A Celestial Near-Miss. On the evening of Feb. 15, an asteroid half the size of a football field will zip past the Earth, coming within 17,200 miles of the surface. This is beneath the orbits of the various communications satellites! It will NOT strike the Earth, and almost certainly will not hit a satellite, but it is the first asteroid of such a size to come this close since comprehensive asteroid observations began in the early 1990s.
You can read an article about this object in the South Jersey Times here. Below is a starchart for those of you brave enough to try viewing it in a telescope, and also a diagram of its orbit.
IMPORTANT NOTE: The diagram previously posted here was quite incorrect, due to my using a simple piece of software that was not sufficiently sophisticated to track an object coming this close to Earth. The revised diagram now appears below. Also, the asteroid will not be as bright as I previously claimed: it may not be visible in binoculars, so you may have to find a telescope to view it. But at least you'll know where it is!
Many thanks to Joe Stieber of the Willingboro Astronomical Society for bringing this to my attention, and for providing more accurate information.
International Space Station. The International Space Station (more info here), the largest satellite in orbit and the only permanent one continuously inhabited by human beings, is occasionally visible to the naked eye. It looks like a moving star. Its brightness varies, but it can rival the brightest planets and outshine the brightest stars when conditions are optimum.
Here are some upcoming passes.
Thur., Feb. 7, 7:00-7:03 p.m. Rises SSW; reaches maximum altitude of 46 degrees (about halfway up the sky) in SSE, where it disappears in Earth’s shadow. Magnitude -2.8, a bit brighter even than Jupiter, high in the south.
Sat., Feb. 9, 6:55-7:00 p.m. Rises WSW; peaks high (64 d) in NW; disappears fairly low (39 d) in NNE. Mag. -3.0, slightly brighter than Thursday’s appearance.
Sun., Feb. 10, 6:05-6:11 p.m. Rises SW; peaks high (68 d) in SE; sets ENE. Mag. -3.2, even a tad brighter than yesterday’s pass. It’s very unusual to get two bright passes on successive days: take advantage of it!
For more information about all the passes and the ISS itself, and about other satellites' appearances (including the amazing Iridium flares), look at Heavens Above (from where the preceding information was obtained, to be honest, and you can download it yourself if you want).
* Altitude: angular distance in degrees above horizon, NOT distance in miles above Earth's surface. Straight overhead is 90 degrees, halfway up the sky is 45, the horizon is 0.
Zenith: the point straight overhead.
Magnitude: brightness. The brightest star in the winter sky, Sirius, has a magnitude of -1.4 (negative numbers are brighter); the brightest summer star, Vega, is at 0.0. Jupiter stands at -2.5, Venus at -4.0. The faintest star visible to someone with excellent eyesight is around +6. The Sun is -26! Magnitude estimates for the Station and Shuttle are typically underestimates: they usually appear significantly brighter than the numbers would lead you to expect. Also note: an evening pass starts out quite dim (because the Sun is shining mostly on the part of the spacecraft facing away from us). The satellite becomes brighter as it reaches its peak altitude. So have patience: don't give up too soon! Sweep your eyes along the expected path; look for a moving dot that doesn't blink. Morning passes start out a bit brighter, so are easier to pick up right away. Yes, I agree that the magnitude scale seems to be backwards: the negative numbers are brighter. That's a result of historical events; we're stuck with it.
Weather conditions: as I tell my students, I can't be held responsible for anything that happens less than 100 miles above Earth's surface.
Star charts, sky maps. One of the most comprehensive star charts available is at SkyMaps.com.
Questions about this page? Contact the planetarium director.
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