A Quick Look At 1 Ceres

Is it a giant asteroid? Is it a dwarf planet? Is there a difference?

1 Ceres has been classified as both. Ceres is the largest object in the Asteroid Belt between Mars and Jupiter – something like 900 km across. We will get our first really good look at it in about 2 years when NASA’s Dawn spacecraft arrives in its orbit. It was in fact the first “asteroid” discovered, in 1801. It ranges from magnitude 7 to 9, so is almost never visible to the unaided eye, but it’s also pretty easy to find with most telescopes.

I thought I’d take a look using the University of Iowa’s Rigel telescope in Arizona, using the web-based Sierra Stars Observatory Network. Here’s a shot of 1 Ceres captured during the night of 1 May 2013. Ceres is the bright “star” in the middle of the frame. It’s so bright (around magnitude 8) that it’s actually quite overexposed on this cropped image. The image here was made by stacking three 150 second exposures.

2_112103_3 ceres cr1 800px

The dwarf planet 1 Ceres photographed early on the morning of 1 May 2013 using the University of Iowa Rigel Telescope in Arizona. Ceres is the brightest object in this image, in the centre of the frame. It’s so bright compared to the many background stars that it’s actually over-exposed here. A composite of three stacked 150 second exposures without filters taken with the 31 cm robotic telescope, over the Sierra Stars Observatory Network.

The particulars from the FITS file of the first of three images taken by Rigel:
DATE-OBS= '2013-05-01T03:25:00.311' / UTC, start of exposure
LST     = '10:39:31'           / Local sidereal time at exposure start
POSANGLE= '  70:48:39'         / Position angle, degrees, +W
LATITUDE= ' 31:39:56'          / Site Latitude, degrees +N
LONGITUD= '-110:36:05'         / Site Longitude, degrees +E
ELEVATIO= ' 38:22:26'          / Degrees above horizon
AZIMUTH = '283:31:10'          / Degrees E of N
OBJRA   = '  6:39:18.3'        / Target center J2000 RA
OBJDEC  = ' 28:48:59.6'        / Target center J2000 Dec

 

Copyright © 2013 David Allan Galbraith
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Canada’s Own “Big Meteor” – of 1966

It could be said that the coincidence of the century happened on 15 February 2013, when  on the same day that earth was approached by a sizable asteroid (2012 DA14) an amazing meteorite streaked through the sky over the Ural Mountains, exploding with enough force that over 1,000 people were injured by glass and other debris from building that were knocked about by the blast.

On September 17, 1966 a similar event – a major meteorite – streaked over Southern Ontario and likely ended up splashing down in Lake Huron, some dozen miles off of Kincardine. My family and I were  witnesses to it, recorded as “The Bolide of September 17, 1966” in the Journal of the  Royal Astronomical Society of Canada. While not cited by name, the reference on the second page of the journal article, “One key observation from about eight miles south of Kincardine, on Lake Huron…” is a note about my father’s report of our family’s experience of the event.

We were at our cottage that Saturday evening; I was 6, my sister was 3, and my parents had some friends over for a barbecue. About 12 minutes before 9 PM the sky suddenly lit up all around us. I was actually in the cottage when the flash occurred, but my father was outside. I rushed out and did see the vapour trail high overhead. My overwhelming memory of the light from the bolide was that it was strongly green.

Being just a few years after the Cuban Missile Crisis, some of the adults immediately thought we were in the middle of World War III. My father, though, knew just what he had seen, and he wrote up an account in a letter to the Dominion Observatory in Ottawa.

As a child I often dreamt of setting out in search of fragments of the meteorite. I would examine rocks along the Lake Huron shore, hoping that one might look like a meteorite. Alas, I never did find it! However, it’s not impossible that it could be found one day. The likely location is well-known, and the waters off of Kincardine aren’t too deep – but the search would be tedious. Any remains of the space rock would likely be foot-ball-sized or smaller, possibly scattered over a square km or more of lake floor.

