Chris McKitterick (mckitterick) wrote,
Chris McKitterick

Astro-Image of the Day: Sunspot Emergent

The SOHO spacecraft took this photo in extreme UV light. The bright region is an emerging sunspot, just burst through the surface of the Sun while SOHO was taking the image.

Click the image to see the story.

A sunspot is an area of strong magnetic activity in the Sun's photosphere (what appears to be its "surface"). This reduces convection - the Sun doesn't have a solid surface; it acts more like a liquid - forming areas of reduced surface temperature. Because they're cool by comparison, in visual light sunspots appear black. Actually, they're about 3700° Kelvin compared to about 5700° K for the surrounding area. So "cool" is only relative here. Here's what sunspots look like in visual light:

Click the image to see the story.

SOHO (the Solar and Heliospheric Observatory) orbits the Sun around L1 (Lagrange Point 1), where gravity keeps it in alignment with the Sun and Earth. L1 is about four times the distance to the Moon toward the Sun. Because it doesn't have to orbit Earth, SOHO can observe the Sun without it being obscured by our planet.

PS: New research shows that climate change is irreversible for at least 1000 years. But look at the pretty shot of the Sun!

PPS: I wish I'd seen this earlier so I could have taken astrophotos! Sunspots typically only last a few days, so it's likely diminished by now. However, because we're just entering a period of higher Solar activity, we'll be seeing more and more sunspots... and flares, and other fun stuff that'll wreck wireless communications. The Sun operates on an 11-year Solar cycle; the last peaked in 2000-2002.

On January 4, 2008, astronomers observed a reversed-polarity sunspot, signaling the start of Solar Cycle 24. The number comes from when astronomers first started observing sunspots in 1745... but that's a different discussion.

Tags: astronomy

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