Touch The Milky Way And Visit Lutetia, An Asteroid Far From Home

The planet Jupiter makes a brilliant arc of light during this one-hour time exposure shot recently north of Duluth, Minn. The extra glow in the trail is from dew and passing clouds. Details: 24mm lens at f/2.8, ISO 200. Photo: Bob King

Much as I like the moon, I also like the dark sky that returns when the moon rises long after twilight. Tonight we’ll have a morsel of dark, moonless sky – about a half hour’s worth – before its cheery face appears again in the northeast. I hope to use the time to check on supernova 2011 fe which flashed to life in the Pinwheel Galaxy months ago. The brightest supernova in 20 years, 2011 fe peaked at magnitude 9.9 in late September when some observers were able to see it in binoculars! It’s presently around 12.8, still bright as supernovae go, and slowly fading.

The Milky Way - an edge-on view of our galaxy seen from its insides - cascades from the zenith to the southwestern horizon just after twilight on mid-November evenings. Created with Stellarium

This little slice of time also means the Milky Way will once again spread its carpet of misty jewels across the sky for those living in rural areas and outer ring suburbs.

To fully appreciate what we’re seeing, context is important. Look up on a clear night and you’ll see thousands of stars, all tiny pinpricks in black velvet, beautiful but distant. Only one – the sun – is close enough to experience as a real star. When it casts big shadows and faintly warms our cheekbones, it helps us picture how Vega or Betelgeuse would do the same if we could somehow transport ourselves there. Imagination fueled by a touch of the real is always the best rocket propellant.

Just as the sun is the only star among the trillions out there whose warmth we can feel, so the Milky Way is the only galaxy among an uncountable many that is part of our direct experience.

We can study one galaxy after another in a telescope, but to realize we’re standing on a rocky spheroid orbiting a star encircled by 400 billion other suns in a scintillating arch reaching from one end of the sky to the other is to feel immersion in something greater than oneself. Despite our tininess, each person, tree, dog and microbe out there is an essential ingredient in what makes up a galaxy. It is us and we are it. On the best nights, when our minds are wide open and the Milky Way thick and bright, we look up and almost float away.

This image of the asteroid Lutetia was taken by ESA’s Rosetta probe during its closest approach in July 2010. Lutetia seems to be a leftover fragment of the same original material that formed the Earth, Venus and Mercury. Click to enlarge. Credit: ESA 2010 MPS for OSIRIS Team

Last July, the European Space Agency’s Rosetta spacecraft flew by the 62-mile long asteroid Lutetia and revealed a heavily cratered world. Just this past week, a team of astronomers using data from both the probe and three large telescopes here on Earth created the most detailed spectrum ever of the asteroid.

This spectrum of an orange giant star shows it contains hydrogen (H) and sodium (Na) among other elements.

You make a spectrum by using a prism or diffraction grating to spread out the light reflected by an asteroid into a rainbow of colors. Imprinted on the rainbow are dark lines that represent the signatures of elements and compounds present on the surface of that object. When scientists did this, they discovered that Lutetia’s surface was a near perfect match to a type of meteorite called enstatite chondrites, which are similar to rocks found on Earth.

Enstatite is a magnesium silicate material that dates from the very early days of the solar system. It formed near the sun and is thought to be a key building block in the formation of Earth, Mercury and Venus. So how did Lutetia migrate from the Earth’s vicinity to way out in the asteroid belt between Mars and Jupiter? Scientists suspect that either a close encounter with one of the rocky planets or a gravitational boot by Jupiter altered its orbit. Like some of us, Lutetia finds itself far from its original home. Learn more about this interesting asteroid HERE.

Fragment of Lutetia? A slice of the enstatite meteorite NWA 2965 found in the Sahara Desert. Photo: Bob King

I hope you’ll excuse the length of this blog, but before I sign off, I wanted to let you know that three interesting satellites will be crossing the sky tonight through the coming week: the ever-popular International Space Station (ISS), the Chinese space station precursor module called Tiangong 1 and the struggling Phobos-Grunt probe. Ground controllers still can’t communicate with the probe placing its mission to scoop up soil from Mars’ moon Phobos in great jeopardy.

Tiangong 1 should be bright enough to easily see with the naked eye especially on good passes. Phobos-Grunt may also be a naked eye object, but binoculars will help. All three satellites will appear as unblinking lights moving from the west to east direction.

The times below are for the Duluth, Minn. region. For times for your town, go to Spaceweather Flybys or Heavens Above. To help you anticipate exactly where to look  – especially for Phobos-Grunt – I highly recommend logging on to Heavens Above, clicking on the link for the satellite and then clicking on the time to get a map of its path across the sky.

ISS

* Tomorrow morning Nov. 14 starting at 6:25 a.m. low in the south moving southeast. Passes in front of Saturn three minutes later.
* Wednesday Nov. 16 at 6:05 a.m. High, bright pass across the south-southeast.
* Thursday Nov. 17 at 5:09 a.m. Tracks low in the southeast-east.
* Friday Nov. 18 at 5:47 a.m. beginning in Orion in the southwest and crossing high in the northern sky. Brilliant pass!
* Saturday Nov. 19 at 6:25 a.m. low in the north.

Tiangong 1

* Tonight Nov. 13 at 5:37 p.m. crossing low in the south-southeastern sky
* Monday Nov. 14 at 5:55 p.m. straight across the top of the sky. Bright pass!
* Tuesday Nov. 15 at 6:15 p.m.across the north. Passes under the North Star at 6:18 p.m.
* Friday Nov. 18 at 5:36 p.m. low across the north

Phobos-Grunt

* Saturday Nov. 19 at 6:15 p.m. traveling low in the south-southeastern sky. Brightness is magnitude 2.4 or similar to the stars in the Big Dipper. Visibility ~ 2 minutes
* Sunday Nov. 20 at 6:11 p.m. from northwest to northeast. Could be bright – like a first magnitude star. Visibility ~ 3 minutes
* Monday Nov. 21 at 6:08 p.m. from northwest to northeast. Visibility ~ 2 minutes

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