“A report warns that fleets of new communication satellites in low-Earth orbit will spoil some astronomical observations, even if all known mitigation strategies are taken.”
Astronomers and the operators of new, thousands-strong […] low-orbiting satellites will have to work together to prevent them from having a devastating impact on ground-based observations of planets, stars and other celestial objects, says a [recent] report […]. Even then, there is no escaping some harm from the fleets of commercial orbiters.
“No combination of mitigation will eliminate their impact,” added astronomer Connie Walker of the U.S. National Optical-Infrared Astronomy Research Laboratory.
The satellites, designed to provide internet access in remote areas, now number in the hundreds. [Following] the launch of the first batch by SpaceX in May 2019, astronomers were alarmed by how bright they appear in the sky. If all the planned [launches] go ahead, the number of satellites will grow beyond 100,000. Since last year, there have been a number of independent studies of [satellites’] possible impact. [The] workshop’s report is the first time the satellite companies, and those who would be affected (astronomers to the agencies that fund them and their telescopes), have pooled their results and worked out a strategy for the future.
The satellite trails are very bright, and out of focus slightly, so they’re wide and cover several pixels on images taken with a test version of the (soon to open Vera C.) Rubin Observatory’s camera, notes Tyson. [Telescopes] that need to work during twilight will also run into problems. Because the satellites are in low orbits, they will often be seen close to the horizon and will be most visible when they are still in sunlight but, the observer is not. If, however, satellite operators choose orbits above 600 kilometers, the situation gets worse because, then, their spacecraft are visible for more of the night, and in [the] summer, all night long. Astronomers should also develop software tools to remove satellite trails from images and the companies should make accurate orbital data available for their orbiters so telescopes can try to avoid them.
The only measure the report could offer to totally eliminate the damage to astronomy was to launch fewer or no low-orbiting satellites…likely not an option given the financial investments the companies are making in the [satellites] and the lucrative market they foresee.
Tyson and his colleagues have been working with SpaceX engineers to modify their satellites to reduce their brightness. His team has also modeled trying to steer the Rubin Observatory telescope to avoid passing satellites but, Tyson says there are simply too many. Astronomers are already actively pursuing image processing solutions but, he says “the jury’s out” on how much that can help.
Report Offers Roadmap (American Astronomical Society)
SATCON Report (NOIRLab)
Satellites Could Spoil View of Giant Sky Telescope (Science Magazine February 27, 2020)
SN 1054 is a supernova that was first observed on 4 July 1054 and remained visible for around two years. The event was recorded in contemporary Chinese astronomy [..]. [There is] a pictograph associated with the Ancestral Puebloan (Anasazi) culture found near the Peñasco Blanco site in New Mexico. The remnant of SN 1054, which consists of debris ejected during the explosion, is known as the Crab Nebula (M1). It is located in the sky near the star Zeta Tauri (ζ Tauri) The core of the exploding star formed a pulsar called the Crab Pulsar. When the French astronomer Charles Messier watched for the return of Halley’s Comet in 1758, he confused the nebula for the comet as he was unaware of the former’s existence. Motivated by this error, he created his catalogue of non-cometary nebulous objects, the Messier Catalogue, to avoid such mistakes in the future. The nebula is catalogued as the first Messier object […].
Chinese astronomers watching the sky on July 4, 1054, noted the appearance of a new or guest star just above the southern horn of Taurus. Other observations of the explosion were recorded by Japanese, Arabic and Native American stargazers. In 1731, British astronomer John Bevis observed a cloudy blob in the sky and added it to his star atlas. Although [Messier] credited himself with its discovery in his first publication of the Messier Catalog, he acknowledged Bevis’ original finding in subsequent versions after receiving a letter from the astronomer. Around 1844, [Irish] astronomer William Parsons, the third Earl of Rosse, sketched the nebula. The resemblance of the image to a crustacean led to M1’s other name, the Crab Nebula. In the early 20th century, astronomers (Carl Lampland/1921 & Edwin Hubble/1928, included) were able to take more detailed measurements of M1 and determined that it is expanding. Working backwards, they determined its origination date and matched the explosion up with observations from Chinese and Native American records.
It is likely that skywatchers of the Anasazi People in the American Southwest also viewed the bright new star in 1054. Historic research shows that a crescent moon was visible in the sky very near the new star on the morning of July 5, the day following the observations by the Chinese. The pictograph above, from Chaco Canyon in New Mexico, is believed to depict the event. The multi-spiked star to the left represents the supernova near the crescent moon. The handprint above may signify the importance of the event, or may be the artist’s “signature.”
Happy 4th, everyone! ~Vic