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Does Earth Have a New Moon? Kinda But Not Really

Concept image of a large asteroid passing by Earth and the Moon

Earth currently has a new asteroid companion in its orbit around the Sun (Illustration composite of NASA and ESO images by J. Major)

This week NASA’s Jet Propulsion Laboratory announced news of an object traveling around the Sun in an orbit that keeps it relatively close to our own planet. The object, a near-Earth asteroid (NEO) less than 300 feet (100 m) across, is designated 2016 HO3 and has in some reports been called a “new” or “mini” moon of Earth…but that’s not entirely true. More accurately 2016 HO3 is what’s known as a quasi-satellite, and is in a temporary (albeit long-lived by human standards) orbit that takes it on a “leapfrog” path around Earth, never getting closer than 38 times the distance to the Moon—about 9.1 million miles.

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Europe’s Sentinel-3A Returns Gorgeous “First Light” Earth Images

Day to night transition over Norway captured by ESA's Sentinel 3A satellite. Credit: Copernicus data (2016).

Day to night transition over Norway captured by ESA’s Sentinel 3A satellite. Credit: Copernicus data (2016).

Captured by the EU’s Copernicus Sentinel-3A satellite on Feb. 29, 2016, this beautiful composition of blacks, purples, and blues shows the twilight transition across the Norwegian archipelago of Svalbard, located north of the Arctic Circle between Norway and the North Pole.  The snow-covered and fjord-cut large island of Spitsbergen can be seen at the right edge, while sea ice and clouds follow their own swirling currents on and above the Greenland sea.

This is the first image acquired by the spacecraft, which was launched aboard a converted-ICBM Rockot vehicle on Feb. 16 from Russia’s Plesetsk Cosmodrome. The first of two planned Sentinel-3 satellites, 3A is currently in a high-inclination orbit at an altitude of 505 miles (814 km).

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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

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