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Astronomy

NASA’s Big Gamble on Spot 5

When you have a $446 million spacecraft funded by public money, there is a considerable amount of pressure to squeeze it for every last drop of science.  The Dawn mission has already made spectacularly successful visits to two asteroids, Vesta and Ceres.  It is now orbiting around Ceres, having completed a “final” Low-Altitude Mapping Orbit.  There’s not more to see if we can’t get any closer, right?  That’s what Dawn’s engineering team thought, and so they came up with a plan that carefully used the remaining fuel to get to a third target, asteroid 145 Adeona.  They also thought the plan was official enough that it was announced in the Dawn Journal on June 30 only to be quickly removed, followed by an announcement the next day from NASA’s Director of Planetary Science Jim Green that Dawn was to remain at Ceres because “[t]he long-term monitoring of Ceres, particularly as it gets closer to perihelion – the part of its orbit with the shortest distance to the sun — has the potential to provide more significant science discoveries than a flyby of Adeona.”

So what exactly is Dawn waiting for?  A big clue comes from one of the very first things noticed as Dawn approached Ceres, a cluster of spots in Occator crater collectively known as Spot 5.  The unusual and variable appearance of Spot 5 generated serious scientific contemplation and allegations of alien mining activity.  Currently it is believed that Spot 5 consists of sodium bicarbonate and ammonium either as a chloride or a bicarbonate brought forth from within by water which then evaporated or boiled away at some point in the 80 million year history of the host crater.  That’s not all though.  The variable appearance of Spot 5 has been ascribed to a fog or haze that builds up in the crater and is allegedly pictured in this low-angle view:

Haze in Occator Crater

Haze in Occator Crater
Image Credit:   NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA’s explanation of this image can be found here:  http://photojournal.jpl.nasa.gov/catalog/PIA20181

Water may still be evaporating or subliming from the floor of this crater, and the big idea at NASA appears to be to wait until Ceres gets to the point in its orbit where it is closest to the Sun.  Will the extra warmth cause a thicker fog, or something more exciting – a geyser or comet-like jet?  I don’t think anyone knows, and it could fizzle, in which case NASA will have blown a chance to visit a third asteroid.  The decision to wait and watch is in line with the big hoopla preceding the recent announcement that water plumes may have been spotted at Europa.  Where there’s water, there may be life,  or at at least some interesting organic molecules, and it’s possible that NASA is leveraging interest in this to justify some of its funding into the future.

The Eclipse You Didn’t See

This week’s lunar eclipse was seen by by thousands of people, but simultaneously there was an eclipse that was much harder to see.  Had we been standing on the surface of the Moon, we would have seen the Sun silently glide behind the black Earth, leaving only a broken, fiery ring – all the sunrises and sunsets happening around the world.  APOD released a rare “movie” of such an eclipse taken by Surveyor III, a small craft that landed on the Moon in 1967 in preparation for the Apollo missions.  The APOD/R.D.Sampson version had a few flaws I knew I could fix, or at least lessen:  vertical striping (probably photos taken of a tv screen), and low contrast (perhaps because increasing the contrast would have brightened the stripes).  What you see here is my version.

Solar Eclipse From the Moon.  Credit:   NASA, Surveyor 3; Acknowledgement: R. D. Sampson (ECSU)

Solar Eclipse From the Moon. Credit: NASA, Surveyor 3; Acknowledgement: R. D. Sampson (ECSU)

Flaws remain.  There’s only 4 frames in low-resolution black and white.  This color (or colorized?) image hints that different versions of this data exist or existed.  The Lunar Orbiter Image Recovery Project (LOIRP) has been rescuing data from original tapes, leading to dramatic improvements in image quality.  But Surveyor III was a lander and LOIRP is focused on orbiters?  I can only hope that someone will improve upon my version using a better data source.

The Geminids of 2012

Twin Geminids visit Orion and a pair of pines

Things have gotten pretty busy since the kid started going to preschool, and the website has suffered from neglect.  It seems like the only thing I can make time for is the occasional meteor shower.  And so here are the Geminids, in photos taken from the same mountain pass as the Perseids in my previous post.  I like the Geminids.  They are bright, slow-moving, yellow, and clumpy.  Clumpy is not a technical word, it is my own description.  I found that meteors in this particular shower were far more likely to occur in pairs, appearing virtually simultaneously and in the same area of the sky, than any other shower I’ve seen.  That fact that I was able to capture two in the same 20 second exposure appearing near the same trees should attest to that.  It is not lost on me that the radiant is in Gemini, the Twins.

The Perseids of 2012

Perseid over Idaho, 2012

The night sky is beautiful but generally isn’t dynamic.  Other than the slow rolling of the entire sky as the night progresses (as if the stars were affixed to a sphere), there’s very little movement.  Until you see the bright flash of a meteor.  And a meteor shower can turn the sky into a show.  The Perseid meteor shower may be easier to see than most.  Its radiant is in the constellation Perseus, making it visible to most people in the northern hemisphere, where the majority of the Earth’s population resides anyways.  It starts in mid July and peaks August 11th or 12th.  August nights are longer than June or July nights, affording more time to view the shower, but are also warm enough to make lying or sitting still for long periods of time comfortable.  The shower’s large footprint on the calendar makes it easy to coordinate viewing around a busy schedule.

