Number 10: A Comet Bursts Forth
People all over the world took pictures of the comet’s outburst (the cause of which is still something of a mystery).
This picture was taken on November 29, 2007 by the gifted astrophotographer Tamas Ladanyi This remarkable shot covers several degrees of sky.
Comet Holmes is still fading away. But will it brighten again? In 1892, just after it was first discovered, Holmes had an outburst very similar to this modern one. So even as it dims and moves into the outer solar system, is it gearing up for another exciting run?
Number 9: A Black Hole on Mars
What is it about Mars that draws us in? Even through a big telescope it’s small, distant, and fuzzy. But when you gaze up on it in the night sky it’s a bright bloody beacon, a glaring eye staring back at you. No wonder the ancients thought it the god of war!
The picture shows a pit crater, a collapsed shaft going down into the surface of Mars. It’s on the side of a volcano. Most likely they form when magma under the surface subsides, and the ground above it collapses.
Number 8: The Wonderful
The red giant star Mira is called "The Wonderful" because it brightens and dims noticeably to the naked eye, sometimes going from quite bright to total invisibility in just a few weeks. Mira is a star on its death bed; it is in the final stages of sloughing off its outer layers, and in a few hundred thousand years the entire envelope of the star will have been ejected, leaving only a naked and very hot white dwarf star.
Mira is like a comet! But a lot, lot bigger: the tail of Mira is 13 light years (130 trillion kilometers/80 trillion miles) long.
The tail is really the gas ejected by the star as it dies. As Mira moves through space, the gas between the stars slows the ejected material, forming the long streamer. In the picture, the motion is left to right, so the left-hand side of the tail is the oldest. On the right you can actually see the bow shock as the star plows through the gas between stars.
Mira is much like the way the Sun will be in a few billion years when its time runs out, for one, so by studying this image we are perhaps peering into our own future. But it also tells us that even a familiar object can surprise us, when we look at it with different eyes.
Number 7: The Lover’s Embrace of Arp 87
Galaxies seem like immutable giants of the cosmos; serene, majestic, and unmoving. But that’s an illusion. Everything in space is in motion, including galaxies. As you can imagine, when you take a collection of several hundred billion stars and set it in motion, it can be pretty hard to stop it. Galaxies move through space at numbing speeds, and the forces built up are mighty.
But then, sometimes, another galaxy gets in the way.
Then those vast forces come into play. Gravity twists and pulls at the galaxies as they dance past each other. And, as if they resist the inevitable recession of their partner, they reach out to one another in what looks like a tender embrace, but is in reality a stark (if lovely) portent of the destruction wrought on both galaxies.
Arp 87 is the name given to the system of two galaxies, NGC 3808A and NGC 3808B. They passed each other just as the age of dinosaurs was starting to get going on Earth, 200 million years ago.
We can see reddish gas clouds collapsing to form stars in the galaxies, and we can (just barely) tell that NGC 3808B is looking a little disturbed. Will the two galaxies continue to separate, or will gravity eventually win, drawing them together? Perhaps the latter. In a few hundred million years the merged remnant will settle down and look like a normal galaxy once again. And while this may look like a totally alien tableau, keep in mind that the Milky Way Galaxy has suffered through such collisions in the past… and will again: the Andromeda Galaxy is bearing down on us. In a couple of billion years, the fireworks here will begin.
Number 6: Lightning at Weikerscheim Observatory
Astronomy only plays a tangential role in this picture… you can see stars in the sky, and the observatory is pretty obvious. But it’s the terrestrial drama that steals the show.
Jens Hackmann took this stunning picture of a lightning storm near the Weikerscheim Observatory; the 300 second exposure is enough to see the stars streak and the observatory lit up by ambient light. Sometimes, when it’s cloudy, observing is difficult… but you can still get incredible pictures.
Number 5: A Meeting of the Moons
Jupiter is fantastically massive, and the most interesting of its family are the moons Europa and Io.
Europa is an ice world, covered in a thick sheet of ice that might reach down to depths of over perhaps several kilometers. It’s nearly a dead certainty that underneath that forbidding icecap is an ocean of water, kept liquid from energy input by gravitational stress as Europa passes by her sister moons. Of all the real estate in the solar system, many astronomers have their money on Europa as the best place to look for alien life.
Io, on the other hand, is perhaps the worst place for life. It has an incredibly high sulfur content, for one thing. For another, the same gravitational heating that keeps Europa’s ocean liquid also keeps Io’s interior molten, but it gives the moon a cosmic case of indigestion.
Io is wracked with volcanoes. They are almost constantly erupting molten sulfur over a kilometer high in the low gravity, and plumes of dust and gas blast hundreds of kilometers off the surface. This activity was first discovered when the Voyager 1 probe passed the moon in 1979, but subsequent space probes have gotten even more detailed images. When the New Horizons Pluto probe passed Jupiter in March 2007 for a gravity boost, it snapped a beautiful picture of the sisters.
Europa is the crescent on the lower left, and Io (obviously) is the one on the upper right. The plume you see is from the volcano Tvashtar, which has been active for quite some time now. If you look right at the bottom of the plume, you can see molten sulfur glowing red. Two other volcanoes appear to be making some noise as well.
While they appear to be close together, the two moons were actually nearly 800,000 kilometers apart when this picture was taken; Io was on one side of Jupiter and Europa on the other, but from the spacecraft’s perspective they were next to each other in the sky.
Number 4: Dark Matter Makes an Appearance
The gravity of dark matter has a subtle effect: it acts like a lens, bending the path of light coming from objects behind it.
In this Hubble image, the white dots are entire galaxies. They are part of a cluster called CL0024+1652, which is a whopping 5 billion light years away. The blue glow is the location of the dark matter, revealed by its distortion of the shapes of more distant galaxies behind it. The dark matter is in the shape of a ring surrounding the cluster, which indicates that a long time ago, CL0024 suffered a mighty blow, colliding head-on with another cluster. The dark matter from the two clusters passed right through each other, and their gravity caused the material to form the ring shape. We’re seeing this right down the barrel of the collision.
This image is a stunning confirmation of the existence of dark matter, and our understanding of how it works. Many people — who don’t understand the science — claim dark matter doesn’t exist, and that astronomers are making it all up. Well, there’s a giant smoke ring in the sky indicating they are quite wrong.
In this image red is normal matter heated to millions of degrees, and blue shows the location of the dark matter.
Number 2: STEREO Eclipse
Studying the Sun seems like a pretty good idea; as the major source of light and heat for our planet, it’s a good thing that we try to understand it. And the Sun is a star, with all that implies: it’s huge in size, and frightening in its energy production.
To better understand it and the complicated nature of its surface activity, NASA launched a pair of satellites that can take pictures of the Sun simultaneously from different angles, providing a 3D view of our nearest star. They’re called the Solar Terrestrial Relations Observatory, or STEREO.
This sequence shows something we can never see from the Earth: a shrunken Moon passing in front of the Sun. Technically, it’s not even really an eclipse; it’s a transit (when something small crosses in front of something large). That video, only 8 seconds long, is incredible.
The Beautiful Face of IC 342
They are sweeping, majestic, chillingly beautiful, and utterly mesmerizing. There are many such grand design spirals in the sky, and astronomers are almost all familiar with the roster: M81, M51, M101, and others. But there is one that is a bit less seen, less well known. That’s because it hides itself, tucked away in a part of the sky where stars and dust are thick, obscured by the fog of our own Galaxy.
This creature is IC 342, a nearby spiral lying only 11 million light years away, very close on a galactic scale.
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