Nova update, new radar pix of asteroid 2005 WK4, a phony double star

AAVSO chart for binocular users showing the nova and comparison star magnitudes. Click to download a full-size version. Copyright: AAVSO

Before we embark on today’s topic, let’s update where we’re at with Nova Delphini 2013. For the past day it’s plateaued around magnitude 5.0, maybe even rising a tad to 4.9. It remains easily visible in binoculars high in the southeastern sky at nightfall.

Light from the nearly full moon now drenches the sky, making it nearly impossible to glimpse the nova with the naked eye. Dark skies return about Aug. 23. Let’s hope it hangs in there till then.

On August 8 NASA scientists used the 230-foot (70-meter) Goldstone radar antenna in Goldstone, Calif. to bounce radio waves off near-Earth asteroid 2005 WK4.

Sequence of radar images of 2005 WK4 obtained on August 8 at Goldstone. The asteroid looks roughly oval-shaped with a bulge near the equator and some flat regions. Click for large image. Credit: NASA/JPL-Caltech/GSSR

By studying the reflected radar echoes, they reconstructed a sequence of images of the giant boulder, estimated at between¬†660 and 980 feet (200-300 m) in diameter. In a delightful coincidence that’s about as big as the 1,000-foot Arecibo radio telescope in Puerto Rico, the largest in the world. Astronomers used this dish to observe 2005 WK4 in July 2012.

Video of 2005 WK4 on Aug. 7 by Gianluca Masi. The asteroid appears only as a point of light in even the largest optical telescopes. The radar technique not only gives precise positions of nearby asteroids but also reveals their shapes and surface features

The asteroid missed Earth by a long shot –¬†1.93 million miles (3.1 million km) – but the data gained by radar studies will help refine 2005 WK4’s orbit well into the future. It also transformed what had been a mere point of light into a real world, albeit a small one. The Goldstone sequence covers 6 1/2 hours during which the asteroid completed 2.4 rotations.

The moon and stars Alpha and Beta Capricorni form a right triangle tonight in binoculars. The field of view shown above is about 5 degrees. Stellarium

While you’re out gandering at the nova tonight, give a look at the big, bright moon in your binoculars. About 4-5 degrees to its left on the opposite side of the field of view are two bright stars, Alpha and Beta Capricorni in Capricornus the Sea Goat. Alpha looks like the perfect double star, where you might envision each in orbit around the other. Guess again. It’s a total fake – just a chance alignment that convincingly mimics the real thing.

Below it shines Beta. Here we have a genuine double with a 6th magnitude companion orbiting close by to the west. The moon helps us find Alpha and Beta Cap with ease, but glare could make spotting Beta’s companion a bit of a challenge at least tonight. Give it a try to see for yourself.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

4 thoughts on “Nova update, new radar pix of asteroid 2005 WK4, a phony double star

  1. In 100 days, we will be within the critical 24 hours of the perihelion of Comet ISON. It excites me to think that we may have a comet this year that comes on the brighter side of Magnitude -10. Maybe not. But I like to think positive. If it does, it will likely be the brightest comet that I ever see. If it does, the tail should be a fascinating item to see, a week or so later.

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