Tag: comets

Protecting the Mars orbiters from comet flyby

4:10 pm

Engineers are repositioning the American spacecraft orbiting Mars so that they will be better protected by the planet when Comet Siding Spring flies past on October 19.

The comet’s nucleus will miss Mars by about 82,000 miles (132,000 kilometers), shedding material hurtling at about 35 miles (56 kilometers) per second, relative to Mars and Mars-orbiting spacecraft. At that velocity, even the smallest particle — estimated to be about one-fiftieth of an inch (half a millimeter) across — could cause significant damage to a spacecraft.

NASA currently operates two Mars orbiters, with a third on its way and expected to arrive in Martian orbit just a month before the comet flyby. Teams operating the orbiters plan to have all spacecraft positioned on the opposite side of the Red Planet when the comet is most likely to pass by.

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New Rosetta comet images

6:34 pm

New images from Rosetta have a resolution of 100 meters per pixel and are finding that the neck connecting the comet’s two sections is apparently much brighter than the rest of the nucleus.

As earlier images had already shown, 67P may consist of two parts: a smaller head connected to a larger body. The connecting region, the neck, is proving to be especially intriguing. “The only thing we know for sure at this point is that this neck region appears brighter compared to the head and body of the nucleus”, says OSIRIS Principal Investigator Holger Sierks from the Max-Planck-Institute for Solar System Research (MPS) in Germany. This collar-like appearance could be caused by differences in material or grain size or could be a topographical effect.

It looks like this comet is going to turn out to be one of the most fascinating objects any space probe has visited in a long time.

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More images from Rosetta

5:24 pm

67P

The comet that Rosetta will orbit is getting stranger and stranger, with new images suggesting that it is really two objects stuck together.

The pictures show that 67P/Churyumov-Gerasimenko appears to be not one but two objects joined together. It is what scientists call a “contact binary”. How the comet came to take this form is unknown. It is possible that 67P suffered a major fracture at some point in its past; it is also possible the two parts have totally different origins.

What is clear is that the European Space Agency (Esa) mission team now has additional and unexpected considerations as it plans how to land on the comet later this year – not least, which part of the comet should be chosen for contact?

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Rosetta snaps more comet pictures

9:23 am

rotating comet nucleus

Rosetta’s new images of Comet 67P/Churyumov-Gerasimenko show the very irregular shape and rotation of its nucleus.

These images were taken on July 4 from a distance of only 23,000 miles. The rendezvous is expected in early August, with the touchdown of Rosetta’s landing probe Philae sometime in November after they have done a reconnaissance of the nucleus to pick a landing spot.

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Rosetta measures its comet

11:09 am

As Rosetta approaches Comet 67P/Churyumov-Gerisimenko, it has measured the amount of water evaporating of the comet as it slowly comes to life as it approaches the Sun.

ESA’s Rosetta spacecraft has found that comet 67P/Churyumov–Gerasimenko is releasing the equivalent of two small glasses of water into space every second, even at a cold 583 million kilometres from the Sun. The first observations of water vapour streaming from the comet were made by the Microwave Instrument for Rosetta Orbiter, or MIRO, on 6 June, when the spacecraft was about 350 000 kilometres from the comet. Since the initial detection, water vapour has been found every time MIRO has been pointed towards the comet.

That rate of evaporation will increase with time.

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Rosetta’s comet has unexpectedly gone to sleep.

10:04 am

Rosetta’s comet has unexpectedly gone to sleep.

An image snapped earlier this month by ESA’s Rosetta spacecraft shows its target comet has quietened, demonstrating the unpredictable nature of these enigmatic objects. The picture was captured on 4 June by Rosetta’s scientific camera, and is the most recent full-resolution image from the narrow-angle sensor. It has been used to help fine-tune Rosetta’s navigation towards comet 67P/Churyumov–Gerasimenko, which was 430 000 km away at the time.

Strikingly, there is no longer any sign of the extended dust cloud that was seen developing around nucleus at the end of April and into May, as shown in our last image release. Indeed, monitoring of the comet has shown a significant drop in its brightness since then.

Rosetta’s approach for the next few months and arrival at the comet in August should be quite exciting.

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Rosetta photographs its target comet as it comes to life.

6:25 am

Rosetta photographs its target comet as it comes to life.

The comet 67P/Churyumov-Gerasimenko, target of ESA’s Rosetta mission, has begun to develop a dust coma. This can be seen in a series of images taken by OSIRIS, the spacecraft’s scientific imaging system, between March 27th and May 4th. In the images from the end of April, the dust that the comet is already emitting is clearly visible as an evolving coma and reaches approximately 1300 kilometers into space.

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The German-built comet lander Philae has been successfully reactivated on Rosetta.

9:24 am

The German-built comet lander Philae has been successfully reactivated on Rosetta.

Philae will be ejected from the Rosetta mothership in November to latch itself onto the comet’s icy surface with harpoons and screws. The lander has its own suite of science instrumentation to take the first-ever photos and measurements from a comet’s surface. Engineers plan a four-week commissioning phase for Philae to check on its health and activate the lander’s 10 instruments.

