Eye on the Sky

Helen Hill
Thursday, July 7, 2016

Observing the May 2016 Mercury Transit

Viewed from the Earth, Mercury only passes in front of the sun a few times each century. Because the May 9, 2016 transit was relatively rare and, weather permitting, would be visible from the Northeast, members of the Department of Earth, Atmospheric and Planetry Sciences (EAPS) decided to set up telescopes both on campus at MIT and also at the Wallace Astrophysical Observatory in Westford, MA to provide hands on and online opportunities to view the inner most planet's stately passage across the face of our nearest star.

May 9, 2016 Mercury Transit - Video credit: J. Kastorf

The campus location in McDermott Court included a number of telescopes. Senior Lecturer Dr. Amanda Bosh arrived at MIT at 6am, meeting undergraduates Sophia Tigges and Ryuga Hatano; they scouted locations, searching for the perfect spot to place the telescopes where they would have a clear view of the sun for eight hours and also be close to a source of electricity. Throughout the day, several students and staff from EAPS and Physics rolled up their sleeves to help out, by talking with passersby about what they were seeing, adjusting the telescopes, and taking pictures. Hundreds of people stopped by during the eight hours event.

Two of the telescopes were set up to capture the Sun and Mercury in white light so that Mercury appeared as a small sharp black dot moving slowly across the yellow of the sun. The team also had one telescope fitted with an H alpha filter, a deep red wavelength that highlights processes in the chromosphere of the sun, where temperatures rise from 11,000 to 36,000 F. Here, the temperatures are high enough to coax electrons in hydrogen atoms into higher energy levels; when they fall back down, they emit light at one specific wavelength, 6562 Å. Observers could also see prominences along the sun’s rim ­­-- spectacular ribbons and loops of gas, rising off the sun's surface and extending into space.

The telescopes at the Wallace Astrophysical Observatory also gathered quite a crowd; more than 30 people stopped by to watch the transit themselves, with thousands more connecting through the live feed that EAPS Research Associate Tim Brothers was broadcasting throughout the event.

Dr. Bosh does not study the sun or Mercury as part of her research, instead focusing on cold objects very far away from the sun, this Mercury observing session was a part of the monthly observe@MIT events that Bosh arranges. "I hold monthly stargazing sessions for the MIT community. We usually observe at night when we view stars, planets, galaxies, and more. This time though it was broad daylight and the star we were observing was our own sun!"

Story Image: All hands on deck in McDermott Court May 9th - Here Prof. Rick Binzel drops by to give an impromptu planetary science lesson - Image credit: Helen Hill