Cassini Survives Close Encounter of the Death Star Kind!

Cassini's Mimas, from 70,000 km (Credit: NASA/JPL/Space Science Institute)

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On February 13, 2010, Cassini flew by Saturn’s moon Mimas, coming as close as 9,500 km.

It passed directly over Herschel, a giant crater whose creation almost shattered the moon … and which, in its appearance in some earlier images, earned Mimas the nickname “Death Star”, after the iconic Star Wars prop.

The Cassini team has just released some “Raw Previews” of Cassini’s close encounter; time to feast your eyes.

35,000 km-distant Herschel, from Cassini (unprocessed image; credit: NASA/JPL/Space Science Institute)

The Cassini Equinox Mission, of which the Mimas flyby is but a small part, is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.
Herschel, from 16,000 km above (unprocessed image; credit: NASA/JPL/Space Science Institute)

Source: CICLOPS (Cassini Imaging Central Laboratory for Operations)

Gemini’s New Filters Reveal the Beauty of Star Birth

Sharpless 2-106 (Gemini Observatory/AURA, right; left: copyright Subaru Telescope, National Astronomical Observatory of Japan; All rights reserved)

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About 2,000 light-years away, in the constellation of Cygnus (the Swan), lies Sharpless 2-106 (after Stewart Sharpless who put the catalog together in 1959), the birth-place of a star cluster-to-be.

Two recent image releases – by Subaru and Gemini – showcase their new filter sets and image capabilities; they also reveal the stunning beauty of the million-year-long process of the birth of a star.

Sharpless 2-106 (Gemini Observatory/AURA)

The filter set is part of the Gemini Multi-Object Spectrograph (GMOS) toolkit, and includes ones centered on the nebular lines of doubly ionized oxygen ([OIII] 499 nm), singly ionized sulfur ([SII] 672 nm), singly ionized helium (HeII 468nm), and hydrogen alpha (Hα 656 nm). The filters are all narrowband, and are also used to study planetary nebulae and excited gas in other galaxies.

The hourglass-shaped (bipolar) nebula in the new Gemini image is a stellar nursery made up of glowing gas, plasma, and light-scattering dust. The material shrouds a natal high-mass star thought to be mostly responsible for the hourglass shape of the nebula due to high-speed winds (more than 200 kilometers/second) which eject material from the forming star deep within. Research also indicates that many sub-stellar objects are forming within the cloud and may someday result in a cluster of 50 to 150 stars in this region.

The nebula’s physical dimensions are about 2 light-years long by 1/2 light-year across. It is thought that its central star could be up to 15 times the mass of our Sun. The star’s formation likely began no more than 100,000 years ago and eventually its light will break free of the enveloping cloud as it begins the relatively short life of a massive star.

For this Gemini image four colors were combined as follows: Violet – HeII filter; Blue – [SII] filter; Green – [OIII] filter; and Red – Hα filter.

Sharpless 2-106 (Copyright Subaru Telescope, National Astronomical Observatory of Japan. All rights reserved)

The Subaru Telescope image was made by combining images taken through three broadband near-infrared filters, J (1.25 micron), H (1.65 micron), and K’ (2.15 micron).

Sources: Gemini Observatory, NAOJ

On New Year’s Eve, Cassini Will Stare at the Death Star’s Superlaser

Saturn's moon Mimas. Image credit: NASA/JPL/SSI

OK, it’s actually the Herschel crater on Mimas, a smallish moon of Saturn (and it’s the eve of Chinese New Year, February 13th, 2010), but it’s a cool headline, don’t you think?

Cassini will be very busy that day, which begins with a rare sunrise – the Sun goes behind Saturn (from Cassini’s perspective) – followed by a rare blackout, as the Earth goes behind Saturn. Then there’s three “Forward shields up!” moments, as Cassini tries to dodge a Klingon missile flies through regions of “increased ring particle concentration”, a couple of distant flybys (Epimetheus, Janus; ~100,000 km each), a ring-plane crossing, another “Shields up!” moment, and a 9,500 km close approach to Death Star Mimas. And the day ends with a distant (112,000 km) flyby of Tethys. Whew!

