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Views of Moons

Jonathan Nally — Tue, 24 Apr 2012 14:00:02 +0000

NASA’S CASSINI SPACECRAFT, in orbit around the planet Saturn, has been sending back some wonderful views of its moons. In particular, it has captured images where one moon seems to float in front of the other. Here we present a selection of recent images.

Can you tell which of these moons in the foreground? It's Titan, the large one (diameter 5,150 kilometres; bigger than our Moon) with the orange atmosphere, with smaller, shiny, icy Tethys in the background. Titan was 2.3 million kilometres from Titan, and 3.4 million from Tethys when it took this image. Saturn's rings can be seen edge-on in the distance.

This black-and-white image shows the moon Rhea (1,528 km diameter) in front of Titan. Cassini was 2 million kilometres from Titan and 1.3 million kilometres from Rhea when it took this image.

This view shows Titan again, this time with the much smaller moon Dione (1,123 km diameter) peering around from behind, with Saturn and its rings (edge-on) in the background. Cassini was 2.3 million kilometres from Titan and 3.2 million kilometres from Dione when it took the image. The haze that surrounds Titan can clearly be seen. Titan has a mostly nitrogen atmosphere that extends far from the surface. The surface pressure is about 1.5 times that on Earth.

In this view, Titan appears to float in front of Saturn and its rings. Titan is not only the second-largest moon in the Solar System; it's also about 300 kilometres wider than the planet Mercury!

More information: Cassini mission

Story by Jonathan Nally. Images courtesy NASA / JPL-Caltech / Space Science Institute.

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In the footsteps of Apollo 11

Jonathan Nally — Sun, 22 Apr 2012 03:25:20 +0000

NASA's Lunar Reconnaissance Orbiter took this image of the Apollo 11 landing site, showing the equipment left on the surface of the Moon.

NASA’S LUNAR RECONNAISSANCE ORBITER spacecraft took this amazing image from an altitude of just 24 kilometres above the surface of the Moon. It shows the descent stage of the Apollo 11 lunar module, right where Neil Armstrong and Buzz Aldrin left it in July 1969. Also visible are the instrument packages the two astronauts set out on the lunar surface not far from the lunar module.

So take that, Moon landing conspiracy theorists!

Visible are dark squiggly lines joining the various man-made objects. These are the tracks left by the astronauts as their boots scuffed up the powdery lunar dust.

The LRRR was the Laser Ranging RetroReflector, a device that contained “corner reflectors”—special lenses that send a light beam back out in the same direction it enters. Scientists fired laser beams at the LRRR and timed how long it took for the signals to return to Earth, enabling them to make incredibly accurate measurements of the distance to the Moon.

And because the LRRR is a passive device with no electrical requirements and no moving parts, it is still used today.

Also visible is the Passive Seismic Experiment Package(PSEP), a seismometer that detected “moonquakes” and the impact of spacecraft and radioed the data back to Earth.

Neil Armstrong (whose shadow can be seen at left) ran over to take a look at Little West crater, about 50 metres from the lunar module.

You can see a trail leading to the crater (called Little West) on the right of the lunar module. This is where Neil Armstrong ran over to take a look. The distance is about 60 metres, and marks the furthest point either of the astronauts ventured from the lunar module.

(Take a look at this Apollo Lunar Surface Journal page for a more detailed image.)

Astronauts on later missions were far less constrained in their movements, as they had more time for their spacewalks. In addition, the final three Apollo mission carried lunar rovers that enabled their astronauts to travel further.

Story by Jonathan Nally. Images courtesy NASA.

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Hubble’s birthday view of starbirth nebula

Jonathan Nally — Tue, 17 Apr 2012 21:24:48 +0000

The amazing twirls and swirls of 30 Doradus, a starbirth region of gas and stars located in the Large Magellanic Cloud galaxy 170,000 light-years from Earth.

IT SEEMS HARD TO BELIEVE, but the Hubble Space Telescope has now been in orbit for 22 years. In that time it has advanced our understanding of the universe overall and of the stars, galaxies and nebulae within it.

To celebrate it’s birthday, Hubble scientists have released stunning new views of a “starbirth” region deep in the southern sky, known as 30 Doradus.

30 Doradus is part of the Tarantula Nebula, so-called for its resemblance to a spider, with tendrils of interstellar gas extending in many directions.

