The Cassini team has released a global topographic map of Saturn’s moon Titan. What makes this map interesting is the fact that, due to its thick atmosphere, Titan can only be mapped by radar during Cassini’s close flybys. As a result, only half of its surface has been imaged, and only 11 percent has topography data. For this map, the remainder was, well, extrapolated:

Lorenz’s team used a mathematical process called splining — effectively using smooth, curved surfaces to “join” the areas between grids of existing data. “You can take a spot where there is no data, look how close it is to the nearest data, and use various approaches of averaging and estimating to calculate your best guess,” he said. “If you pick a point, and all the nearby points are high altitude, you’d need a special reason for thinking that point would be lower. We’re mathematically papering over the gaps in our coverage.”

Topo maps of parts of Titan have been released before, but not for the entire moon. See previous posts on The Map Room: Titan in Stereo; Topography of Titan.

Image credit: NASA/JPL-Caltech/ASI/JHUAPL/Cornell/Weizmann.

Last week, the European Southern Observatory released this image of NGC 6559, a nebula some 5,000 light years away in the constellation Sagittarius. This image combines visible light with the hydrogen-alpha emission band (also visible, but specific) and was taken by the Danish 1.54-metre telescope at ESO’s La Silla observatory in Chile. Image credit: ESO.

The Sun never looks like this. This is a composite image, assembling 25 separate observations by NASA’s Solar Dynamics Observatory in the extreme ultraviolet wavelength of 171 ångströms (17.1 nm) over an entire year (April 2012 to April 2013). It reveals where the active regions on the Sun (sunspots, solar flares) are most commonly found. For something even more neat, follow this link and watch the video showing the Sun over a three-year period, two frames per day. Image credit: NASA/GSFC/SDO.

A magnificent new infrared image of the iconic Horsehead Nebula from the Hubble Space Telescope has been released to mark the 23rd anniversary of its launch (NASA, ESA). The false-colour image takes observations in the near infrared wavelengths of 1.1 and 1.6 µm and assigns them to the red and green channels, respectively. Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

The Kepler mission has discovered two new star systems with planets in the stars’ habitable zones. Two of the five planets detected in the Kepler-62 system, 62e and 62f, and one of the two planets detected in the Kepler-69 system, 69c, orbit at a distance where surface water is possible. These are the smallest habitable-zone planets to be discovered to date: 62f is only 40 percent larger than the Earth, 62e is 60 percent larger, and 69c is 70 percent larger.

Kepler-62 is a K2 orange dwarf some 1,200 light years away; 62e and 62f have orbital periods of 122 and 267 days, respectively; the three other detected planets orbit very near their sun. Kepler-69 is a G-type star similar to (but a little smaller than) the Sun, 2,700 light years away; 69c’s orbital period is 242 days. Kepler uses the transit method to detect extrasolar planets.

Image credit: NASA Ames/JPL-Caltech (artist’s concept of Kepler-62f).

Previously: First Habitable-Zone Planet Confirmed.

Here’s a look at the tip of the “wing” of the Small Magellanic Cloud — more precisely, a group of open clusters known collectively as NGC 602, surrounded by a nebula known as N90. It’s a composite image combining visible-spectrum light from the Hubble telescope, infrared light from the Spitzer telescope (in red) and X-ray light from the Chandra telescope (in purple); visit the image’s page on the Chandra website to see each separately. The X-ray observations reveal stellar formation in areas that did not turn up in visible or infrared light. Image credit: NASA/CXC/Univ. Potsdam/L. Oskinova et al. (X-ray); NASA/STScI (optical); NASA/JPL-Caltech (infrared).

I have a weakness for pretty pictures of spiral galaxies. This Hubble image of Messier 77, a barred spiral 47 million light years away in the constellation Cetus, more than qualifies. It’s a somewhat false-colour image, combining hydrogen-alpha (red), infrared (814 nm) and blue light. Image credit: NASA, ESA and A. van der Hoeven.

Or if star-forming regions are your thing the way spiral galaxies are mine, how about this Herschel image of molecular cloud W3?