“Mimas bears the mark of a violent, giant impact from the past – the 140-kilometer-wide Herschel Crater – and scientists hope the encounter will help them explain why the moon was not blown to smithereens when the impact happened. They will also be trying to count smaller dings inside the basin of Herschel Crater so they can better estimate its age,” JPL’s Jia-Rui C. Cook said, “The Mimas flyby involves a significant amount of skill because the spacecraft will be passing through a dusty region to get there. Mission managers have planned for the Cassini spacecraft to lead with its high-gain antenna to provide a barrier of protection.”

To date, the best images of Mimas – and its Herschel crater – were obtained on August 2nd, 2005, during Cassin’s distant flyby.

Mimas is an inner moon of Saturn that averages 396 kilometers in diameter. The diameter of Herschel Crater is about one-third that of the entire moon. The walls of the crater are about 5 kilometers high, and parts of the floor are approximately 10 kilometers deep.

Map of Mimas (Credit: NASA/JPL/Space Science Institute )

Mimas would have beaten another of Saturn’s moons, Rhea, for the record of “most battered moon”, but for the fact that it was warmer – and so softer – for longer than Rhea (because it’s closer to Saturn), so many of the earliest craters were more degraded.

Have you heard of the “Mimas paradox”? Mimas’ orbit is more eccentric than Enceladus’, and is in resonance with Dione and Enceladus – so it should be heated, tidally, more than Enceladus – but its surface has not, apparently, changed for a very long time (while geysers on Enceladus show that it is still quite active). Further, the two moons seem to have similar compositions.

On this flyby, Cassini’s composite infrared spectrometer will be working to determine the thermal signature of the moon, and other instruments will be making measurements to learn more about the surface composition. Perhaps that will shed some light on the Mimas paradox.

Sources: Cassini Set to Do Retinal Scan of Saturnian Eyeball, Mimas (NASA/JPL)

Nebula Wallpaper

Nebula Wallpaper

Want a nebula wallpaper to put as the background image of your computer desktop? Here’s a handful of nebula images. To make any of them your computer’s background image, just click on the image to see a larger version. Then right-click on the image and choose to set the image as your desktop background.

The nebula wallpaper is the Flame Nebula, captured by the European Southern Observatory. Also known as NGC 2024, it’s a famous nebula located about 1,500 light-years away in the constellation of Orion. The bright star at the top of the image is Alnitak, one of the belt stars of Orion.


Crab Nebula

This is a wallpaper image of the Crab Nebula taken by the Hubble Space Telescope. Also known as M1, the Crab Nebula is the results of a supernova explosion that occurred almost 1000 years ago. Astronomers in 1054 AD reported a star brighting in the sky, and lasting for a few weeks before it dimmed again. That was the supernova that went on to create the Crab Nebula.


Butterfly Nebula

This is a wallpaper of the Butterfly Nebula (or NGC 6302) captured by Hubble. This is a planetary nebula, the result of a dying star blasting out its outer layers into space. This is what our own Sun might do in about 7 billion years from now after it becomes a red giant star.


Ring Nebula

This is Hubble Space Telescope image of the Ring Nebula, also known as M57. It’s actually a planetary nebula, where the outer layers of a dying star are puffed out into space. The Ring Nebula is located about 4000 light-years away, and measures about 500 times larger than the Solar System.


Carina Nebula

This is the Carina Nebula, photographed by the Hubble Space Telescope. This is just one pillar of gas and dust in the nebula, measuring 2 light-years across. It’s located about 7,500 light years from Earth.

We’ve written many articles about nebulae for Universe Today. Here’s an article about dust in the Iris Nebula, and here’s an article about Hubble images of the Helix Nebula.

