Blog Archives

And the Award for Leading Trojan Moon Goes To…

Raw image of Telesto from Cassini's narrow-angle camera on Jan. 14, 2016. (NASA/JPL-Caltech/SSI)

Raw image of Telesto from Cassini’s narrow-angle camera on Jan. 14, 2016. (NASA/JPL-Caltech/SSI)

Drumroll please… the little moon Telesto! (You like it, you really like it!) This image, captured by Cassini on Jan. 14, 2016, shows Saturn’s moon Telesto – a “leading trojan” of the much larger satellite Tethys.

A trojan moon is one that orbits a parent body within the same path as a more massive satellite, positioned at the Lagrangian points L4 and L5… usually at 60º ahead and behind within the orbit relative to the overall center (which, in the case of Tethys, is Saturn.)

The irregularly-shaped, 15-mile (24-km) -wide Telesto rides around Saturn ahead of Tethys, making it the moon’s “leading” trojan. Its slightly larger sister Calypso follows behind Tethys as the trailing trojan. All three orbit the ringed planet at a distance of over 183,000 miles (294,000 km).

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Passing 2-Mile-Wide Asteroid Has Its Own Little Moon

Goldstone radar images of 1998 QE2 shows an orbiting moon (NASA)

Goldstone radar images of 1998 QE2 shows a small moon in tow (NASA/JPL-Caltech/GSSR)

On the afternoon of Friday, May 31, 2013, at 4:59 p.m. EDT, the nearly two-mile-wide asteroid 1998 QE2 will pass by our planet at a distance of about 5.86 million km (3.64 million miles)… about 15 times the distance between Earth and the Moon. And although it poses no threat of impacting Earth neither during this pass nor in the foreseeable future, on the eve of its close approach NASA revealed a surprising discovery about this cosmic visitor: it has a little moon of its very own!

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Our Electric Earth at Night: the “Black Marble”

Suomi NPP composite satellite image of North and South America at night

Suomi NPP satellite image of North and South America at night

In daylight our big blue marble is all land, oceans and clouds. But the night is electric.

This image of North and South America at night is a composite assembled from data acquired by the Suomi NPP satellite in April and October 2012. The new data was mapped over existing Blue Marble imagery of Earth to provide a realistic view of the planet.

The nighttime view was made possible by the new satellite’s “day-night band” of the Visible Infrared Imaging Radiometer Suite. VIIRS detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe dim signals such as city lights, gas flares, auroras, wildfires, and reflected moonlight. In this case, auroras, fires, and other stray light have been removed to emphasize the city lights.

Although the view looking down from space is of a sparkling show, the downside of course is light pollution over major metropolitan areas which impede the view of the night sky from the ground. (Find out more at the International Dark Sky Association site.)

Read more (and watch a video of these nighttime images of Earth) below:

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Hello, Earth!

NASA satellite image of Earth. January 2012

It’s the 2012 version of the “Blue Marble“! Here’s an amazing new high-definition portrait of our planet, made by NASA’s Suomi NPP satellite launched back on October 28. This is a composite image created from multiple scans taken with the satellite’s Visible/Infrared Imager Radiometer Suite (VIIRS).

The Suomi NPP satellite. Click for animation.

Suomi NPP is the first satellite designed to collect critical data to improve short-term weather forecasts and increase understanding of long-term climate change. It orbits Earth about 14 times each day and observes nearly the entire surface.

Learn more about the Suomi NPP satellite here.

Credit: NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

Ripples in the Sky

Here’s something interesting…

This Saturday I was looking at some timelapse video from the Canada-France-Hawaii Telescope’s Cloudcam… those are beautiful in their own right, but really I was interested in seeing if there was any visual of the reentering UARS. After doing some time-zone math, I realized that the satellite would be reentering before it was really dark over Hawaii, but I did see something unusual in this sequence from the 23rd-24th:

Vodpod videos no longer available.

If you notice, around 21:33 HST (about 30 seconds in) in the video, there are some “ripples” high in the atmosphere visible in the upper left of the frame. These extend for some time before dissipating completely. Could that be a “shockwave” from the reentering UARS, further north and east on the globe? Based on this trajectory map, UARS could have reentered the atmosphere not too far from that site.

NASA scientists still aren’t exactly sure where and when UARS came down, but it’s suspected all remains went into the Pacific Ocean west of Canada.

I’m looking into this with those much more specialized in such things than I am. Stay tuned…

Video credit: Canada-France-Hawaii Telescope (Check out the original HD version on the site here.)

UPDATE: I am being told by a couple of experts that this may be “just” a case of high-level cirrus clouds, or else something created by the video compression. Not sure, I think I am going to look into it a bit further.

UPDATE 2: It’s 99% surely cirrus clouds. After hearing back from several reputable expert sources, and seeing where the UARS eventually did enter the atmosphere (off the eastern coast of Africa) it’s definitely not shock waves. Oh well. But that’s how you find things out… asking the right people their thoughts! 


Grimsvotn GOES Boom

Iceland's Grímsvötn volcano sends a plume of ash 65,000 into the atmosphere – CLICK TO PLAY.

Watch as a huge cloud of ash bursts into the upper atmosphere from Iceland’s Grímsvötn volcano in this sequence of images taken by NASA’s GOES-13 weather observation satellite. The oblique angle of illumination and position along the edge of the globe emphasizes the incredible vertical scale of the eruption. (Click to play.)

Grímsvötn erupted on Saturday, May 21, sending an ash plume 12 miles high and closing local airports. Covered by glacial ice, the eruption was rather explosive and very dramatic…as seen in many photos circulating online today.

Iceland’s most active volcano, Grímsvötn hasn’t erupted this forcefully in almost a century.



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