The observation of the 1966 event was considerably enriched by a photograph taken from Guelph, Ontario, as well as the verbal reports provided by observers such as my father. Astronomers calculated that the meteor likely first became visible over south-western Ontario north of the Lake Erie shoreline south of Brantford, and then moved north-west at about 17 km per second; it was likely luminous for at least 10 seconds.

In a review of meteor observations over Canada, Hodgson (1994) related that it’s likely that the 1966 Southern Ontario Bolide had its origin in the asteroid belt, because of its velocity.

References

Halliday, I. 1966. The Bolide of September 17, 1966. Journal of the Royal Astronomical Society of Canada. 60 (Dec.): 257. Available on-line at: http://articles.adsabs.harvard.edu/full/1966JRASC..60..257H

Hodgson, J. H. 1994. The Heavens Above and the Earth Beneath: A History of the Dominion Observatories Part 2: 1946-1970. Geological Survey of Canada, Open File 1945 (Accessed as a Google eBook 16 Feb 2013)

My Favourite Amateur Astronomy News from 2012: September’s Impact on Jupiter

There were some great astronomy news stories in 2012, but one really stands out for me as a demonstration of why amateur astronomy can still be “more” than a hobby. Dedicated amateur astronomers can make real contributions to science.

Early on the morning of September 10, Mr. Dan Peterson was observing the planet Jupiter with a 12″ telescope in Texas, and saw a bright flash on one side of the planet. The flash lasted perhaps 1.5 to 2 seconds, and was reported to be very bright. Mr. Peterson posted his observation on an astronomy web forum (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5413921/Main/5413225). A few hours later another amateur, Mr. George Hall, posted a photograph of the flash, confirming the earlier report (http://georgeastro.weebly.com/uploads/1/3/3/4/13344093/jupiterimpact.jpg).

This event – likely the impact of a small, previously unknown comet – into the Solar System’s largest planet – would not have been observed at all unless amateurs had seen it, as was the case. With the large number of planets and other interesting objects in our Solar System (especially comets and asteroids), the professional scientific community and the incredible instrumentation provided by earth-based and space-based telescopes can’t monitor everything all the time. There are no spacecraft in the vicinity of Jupiter, and even if there had been, observing an unpredictable event that lasted 2 seconds would be down to sheer luck even if there was a spacecraft near-by.

Even the world-wide network of amateur astronomers can’t catch everything that happens, of course, but the chances are that transient events will be picked up by an amateur first. This isn’t a new situation. The Association of Planetary and Lunar Observers (yes, they use the acronym A.L.P.O. – http://www.alpo-astronomy.org/) has been organizing, recording, and helping people to share observations on the planets, comets, asteroids, and just about everything else in the solar system, for decades. With 14 different “observing sections” covering everything from meteors to remote planets, A.L.P.O. is a great example of people contributing to new knowledge – true citizen scientists. A.L.P.O. even publishes its own journal, in production since the 1940s. Membership is open to anyone interested, whether or not you are making regular observations. They are international and welcome all interests.

There are several ways in which amateurs are contributing to astronomy around the world right now. In addition to observations of Solar System events and the discovery of comets, some are making detailed measurements of the brightness of individual stars over time, called stellar photometry. Many stars are variable, changing their brightness over time for several different reasons. For example, the American Association of Variable Star Observers (http://www.aavso.org/) links up and supports people making observations of stars that are changing brightness because of their intrinsic physics, or even because of orbiting companion stars (occulting binaries).

What’s more, even in today’s light-polluted urban environments, like Southern Ontario, amateur observing programs like these can continue. The moon and the planets out to Saturn, at least, are so bright that useful observations can be made even with the ubiquitous background glow in the sky reducing the contrast of what we can see. Getting involved in a meaningful way in these programs is also not dependent on having large, expensive telescopes. There are observing sections in A.L.P.O. for people observing the sky with nothing more sophisticated than a pair of binoculars, or just their eyes. Knowledge of the sky, patience, and making careful, organized notes are the most important tools any astronomer – amateur or not – brings to the science.

© 2012, David Allan Galbraith