Showing posts with label astronomy. Show all posts
Showing posts with label astronomy. Show all posts

Friday, June 02, 2017


Why are there no nebulas visible in the night sky...I mean nebulas large enough to be seen with the naked eye? The answer is that there's several. They're just faint because they're so close.

A lot of the bright nebulas you see in photos are color enhanced, are shot with time lapse photography, and are composites. Given those advantages they look great. If they were closer and untreated, most would look as dim as our local samples.

Here's a few of the nebulas visible in the Southern sky. The biggest ones are Barnard's Loop and the Gum Nebula. On a clear night all are visible with the naked eye. Of course the Magellanic Clouds (actually small captive galaxies) are visible with the naked eye and so is The Milky Way.

Here's a clearer telescopic shot of the Gum Nebula. The name comes from Gumm, the astronomer who discovered it in the 1950s.
In the middle of the picture you see "Vela SNR". That's short for the Vela Supernova Remnant.

BTW, have you been paying attention to the close shots of Jupiter we're getting from the Juno probe? They're awesome! The picture above was made without color code manipulation.

Here's (above) what Juno saw when it flew over Jupiter's North Pole in mid-May. Watch it on the biggest screen that you can.

Wednesday, December 02, 2015


The New Horizons probe has been slow to send back its images of Pluto, but they're coming in now and they're exceeding expectations.

Here's (above) an Everest-type series of mountains next to what appears to be a lava lake or a glacier.

Here's (above) the remnant of a shield volcano. It's possible that the lava coming out of Pluto's mantle was liquid water. 

Here's (above) a field of craters, most of which are about a kilometer across. They're not impact craters, but are cheese-type holes only ten feet deep in a bed of solid nitrogen. 

 Above, the five moons of Pluto and their relative sizes.

Above, that's Charon, the biggest of Pluto's moons. It's half the size of Pluto which makes it the largest moon in the solar system relative to the size of its host planet. This is an astonishing photo because it reveals a world which is divided into two distinct parts separated by a belt of stress cracks.

Seeing this reminds me of the speculation that Earth once had two moons, one following behind the other in the same orbit. The smaller moon caught up with the larger one and slowly squashed into it with the result that today half of our moon has a substantially thicker crust than the other half.

I call this speculation because there's another scenario that might also explain the thinner crust on our side. Advocates say that early on, our moon was closer than it is now, and was heated by the newly formed molten Earth. The heat softened the moon's crust on our side allowing volcanoes to spew out lava that changed the surface of the side facing us. This explanation has less credibility for me because it would lead to a thickening on our side, not a thinning, which is what we see.

Anyway, the squashed appearance of Charon lends support to the idea that some sort of gradual collision happened there.

That's all I have to say about Pluto, but I can't resist putting up this photo of Phobos, a moon of Mars. Phobos is much closer to Mars than our moon is to us, and it appears to be spiralling in for a crash. The white smears on the right are thought to be stretch marks as the moon is being pulled apart by tidal forces.

My source for this photo didn't include an estimate for the time of impact, so maybe it's no time soon. When it occurs the debris is expected to form a ring around the planet.

Friday, August 28, 2015


This is Puppis A, a supernova remnant seen through a gap in a large foreground nebula, the Vela Super Nova Remnant. If you're a longtime reader of the astronomy posts here then you probably realize that this is not the way nova remnants are supposed to look.

Look how fragmented the red clouds are, as if they were torn to pieces by an angry giant. Not only that but the blue pieces of the cloud are long and fibrous, and the pieces are parallel...not the shape you'd expect in a conventional explosion. One of the red clouds on the right has a corkscrew shape. So what gives here? I don't know. 

Do you suppose there was one big explosion then ejected fragments blew up in secondary explosions the way some fireworks do? I'm probably wrong. 

For context, here's a much wider shot of the foreground cloud we were peeking through in the topmost photo. Look at the number of stars in the background. This is somewhere in the star-dense middle region of the galaxy. Stars are born and die quickly there.

It's a violent place with (I'm guessing) cumulative solar winds of an intensity that's hard to imagine. Maybe we should be surprised when any remnants have a normal shape in a rough neighborhood like this one.

Back in our neighborhood, here's (above) the familiar Crab Nebula, looking better than you've ever seen it before. The star that created it went nova in 1054 AD. When I was a kid a local science museum sold black and white glossies of this object and I bought one. It looked like a simple doughnut with slightly fuzzy edges and a star in the middle. Now,   with aid of the Hubble, it looks like an explosion in a cat fur warehouse.

