The Iconic Ring Nebula in a Different Light

Earlier this summer the folks at the Hubble Space Telescope Science Institute released a gorgeous multi-wavelength view of the Ring Nebula.  It’s a summertime sight for those of us in the northern hemisphere and a wintertime sky object for those in the southern hemisphere who live far enough north to see it. You need a telescope to spot it, and to really see the great details of this expanding cloud of gas and dust, you need the combined power of the Hubble Space Telescope along with several ground-based telescopes, and infrared data from the Large Binocular Telescope in Arizona.

What they show us is not just the iconic Ring Nebula we’ve all come to know and love, but they also give us an infrared peek at the space around the nebula. This is a planetary nebula —the last gasp of a sun-like star as it dies. Hidden from optical view but clearly apparent in infrared light are scallop-shaped bands of material that were actually blown away from the central star earlier in its evolutionary path toward forming the nebula.

The blue-colored gas in the central area of the  is actually a football-shaped structure that pierce into a surrounding cloud of reddish-colored doughnut-shaped material. If you click on the image at left you’ll get a much larger version that you can explore and spy out dark, irregular knots of dense gas embedded along the inner rim of the ring. The knots look like spokes in a bicycle.

Someday our Sun could look something like this as it takes the pathway toward planetary nebula-hood and eventual old age as a white dwarf. Once it uses up all the hydrogen in its core (in about 5 billion years), the Sun will star to expand and become a bloated red giant. Then, it will expel all its outer layers, leaving behind a very hot, very small and dense white dwarf. It will take billions of years to cool down and become a darkened cinder of a once-bright star. If you look closely at the enlargement of the Ring Nebula, you’ll see its little white dwarf. It could live as long as 15 or 20 billion years!

I find planetary nebulae very intriguing. They are at once spooky and gorgeous, and they tell a story of star life that we’ve only recently come to comprehend. There are still many details of the story for astronomers to learn. Knowing how our star will come to its end helps them understand the endless cycles of star birth and death in the cosmos.

Grin at Mercury!

Not only can you smile at Saturn tomorrow (Friday, July 19), but you can also grin at Mercury.  The scientists using the MESSENGER mission to study the closest planet to the Sun will also capture Earth photobombing the view of the region around Mercury. They’re actually looking for any natural satellites the planet may have and realized that Earth will also be making a cameo appearance in images taken on Friday and Saturday  at 7:49 a.m., 8:38 a.m. and 9:41 a.m. EDT (11:49, 12:38 and 13:41 UTC). If the Sun is in the sky during any of these times and reasonably well above the horizon, then it’s your time to shine and wave for the cameras. Just don’t look at the Sun!  Mercury is about 12 degrees from the Sun, too close to be seen with the unaided eye.

Don’t forget to wave for Saturn, too. Check out my previous entry for details!

If you haven’t heard of MESSENGER before, the name stands for MErcury Surface, Space Environment, GEochemistry, and Ranging mission, and it sent the the first spacecraft to orbit Mercury. It has been studying the planet closeup for a few years now, and in that time has mapped the surface and provided many new insights into Mercury’s cratering rates, internal structure, and “weather” characteristics. Because the surface is so heavily cratered, it’s clear that the planet hasn’t been active (geologically) for billions of years (since the period called the Late Heavy Bombardment. Mercury is a very dense planet, with dense iron-rich core that is very likely still molten. Nobody expected Mercury to have much of an atmosphere, but it turns out that it does have a very tenuous cloud of material around it made up of hydrogen, helium, sodium, calcium and potassium. It’s very likely that this so-called “exosphere” is continually replenished by interactions between the solar wind and the surface of the planet.  There’s also a possibility that water exists on Mercury, but only in the polar regions that never get any direct sunlight. Elsewhere on the planet, surface ice wouldn’t last long; surface temperatures range upwards to around 800° F during the day!  In the early morning times before sunset, the surface temperatures plunge to close to -300!

If you want to know more about MESSENGER‘s explorations of Mercury, check out the mission website. It’s chock full of images and news releases outlining the amazing things planetary scientists are finding out about the closest planet to the Sun.