Blogs / Bad Astronomy

One thing I love about Colorado is that things I used to think were rare are actually rather common here. For example, lenticular clouds are lens-shaped (hence the name) clouds that sometimes form when air flows over the mountains in a certain way. Where I grew up on the east coast they were non-existent, but here, a few miles downwind of the Rocky Mountains, I see them pretty often.

While I was at the gym the other day I saw a nice one, and posted a pic using my phone, but the cloud is a bit small and hard to see. After my workout, I got home, climbed onto my roof and, using a better camera, got this shot:

Sadly, by the time I got home the formation started to falter, but you can still see the elongated, oddly-sculpted shape. The knobby formation on the ridge line is called The Devil’s Thumb, and is located south of Boulder on the foothills.

I took a second picture at a faster exposure time so that details weren’t washed out, and that one is on the right (you can click both to embiggen).

I remember seeing lenticular clouds practically every day last fall, so I’m looking forward to seeing better ones here soon. They’re very cool, and another in a long list of things you might miss if you don’t simply look up every once in a while.

Just a quick note: The Big Picture did Saturn today, and it’s gorgeous. You need to a) get over there and check it out, and 2) bookmark it or put it in your RSS feed or whatever. It always delivers, and never disappoints.

When NASA slammed the 700 kg (1500 pound) 2400 kg (5200 pound) Centaur rocket booster into the Moon on October 9, the hope was that it would make a plume visible from Earth. Terrestrials were disappointed, however, when none was seen.

However, a better view was to be had by LCROSS, the Lunar Crater Sensing and Observation spacecraft, which shepherded and closely followed the rocket booster, impacting itself just minutes later. From its much closer (and doomed) location it spotted both the plume and the flash of impact! Here’s the plume:

I’ll be honest with you, it’s not much to see. For some reason, the plume was not several kilometers high as hoped, but instead more like only one or maybe two (and, it seems, blocked from our Earthly view by the rim of a crater). In the above image, taken 15 seconds after the booster impact, the plume was 6-8 kilometers wide. The fact that it was not as bright as hoped is itself interesting, however! The actual plume brightness was at the low end of what was expected, which may be due to the nature of the material it slammed into.

There was never really a chance to see the flash from Earth, since it was at the bottom of a crater blocked from our view. But LCROSS was directly above the crater when the Centaur hit, and took several images, including the one shown here right at the moment of impact. This image shows the flash in the mid-infrared, beyond what our eyes can see but where a lot of the energy of the impact went. Other images can be found on the NASA site.

The crater carved out by the Centaur was less than 30 meters across. That’s far too small to be seen from Earth (our limit, even with Hubble, is more than 100 meters in size), but the orbiting Lunar Reconnaissance Orbiter should be able to see it easily, and in fact did take observations of the impact just a minute or so after it happened.

All of these data are being analyzed right now. Did any of those instruments see the signature of water in the plume? Did the much larger LCROSS impact (it had a mass of 2000 kg) dig up any water? No one’s telling right now, but I suspect we’ll know soon enough. You can read more about this at Universe Today.

Update: Somehow, in my head, I got the masses of LCROSS and the Centaur reversed. Apologies, and thanks to IVAN3MAN for correcting me!

The Mars Global Surveyor was in operation around the Red Planet for over nine years. From 1997 to 2006 it snapped away with its Mars Orbiter Camera, taking more than 240,000 images. One of these pictures from the MOC is circulating the web right now; but no one is giving the supplemental info on what it is or linked to where it’s from! So I’m chiming in.

The picture was taken in May 2003, but its impact has not lessened with time. It shows Earth and Jupiter in one shot as seen from Mars! The whole image can be found here, but it’s huge (basically a long strip) so I’ve extracted the two planets here:

Whoa. You can clearly see the Earth and Moon, and even the continent of South America! On Jupiter, the banding of the clouds of obvious, as are three of the Galilean moons.

But I think you really need to click through and see the whole image (as well as the accompanying explanation on the MOC site). In this case, context is important. It’s critical! It’s images like this that remind us that we live on a planet, a world like any other and yet unique in that it’s our home. I get people asking me if space exploration is worth it, and then I see images like this, and I know the answer is yes. We need this perspective. It’s said that the Apollo 8 shot of the Earth rising over the Moon launched the modern environmental movement, because it showed all of us eggs sitting in our one, lone basket. We should be reminded of this idea as often as possible, and images like this one from the MOC need to be spread far and wide.

A couple of days ago, the Netherlands and Germany were treated to a spectacular fireball, a very bright meteor burning up over their skies. Photographer Robert Mikaelyan was at the right place at the right time and got tremendous photos of the bolide:

Wow! Click through to see the series; you can see the meteoroid breaking up as it slams through our air. Robert took beautiful shots, especially given that he couldn’t have had more than a few seconds to get them; things like this appear very suddenly and are gone in less than a minute at best. The event took place around 19:00 local time and was probably witnessed by thousands of people. I’m totally jealous.

Also in the meteor news category, apparently scientists have verified that a piece of metal that fell through a UK man’s roof in July is in fact space debris of some kind — meaning from a man-made object, not a natural meteorite. The Daily Mail (I know, barf) has the story and a picture of the object. Interestingly, the man claims the object was too hot to touch when it hit his house. In general, meteorites from deep space are not hot, but this is a bit different; it would have fallen from a decaying orbit, meaning a slower speed and a shallower angle as it came in at the top of the atmosphere. I’m not exactly sure why that would mean it would stay hot, but I’ll note it wasn’t hot enough to start a fire. I’ll have to look into this further.