The rapidly enlarging cloud is now 10 light years across.

Above, a color enhanced Pluto as seen by the New Horizons spacecraft in July. The probe is now headed for an asteroid in the Keiper Belt. It's a billion miles more remote than Pluto.

Monday, August 17, 2015


Hold your hats because this (above) is a much more significant picture than it seems. It's the Andromeda Galaxy, AKA M31, as seen recently on a clear night over the Swiss Alps. "So what?" you say. "What's so special about this?"

The answer is that we've all seen good pictures of M31 taken with the aid of long  exposures, pictures like the small colorful one above,...but the large picture at the top was taken with an ordinary camera. It's what the naked eye would have seen. In other words, the rounded disk of another galaxy was visible to the unaided eye in the night sky over Switzerland, not as a pinpoint of light, but as a hazy blue disk with a bright center. It'll be visible in American skies starting in September and lasting through the Fall. Amazing, eh?

Here's (above) a shot taken from the Curiosity Rover on Mars. The camera was about four feet high.

Above, layered Martian rocks, also taken by Curiosity. The layers are believed to be deposits made a couple of billion years ago near the shore of an ancient, long-gone river.

Here (above) a comet has just "turned on" as its orbit takes it closest to the Sun.

Lastly, here's (above) a small cluster of galaxies which is independent of our own Local Group of galaxies.

Our own group is a much larger one consisting of 54 galaxies, many of them dwarf galaxies that orbit the two local giants, Andromeda and The Milky Way.  According to Wikipedia the center of our local group is a point between these two galaxies.

Wednesday, July 08, 2015


Above, the side of Pluto facing its largest moon, Charon, as seen by the New Horizons probe two days ahead of rendezvous. The nearest pass will show the other side of the planet and will be in much sharper focus. Unfortunately this is the best picture of this side of Pluto that we'll get on this mission. Nobody knows what the dark areas are and why they're so regularly spaced. 

This is exciting! When I was a kid I had a special affection for Pluto because it seemed like the most mysterious and unknowable place in the Solar System. I never dreamed that I'd be able to see it up close in my lifetime.

Here's a picture of Antares, one of the brightest stars in the night sky. That's Antares in the middle of the blue haze within the orange dust cloud. The star is red but appears here as white, maybe because false color was applied. Anyway, the reason I put this up is for the dense star field that fills the picture. Isn't that incredible?

With all those closely packed stars constantly spewing high energy particles I can't even imagine how radioactive that environment must be. You have to wonder if it'll ever be possible to explore that part of the galaxy.

Have you ever wondered why we don't see giant nebulae in the sky at night? There's at least one pretty big one come we don't see it?

The answer is that the cloud is just too thin to be easily seen when it's this close, but cameras can see it. It looms over our cities at night. It's Sharpless 2-308 (above), a.k.a. The Bubble Nebula, and it covers more of the night sky than a full moon.

Here's (above) a familiar picture: The Southern Ring Nebula. But what's that straight line crossing it? Nobody knows.

Thursday, June 04, 2015


This (above) should get an award for the best astronomy photo of the year. It's a jagged cliff looming over a gravel foreground on the comet Churyumov-Gerasimenko. The part of the cliff we see in this picture is 850 meters wide.

Here's (above) Saturn's moon, Hyperion. Despite its 250 kilometer size, the spongey moon exerted very little gravitational pull on the probe that took the picture. It's mostly hollow inside, in the way that a sponge is hollow. The oddly-shaped craters are thought to be that way because the impacts that created them threw the ejecta into space rather than compacting it into the surface.

Here's (above) a creepy picture that's generating a lot of controversy. The star on the lower left is a supernova first seen a few weeks ago near the disk galaxy it seems to be associated with.

Calculations of the star's distance and brightness have led some to conclude that the great majority of energy in the universe is contained in the fabric of space itself, and not in galaxies and stars.

These computer-generated pictures show Pluto's moon "Nix" tumbling wildly around the common center of the double planetoid, Pluto/Charon. We'll know more about this in a month when NASA's Pluto probe passes these bodies.

Wednesday, November 19, 2014


Well I guess everybody's already heard of the problems encountered by the Philae lander when it landed on the comet last week. It's in a shadow that prevents its batteries from charging up sufficiently. Things might improve when the comet veers closer to the sun in the months ahead but for now information gathering is minimal.

