More On The Asteroid Flyby Plus Mars At Dawn

Asteroid 2011 MD gets its orbit bent strongly by Earth's gravity during its close swingby today. Credit: NASA

Asteroid 2011 MD is still on the way. I was paying so much attention to its brightness and finding up- to-date positional information, I failed to notice that its refined orbit changed the time of closest approach to Earth from around 8:30 a.m. CDT today to noon.

Australian and New Zealand observers are at their telescopes as I write this, watching the flying boulder brighten as it moves swiftly from Libra the Scales to the southern circumpolar constellation of Volans the Fish. Less than an hour after closest approach, 2011 MD will return to the northern daytime sky as it glides across Fornax the Furnace. And by midnight CDT tonight, the asteroid, now 93,000 miles away, will have traveled all the way up into the constellation Andromeda not far from the Andromeda Galaxy. That’s an amazing amount of sky to cover in a day! Too bad 2011 MD will be shining at only 17th magnitude by then. That’s much too faint to see visually except through the very largest amateur telescopes.


Nice series of five video clips in real time made by Australian Dave Herald showing 2011 MD moving faster across the starfield as it gets closer to Earth.

The crescent moon, Mars and the Seven Sister star cluster or Pleiades are gathered together at dawn tomorrow morning June 28 low in the northeastern sky.

I had originally planned to do a Comet Elenin update today, but will hold off a bit until I get another shot at seeing it in the scope tonight. We’ve been clouded out of late. Instead I wanted to alert morning sky watchers to yet another nice conjunction of the moon and a planet. Mars will be about 4 degrees to the lower left of the moon tomorrow morning. Some 3 degrees directly above the crescent you might catch sight of the Pleiades star cluster. Have your binoculars at hand in case the dawn light overwhelms.

Mars is faint right now, because it’s on the opposite side of its orbit from Earth and hence very far away. 207 million miles separate the two planets today. Through a telescope, Mars’ disk is only a little bit bigger than than of the outer planet Uranus. Very tiny! Next March it will come in for another close approach to Earth in the constellation Leo the Lion. At that time the planet will be 63 million miles distant and appear brighter than Vega or Arcturus. Hang in there.

The yellow line on this map shows where NASA's Mars Rover Opportunity has driven from the place where it landed in January 2004 -- inside Eagle crater, at the upper left end of the track -- to a point about 2.2 miles away from reaching the rim of Endeavour crater. I've added names and dates in black for an easier read. Credit: NASA/JPL-Caltech/MSSS

The Mars Opportunity rover continues trekking toward its next goal, the 14-mile diameter crater Endeavour, where scientists hope to study the oldest rocks yet available to the robot. The larger the crater, the deeper the rock excavated from the crust. Deeper rocks are older because they’re generally found beneath younger ones. Spirit Point, named for the now inoperable Spirit Rover, is Opportunity’s first destination at the crater.

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