Saturn’s moons Tethys and Hyperion appear to be near neighbors in this Cassini view, even though they are actually 930,000 miles (1.5 million kilometers) apart here. Tethys is the larger body on the left.
These two icy moons of Saturn are very different worlds. To learn more about Hyperion (170 miles or 270 kilometers across), see Odd Hyperion; to learn more about Tethys (660 miles or 1,062 kilometers across) see Dark Belt of Tethys.
This view looks toward the trailing side of Tethys. North on Tethys is up and rotated 1 degree to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 15, 2015.
The view was acquired at a distance of approximately 750,000 miles (1.2 million kilometers) from Tethys. Image scale is 4.4 miles (7.0 kilometers) per pixel. The distance to Hyperion was 1.7 million miles (2.7 million kilometers) with an image scale of 10 mile (16 kilometers) per pixel.
From the ESA press release (linked above):
This dramatic burst of colour shows a cosmic object with an equally dramatic history. Enveloped within striking, billowing clouds of gas and dust that form a nebula known as M1-67, sits a bright star named Hen 2-427 (otherwise known as WR 124).
This star is just as intense as the scene unfolding around it. It is a Wolf-Rayet star, a rare type of star known to have very high surface temperatures – well over 25000ºC, next to the Sun’s comparatively cool 5500ºC – and enormous mass, which ranges over 5–20 times our Sun’s. Such stars are constantly losing vast amounts of mass via thick winds that continuously pour from their surfaces out into space.
Hen 2-427 is responsible for creating the entire scene shown here, which has been captured in beautiful detail by the NASA/ESA Hubble Space Telescope. The star, thought to be a massive one in the later stages of its evolution, blasted the material comprising M1-67 out into space some 10 millennia ago – perhaps in multiple outbursts – to form an expanding ring of ejecta.
Since then, the star has continued to flood the nebula with massive clumps of gas and intense ionising radiation via its fierce stellar winds, shaping and sculpting its evolution. M1-67 is roughly ring-shaped but lacks a clear structure – it is essentially a collection of large, massive, superheated knots of gas all clustered around a central star.
Hen 2-427 and M1-67 lie 15 000 light-years away in the constellation of Sagitta (The Arrow). This image uses visible-light data gathered by Hubble’s Wide Field Planetary Camera 2, and was released in 2015 (the same data were previously processed and released in 1998).
Four years down and now there are two more to go for the Mars Science Laboratory or Curiosity. The rover looks to be in rather good condition, the wheels are a bit worn but not seeming to be getting worse, so who knows we could have Curiosity around for quite a while.
Ever notice how spacecraft destined to stay in orbit for some period of time always seem to have reflective foil around them? Ever wonder how that could possibly work?
You’re in luck! ESA shows us the state-of-the-art in space insulation:
Blankets of multi-layer insulation (MLI) are used to cover satellite surfaces to help insulate them from orbital temperature extremes. These are the reason that satellites often look as though they’ve been covered in shiny Christmas wrapping.
MLI blankets are made up of multiple layers of very thin, metal-coated plastic film, with low-conducting ‘spacer’ material placed in-between such as silk, nylon or glass-fibre netting. Alternatively, MLI is sometimes deliberately crinkled to minimise any contact between layers.
In the airlessness of space, objects can be hot and cold at the same time, especially if one side is in sunshine and another is in shade. In such conditions, thermal radiation is the main driver of temperature change (rather than convection or conduction), and reflective MLI serves to minimise it.
Thermal control specialists aim to maintain the temperature of the satellite within set limits, to keep electronic and mechanical parts working optimally and to prevent any temperature-triggered structural distortion.
Placing MLI blankets on a satellite body is a skilled art in itself, with complex shapes needing to be created to fit around around edges or joints.
I wanted to make sure I posted a reminder about the Perseid meteor shower set to peak on the night of 11 to 12 August. The could be a great shower! Well yes, the Perseids are always good, I’m talking GREAT in terms of meteor rate which could approach 200 per hour! Once seen, a shower like this will not be soon forgotten and it would be super to get the kids out. It would make a great project for an organized outing, like for example a Boy Scout or Science Club camp out – brought up because organizing such an event is on my bucket list of things to do. Anyway –
In 2009 there was a similar display and it was nothing short of spectacular. A good portion of my viewing that night was spent in the back seat of a hatchback car riding home from a class. It was an amazing show and I created two other avid meteor shower observers just by telling to “look up”. The image shown here was from that very 2009 shower (Credits: NASA/JPL)
This year the moon could put a damper on things at least a little bit. While the moon will be something like 62 percent illuminated it will be towards the south and on the way to setting by the time it is dark enough.
EARLY morning Friday is my plan. Showers radiating from a very favorable direction (about north) and the moon setting or set, I will be in my new patio recliner (dragged to the back lawn). ERT or Expected Recliner Time should be about 03:30 local – sorry I couldn’t resist I am really pretty excited to try the new observing set up out. I’d like to think I might get a nice image like the one above and the potential is there, I’m not sure. The good thing is with “most things astronomy” the fun is in the trying.
Here are a few viewing tips from the NASA Meteoriod Environmental Office’s Rhiannon Blaauw:
Saturn is nearing the northern-hemisphere solstice. The shadow on the rings is shortening as the time gets closer in this image taken in May 2016 – compare to this image taken in 2007.
Notice the shadow is just beyond the Cassini Division, by the time the solstice gets here in May 2017 the shadow will be just past the half-way point of the B-ring (the wide light colored ring). A year to wait for the solstice might seem like a long time, but consider it takes about 29.5 Earth-years for ONE Saturn year. Visit our Saturn page for a lot more information on the planet and the moons.
Shadows on the Saturn system are not new. Years before the Cassini spacecraft took these images, a gentleman named Robert Hooke noted shadows in drawings he made of Saturn in 1666.
Cassini took this image from about 3.2 million km / 2 million miles and there are a couple of things other than the shadow to take note of: the northern polar vortex stands out nicely and the moon Mimas is visible to the lower left of the planet.