7, 2006 at 7:31 pm.
1 Comment.
Filed under radio astronomy, telescopes, travel.
I know that this isn’t a travel blog, but there are several people from the airlines who read the blog, and so that has gotten me to thinking of having an occasional astronomical travel destination. There are many places around the world that have astronomical sites. Some of these are far off the beaten trail, so people who like to get away from it all would might enjoy such destinations. Others are not really all that far from places that people go to anyway. So, an astronomical trip would be a nice side jaunt. A few are even right in the middle, or very near, some very popular tourist destinations. So, you might can add something to stimulate the mind during your vacation.Â
But, what should I do as my first travel destination? So, this will be a blog entry on the world’s largest telescope. That would be hard to beat, right? And even better, it is on a Caribbean island! Just about an hour and a half drive from San Juan, Puerto Rico, you find the Arecibo Observatory. Actually, the observatory itself is a little ways outside of the town of Arecibo. This is one place that I have not been, but I would love to go visit. (I have not had need to go there professionally yet, but it would still be fun to do the tourist thing.) There are other sites, such as the Very Large Array, near Socorro, New Mexico, where a large number of smaller radio telescopes can be used to simulate a larger telescope (and this may be the subject of a future travel entry), but Arecibo is the largest single reflector telescope on Earth.
Now, don’t expect to go there and look through a telescope. The Arecibo observatory is home to the world’s largest telescope, but this is a radio telescope. Astronomers refer to any instrument picking up signals from space as a telescope. Back in the 1930’s astronomers realized the value of using radio receivers to study celestial objects. There are some things in space that emit only radio waves, and so that would be the only way to see them. Now, the unfortunate thing is that radio waves are much longer wavelengths than visual light, so the telescopes need to be correspondingly bigger than their optical counterparts. Most professional radio telescopes are monsters. Several radio observatories are open to the public, and I might talk about some of them as future travel destinations. After all, structures so BIG are impressive to visit. And, many radio observatories either have tours through them, or allow visitors to do self guided tours. You can’t beat the photo opportunities, either. Most of these are pretty impressive. The Arecibo telescope has actually been used as a backdrop for at least three movies, including the James Bond movie Goldeneye.
So, what’s so special about Arecibo? First of all it is HUGE. The reflecting dish is 1000 feet across! In other words, you could line up three football fields end to end across the reflector! All of the radio energy gathered by the reflector is concentrated to receivers suspended 450 feet above the center of the dish!  The dish is far too big to be built to be movable. So, it is constructed in a valley, and it just points up. In order for the Arecibo telescope to observe anything, then that object has to be more-or-less overhead in Puerto Rico. This limits the objects that can be observed, but with such a huge dish, there are still a lot of objects within reach of this telescope.Â
In addition to the radio reception capabilities of the Arecibo telescope, it has a powerful radar transmitter. This transmitter has been used to bounce radar signals off of passing asteroids, yielding our first views of several asteroids. Radar has also been bounced off of Mercury and Venus, yielding great discoveries on those worlds. Until radar studies of Mercury in the 1960’s it had been assumed that Mercury always kept the same face towards the Sun (not true!). Besides astronomical studies, the Arecibo telescope is also used to study Earth’s ionosphere and upper atmosphere.
So, besides being impressive to look at, the Arecibo telescope has a rich legacy of astronomical discoveries. For anyone interested in astronomy, this makes it well worth the trip. So, if you are looking for a place to vacation, then you can take in the island of Puerto Rico, with all that it has to offer, and you can also visit Arecibo. You can find out more about the observatory and visiting the facility at its web page. Click on the “outreach” tab to get information for visitors. Remember, though, if you go that this is a working radio telescope. It is used at all times of the day, and it is VERY sensitive. So, that means no cell phones or any other type of radio transmissions would be allowed nearby. But, after all, if you are vacationing in a Caribbean paradise, would you really want to be disturbed?
-Astroprof
Astroprof’s Page » Arecibo Observatory on July 26, 2007 at 3:07 am: 1
[…] The National Astronomy and Ionosphere Center, aka the Arecibo Observatory, is the site of the largest single dish radio telescope (or any other telescope, for that matter) on Earth, and I wrote about it once before. The facility is located just outside of the town of Arecibo, in Puerto Rico. The telescope’s dish is 1000 feet (305 meters) in diameter. The receiver is suspended 450 feet (150 meters) above the dish. The dish itself is a spherical reflector, rather than a parabolic reflector. A parabolic reflector at this site would only be able to focus directly upwards. However a spherical reflector does not focus all of the incoming radiation to the same point like a parabolic reflector. So, the receivers only pick up signals from a portion of the dish at a time. But, this gives the telescope some flexibility in where to point. The receivers and secondary reflectors can move somewhat on a track at the bottom of the platform suspended above the dish. Thus, they can pick up signals reflecting off of different portions of the dish by simply moving a little ways. This permits the telescope to pick up signals up to 40 degrees off of the zenith, greatly expanding its range of operations. […]