We just found another star system in the neighbourhood. Say hello to WISE J104915.57-531906, a brown dwarf binary star system recently discovered by astronomer Kevin Luhman only 6.5 light years away. That makes it the third-closest star system, after the Alpha Centauri trinary (AB plus Proxima) and Barnard’s Star. Don’t be surprised it’s taken so long to find. Close stars aren’t always visible: even the closest red dwarfs — Proxima Centauri and Barnard’s Star — can’t be seen without a telescope, and brown dwarfs are fainter still; they’re pretty much infrared-only. WISE 1049-5319 (for short!) was detected by its rapid motion relative to background stars in Wide-field Infrared Survey (WISE) imagery, which suggested that it was close by. Checking older sky survey images confirmed its distance; subsequent observations by the Gemini Observatory (above) confirmed that it was a brown dwarf binary. Article (PDF). Image credit: NASA/JPL-Caltech/Gemini Observatory/AURA/NSF. Via Bad Astronomy.

Mercury isn’t normally this colourful. This is a false-colour mosaic built from images taken by the MESSENGER probe through several different narrowband filters during its colour base map imaging campaign. The colours accentuate differences in the composition of Mercury’s surface rocks. Caloris Basin is at the upper right in this view. Here’s the other side of the planet. More information here. Image credit: NASA/JHUAPL/Carnegie Institution of Washington.

NASA has released a free-air gravity map of the Moon: “If the Moon were a perfectly smooth sphere of uniform density, the gravity map would be a single, featureless color, indicating that the force of gravity at a given elevation was the same everywhere. But like other rocky bodies in the solar system, including Earth, the Moon has both a bumpy surface and a lumpy interior. … The free-air gravity map shows deviations from the mean, the gravity that a cueball Moon would have.” Gravity data comes from the GRAIL mission, with the digital elevation model provided by the Lunar Reconnaissance Orbiter laser altimeter. Image credit: NASA’s Goddard Goddard Space Flight Center Scientific Visualization Studio.

An image released today of spiral galaxy Messier 106, 23.5 million light years away in the constellation Canes Venatici, is the work of astrophotographer Robert Gendler; he combined archived Hubble image data with his and Jay GaBany’s ground-based observations, which provided colour data for the outer spiral arms. M106 is an active Seyfert galaxy with a supermassive black hole at its centre. Image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and R. Gendler (for the Hubble Heritage Team); acknowledgment: J. GaBany.

Time for some more awesome space pictures. Last month the Cassini team released this exquisite backlit image of Saturn, taken while the Cassini probe was in Saturn’s shadow. It’s an enhanced-colour view through infrared, red and violet filters.

Elsewhere in the Saturn system, there’s Jason Major’s colour composite of Saturn’s moon Dione, based on Cassini imagery from December 23. Moving from one of Saturn’s moons to our own, here are an oblique view of Taurus Littrow, the landing site of Apollo 17, from the Lunar Reconnaissance Orbiter, and César Cantú’s excellent wide-field shot of the Moon.

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Tau Ceti has been a focus of the science-fictional imagination for decades. Because we knew nothing about exoplanets, because we believed that binary star systems were unlikely to have room for planets in stable orbits, because we believed that life-sustaining planets were not possible around red dwarfs (neither of which are believed to be true now), we focused on Tau Ceti — a G-type yellow sun much like ours (though smaller) less than 12 light years away, with no stellar companion — as the most likely candidate for nearby habitable planets. Later theories discounted the possibility, citing the star’s low metallicity (which reduced the likelihood of rocky planets).

By now you’ve probably heard, though, that Tau Ceti may — may — harbour at least five planets, if what has been found through a new detection method is in fact signal and not noise. If correct, the planets range from two to more than six Earth masses, with orbital periods ranging from 16 to 640 days. At least one of the planets falls within the star’s likely habitable zone. Article, press release.

It’s fuel for the imagination, like Alpha Centauri’s planet, and the fact that Tau Ceti is both visible to the naked eye (magnitude 3.5, easy but not particularly bright) and visible from the northern hemisphere doesn’t hurt. I’ve seen it, and wondered, myself.