And this year the Perseid viewing should be good.  The peak nights happen to occur on a weekend when the Moon will be a waning crescent that only appears late – on the 12th it rises a few hours after midnight and won’t reach its highest point in the sky until well after the sun has risen.  Unless you have to contend with forest fire smoke or clouds, it could be grand.

Is there a special technique to viewing a meteor shower?  Here I will avoid insisting that you keep scientific records (time, apparent magnitude, constellation), and in fact will assume you are not particularly interested in photographing them (expensive SLR camera on a tripod).  Make sure you have beverages and snacks.  Warm clothing, blankets, or sleeping bags may not seem necessary on a summer night, but ideal viewing conditions are in areas with no clouds and low humidity, and thus radiational cooling and a cold night.  Consider bringing a reclinable chair, cot, or air mattress.  Seek the country – city lights are anathema to good viewing.  Binoculars and telescopes are pointless unless there are other things you are planning on looking at.  Don’t set overly-optimistic expectations:  even at peak, one meteor a minute is the likely rate.

And now you’ll have to decide where to point your face.  If a straight line is drawn through each meteor trail, all such lines will merge at a point called the radiant.  Experts agree that looking directly at the radiant is not the best place to look.  The closer a meteor starts to the radiant, the shorter its trail will appear to you, although paradoxically it means the meteor’s true path was pointed more directly at your head than others.   But after discussing the radiant, opinions diverge.  The advice at Spacedex is simply to “look approximately half way up the sky facing northeast…. Looking directly up at the sky or into the radiant is not recommended….”  These people are wrong.  Halfway up the sky in the northeast is  where the radiant in Perseus will be, at least for the early night, so they’ve told you to look at the radiant and not to look at it in the same paragraph.  Unfortunately the northeast is also the direction the moon will be rising in later, and you don’t want to ruin your night vision by looking at that.

Theoretically, to see the longest meteor trains, you should be looking 90 degrees away from the radiant.  However, there are other factors to consider.   Near to the horizon, the increased thickness of atmosphere leads to greater light scattering, decreasing the brightness of meteors there slightly but also increasing the amount of background light, thus leading to decreased contrast between meteor and sky and poorer viewing.  Also , if you are looking towards the horizon, part of your field of view is of the ground, and meteors don’t appear there.  Most of your field of view should be filled by sky.  So just after sundown when Perseus is close to the horizon, you should be looking straight up.  As Perseus rises  in the northeast, you should consider looking slightly southwest and as the night progresses toward dawn look more to the west.  If you get bored of the meteor show, consider looking at Perseus.  Below him you will see the Moon and Jupiter, and later at night even Venus, all in the same area of sky.

Does REI Grok Dark Skies?

I was at REI  in Missoula, MT, one day and noticed several lights outside pointed downwards towards some tall grasses planted against the wall.  Intrigued, I returned after dark to take some photos.

REI After Dark

REI After Dark

Notice the downward facing lights along the wall.  The lamp in the parking lot is extremely bright, but faces downward.  The interior is brilliantly lit, but an awning traps most of the upwardly directed light escaping from doors and windows.  The illuminated sign is composed of small lettering and a moderately sized logo (unlike the large, garish, bloated, balloon lettering on the store next door).  This store is not losing much light to the sky above, and as an astronomer, this makes me happy.

The night sky, for most viewers, has lost something.  As cities get bigger, electrical supplies steadier, power cheaper, as lighting technology advances, as particulate matter spews into the air, the night sky has been smothered by the strange glow of light pollution.  Because of its slow, steady progress, each generation is little aware that it has less than the generation before.  The few dozen stars people can see are a mere shadow of the myriad stars, planets, meteors, aurorae, comets, moons, nebulae, and galaxies that are available to the lucky few whose skies are still dark.  For more information on light pollution, including its detrimental affect on wildlife and human health and how to help combat it, visit the International Dark Sky Association.

A few last words.  First, I am a member of REI but am not receiving financial compensation for this post.  Secondly, yes, the sign shows up as a ghost image – inverted green lettering just below the roofline.  This, like the lens flare from the light in the upper right corner, is a camera artifact.

The Unicorn’s Heart

 

V838 Monocerotis Composite

A composite image of V838 Mon

In 2002, a previously unknown star in the constellation Monoceros, The Unicorn, briefly became the brightest star in our galaxy.  Although great debate rages about the reasons for V838 Mon’s flareup, there is general consensus that images taken by the Hubble Space Telescope in the months and years afterward are some of the most beautiful and dramatic ever taken.  A common mistake when viewing the series of images is to assume that they portray a single shell of material expanding outward from some vast explosion, but it’s a bit more complicated than that.  The brief flash of light is sweeping outward from the star, lighting up – a few at a time- a series of shells of gas and dust surrounding V838 Mon that it created during previous episodes.  As far as I know, my composite image is the first and only attempt anywhere to portray what these Russian-doll shells might look like together, illuminated by the dim, steady light of the star between it’s infrequent outbursts.  This is not a scientific-quality composition, but I think it captures the essence of the Unicorn’s Heart slowly beating.