The Tarantula is located within the Large Magellanic Cloud galaxy, a close neighbour of the Milky Way about 170,000 light-years distant.

The main Hubble image is made up of many separate images “stitched” together. In fact, it is one of the largest Hubble images ever produced, and at the distance of the Tarantula covers a field 650 light-years across.

This starbirth region is home to numerous stars, young and old, big and small. Near the nebula’s heart is a star cluster called R136. It used to be thought that R136 contained the largest known star in the universe, R136a at 1,500 the mass of the Sun. It has since been determined, however, that R136a is itself a tight cluster of stars. Nevertheless, one of those stars, R136a1, is still the largest known at 265 times the mass of the Sun and 8,700,000 it’s brightness.

The radiance from all the stars has carved out intricate voids and valleys within the surrounding gas, and in some cases formed shockwaves or regions of increased gas density that could be triggering the inward collapse of gas clumps to form new stars.

See more and larger images of 30 Doradus at HubbleSite.

This close-up of part of 30 Doradus shows a huge cavity in the gas, carved out by the stellar wind of young, powerful stars.

This tight, bright cluster of stars within 30 Doradus is called Hodge 301. Unlike many of the youthful stars in 30 Doradus, many of those in Hodge 301 are ageing, red supergiants.

At the heart of this portion of 30 Doradus lies the star cluster R136, which contains many of the heaviest known stars in the local universe.

Story by Jonathan Nally. Images credit: NASA, ESA, D. Lennon and E. Sabbi (ESA/STScI), J. Anderson, S. E. de Mink, R. van der Marel, T. Sohn, and N. Walborn (STScI), N. Bastian (Excellence Cluster, Munich), L. Bedin (INAF, Padua), E. Bressert (ESO), P. Crowther (University of Sheffield), A. de Koter (University of Amsterdam), C. Evans (UKATC/STFC, Edinburgh), A. Herrero (IAC, Tenerife), N. Langer (AifA, Bonn), I. Platais (JHU), and H. Sana (University of Amsterdam), and the Hubble Heritage Team (STScI/AURA)

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VIDEO: Two amazing views of Planet Earth

Jonathan Nally — Mon, 02 Apr 2012 00:22:13 +0000

THESE TWO AMAZING NASA VIDEOS were taken by the astronauts aboard the International Space Station. The one above was made in mid March, and shows the view looking down as the Station sailed across Brazil and out into the Atlantic Ocean and across the Earth’s “terminator”. The terminator is the line dividing the half of the planet lit by the Sun and the half in shadow. The camera view also shows Soyuz (manned) and Progress (unmanned) spacecraft docked with the Station.

The video below was taken a little later in March and shows what it’s like to see an aurora from above. The Station was flying over the southern part of the Indian Ocean at the time. Toward the end of the video we can see daylight beginning to break across the horizon in the right-hand half of the screen.

Story by Jonathan Nally. Videos courtesy NASA.

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New images of an icy world

Jonathan Nally — Tue, 13 Mar 2012 02:08:07 +0000

NASA's Cassini spacecraft took this raw, unprocessed image of Saturn's moon Rhea on March 10, 2012. The camera was pointing toward Rhea from a distance of approximately 41,873 kilometres.

THESE RAW, UNPROCESSED IMAGES of Saturn’s second largest moon, Rhea, were taken on March 10, 2012, by NASA’s Cassini spacecraft. This was a relatively distant flyby with a close-approach distance of 42,000 kilometres, well suited for global geologic mapping.

At 1,530 kilometres diameter, Rhea is the ninth-largest moon in the Solar System.

During the flyby, Cassini captured these views of the moon’s cratered surface, creating a 30-frame mosaic of Rhea’s leading hemisphere and the side of the moon that faces away from Saturn.

The observations included the large Mamaldi (480 kilometres across) and Tirawa (360 kilometres across) impact basins and the 47-kilometre-wide “ray crater”Inktomi, one of the youngest surface features on Rhea.

This second raw, unprocessed Cassini image of Rhea was taken from a distance of approximately 42,258 kilometres, and shows the moon's icy, cratered surface. The streaks on the right are an artefact of the imaging.

Shadows help to give a 3D effect to Rhea's craters in this raw, unprocessed Cassini shot taken from a distance of approximately 42,096 kilometres.

This raw, unprocessed shot was taken from much further away, approximately 115,060 kilometres, and shows Rhea's "terminator"—the dividing line between day and night.