The Universe is past its star-making prime: “the rate at which new stars are being produced in galaxies today is barely 3% of the rate back 11 billion years ago, and declining. This indicates that unless our universe finds a second wind (which is unlikely) it will only ever manage to produce about 5% more stars than exist at this very moment.” But don’t worry: while our sun has only a few billion years left to it, most stars are smaller and last much, much longer. We won’t run out for a while. Article.

Alpha Centauri has a planet.

Using the radial velocity method, in which wobbles in the star’s motion indirectly reveals the presence of a planet, European astronomers have discovered a planet orbiting the second star of the Alpha Centauri system. The star is called Alpha Centauri B (α Cen B) and exoplanets are numbered with lowercase letters starting with b (a refers to the star itself), so the planet’s designation is Alpha Centauri Bb.

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This instalment of awesome space pictures focuses on planetary nebulae — the shells of gas ejected by dying stars. (When they were first observed in 18th century telescopes, they sort of looked like planets, hence the name.)

Let’s start with the Helix Nebula, a relatively close planetary nebula. I’ve posted photos of it before, both in infrared and in ultraviolet light. Above is an image of the Helix that combines infrared and ultraviolet light from the Spitzer and GALEX space telescopes, respectively. Image credit: NASA/JPL-Caltech.

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The Dawn spacecraft has left Vesta and is now on its slow way to Ceres. Here’s a last look back on Vesta. And here’s a lovely look at Vesta’s Licinia crater (via). Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

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The Solar Dynamics Observatory provides this fantastic view of a coronal mass ejection that took place last Friday, August 31, at 4:36 PM EDT. The CME generated auroras on Earth on Monday night. This picture displays ultraviolet light at wavelengths of 171 and 304 angstroms (17.1 and 30.4 nanometres). Full disc view, Earth to scale, video. Image credit: NASA/GSFC/SDO.

Previously: Today’s Coronal Mass Ejection.

Just look at this. It’s a test image from one of the two cameras on the Curiosity rover’s Mastcam. This view through the high-resolution telephoto (100mm) camera is toward a ridge on Mount Sharp some 16 kilometres away. The colour has been corrected to resemble lighting conditions on Earth (here’s the raw version). Also on the Mastcam is a medium-resolution wide-angle (34mm) camera: here’s its equivalent test image. And here’s a closeup of the strata on Mount Sharp. Image credit: NASA/JPL-Caltech/MSSS.

This is the light of a dying star: carbon star U Camelopardalis, captured in its death throes by the Hubble. More at Bad Astronomy. Image credit: ESA/NASA.

Nebulae represent birth as well as death. Herbig-Haro objects are jets of hot gas ejected from a newborn star: here’s a Hubble image of HH-110. For a look at a stellar nursery, see this infrared image of the Vela-C molecular cloud from the Herschel Space Observatory (via Universe Today).

Closer to home, the Lunar Reconnaissance Orbiter givies us a melt pond in Linné F crater and a lovely oblique view of Giordano Bruno crater. From Mars, a new panoramic view from the Opportunity rover (via io9); overhead, Mars Express’s stereo camera has yielded perspective views of the Melas Dorsa region.

Exciting new discoveries don’t necessarily result in awesome pictures. The discovery of Pluto’s fifth moon was announced today, but I don’t think the Hubble image will be anyone’s desktop background. Nor will the image behind the discovery of dark galaxies — young, starless and gas-rich, they would have been invisible if they hadn’t been illuminated by a nearby quasar.

We haven’t had a globular cluster in a while; here’s Hubble’s look at Messier 10, about 15,000 light years away in the constellation Ophiuchus, in visible and infrared light. Image credit: ESA/Hubble & NASA.

Elsewhere in the cosmos, some new nebula photos: ESO’s Very Large Telescope has a spectacular view of NGC 6357, the War and Peace Nebula; and NASA just released this infrared image of Orion’s Flame Nebula (NGC 2024) from the Wide-field Infrared Survey Explorer (WISE).

Closer to home, overlapping craters on Mercury look a lot like Mickey Mouse. Some impressive raw images of Saturn from Cassini here and here; a colour composite with Titan is today’s APOD. Speaking of Saturn and colour composites, check out Gordan Ugarković’s portrait of Saturn’s moon Tethys, based on Cassini imagery.

This book makes me feel very small.