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The comet that the European probe Rosetta will visit in August has awakened.

11:37 am

The comet that the European probe Rosetta will visit in August has awakened.

Already 67P/Churyumov-Gerasimenko is approximately 50 percent brighter than in the last images from October 2013. While the comet has moved another 50 million kilometers closer to Earth in this time (and 80 million kilometers closer to the Sun), the increase in brightness cannot be explained by the smaller distance alone. “The new image suggests that 67P is beginning to emit gas and dust at a relatively large distance from the Sun”, says Colin Snodgrass from the MPS. This confirms a study presented by Snodgrass and his colleagues last year in which they had compared the comet’s brightness as recorded during its previous orbits around the Sun. The calculations showed that already in March 2014 its activity would be measurable from Earth.

Update: A preprint paper published today on the astro-ph website predicts that Rosetta will see an unusual topographical feature on the comet’s surface when it arrives in August:

Comet 67P/Churyumov-Gerasimenko. The Secular Light Curve (SLC) of this comet exhibits a photometric anomaly in magnitude that is present in 1982, 1996, 2002 and 2009. Thus it must be real. We interpret this anomaly as a topographic feature on the surface of the nucleus that may be a field of debris, a region made only of dust or an area of solid stones but in any case it is depleted in volatiles. We predict that images taken by spacecraft Rosseta will show a region morphologically different to the rest of the nucleus, at the pole pointing to the Sun near perihelion.

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WISE’s survey of the sky in infrared has now shown that there is no large planet X orbiting beyond Pluto.

12:55 pm

WISE’s survey of the sky in infrared has now shown that there is no large planet X orbiting beyond Pluto.

This recent study, which involved an examination of WISE data covering the entire sky in infrared light, found no object the size of Saturn or larger exists out to a distance of 10,000 astronomical units (au), and no object larger than Jupiter exists out to 26,000 au. One astronomical unit equals 93 million miles. Earth is 1 au, and Pluto about 40 au, from the sun. “The outer solar system probably does not contain a large gas giant planet, or a small, companion star,” said Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University, University Park, Pa., author of a paper in the Astrophysical Journal describing the results.

The theory, popular among planetary scientists and journalists, is that this theorized distant planet would periodically disturb the orbits of comets in the Oort Cloud, sending them raining down on Earth and thus cause the periodic extinction events found in the paleontological record. It was a cute theory, but based on little data. Now we have the data, and no such planet exists.

The data has found a lot of previously unknown nearby stars and brown dwarfs, which is significant in that they are close and can be studied more easily.

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Because of a computer reboot, Rosetta’s revival from hibernation came 18 minutes late.

3:57 pm

Because of a computer reboot, Rosetta’s revival from hibernation came 18 minutes late.

[Rosetta] woke yesterday as planned, to the relief of ESA scientists – but the signal it sent home to confirm it was awake reached Earth late, fraying the nerves of some mission controllers in the meantime. Due to call at 1745 GMT, Rosetta did not announce its revival until 1818. Fifteen minutes could be explained because the spacecraft’s computer checked the on-board clock only every quarter of an hour. The additional 18 minutes, however, was a mystery.

Now, the telemetry has shown that soon after Rosetta’s first revival sequence had started, the on-board computer automatically rebooted and the sequence started again, causing 18 minutes of delay.

It seems all is well now, though the engineers plan to spend some time pinpointing the cause of the reboot.

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After three years in hibernation Europe’s Rosetta comet probe has successfully come back to life.

4:10 pm

After three years in hibernation Europe’s Rosetta comet probe has successfully come back to life.

The craft at the heart of ESA’s €1-billion (US$1.4-billion) comet-hunting mission was shut down in 2011 to save energy while travelling in deep space. Rosetta successfully re-established communications with Earth on 20 January.
With an alarm pre-set for 10:00 GMT, a signal was expected at any time from 17:30 GMT, once the spacecraft had warmed up and turned its antenna towards Earth. But Rosetta kept everyone guessing, with the first sign that everything had gone to plan only arriving around 40 minutes later.

ESA’s European Space Operations Centre erupted in cheering and hugging as small spikes appeared in radio signals received at NASA deep-space communications centres in Canberra and in Goldstone, California.

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Though this conclusion is not final, it appears that Comet ISON was destroyed today in its close fly-by of the Sun.

2:11 pm

Though this conclusion is not final, it appears that Comet ISON was destroyed today in its close fly-by of the Sun.

A sad end to what has been a cometary disappointment. First spotted while it was very far from the Sun, astronomers thus hoped that Comet ISON would blaze brightly when it got closer. Instead, it hardly brightened at all during its journey inward, barely reaching naked eye visibility in the last week. Now it appears to be gone forever.

Scientists will gain some knowledge from this comet, as it was a first time visitor to the inner solar system and thus provides information about the solar system’s beginnings. Nonetheless, for those of us that enjoy watching the beautiful things the heavens give us, this comet will always remain a dud.

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Comet ISON makes its close flyby of the sun today.

8:40 am

Comet ISON makes its close flyby of the sun today.

