25 November 2020
Arab scientists earmark best sites for astronomical observatories
Published online 28 January 2015
Scientists set out to determine the Middle East’s best sites for new observatories to study the stars.
While some Arab countries are making strides in aerospace development, the field of astronomy often gets overlooked.
In 2014, the United Arab Emirates announced plans to send an unmanned probe to Mars by 2021 to mark the country’s 50th anniversary. Also last year, King Abdulaziz City for Science and Technology (KACST) in Saudi Arabia announced its role in the Russian launch of Saudisat-4, designed and developed by the national satellites technology center at KACST. The UAE has also revealed plans to launch Khalifa Sat in 2017, which will be constructed exclusively by 45 Emirati engineers.
But this considerable progress in the aerospace industry, serves to highlight stagnation in the field of astronomy. Nidhal Guessoum wrote in a Nature article in June 2013 that “most Arab nations are generating fewer than ten papers in the field each year, and these are hardly cited.” Currently, the entire Arab world has only one astronomical observatory with a telescope more than one metre in diameter – Egypt’s Qattameya Observatory.
So Guessoum, a professor of physics and astronomy at the American University of Sharjah in the UAE, and two of his undergraduate students set out to identify the most promising sites to construct an astronomical observatory in the Middle East and North Africa.
Initially they developed a list of atmospheric, environmental and physical criteria for the construction of an observatory of international standards, explains Noora Alsaeed, a first-year undergraduate majoring in math. They then undertook a preliminary, theoretical search for potential locations for optical astronomical observatories that satisfied these criteria.
A height of 1,500 metres was set as a minimum altitude for any potential location. “For an optical observatory, air quality is very important,” explains Nada Abdelhafez, a fourth year undergraduate – majoring in electrical engineering – when the study was conducted. At higher altitudes the air will be more stable and the weather cooler, “so the amount of light that will enter a telescope and its quality will be much better since it will not be disturbed by air or dust particles.”
Based on the minimum altitude parameter and by using Google Maps, a list of 14 possible locations in six different Arab countries was compiled.
The team then gathered data to exclude locations that did not fit the rest of the criteria, starting by ruling out areas with dense light pollution. To obtain data for these pollution levels, the team made use of a layer in Google Earth called Earth City Lights. Light pollution levels were determined based on the distance from and the size of the nearest city, eliminating sites with high or very high light pollution.
Even in the best two or three locations, some factors will be compromised to some extent and will have to be compensated for by technological means
The researchers then tried to narrow the list further based on meteorological data. But their remote locations limits the amount of data available. Instead, they obtained information related to the number of cloudy nights and humidity for the nearest possible locations over a one-year period from online weather websites. Average temperatures and diurnal temperature variations were also gathered for the nearest locations to the selected sites. Almost all the locations had a maximum wind speed of seven metres per second, significantly less than the maximum acceptable average of 15 m/s.
This process of elimination left seven sites out of an original 14 as potential locations for building an astronomical observatory in the Arab region.
Mount Catherine in Egypt’s southern Sinai topped the list followed by a peak near the Saudi Arabian city of Tabuk in the Hejaz mountains. Next was Mt. Tahat in Algeria’s Ahaggar mountains, Jabal Umm ad Dami in Jordan’s Wadi Rum, Jebel Toubkal in Morocco’s Atlas mountains, Deriba Caldera in Sudan’s Marrah mountains, and Djebel Chelia in Algeria’s Aures mountains.
“None of these sites is perfect in every respect,” writes the team in their study published in The Observatory in December 2014. “Even in the best two or three locations, some factors will be compromised to some extent and will have to be compensated for by technological means.”
Some of the sites were unexpectedly unsuitable. “We really thought that the mountains of Oman would be terrific places. We have conducted star gazing trips to some of the mountains there and sometimes the mountains of the UAE, one of which has a height of 1,600 metres,” Guessoum says.
“Yemen also has always been a favorite of astronomers in principle because it has mountains over 3,000 metres high, so we expected to find some places that we thought would be very conducive to those kinds of observatories and we didn't.”
He was also surprised at the attributes of Wadi Rum in south Jordan for setting up an observatory.
Despite the promising research, the team lacked funding for on-site measurements for their selected sites. “I would really like to [get] more accurate [data], especially for the UAE, because we haven’t made any onsite measurements,” says Alsaeed.
- Guessoum, N.; Alsaeed, N.; Abdelhafez, N. Preliminary search for astronomical observatory sites in the MENA region. The Observatory 134: 339-347