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Rosa Ursina, 1630

Loan Objects

Rosa Ursina, 1630
Christoph Scheiner (1573-1650), Germany
Codex: partly foliated
Bracciano, Italy: Apud Andream Phaeum, 1626-1630
Gould Library Special Collections, Carleton College

The sunspot is a region whose high magnetic fields impede the flow of heat into it, thereby causing it to be cooler than the rest of the face of the Sun. A sunspot appears dark because its cooler (4000oC) material does not shine as brightly as the rest of the Sun, which is at 6000oC. Surrounding the sunspot is its fine-brush penumbra. The granulated structure beyond the penumbra represents Texas-sized bubbles of hot gas rising from the interior and dumping their heat at the photosphere, the visible face of the Sun. The darker boundaries of the granulations are cooler, sinking gas. The smallest features visible in this image are about 100 km across.

Although sunspots have been occasionally observed since Roman times, the advent of the telescope allowed people like Galileo and Scheiner to truly study them. To Galileo, they proved that the Sun was not a perfect body as the Church taught. To later scientists, they provide a look at the active surface of the Sun and clues about the Sun's 11-year magnetic activity cycles that directly influence Earth's aurora, power grids, and orbiting satellites when energetic particles ejected from the Sun hit our upper atmosphere. We are currently on the upswing of the solar cycle, so we can expect more of these events over the next few years. Scientists predict that occasionally, perhaps once per century, a solar “superstorm” will be so severe as to cause massive damage to our power grid unless steps are taken to protect it beforehand.

Joel Weisberg

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Galileo's Sidereus Nuncius (Sidereal Messenger, 1610), which illustrated the ragged mountains and valleys of the moon's surface, contradicted inherited notions that the moon and other heavenly bodies were perfect spheres, embodiments of a rigorous divine order.

Christoph Scheiner, a Jesuit astronomer, vigorously counters Galileo in the 1626-30 Rosa Ursina, even as he presents his own drawings of sun spots based on meticulous observation; these highly detailed representations embody the most advanced research on the phenomenon until the 18th century. Scientists have only very recently managed to photograph sunspots with visible light.