Three possible fates await Comet ISON, according to Don Yeomans, manager of NASA’s Near-Earth Object Program Office at the agency’s Jet Propulsion Laboratory in Pasadena, Calif.

“It could be tough enough to survive the passage of the sun and be a fairly bright naked-eye object in the early morning sky in the first week of December,” Yeomans said in a statement. “Or, the sun could actually pull it apart. The tidal forces could actually pull this comet apart and so it becomes several chunks rounding the sun and putting on a great show again in early December. Or, if the comet is very weak, it could break up into a cloud of dust and be a complete bust in December.”

So far the comet has been a big disappointment in terms of brightness. However, its flyby today will be interesting as scientists will get a chance to observe one of the largest sun-grazers they’ve ever seen do this.

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Hubble spots an asteroid spout six comet-like tails.

9:42 am

Hubble spots an asteroid spout six comet-like tails.

Astronomers viewing our solar system’s asteroid belt with NASA’s Hubble Space Telescope have seen for the first time an asteroid with six comet-like tails of dust radiating from it like spokes on a wheel. Unlike all other known asteroids, which appear simply as tiny points of light, this asteroid, designated P/2013 P5, resembles a rotating lawn sprinkler. Astronomers are puzzled over the asteroid’s unusual appearance.

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Scientist right now think it is a toss-up whether Comet ISON will survive its dive past the sun on November 28.

10:43 am

Scientist right now think it is a toss-up whether Comet ISON will survive its dive past the sun on November 28.

Essentially, they have no idea what will happen. They know most of the factors effecting the comet, but cannot predict the result. If the comet breaks up, however, it will be very cool, as this will probably be the largest comet ever seen by astronomers to do this.

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One hundred days to wake-up for Europe’s Rosetta comet probe.

8:26 am

One hundred days to wake-up for Europe’s Rosetta comet probe.

Rosetta was launched on 2 March 2004, and through a complex series of flybys – three times past Earth and once past Mars – set course to its destination: comet 67P/Churyumov–Gerasimenko. It also flew by and imaged two asteroids, Steins on 5 September 2008 and Lutetia on 10 July 2010. In July 2011 Rosetta was put into deep-space hibernation for the coldest, most distant leg of the journey as it travelled some 800 million kilometres from the Sun, close to the orbit of Jupiter. The spacecraft was oriented so that its solar wings faced the Sun to receive as much sunlight as possible, and it was placed into a slow spin to maintain stability.

Now, as both the comet and the spacecraft are on the return journey back into the inner Solar System, the Rosetta team is preparing for the spacecraft to wake up.
Rosetta mission milestones 2014-2015 Rosetta’s internal alarm clock is set for 10:00 GMT on 20 January 2014.

The first images are expected back in May 2014.

Posted as we approach the Arkansas-Texas border.

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Scientists in Egypt have found what they think is evidence of a comet impact from 28 million years ago.

10:39 am

Scientists in Egypt have found what they think is evidence of a comet impact from 28 million years ago.

The best part however is this:

At the centre of the attention of this team was a mysterious black pebble found years earlier by an Egyptian geologist in the area of the silica glass. After conducting highly sophisticated chemical analyses on this pebble, the authors came to the inescapable conclusion that it represented the very first known hand specimen of a comet nucleus, rather than simply an unusual type of meteorite.

Assuming this claim is confirmed it is a very significant discovery. As far as I know, no other specimens from a comet nucleus have been identified previously.

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Comet ISON has now brightened to 11th magnitude as it approaches its flyby of Mars.

9:41 am

Comet ISON has now brightened to 11th magnitude as it approaches its flyby of Mars.

The story above is hopeful the comet will put on a show in November, but I am increasingly doubtful. To be even visible to the naked eye it must brighten to 6th magnitude, and it appears to be brightening far slower than expected.

Posted as we drive through El Paso, Texas.

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Linking mass extinctions to the Sun’s journey in the Milky Way

12:53 pm

The Sun's orbit in the Milky Way

In a paper published today on the Los Alamos astro-ph preprint service, astronomers propose that as many as eleven past extinction events can be linked to the Sun’s passage through the spiral arms of the Milky Way. (You can download the paper here [pdf].)

A correlation was found between the times at which the Sun crosses the spiral arms and six known mass extinction events. Furthermore, we identify five additional historical mass extinction events that might be explained by the motion of the Sun around our Galaxy. These five additional significant drops in marine genera that we find include significant reductions in diversity at 415, 322, 300, 145 and 33 Myr ago. Our simulations indicate that the Sun has spent ~60% of its time passing through our Galaxy’s various spiral arms.

The figure on the right, from their paper, shows the Sun’s orbit in red over the last half billion years. The Sun’s present position is indicated by the yellow spot, and the eleven extinctions are indicated by the circles.

There are obviously a great deal of uncertainties in this conclusion. Most significantly, the shape and history of the Milky Way remains very much in doubt, especially since we reside within it and cannot really get a good look at it. Though in recent years astronomers have assembled a reasonable image of the galaxy’s shape — a barred spiral with two major arms and several minor ones — this picture includes many assumptions that could very easily be wrong.

Nonetheless, the paper’s conclusions are interesting.
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