Every year, the Pacific Northwest and California experience “wildfire season,” a period where heat and low humidity combine, leading to an increased risk of fires. This year has been particularly bad and in California alone, wildfires have destroyed over two million acres of land, forced hundreds of thousands of people from their homes, and threatened many historic institutions and landmarks.
One of them is the Mount Wilson Observatory that sits atop Mount Wilson in the San Gabriel Mountains overlooking Pasadena (northeast of LA). This famous observatory is home to several telescopes that were, for a time, the largest of their kind in the world. And thanks to the heroic efforts of firefighters, it looks as though the Mt. Wilson Observatory is now safe amid a particularly bad wildfire season.
That announcement came on September 18th via Twitter, when the observatory thanked the firefighters who had spent the past few days fighting the Bobcat Fire – the wildfire currently raging in Angeles National Forest north-east of Pasadena. It is one of two major fires taking place near Los Angeles, the other being the El Dorado Fire that is still active in the national forest east of San Bernadino.
The Bobcat Fire began on September 6th, 2020, and has since burned almost 100,000 acres in and around the Angeles National Forest and leading to mandatory evacuations throughout Los Angeles County. By Sept. 15th, the fire reached within 150 m (500 ft) of the observatory and firefighters and helicopters were deployed to the area to protect it.
This was accomplished using a tactic known as “strategic firing,” where backfires are set to create a perimeter against the spreading fire.The LA County Fire Air Ops and the California Governor’s Office of Emergency Services (Cal OES) also established a mobile water reload container in the observatory parking lot, where helicopters would reload between making water drops.
By Sept. 18th, the Angeles County section of the USDA Forest Service tweeted that the BobcatFire was still burning within an area of 60,557 acres and containment had increased to 15%. They also declared that the observatory was safe, as the fires encroaching from the south burned around the perimeter. This was echoed in a letter by the observatory chairman (Sam Hale) that went out on the same day:
“We owe our very existence to the firefighters on the ground and the helicopter pilots. They are our heroes. They are true professionals, artists when it comes to the use of ‘strategic firing.’ We will be forever thankful for the 12 crews, some forty to fifty firefighters from all over, who defended our home, risking their lives defending our scientific treasure. The fire is still burning on the northern and southern flanks, where fairly recent fires, in 2009 and 2017, have reduced the fuel load. We are still not completely out of the woods, so the crews will stay on the mountaintop to the end of the month or longer to protect the site from flair ups. Today, tanker planes dropped fire retardant that will further secure the area.”
Hale also included a time-lapse video captured by the south-pointing tower’s camera (see above ), which showed the flames caused by the strategic firing engulfing the southern edge of the property. To the astronomical community, news that the Mt. Wilson Observatory is safe must come as a huge relief. While the observatory is not out of the woods yet, the situation appears to be contained for the time being.
The Mt. Wilson Observatory is home to two historically important telescopes: the 2.5 m (100-inch) Hooker Telescope and the 60-inch Telescope, which were the largest telescopes in the world when completed (1917 and 1908.) It’s also home to the CHARA array, an optical interferometric array of six telescopes built by Georgia State University, which as the largest optical interferometer in the world when it became fully operational in 2004.
According to their most recent updates, the Mt. Wilson Observatory posted that they were able to access the site for the first time in days and thanked the firefighters in person by delivering burritos for lunch (which were apparently well-recieved!) Another update indicated that the observatory was still safe and that firefighters were redeploying their engines to deal with scattered hotspots around the southwest side of the containment line.
In the midst of such calamity, it’s good to know that at least one institution (whose historic and scientific value is immeasurable) is safe. Here’s hoping the same can be said very soon about all the people, land, and wildlife in the area that are still threatened!
Further Reading: Mount Wilson Observatory
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