If you’d like more information on nebulae, check out NASA’s Photo Gallery of Nebulae, and here’s a link to the Hubblesite Homepage for recent stories and images.

We’ve recorded an episode of Astronomy Cast all about nebulae. Listen here, Episode 111: Nebulae.

Amazing Images

Moon from Earth

Here are some amazing images of space:

This is an amazing image of the Moon taken from the International Space Station orbiting Earth. What a view!


M83. Image credit: Hubble

This is a photograph of the spiral galaxy M83, one of the closest best examples we can see of a spiral galaxy. This image was captured by the Hubble Space Telescope.


Hurricane Ike

Here’s an image of Hurricane Ike captured by astronauts on board the International Space Station.


Apollo 11

Here’s a photo of NASA’s Apollo 11 lunar lander rising from the surface of the Moon to dock with the Command and Service module.


Halley's Comet

Here’s a picture of Halley’s comet taken by the Giotto spacecraft. You can see the nucleus of the comet tumbling in space and the tail trailing behind.

If you’d like to get more outer space pictures for yourself, check out NASA’s Astronomy Picture of the Day, as well as NASA’s Image of the Day.

Many of the best pictures of space come from the Hubble Space Telescope. You can see the latest images from the Hubble Site, and then an archive of old images at the Hubble Heritage site. There are also great pictures from the Chandra X-Ray Observatory and NASA’s Spitzer Space Telescope.

If you’d like pictures of the planets, check out NASA’s Planetary Photojournal, and here are links to missions at the planets in the Solar System. MESSENGER, Venus Express, the Lunar Reconnaissance Orbiter, Mars Reconnaissance Orbiter, Cassini, and New Horizons.

We’ve written many articles about amazing images for Universe Today. Here’s an article about some images from STS-129, and here are some images of the shuttle and Hubble transiting across the Sun.

We’ve recorded many episodes of Astronomy Cast about space. Try this one, Episode 99: The Milky Way.

NASA Pictures

NASA has the absolute best resources on the web for pictures of space. We write so many articles about space here on Universe Today, so we’ve learned all the best places to look to get the latest and greatest NASA pictures.

Before we go right to some sites, here’s a general tip that you can use when you’re looking for NASA pictures. Use Google, but have it search for images within NASA’s sites. For example, let’s say that you’re looking for an astronomy picture of Mars, but you want it to be a NASA image. Search in Google for: mars picture site:nasa.gov. You can also switch over to the images tab and see lots and lots of images from NASA. You should be able to find the one you’re looking for.

Perhaps the best place to start is NASA’s Featured Images and Galleries. This is linked from the main NASA page and features current pictures as well as classics from the past. It also links you to other NASA image gallery sites.

Another classic is the Astronomy Picture of the Day. Keep in mind that although it’s endorsed by NASA, the pictures featured in Astronomy Picture of the Day are owned and copyright by the original photographers. So you can’t just use their pictures without asking permission first.

There’s a fairly new service out called NASA Images. It’s got a huge catalog of NASA pictures, with cool tools that let you organize and download your favorites.

The NASA Image Exchange is a huge database of NASA pictures. You can search by object, or by spacecraft and use other constraints to find the exact image you’re looking for.

The Johnson Digital Image Collection has photographs from all of NASA’s human spaceflight, from the original Mercury and Gemini flights, though the Apollo landings, right up until the space shuttle missions.

And if you want pictures of Earth, check out NASA’s Visible Earth site or the NASA’s Earth Observatory.

If you want pictures from the Hubble Space Telescope, here’s their homepage HubbleSite.

Want NASA photos from specific spacecraft? Here’s NASA’s Cassini spacecraft, here are the Mars Exploration Rovers, and here’s Mercury MESSENGER.

That should get you started.

We have written many articles about NASA and its photography here on Universe Today. Check out this gallery of images from the STS-127 shuttle mission. And here are images from the shuttle mission to repair the Hubble Space Telescope.

We have also recorded many episodes of Astronomy Cast about space, and we talk about NASA pictures all the time. Listen to this, Episode 88: The Hubble Space Telescope.