 Even so we're still getting good data from the parent ship, the Rosetta orbiter. So far the data seems to support the argument by some that the Earth's oceans did not come from collisions with icy comets. Our oceans seem to lack sufficient quantities of a trace element that's thought to be contained in cometary water.

BTW, why do so many comets contain surfaces that look like they were smoothed over with a palette knife?

Above, Mimas...a moon of Saturn. It's thought to consist mostly of water ice with a small amount of rock, making it a sort of huge, dirty snowball. A recently detected wobble is believed to indicate an internal sea of liquid water. Does this add another moon to the list of possible sites for life? Probably not. The moon just barely holds together.

Thinking about Mimas reminds me how much has changed in planetary science in the last few years. Do you remember all those TV documentaries about the so-called Goldilocks Zone?  Well, that may be an obsolete concept now. Liquid water is assumed to exist on certain internally heated moons of Saturn and Jupiter, which are way outside of our own Solar System's Goldilocks Zone. Even rogue gas giants that exist between stars might conceivably contain moons with liquid water.

Here's something I didn't know about til I just saw a TV documentary about it: our galaxy is in the final stages of a collision with a dwarf galaxy named "Sagittarius." As I mentioned in an earlier post, we're already slowly absorbing two dwarf galaxies called The Magellanic Clouds, but with few noticeable effects so far. Not so with Sagittarius. Sagittarius has had a big impact on us.

In 2011 astronomers announced that our galaxy may not always have been a pinwheel. Our spiral arms might have been created by brushes with Sagittarius, as shown in the simulation above. If so, that was good luck for us because it drew the material that made up our sun from the toxic radioactive environment closer to the galactic center.

Above is a nearby flat galaxy seen edgewise.  Our own galaxy is thought to be similarly flat, perhaps because of the influence of Sagittarius.

The collision is nothing to worry about. It's been going on for a long time and it's effects may have mostly played out. I say "may" because Sagittarius is thought to contain unusually large amounts of dark matter which have now been dumped into our galaxy with unknown results.

We continue to learn more about the super massive black hole (SMBH) in our galaxy's center. Here's (above) a computer generated picture showing the gravitational lensing effect of that black hole on the surrounding space.

Currently our SMBH is surrounded by a large spinning gas cloud. After a period of relative calm our central black hole is evidently feeding again, voraciously.

Our central black hole is amazingly powerful. Here we are, far out on a spur on a spiral arm and we're orbiting Sagittarius A Star...that's the name of our central black hole... at a speed of 500,000 miles per hour!

'Just one more picture and I'm out of here. Those tadpoles in the center of a nearby nebula (above) are thought to be new stars in the process of forming. That's a more rare event than I'd previously thought. Our galaxy is older than most and most of the star formation that's going to occur here has already been done. That's actually a good thing because a galaxy full of new stars would be intensely radioactive and hostile to life.


Thursday, August 14, 2014


I hadn't intended to do another astronomy post so soon after the last one, but I've come across pictures that are just too interesting to withhold.

This one (above) appears to be a lump of clay shaped by a palette knife, but it's actually a comet called 67P Churyumorov. A probe named Rosetta just arrived there and is now in orbit attempting to locate a landing site for its robot lander.

Here's (above) another view. It looks like Rosetta's current orbit might take it laterally around the asteroid.

Here's Saturn being eclipsed by a shadow from, of all things, our own Moon. A commenter says this event isn't as recent as I thought. It coincided with the 9/11 attack.

It's strange to recall that only a couple of decades ago the proposition that underground moisture existed on Mars was considered controversial. Nowadays the evidence seems to jump out at us with every new batch of photographs.

Here's (above) a 5 kilometer high mesa on Mars which has undergone a collapse, possibly due to groundwater undermining a layer of subterranean salt. Some kind of dark material is revealed and some of it seems to have been carried down to the ground in a pattern possibly influenced by a liquid.

Here's (above) an odd one. It's Galaxy M106, about 23 million light years distant. Those purple spider legs appear at first glance to be carrying material away from the center but actually they're doing the opposite. They're jets fast-tracking matter into a super massive black hole in the galaxy's center. How can the jets be as large as they are? How come they're sticking out of the plane of the rest of the galaxy?

