Lynn’s High Rock Observatory awaits glimpse of asteroid shadow

LYNN – While the Civil War was raging in America, English astronomer Norman Robert Pogson was busy studying the sky over India, discovering 21 stars and eight asteroids during his career, including the asteroid 80 Sappho whose shadow may be visible from Lynn and Nahant through telescopes early Saturday.Such occasions ramp up the excitement among astronomers and stargazers alike and bring attention to facilities like Lynn’s High Rock Observatory.John W. Briggs, an instructor at Dexter & Southfield Schools in Brookline, and Paul D. Maley, an aerospace scientist associated with NASA’s Johnson Space Center in Houston, will attempt to measure the diameter of Sappho in the early morning hours Saturday, using the High Rock Park telescope.The asteroid, also known as a minor planet, was discovered by Pogson in 1864 and orbits Mars and Jupiter. Its diameter has been estimated at about 50 miles, making it too small to be seen as a measurable disk by Earth-based telescopes.For a few seconds Saturday morning, however, the asteroid is set to line up with a far more distant star. The result: a shadow of the asteroid, as measured in starlight, is predicted to pass over Greater Lynn sometime between 11:50 p.m. Friday and 12:05 a.m. Saturday. Astronomers refer to such events as an occultation.According to James Marsh, the city’s community development director who oversaw the observatory’s restoration and introduction of free public tours on summer nights, Maley and Briggs will use a video timing technique to measure the disappearance of the star, which will appear much brighter in the sky than the asteroid itself.”The occultation is like a mini-eclipse and we are very grateful that there happens to be an excellent telescope and observatory right in Lynn that we can use to make the recording,” Briggs said. “Because the speed of the asteroid is already well known, its diameter can be measured from timing how long the star is covered.”Other nearby observatories, such as the Clay Center facility in Brookline where Briggs teaches, are unlikely to be in the shadow path.”If enough observers collaborate on this event, we get a clear picture of Sappho’s silhouette,” he said. “Each observatory in the shadow path that’s able to make a timing will contribute a part of the overall picture.”Maley has traveled to 235 countries, generally in pursuit of similar astronomical events. Last year, he went to Australia as part of an MIT team to observe a similar event. “I’m grateful this one is closer to home,” he said.Pogson, of Nottingham, England, discovered 80 Sappho May 2, 1864 and named it after the Greek poet. By the time he was 18, he had computed the orbits of two comets. He became an assistant at the Radcliffe Observatory in Oxford, England in 1851. In 1860, he traveled to Madras, India to become a government astronomer. It was there he produced the Madras Catalog of 11,015 stars. He headed the Madras Observatory for 30 years until his death in 1891.