After Loss of Lunar Orbiter, India Looks to Mars Mission

India Moon Mission
Artist concept of Chandrayaan-1 orbiting the moon. Credit: ISRO

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After giving up on re-establishing contact with the Chandrayaan-1 lunar orbiter, Indian Space Research Organization (ISRO) Chairman G. Madhavan Nair announced the space agency hopes to launch its first mission to Mars sometime between 2013 and 2015. Nair said the termination of Chandrayaan-1, although sad, is not a setback and India will move ahead with its plans for the Chandrayaan-2 mission to land an unmanned rover on the moon’s surface to prospect for chemicals, and in four to six years launch a robotic mission to Mars.


“We have given a call for proposal to different scientific communities,” Nair told reporters. “Depending on the type of experiments they propose, we will be able to plan the mission. The mission is at conceptual stage and will be taken up after Chandrayaan-2.”

On the decision to quickly pull the plug on Chandrayaan-1, Nair said, “There was no possibility of retrieving it. (But) it was a great success. We could collect a large volume of data, including more than 70,000 images of the moon. In that sense, 95 percent of the objective was completed.”

Contact with Chandrayaan-1 may have been lost because its antenna rotated out of direct contact with Earth, ISRO officials said. Earlier this year, the spacecraft lost both its primary and back-up star sensors, which use the positions of stars to orient the spacecraft.

The loss of Chandrayaan-1 comes less than a week after the spacecraft’s orbit was adjusted to team up with NASA’s Lunar Reconnaissance Orbiter for a Bi-static radar experiment. During the maneuver, Chandrayaan-1 fired its radar beam into Erlanger Crater on the moon’s north pole. Both spacecraft listened for echoes that might indicate the presence of water ice – a precious resource for future lunar explorers. The results of that experiment have not yet been released.

Chandrayaan-1 craft was designed to orbit the moon for two years, but lasted 315 days. It will take about 1,000 days until it crashes to the lunar surface and is being tracked by the U.S. and Russia, ISRO said.

The Chandrayaan I had 11 payloads, including a terrain-mapping camera designed to create a three-dimensional atlas of the moon. It is also carrying mapping instruments for the European Space Agency, radiation-measuring equipment for the Bulgarian Academy of Sciences and two devices for NASA, including the radar instrument to assess mineral composition and look for ice deposits. India launched its first rocket in 1963 and first satellite in 1975. The country’s satellite program is one of the largest communication systems in the world.

Sources: New Scientist, Xinhuanet

Where In The Universe #58



It’s Wednesday, so that means its time for another “Where In The Universe” challenge to test your visual knowledge of the cosmos. See if you can name where in the Universe this image is from, and give yourself extra points if you can name the spacecraft responsible for the image. Make your guess and post a comment, but please no links to the answer. Check back sometime on Thursday to find the answer and see how you did.

UPDATE: The answer has now been posted below.

This one, I admit, was a little tough. But fun! Although I think a lot of people were too perplexed to post an answer.

This image was taken by the Spitzer Space Telescope, and it is of a star located 1,140 light-years away from Earth. The star is a small baby star named HH 46/47, and it appears to be blowing bubbles. The infant star can be seen as a white spot toward the center of the Spitzer image. The two bubbles are shown as hollow elliptical shells of bluish-green material extending from the star. Wisps of green in the image reveal warm molecular hydrogen gas, while the bluish tints are formed by starlight scattered by surrounding dust.

These bubbles formed when powerful jets of gas, traveling at 200 to 300 kilometers per second, or about 120 to 190 miles per second, smashed into the cosmic cloud of gas and dust that surrounds HH 46/47. The red specks at the end of each bubble show the presence of hot sulfur and iron gas where the star’s narrow jets are currently crashing head-on into the cosmic cloud’s gas and dust material.

Find out more about this Spitzer image here.

Check back next week for another Where In The Universe challenge!