Here's (above) an even odder one. It's a supernova occuring in a double star system in a nearby galaxy,  Galaxy M82SN. The star had already explosively thrown off it's shell, alerting astronomers on Earth that it was about to enter the next stage where it turns into a white dwarf and emits jets of Xrays. Telescopes all over the world (including Chandra, the orbiting Xray telescope) were immediately trained on this star, only....only there were no Xrays. "So what?" you say.

Well, it's an important discovery. The two squares at the bottom are before and after shots of the dwarf, and they're empty. That indicates that our model for how supernovas occur is wrong. Good Grief! The universe continues to amaze!

Friday, June 20, 2014


I never tire of looking at pictures of the Milky Way taken from the surface of the Earth. This one (above) was taken from Reunion Island in the Southern Indian Ocean. 

What we call the Milky Way is actually a spiral arm of our own galaxy which is closer to the galactic center than we are. 

One of the biggest fears of space scientists is that Earth might might one day find itself looking down the polar axis of a nearby star which is about to go supernova. Until now no star fit the description but one has recently been discovered and we appear to be looking right down the barrel of the gun. 

That star (possibly a double star) is Wolf-Rayett 104, about 8,000 light years distant. Sometime in the next million years this star (above) will explode and the remaining core will fire a massive gamma ray jet in our direction. We don't know enough yet to predict whether the jet will hit us directly or score a near miss.

It's unlikely but we can't rule out the possibility that the star has already exploded thousands of years ago and the gamma rays simply haven't arrived yet. They could be here tomorrow.

 Above. the rings of Neptune. 

Above, a heat map of the sky taken by the COBE satellite. It shows that one side of the sky is warm and another relatively cold. By measuring the difference scientists can calculate how fast the Earth is moving through the universe relative to the background radiation. Our speed it turns out, is an unexpected 600 kilometers per second. That's very fast. No one knows why we should be moving at that speed. 

What you see here (above) is a recent imrovement on the deep field picture we all saw on the news a couple of years ago.  These are some of the most distant stellar objects it's possible to see. The galaxies shown here are all very young, only a few hundred million years old. 

It's puzzling because you'd think that stars would form first then clump together into galaxies, but that doesn't seem to be the case here. Maybe stars were abundant but were too small for the Hubble to resolve, but it's also possible that galaxies of some sort precede stars.

Monday, April 21, 2014


Before I get started with what's new, I'll put up this beautiful shot of an erupting Icelandic volcano. It reveals three different kinds of lightning occurring simultaneously.

Most people believe that stars are formed by the action of gravity on rotating disks of gas and dust. That's widely believed but last year two physicists got the million dollar Shaw Prize for proving it wrong. According to them gravity alone wouldn't be able to destabilize the disk and attract matter inward while angular momentum was simultaneously pushing it out.

These guys claim the missing ingredient is magnetism. Apparently not all disks are sufficiently conductive and those that aren't will never form stars. Some disks remain...disks.

Above, the far side of the Moon. It's cratered more than the side facing us, but that's what you would expect of the side facing outer space. What people want to know is how come it's not covered by smooth, dark, volcanic maria (seas) like the near side. The answer appears to  be that the Lunar crust on our side is simply thinner for some reason.

Here's an odd one: a distant asteroid named "Chaklido" has just been discovered to have rings like Saturn. Chaklido is 250 km in diameter.

Monday, April 07, 2014


Above is Enceladus, a moon of Saturn. It's tiger stripe surface constantly changes due to water ice escaping from the interior and reshaping the surface. Recently discovered gravitational fluctuations indicate that a large liquid ocean may exist under the surface, making Enceladus a candidate for life.

Where the moon gets its warmth isn't understood. Another moon of more or less the same size and distance from Saturn is completely dead.

The inflation theory has come under attack recently by scientists who claim that it's not needed to explain why the universe is as uniform as it is. In March new data was recorded by a microwave observatory at the South Pole that seems to confirm the inflation theory. The findings are controversial and the facts are still being checked.

Here's (above) an odd one: a galaxy that's tearing itself apart from the inside. Not much star formation is visible in the pinwheel, but lots of recently created star clusters appear in the matter ejected from the galaxy.

Above, the Great Nebula in Orion, about 1500 light years away. It's in the same spiral arm that we inhabit. The colors are unfortunately false. They're added to code  temperature and composition.

Here (above) are new gamma ray photos of the center of our galaxy. They've caused quite a stir because they may be evidence that particles of dark matter (called "WIMPS) are colliding with each other there, and producing much more gamma rays than present theory allows for. This conclusion is so far hotly contested.