Cassini has been investigating Saturn and its moons since 2004. This included dropping a probe called Huygens onto the surface of Saturn’s largest moon, Titan, in 2005. Launched in 1997, Cassini-Huygens mission is a co-operative project of NASA, the European Space Agency and the Italian Space Agency.

See all of Cassini’s raw images at NASA’s Saturn page.

Adapted from information issued by NASA / JPL-Caltech / SSI.

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Gallery: The Omega Nebula

Jonathan Nally — Tue, 10 Jan 2012 10:03:34 +0000

This image of the Omega Nebula (Messier 17), captured by the European Southern Observatory's Very Large Telescope (VLT), is one of the sharpest of this object ever taken from the ground. It shows the dusty, rosy central parts of the famous star-forming region.

A NEW IMAGE OF THE HEART of the Omega Nebula, captured by the European Southern Observatory’s (ESO) Very Large Telescope (VLT), is one of the sharpest of this object ever taken from the ground.

It shows the dusty, rose-colored central parts of this famous stellar nursery and reveals extraordinary detail in the cosmic landscape of gas clouds, dust and newborn stars.

The colourful gas and dark dust in the Omega Nebula serve as the raw materials for creating the next generation of stars.

In this particular section of the nebula, the newest stars on the scene—dazzlingly bright and shining blue-white—light up the whole ensemble. The nebula’s smoky-looking ribbons of dust stand in silhouette against the glowing gas.

The dominant reddish colours of this portion of the cloud-like expanse, arise from hydrogen gas, glowing under the influence of the intense ultraviolet rays from the hot young stars.

The Omega Nebula goes by many names, depending on who observed it when and what they thought they saw. These other titles include the Swan Nebula, the Horseshoe Nebula and even the Lobster Nebula. The object has also been catalogued as Messier 17 (M17) and NGC 6618.

The nebula is located about 6,500 light-years away and is a popular target for astronomers, as it ranks as one of the youngest and most active stellar nurseries for massive stars in the Milky Way.

A wider view of the Omega Nebula.

Download wallpapers of the Omega Nebula:

1024×768 (286.1 KB)

1280×1024 (450.0 KB)

1600×1200 (664.9 KB)

1920×1200 (707.6 KB)

Adapted from information issued by ESO.

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Gallery – The Sculptor Galaxy

Jonathan Nally — Sat, 31 Dec 2011 13:01:54 +0000

Bright regions of ongoing star formation are spread throughout the Sculptor Galaxy, which is pumping out new stars at a furious pace.

ELEVEN AND A HALF MILLION light-years away in the direction of the southern constellation Sculptor, lies the beautiful galaxy NGC 253. Also known as the Sculptor Galaxy, it has been given the names Silver Coin Galaxy or Silver Dollar Galaxy by amateur astronomers.

Indeed it is a popular target for amateurs, and can even be glimpsed through binoculars. It is one of the brightest galaxies in the sky after the Milky Way’s closest, big galactic neighbour, the Andromeda Galaxy.

But professional astronomers are interested in it too, having noted widespread active star formation within it, hence its other label as a “starburst” galaxy.

The many bright clumps dotted throughout the galaxy are “stellar nurseries” where hot, young stars have just ignited. The radiation streaming from these giant blue-white baby stars makes the surrounding hydrogen gas clouds glow brightly (green in this image).

NGC 253 was discovered by the German–British astronomer Caroline Herschel, the sister of the famed astronomer William Herschel, as she searched for comets in 1783.

The image was captured by the European Southern Observatory’s VLT Survey Telescope (VST), and is probably the most detailed wide-field view of this galaxy and its surroundings ever made.

As well as NGC 253, zooming in also reveals a very rich tapestry of much more distant galaxies far beyond NGC 253, a handful of which are marked on the enlargement below – there are many more:

This enlargement shows a handful of background galaxies (marked with arrows) – there are many more.

The VST – Super survey telescope

This latest image of NGC 253 was taken during VST’s science verification phase of the European Southern Observatory’s VLT Survey Telescope (VST), when the telescope’s scientific performance is assessed before it enters operations.

The VST data are being combined with infrared images from another telescope called VISTA to identify the younger generations of stars in NGC 253.

VLT Survey Telescope (VST)

This picture is more than 12,000 pixels across and the superb sky conditions at ESO’s Paranal Observatory, combined with the fine telescope optics, result in sharp star images over the entire image.