The key takeaway of The Life and Death of Planet Earth: How Science Can Predict the Ultimate Fate Our World (Times Books, 2003), Peter Ward and Donald Brownlee’s follow-up to their earlier book, Rare Earth (Springer, 2000), is that complex life has been — and will be — on this planet for only a short period of time: a billion years out of the planet’s 12-billion-year estimated lifespan, and we’re already past the halfway point. The end of multicellular life is only a few hundred million years away, when so much carbon dioxide is sequestered away that plants suffocate. Of course, at that point the increasing output of the sun will render the planet too hot to inhabit in any event: the future, they argue, strongly resembles Earth’s Archean past, where the temperatures are hot, the atmosphere is toxic, and nothing more complex than bacteria can survive.

This is a really big-picture look at our planet, one that makes our presence upon it look very tenuous indeed. Everything on our planet is in flux, not static, every change we make to our world insignificant in terms of the big picture. The Earth of a few hundred million years ago was warmer, more biodiverse and had more CO₂ in the air; our “normal” is the result of hundreds of million years of carbon sequestration by plants that has led to cooler temperatures, low CO₂ levels — and ice ages. We are creatures of the interglacial period. Indeed, they point out while global warming is a problem in the immediate near term (and by immediate I mean the next few centuries), the glaciers are coming back; global warming may delay them, but the carbon cycle is inexorable.

In astrobiological terms — the search for life on other planets — the authors point out that the Drake equation needs another variable: the “habitable life span” of planet, the time during which a planet can sustain multicellular life. In Earth’s case, that’s one-twelfth of its existence.

Buy at Amazon (Canada, UK) • publisher’s page

NGC 3314 is a pair of galaxies that look like they’re colliding, but aren’t: one of these galaxies is more than 20 million light years further away than the other one. Funny thing, perspective. This Hubble image, released today, is a colour composite assembled from blue and red light. Image credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama).

If you follow me on any of the social networks you’ll have already heard about this, possibly more than once, in which case bear with me while I tell everyone else.

Hey everyone else, I caught the Transit of Venus tonight! I didn’t think I’d see it (clouds usually conspire against me seeing interesting astronomical events like conjunctions and transits), but things worked out this time, and I had a pretty good view of the black drop effect and second contact before the Sun set behind the trees.

Of course I took some photos. They didn’t turn out as well as I’d liked; I overexposed them rather badly, shooting at 1/60 sec when it should have been more like 1/250 sec, and I never seem to get the tinting right on solar photos (the originals are rather purple fringed and need some colouration). They’re certainly not as good as NASA’s photos, but for backyard shots taken in haste, not bad. (Also, I lack satellites. For now.)

Some clouds passed in front of the Sun while I was taking pictures, so I decided to seize the opportunity and shoot this rather atmospheric video.

We already knew that the Andromeda Galaxy was heading our way, but it wasn’t clear whether it was going to hit the Milky Way head-on, deliver a glancing blow, or miss us. Now the Hubble has measured Andromeda’s tangential motion, and yes, it’s coming right at us. It’ll hit in about four billion years. The two galaxies will interact for a few billion years after that before reforming into a single elliptical galaxy (see this animation; Flash required). This news really shouldn’t disturb you. It’s not like you’re going to live that long anyway, and the brightening Sun will render the Earth uninhabitable long before Andromeda hits. And space is big: when galaxies collide, stars don’t (though they do get tossed around gravitationally, and are occasionally ejected from the galaxy). Illustration credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger.

This spectacular view of the Sun’s corona at the 171-ångstrom wavelength, deep in the ultraviolet, comes courtesy the Solar Dynamics Observatory. More images and video here. Image credit: NASA/GSFC/SDO.

All kinds of ultraviolet imagery has turned up in the last couple of weeks, many of which courtesy the ultraviolet space telescope GALEX. For example, the Helix Nebula, which we’ve seen before in infrared. Or how about the bowshock of interstellar material piled up by runaway star CW Leo. Maybe that’s not spectacular enough; how about the mighty Andromeda Galaxy in ultraviolet? Or how about this composite image of Messier 101, the Pinwheel Galaxy, which combines GALEX ultraviolet with Spitzer infrared, Chandra X-ray and Hubble visible light observations?

