Sky Roundup: January 30, 2007

This image, taken by the Solar & Heliospheric Observatory, nicknamed SOHO, shows the eruption in late December to early January of a coronal mass ejection (or CME).  The bright disk of the Sun is blotted out, to make a CME more visible.  (Note the bulge on the right of the central disk; that’s the CME erupting.)  This particular CME was aimed away from the Earth, but may have contributed to recent auroral displays, along with a strong solar wind due to coronal holes.  (Image by NASA.)

More on recent solar activity

Though gigantic compared to the Earth, the coronal mass ejection that erupted off the surface of the Sun this past month and the recent strong stream of particles from the solar wind have contributed to an alert for auroras among countries in high northern and southern latitudes. 

The solar wind is the constant stream of particles, namely protons and electrons, away from the surface of the Sun.  Though the actual density in outer space of particles streaming off the Sun can be relatively sparse, that stream does fluctuate with changes in atmosphere of the Sun, known as the corona.

For example, a strong solar wind can result from a thinning in, or absence of, the corona.  The actual thinning over a portion of the Sun’s surface, or even a prolonged absence of the Sun’s corona, known as a coronal hole, can allow more protons and electrons to escape the Sun.  A strong stream of particles can result in auroral displays on Earth, as was predicted for mid-January due to recently observed coronal holes.

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Sky Roundup: January 16, 2007

Good-bye comet, hello aurora!

As we bid farewell to Comet McNaught , the bright, gassy visitor from deep space has rounded the Sun and is now a special visual treat for observers in the Southern Hemisphere; it’s even visible in broad daylight at sunset!

While that comet wends its way past the Sun, our Solar System’s home star has been actively churning out high-energy particles from its surface into interplanetary space. A recent, gigantic blast, known as coronal mass ejection, has crossed the gulf of space to Earth and is currently pounding the Earth’s magnetic field. This is the perfect recipe for a display of the aurora borealis, also known as the Northern Lights.

(Coincidentally, when there is an auroral display around the Earth’s north magnetic pole, there is a mirror-image display, known as the aurora australis, arrayed around the Earth’s south magnetic pole.)

If the skies over Cleveland clear up, one might see the telltale, wispy greenish glow of the Northern Lights. Of course, be sure to look to the north to try and spot the aurora. If you don’t know how to find your way around the night sky, visit the Shafran Planetarium and we’ll show you how to become an expert star-hopper.

Star light, star bright

If you tried to spot that comet at sunset this past week, you might also have noticed a brilliant starry light low toward the southwest. That’s not a star; that’s the planet Venus, one of the brighter celestial objects in the sky after the Moon and Sun. In old almanacs and newspapers decades ago, Venus was often referred to as an evening star, even though it is indeed a planet.

A cloud-shrouded world that reflects most of the Sun’s light into space, the planet Venus appears very bright in evening twilight, and will remain a well-placed jewel in the sky after sunset for the next several months. A telescope will not reveal any visible surface features on Venus, since the planet is far cloudier than Cleveland has been lately. However, with careful observation, an observer with a telescope will notice that Venus moves through phases much like the Moon! If you’d like to learn more about how to observe Venus and the other planets, visit the Mueller Observatory on Wednesday evenings when the Cleveland Museum of Natural History remains open late.

Look at all the planets

In addition to Venus, several other bright neighboring worlds are visible in the skies over Cleveland. Unfortunately, planet Mercury is fairly lost in the glare of the setting Sun, but becomes briefly visible by month’s end as a pinkish dot near bright-white Venus.

Saturn maintains its vigil high in the sky all evening long for the month of January. The brightly ringed planet is a showpiece in telescopes and shows a pale yellow color even to the untrained eye. A telescope will also reveal the underside of the rings at an increasing angle for the coming months. Again, observing from the Mueller Observatory will show Saturn in its evening splendor.

If you’re out early, look for brilliant Jupiter about an hour before sunrise. The Solar System’s largest planet, Jupiter sports bands of clouds in its thick atmosphere, visible even with a modest telescope, and two red spots (not just one), which require a far larger telescope to see clearly.

Mars also rises before the Sun in January, but is far dimmer than Jupiter. Its pale orange color contrasts greatly with the white brilliance of Jupiter. Mars will remain a morning planet throughout much of this year.

The more distant planets, namely Uranus and Neptune, require strong magnification with a telescope just to glimpse. Observers in certain countries across East Asia (but no one in Cleveland) will see the Moon blot out the planet Uranus later this month. This is known as an occultation, and happens periodically when the Moon appears to pass in front of planets and bright stars as seen from Earth.