Proxima Centuri’s Orbit

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Credit:  P. Kervella (CNRS/U. of Chile/Observatoire de Paris/LESIA), ESO/Digitized Sky Survey 2, D. De Martin/M. Zamani

From the ESO:

Interest in our neighbouring Alpha Centauri star system has been particularly high since the recent discovery of an Earth-mass planet, known as Proxima b, orbiting the system’s third star — and the closest star to the Sun — Proxima Centauri. While the system’s larger stellar pair, Alpha Centauri A and B, appear to have a proper motion on the sky that is very similar to that of the smaller, fainter Proxima Centauri, it has not been possible to demonstrate that the three stars do actually form a single, gravitationally bound, triple system.

Now three astronomers, Pierre Kervella, Frédéric Thévenin and Christophe Lovis, have concluded that the three stars do indeed form a bound system. In the century since it was discovered, Proxima Centauri’s faintness has made it extremely difficult to reliably measure its radial velocity — the speed at which it moves towards and away from Earth. But now ESO’s planet-hunting HARPS instrument has provided an extremely precise measurement of Proxima Centauri’s radial velocity, and even greater accuracy has been achieved by accounting for other subtle effects [1].

As a result, the astronomers have been able to deduce very similar values for the radial velocities of the Alpha Centauri pair and Proxima Centauri, lending credence to the idea that they form a bound system. Taking account of these new measurements, calculations of the orbits of the three stars indicate that the relative velocity between Proxima Centauri and the Alpha Centauri pair is well below the threshold above which the three stars would not be bound together by gravity.

This result has significant implications for our understanding of the Alpha Centauri system and the formation of planets there. It strongly suggests that Proxima Centauri and the Alpha Centauri pair are the same age (about 6 billion years), and that in turn provides a good estimate of the age of the orbiting planet, Proxima b.

The astronomers speculate that the planet may have formed around Proxima Centauri on a more extended orbit and then been brought to its current position, very close to its parent star, as a result of the close passage of Proxima Centauri to its cousins in the Alpha Centauri pair. Alternatively, the planet may have formed around the Alpha Centauri pair, and was later captured by the gravity of Proxima Centauri. If one of these hypotheses is correct, it is possible that the planet was once an icy world that underwent a meltdown and now has liquid water on its surface.

Pandora

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This is the Saturn moon Pandora like we’ve never seen before and likely not to see again for a long-long time once the Cassini mission comes to an end.

The details from the Cassini mission team:
This image from NASA’s Cassini spacecraft is one of the highest-resolution views ever taken of Saturn’s moon Pandora. Pandora (52 miles, 84 kilometers) across orbits Saturn just outside the narrow F ring.

The spacecraft captured the image during its closest-ever flyby of Pandora on Dec. 18, 2016, during the third of its grazing passes by the outer edges of Saturn’s main rings. (For Cassini’s closest view prior to this flyby, see PIA07632, which is also in color.)

The image was taken in green light with the Cassini spacecraft narrow-angle camera at a distance of approximately 25,200 miles (40,500 kilometers) from Pandora, or phase, angle of 29 degrees. Image scale is 787 feet (240 meters) per pixel.

Image: NASA/JPL-Caltech/Space Science Institute

Happy Solstice!

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Happy Solstice!  This of course the December solstice.  The Sun’s rays are directly over the Tropic of Capricorn.  As the Earth continues on its journey around the direct rays of the  Sun will move north  until the June solstice.

Watch where the Sun sets once a week for a while and and you will see the point move.  You can do this at sunrise too.  After the June solstice you will see the sunset point start moving in the opposite direction.

Of course we (probably) all know for people in the southern hemisphere this is the longest day of the year thanks to the tilt of the Earth as the image aptly depicts and the shortest day for people in the north. Being in the northern hemisphere one thought always comes to mind about now; as a long time weather man by the name of Stuart Hall used to say: “As the days grow longer the cold grows stronger”.

Time of the December Solstice: 10:44 UTC on 21 December 2016

Get Sun and Moon data for your location.

A Galactic “Winter Wonderland”

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This space telescope collaboration (see below) was the NASA Image of the Day.  It kind of reminded me of the holiday lights so evident around the neighborhood.

Here’s the NASA description:

Although there are no seasons in space, this cosmic vista invokes thoughts of a frosty winter landscape. It is, in fact, a region called NGC 6357 where radiation from hot, young stars is energizing the cooler gas in the cloud that surrounds them.

This composite image contains X-ray data from NASA’s Chandra X-ray Observatory and the ROSAT telescope (purple), infrared data from NASA’s Spitzer Space Telescope (orange), and optical data from the SuperCosmos Sky Survey (blue) made by the United Kingdom Infrared Telescope.

