Category Archives: ESA

Moving a Boulder on a Comet

Take a look at these images of a boulder that moved on Comet 67P/Churyumov-Gerasimenko as seen by the Rosetta spacecraft.  Fascinating stuff.  The boulder clearly moved.  But how?

Here’s ESA’s caption (via NASA):
A 100 foot-wide (30 meter), 28-million-pound (12.8-million-kilogram) boulder, was found to have moved 460 feet (140 meters) on comet 67P/Churyumov-Gerasimenko in the lead up to perihelion in August 2015, when the comet’s activity was at its highest. In both images, an arrow points to the boulder; in the right-hand image, the dotted circle outlines the original location of the boulder for reference.

The movement could have been triggered in one of two ways: either the material on which it was sitting eroded away, allowing it to roll downslope, or a sufficiently forceful outburst could have directly lifted it to the new location. Indeed, several outburst events were detected close to the original position of the boulder during perihelion.

The images were taken by Rosetta’s OSIRIS camera on May 2, 2015 (left) and Feb. 7, 2016 (right), with resolutions of 7.5 feet (2.3 meters) per pixel and 2.6 feet (0.8 meters) per pixel, respectively.

Rosetta is a European Space Agency mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the U.S. participation in the Rosetta mission for NASA’s Science Mission Directorate in Washington.

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So first I’m siding with the erosion idea by way of off gassing or jets. It seems that a jet strong enough to directly lift a “12.8 million-kg” boulder would lift more material than just the boulder and if it did the boulder would likely show more of an impact mark as the soil looks sand-like. True the same forces could erase those marks but you’d think there would be some physical sign of such a powerful event. Still there are no “boulder-tracks” and again off-gassing might erase the tracks.

The other thing that isn’t explained is this: Is the 12.8 million-kg / 28 million-lb boulder a true 67P weight or is that what it would weigh here on Earth?  OR is this a measure of mass but not stated as such? This is a case where knowing the mass would be helpful. Like I said – fascinating stuff!

Image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Sentinel-2B Ready to Go

The Sentinel-2B Earth observation satellite will soon be launched and join the Copernicus program, the world’s largest environmental monitoring program which is headed by the European Commission in partnership with ESA.

Sentinel 1 and 2 are already in orbit and providing valuable data for science and safety. Data from the satellites prompted the evacuation of the Halley VI research station in Antarctica. The satellites are monitoring a large crack that formed in the Brunt Ice shelf, a floating ice shelf in the Weddell sea region The crack formed in October and was dubbed the Halloween Crack. The crack grew by as much as 600 meters a day during November and December and the British Antarctic Base (BAS) Halley VI found itself only 17 km away.

Now new cracks have formed and puts the base and the between 20 and 70 people in jeopardy. The base is mobile and has already moved 23 km inland.   BAS used radar images from Sentinel-1 and optical images from Sentinel-2 to monitor the situation and out of an abundance of caution have decided to close the base at least temporarily.

Active Galactic Nucleus

ic3639

The galaxy above called IC-3639 has an Active Galactic Nucleus that is actually obscured which leads to even more questions.  AGN’s are super-massive black holes (in the order of a million to probably hundreds of million solar masses) that are accreting massive amounts of matter, which is to say “feeding”. The accretion disc makes the Active Galaxies among the brightest objects in terms of electromagnetic radiation, so bright it is not often whether or not a galaxy is active, is in question, IC 3639 is such a galaxy.

A word about black holes in general because some people have a mistaken impression of black holes as marauding monsters roaming the universe looking for innocent planets to swallow up, that just came up on an outing with friends. No, a black holes don’t really do that. In fact if you took a black hole of one-solar-mass and swapped it with our Sun our solar system would just keep right on going just like it does now, aside from light and heat of course, the fabric of space-time would be just as it is now.

From NuSTAR:
IC 3639, a galaxy with an active galactic nucleus, is seen in this image combining data from the Hubble Space Telescope and the European Southern Observatory.