The VST is a 2.6-metre-diameter, wide-field survey telescope with a one-degree field of view — which means it can see an area of sky twice as broad as the full Moon.

The 268-megapixel camera OmegaCAM at its heart is designed to map the sky both quickly and with very fine image quality. VST is the largest telescope in the world designed to exclusively survey the sky in visible light, complementing ESO’s VISTA infrared survey telescope, also located at Paranal.

The VST programme is a joint venture between the INAF–Osservatorio Astronomico di Capodimonte, Naples, Italy and ESO.

Adapted from information issued by ESO / INAF-VST. Acknowledgement: A. Grado/L. Limatola/INAF-Capodimonte Observatory.

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Gallery — Moon through the murk

Jonathan Nally — Thu, 01 Dec 2011 03:00:52 +0000

Photo from the International Space Station shows the layers of Earth's atmosphere, with the Moon in the far background.

THIS STUNNING PHOTOGRAPH taken from the vantage point of the International Space Station, shows us what the layers of Earth’s atmosphere look like when seen edge on.

The darkest patch at the bottom of the image is likely to be cloud cover, showing a characteristic unevenness to its upper limits.

Just above that is an orange-red glow that marks the extent of the troposphere, the thick, lowest layer of the atmosphere that reaches up from the surface. The troposphere is where pretty much all of our weather occurs.

Just above the troposphere is a thinner, brown layer. This is the tropopause, which separates the troposphere from the next layer up, the stratosphere.

Indeed, the next layer we see in the image—a whitish-grey colour—is probably part of the stratosphere.

Above that are the topmost layers of the atmosphere—the mesosphere, thermosphere, and exosphere—which gradually fade from a pale blue into the black of space.

The gases and aerosols (tiny particles) in each atmospheric layer are good at filtering out particular colours in the light spectrum, and that’s why they appear to contrast each other so well.

Finally, in background we can see the Moon, 384,400 kilometres away, but seeming to be a lot closer.

See the full-size image here.

Story by Jonathan Nally. Astronaut photograph provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre.

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Gallery – Geyser moon seen in silhouette

Jonathan Nally — Mon, 28 Nov 2011 13:01:17 +0000

Saturn's moon Enceladus appears in silhouette in this image taken by NASA's Cassini spacecraft. The bulk of Saturn is in the background, the planet's rings seen edge-on appear as the dark horizontal line.

NASA’S CASSINI SPACECRAFT took this image of Saturn’s moon Enceladus on October 19, 2011. As the spacecraft passed Enceladus, its infrared instruments, cameras and other instruments monitored activity on the moon, in particular the famed jets erupting from the its south pole. The orbiter flew within about 1,230 kilometres of Enceladus’ surface.

Although it appears dark in the silhouetted view, Enceladus, 504 kilometres wide, is actually one of the most reflective bodies in the Solar System because it is constantly coated by fresh, white particles of ice.

Also visible are Saturn’s rings, seen edge on.

More information:

Enceladus – Saturn’s shiny moon

The eruptions of Enceladus

Adapted from information issued by NASA/JPL-Caltech/Space Science Institute.

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Gallery – Quintet of Saturnian moons

Jonathan Nally — Thu, 17 Nov 2011 13:01:03 +0000

Five of Saturn's moons can be seen in this image taken by NASA's Cassini spacecraft.

A QUINTET OF SATURN’S MOONS can be seen in this view taken by the Cassini spacecraft.

Janus (179 kilometres wide) is on the far left. Pandora (81 kilometres) orbits between the A ring and the thin F ring near the middle of the image. Brightly reflective Enceladus (504 kilometres) appears above the centre of the image. Saturn’s second largest moon, Rhea (1,528 kilometres), is bisected by the right edge of the image. The smaller moon Mimas (396 kilometres) can be seen beyond Rhea also on the right side of the image.

This view looks toward the northern, sunlit side of the rings from just above the ringplane. Rhea is closest to the camera. Saturn’s rings are beyond Rhea and Mimas. Enceladus also is beyond the rings.

The image was taken with the Cassini spacecraft narrow-angle camera on July 29, 2011. The view was acquired at a distance of approximately 1.1 million kilometres from Rhea and 1.8 million kilometres from Enceladus.

Adapted from information issued by NASA / JPL-Caltech / Space Science Institute.

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