Located in our galaxy about 5,500 light years from Earth, NGC 6357 is actually a “cluster of clusters,” containing at least three clusters of young stars, including many hot, massive, luminous stars. The X-rays from Chandra and ROSAT reveal hundreds of point sources, which are the young stars in NGC 6357, as well as diffuse X-ray emission from hot gas. There are bubbles, or cavities, that have been created by radiation and material blowing away from the surfaces of massive stars, plus supernova explosions.

Astronomers call NGC 6357 and other objects like it “HII” (pronounced “H-two”) regions. An HII region is created when the radiation from hot, young stars strips away the electrons from neutral hydrogen atoms in the surrounding gas to form clouds of ionized hydrogen, which is denoted scientifically as “HII”.

Researchers use Chandra to study NGC 6357 and similar objects because young stars are bright in X-rays. Also, X-rays can penetrate the shrouds of gas and dust surrounding these infant stars, allowing astronomers to see details of star birth that would be otherwise missed.

A recent paper on Chandra observations of NGC 6357 by Leisa Townsley of Pennsylvania State University appeared in The Astrophysical Journal Supplement Series and is available online. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

Image credit: X-ray: NASA/CXC/PSU/L. Townsley et al; Optical: UKIRT; Infrared: NASA/JPL-Caltech

Mimas

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NASA’s caption:
It may look as though Saturn’s moon Mimas is crashing through the rings in this image taken by NASA’s Cassini spacecraft, but Mimas is actually 28,000 miles (45,000 kilometers) away from the rings. There is a strong connection between the icy moon and Saturn’s rings, though. Gravity links them together and shapes the way they both move.

The gravitational pull of Mimas (246 miles or 396 kilometers across) creates waves in Saturn’s rings that are visible in some Cassini images. Mimas’ gravity also helps create the Cassini Division (not pictured here), which separates the A and B rings.

This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 15 degrees to the right. The image was taken in green light with the Cassini spacecraft narrow-angle camera on Oct. 23, 2016.

The view was acquired at a distance of approximately 114,000 miles (183,000 kilometers) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 29 degrees. Image scale is 3,300 feet (1 kilometer) per pixel.

Image: NASA/JPL-Caltech/Space Science Institute

Fly Over Occator

Thanks the the Dawn spacecraft we can take a “fly-over” of Occator crater on the dwarf-planet Ceres. The bight areas are may have been produced by upwelling of salt-rich liquids after the impact that formed the crater.

The animation was produced by the German Aerospace Center (DLR). Original music by Stefan Elgner, DLR.

Video – JPL / NASA

A View From Above

And what at first looks something like an image of a herd of animals or something of the like. . .

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. . . turns out to be nothing even close. These are the remains of gas pockets below the seasonal ice on Mars.

The image comes from the HiRISE imager on the Mars Reconnaissance Orbiter.

The original caption:

Gas under pressure will choose an easy escape route. In this image, the terrain is covered with a seasonal layer of dry ice.

The weak spots, for gas sublimating from the bottom of the seasonal ice layer to escape, appear to be around craters, where the surface was broken and pulverized by an impact. Fans of surface material deposited on top of the seasonal ice layer show where the escape vents are.

Image: NASA/JPL-Caltech/Univ. of Arizona

CYGNSS Launch – Third Attempt

UPDATE:  YES!  The Pegasus rocket was launched and it delivered its payload of the Cyclone Global Navigation Satellite System (CYGNSS)

Ok, this is the third attempt to get the CYGNSS into orbit!

Launch time is 08:26 ET / 13:26 UTC, pop in and have a look.

I’ll leave the live link up located in an earlier post: CYGNSS Launch.  Fingers crossed, let the third time be a charm.

 

Juno Sees a Pearl on Jupiter

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Happy to see Juno made it through the close encounter with Jupiter!

This is one of the images returned from the spacecraft.  I’ve cropped and tried to enhance the features of the original, seems to have worked out nicely – click the image for a larger version.

I’ve included the original as a link in the caption released with the image below (it will also explain the odd angles in my cropped image:

This image, taken by the JunoCam imager on NASA’s Juno spacecraft, highlights the seventh of eight features forming a ‘string of pearls’ on Jupiter — massive counterclockwise rotating storms that appear as white ovals in the gas giant’s southern hemisphere. Since 1986, these white ovals have varied in number from six to nine. There are currently eight white ovals visible. Since 1986, these white ovals have varied in number from six to nine. There are currently eight white ovals visible.

The image was taken on Dec. 11, 2016, at 9:27 a.m. PST (12:27 EST) as the Juno spacecraft performed its third close flyby of the planet. At the time the image was taken, the spacecraft was about 40,000 miles (24,600 kilometers) from Jupiter.

JunoCam is a color, visible-light camera designed to capture remarkable pictures of Jupiter’s poles and cloud tops. As Juno’s eyes, it will provide a wide view, helping to provide context for the spacecraft’s other instruments. JunoCam was included on the spacecraft specifically for purposes of public engagement; although its images will be helpful to the science team, it is not considered one of the mission’s science instruments.

Image and caption: NASA/JPL-Caltech/SwRI/MSSS