You may be preoccupied with Tuesday’s asteroid 2005 YU55 flyby, but there’s another astronomical event currently unfolding in the solar system. Zoom out from the Earth-moon system for a moment and focus your attention to the surface of our nearest star, nearly 100 million miles away. Yes, that star: the sun.

A few days ago, solar observatories became fixated with a rather big blemish slowly rotating across the surface of the sun. In fact, it wasn’t one blemish, it was a cluster of blemishes.

WATCH VIDEO: A solar eruption sends a wave of plasma hurtling towards Earth on August 1st, 2010. The event was captured by NASA satellites

BIG PIC: Monstrous Sunspot Rotates Toward Earth

This cluster — known as AR (active region) 1339 — is a group of sunspots and the site of powerful magnetic fields protruding from the solar interior. It just so happens that AR 1339 is also the site of recent solar flare activity, causing speculation that a flare or two may be launched in our direction.

As the active region now faces Earth, what can we expect? Well, according to the NASA Solar Dynamics Observatory’s (SDO) Facebook update, “AR 1339 has a delta-class magnetic field that harbors energy for X-class solar flares. We will keep watching!”

SCIENCE CHANNEL: Wonders of the Solar System: The Sun

So, as we await the flyby of asteroid 2005 YU55, also remember to keep an eye on the sun’s AR 1339 — it’s the largest sunspot cluster since 2005, and as helpfully pointed out by the ever-watchful @TheSunToday, it’s “Larger than Jupiter! Now that is a big active region!”

If a solar flare and/or a coronal mass ejection (CME) hit Earth, what’s the worst that could happen? Read the Discovery News article “Is a Devastating Solar Flare Coming to a City Near You?” to find out.

Image: The sun on Nov. 7 as observed by the SDO’s Helioseismic and Magnetic Imager (HMI). Credit: NASA/SDO/HMI