This galaxy contains an example of a supermassive black hole hidden by gas and dust. Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA’s Chandra X-Ray Observatory and the Japanese-led Suzaku satellite. The findings from NuSTAR, which is more sensitive to higher energy X-rays than these observatories, confirm the nature of IC 3639 as an active galactic nucleus that is heavily obscured, and intrinsically much brighter than observed.

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA.

Image and caption: NASA/JPL-Caltech/ESO/STScI

A Solar Storm From Years Ago

solarstorm2003

I remember this very well!

From ESA:
While this scene looks like the mesmerising result of shaking up a festive snow globe, it is in fact the disturbing effect of one of the most powerful solar storms ever recorded.

Over two weeks in October and November 2003 the Sun was unprecedentedly active, with giant sunspots – over 10 times the diameter of Earth – generating flares on an almost daily basis.

Solar flares are classed according to the energy they release at X-ray wavelengths. There are five major categories: A, B, C, M and X, further divided into 10 subclasses. M1 flares are 10 times more powerful than C1, and X1 flares are 10 times more powerful than M1 flares, or 100 times more powerful than C1.

Some of the flares witnessed in this two-week period were so powerful they broke right through the top of the X-class range, which is usually given as X10. A flare erupting on 4 November was estimated to have reached at least X28.

The ESA/NASA Solar and Heliospheric Observatory (SOHO), launched in 1995 and still operating today, was monitoring the Sun’s stormy behaviour during this time. This image shows its detectors being completely swamped by high-energy protons that were accelerated to nearly the speed of light (300 000 km/s) in the X17 flare of 28 October 2003.

When Earth is in the firing line of associated coronal mass ejections (CMEs), it can lead to beautiful and bright auroras in the atmosphere, giving unparalleled insight into the interaction of the Sun and Earth.

CMEs can also cause serious disruption to radio communications, air traffic control and power grids.

Although these powerful storms reveal the extremes of the Sun’s activity, fortunately for Earth, those on the scale of the 2003 events do not occur very often.

The image was taken by SOHO’s LASCO C3 instrument. A special disc (indicated by the large blue circle) inside the instrument blocks the Sun (indicated by the inner white circle), so that details of the extended outer solar atmosphere can be observed. Watch a movie of the event depicted in this scene, here.

Credits: SOHO (ESA & NASA)

Gaia’s Milky Way

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Having examined and precisely measured the positions and brightness of over a BILLION stars, Gaia could well be the greatest mission nobody talks about.

Image: ESA

From ESA:

ESA’s Gaia is surveying stars in our Galaxy and local galactic neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its structure, origin and evolution.

Launched in 2013, Gaia has already generated its first catalogue of more than a billion stars  – the largest all-sky survey of celestial objects to date.

To achieve its scientific aims, it points with ultra-high precision, and to enable the control team to monitor spacecraft performance, Gaia regularly reports to the ground information about its current attitude and the stars that have been observed.

These engineering data have been accumulated over 18 months and combined to create a ‘map’ of the observed star densities, from which a beautiful and ghostly virtual image of our magnificent Milky Way galaxy can be discerned, showing the attendant globular clusters and Magellanic clouds.

Where there are more stars, as in the Galactic centre, the map is brighter; where there are fewer, the map is darker. The map includes brightness data corresponding to several million stars.

More information on Gaia mission operations

Rosetta Archive

rosettafinal5a

The last of the NAVCAM images are now archived. The images in the latest  archive release are from the Rosetta’s last month of activity during the fantastic mission around Comet 67P/Churyumov-Gerasimenko.

This and other images can be found with the ESA Archive Image Browser

ESA’s description of the image above, one of the last five from Rosetta’s NAVCAM taken on 30 September 2016:

Single frame enhanced NavCam image taken on 29 September 2016 at 23:25 GMT, when Rosetta was 19.4 km from the centre of the nucleus of Comet 67P/Churyumov-Gerasimenko. The scale at the surface is about 1.7 m/pixel and the image measures about 1.7 km across.

Image (and description): ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0