Tip o’ the Whipple Shield to IVAN3MAN. Image from Robert Mikaelyan used with permission.

It’s been a while since I’ve sung the praises of the Mars Reconnaissance Orbiter’s HiRISE camera, which takes incredibly hi-res images of the surface of Mars. Thanks to the HiRISE Twitter feed, I found this incredible picture:

Can I get a Holy Haleakala! from the congregation?

Wow. I mean seriously, wow. You really really want to go look at the embiggened version. What you’re seeing here are sand dunes on Mars. This region is in the center of a large crater at mid-north latitude on Mars, a couple of hours past local noon, and with a resolution of 50 cm (18 inches) per pixel. Sand dunes are common in crater beds, where the wind can blow steadily across the surface and sculpt the ever-present sand into those flowing sculptures.

But what this picture so spectacular are the graceful blue-gray swirls arcing across the dunes. These are caused by dust devils, which are a bit like mini-tornadoes. If the ground gets heated, rising air can punch through cooler air above it. This starts up a convection cell, with warm air rising and cool air sinking. If there is a horizontal wind the cell can start spinning, creating a vortex like a dust devil. I’ve seen hundreds of these on Earth, and they are wonderful and mesmerizing to watch.

The important thing to note here is that the sand in the craters of Mars is actually dark grey in color, since it’s made of basalt. The reason it looks red in pictures is because covering the sand is a thin layer of much finer dust, and the dust is what’s red. When a dust devil moves over the Martian surface, it can pick up the very light dust particles, but not the heavier sand grains. So those blue-grey swirls are tracks where the dust devil has vacuumed up the dust, revealing the darker sand underneath. If you look carefully in the tracks, you can see the sand dune ripples are undisturbed. Only the dust is gone.

There’s more to see in the picture as well. There is a sloping dune peak cutting across from top left to lower right (it’s more obvious in the larger context view of this region), and again more dark streaks, linear this time, probably caused by sand sliding down the dune face. When the sand moves, the dust covering it gets disturbed and once again you see the darker color of the sand itself. I also love the way the dune shapes change depending on where they are in the picture, caused by differences in the wind patterns across the floor of the crater.

When I look at pictures like this, I am smacked in the face with the cold, hard fact that Mars is a world. It’s not just a dot in the sky, it’s not just a set in a movie, it’s not just pictures from a space probe. It’s a planet, a vast complex system of interacting environments which produces climates, landscapes, vistas, weather.

And man oh man, does it produce beauty, awe, and wonder. Wow.

My thanks to Dr. Alfred McEwen of HiRISE for taking the time to explain to me the difference in color between the dust and the sand, and how that affects this image.

The Local Group of galaxies is our Milky Way’s neighborhood: a few dozen galaxies dominated by our own, as well as Andromeda and a handful of largish ones.

But by far the majority of galaxies in our group — the majority everywhere, really — are dwarfs; small collections of stars and gas with only a few million stars. Lurking just 1.6 million light years away, half the distance to Andromeda, is Barnard’s galaxy, an irregular dwarf with about 10 million stars. Behold!

[As usual, click to embiggen, or get a ginormous 80 Mb TIF.]

This is perhaps the finest near-true color image of Barnard’s galaxy I have ever seen, courtesy of the European Southern Observatory’s 2.2 meter telescope in Chile… a far cry from the small 12.5 cm (5 inch) refractor Barnard himself used to discover it. Given that this diminutive galaxy is in the direction of Sagittarius — toward the center of our galaxy, which is loaded with stars — it’s incredible Barnard found it at all. In fact, most of the stars in this image are inside the Milky Way, between us and the other galaxy.

Barnard’s Galaxy is not precisely irregular, since it appears to have a bar-like structure across it. The red bubbles are regions where stars are being born in large numbers; the UV and fierce winds of subatomic particles from the massive stars being formed carve out cavities in the gas, creating what look like smoke rings. The red glow is characteristic of hot hydrogen, and is a sure-fire way to know that gas is being excited by the stars nearby. The sharp edges to the bubbles are real, due to the gas piling up as it rams gas in interstellar space in a cosmic snowplow effect. There are over 150 separate bubbles like these in the galaxy, some of which have been observed using the Hubble Space Telescope.

There is another feature here that’s not obvious. On the left and right of the galaxy are faint, thick, blue arcs. This is actually gas that’s being blown out by the stars in the center of the galaxy, forming a weak ring surrounding the entire structure. I expect that gas will blow right out of the galaxy entirely; the gravity from the meager number of stars making up Barnard’s Galaxy can’t possibly be enough to restrain it.

Dwarf galaxies are difficult to observe because they are so faint; they fade with distance rapidly, so only nearby ones can be studied in detail. But since they are the most numerous types of galaxy in the Universe, these tiny smudges are well worth studying, and images like this one of Barnard’s Galaxy will help us understand how these galaxies formed, and what they’re made of, and how they behave. We also think that through collisions, these galaxies can grow to become larger, more magnificent ones like our Milky Way, so, as usual, when we study the Universe, looking ever outward, we are actually turning our gaze inwards to learn more about ourselves.

Image credit: ESO.