Still at galactic scale, but more friendly to the human eye, ESO’s new image of Centaurus A, a giant radio galaxy that I’ve posted about twice before, here and here.

Closer to home, Cassini has captured raw images of Saturn’s tiny, egg-shaped moon Methone, which was only discovered in 2004. It’s one of three moons discovered by Cassini called the Alkyonides, none of which are more than a few kilometres across. Via Universe Today.

Finally, the Lunar Orbiter Image Recovery Project has released a higher-detail version of an iconic image of Copernicus crater.

The above image of Messier 78, a reflection nebula in Orion (but not the Orion Nebula), overlays observations from the ESO’s Atacama Pathfinder Experiment (APEX) telescope on top of Digital Sky Survey imagery. APEX records in the millimetre and sub-millimetre wavelengths — essentially it’s a microwave telescope — and reveals (in orange) cold, dark dust clouds that would otherwise be hidden. Image credit: ESO/APEX (MPIfR/ESO/OSO)/T. Stanke et al./Igor Chekalin/Digitized Sky Survey 2.

Other recent awesome space pictures include the Chandra X-ray Observatory’s discovery of a black hole outburst in M83, the Herschel Space Observatory’s infrared view of the Cygnus X star-forming region and the ESO’s infrared look at globular cluster M55. The Isaac Newton Group of Telescopes released this narrowband image of the Thor’s Helmet nebula. And last but not least, Jason Major’s colour composite of Titan and Saturn, based on new Cassini images.

Just look at this Hubble image of the Egg Nebula, a protoplanetary nebula on its way to becoming a planetary nebula: in particular, note the searchlight beams emanating from the dying central star, itself hidden by a surrounding dust cloud. Wow. Image credit: ESA/Hubble, NASA.

Other recent awesome space pictures include MESSENGER’s look at Mercury’s Donne crater; the ESO’s wide-field view of star cluster NGC 6604; and two infrared views of Messier 104, the Sombrero Galaxy, from the Spitzer Space Telescope that reveal that its well-known disk is actually enveloped by an elliptical galaxy structure: one, two.

If last week’s look at the Tarantula Nebula wasn’t enough for you, and I suspect it might not have been, then your dissatisfaction may be cured by this composite image assembled from three different orbiting telescopes. It shows the exact same view as last time, only this time visible-light observations from the Hubble (now coloured green) have been combined with infrared data from the Spitzer Space Telescope (here coloured red) and X-ray data from the Chandra X-Ray Observatory (here coloured blue). Image credit: NASA/JPL/PSU/L. Townsley et al. (infrared); NASA/STScI (optical); NASA/CXC/PSU/L. Townsley et al. (X-ray).

What’s that you say? Another Hubble image of 30 Doradus, the Tarantula Nebula? I don’t know, I’ve posted an awful lot of images of that nebula before … oh, what the hell. The Tarantula Nebula is awesome. It’s 160,000 to 180,000 light years away in the Large Magellanic Cloud. It’s huge: this image is 650 light years across. It’s so bright that if it were as close to us as the Orion Nebula (a relatively puny star-forming region, but the closest to us at 1,500 light years), it would cast shadows. And I can’t see it through my telescopes because I’m in the wrong hemisphere. Bummer.

This image is a mosaic assembled from infrared observations by the Hubble and ground-based observations of the hydrogen-alpha oxygen-III emission wavelengths by the 2.2-metre MPG/ESO 2.2-metre telescope at the ESO’s La Silla site. It was released to celebrate the Hubble’s 22nd anniversary.

Image credit: NASA, ESA, ESO, D. Lennon and E. Sabbi (ESA/STScI), J. Anderson, S. E. de Mink, R. van der Marel, T. Sohn, and N. Walborn (STScI), N. Bastian (Excellence Cluster, Munich), L. Bedin (INAF, Padua), E. Bressert (ESO), P. Crowther (Sheffield), A. de Koter (Amsterdam), C. Evans (UKATC/STFC, Edinburgh), A. Herrero (IAC, Tenerife), N. Langer (AifA, Bonn), I. Platais (JHU) and H. Sana (Amsterdam).