"The surface of the Earth is the shore of the cosmic ocean... Recently, we've managed to wade a little way out, and the water seems inviting." - Carl Sagan
In the heart of the Rosette Nebula
In the heart of the Rosette Nebula lies a bright open cluster of stars that lights up the nebula. The stars of NGC 2244 formed from the surrounding gas only a few million years ago. The above image taken in January using multiple exposures and very specific colors of Sulfur (shaded red), Hydrogen (green), and Oxygen (blue), captures the central region in tremendous detail. A hotwind of particles streams away from the cluster stars and contributes to an already complex menagerie of gas and dust filaments while slowly evacuating the cluster center. The Rosette Nebula’s center measures about 50 light-years across, lies about 4,500 light-years away, and is visible with binoculars towards the constellation of the Unicorn (Monoceros).
Image credit & copyright: Don Goldman
Mercury’s uneven surface comes into sharp relief when the sun sits low on the planet’s eastern horizon. The relatively smooth floor of the Caloris basin lies on the right, with the rim and exterior of the basin to the left. The knobby texture outside of the basin may have arisen due to blocks of material ejected by the basin-forming impact. MESSENGER spacecraft acquired this image as part of the Mercury Dual Imaging System’s high-incidence-angle base map. High incidence angles, obtained when the sun sits near the horizon, create long shadows that accentuate the small-scale topography of geologic features, as seen here.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
A rainbow-like feature known as a ‘glory’ has been seen by ESA’s Venus Express orbiter in the atmosphere of our nearest neighbour – the first time one has been fully imaged on another planet.
Rainbows and glories occur when sunlight shines on cloud droplets – water particles in the case of Earth. While rainbows arch across wide swathes of the sky, glories are typically much smaller and comprise a series of coloured concentric rings centred on a bright core.
Glories are only seen when the observer is situated directly between the Sun and the cloud particles that are reflecting sunlight. On Earth, they are often seen from aeroplanes, surrounding the shadow of the aircraft on the clouds below, or around the shadow of climbers atop misty mountain peaks.
A glory requires two characteristics: the cloud particles are spherical, and therefore most likely liquid droplets, and they are all of a similar size.
The atmosphere of Venus is thought to contain droplets rich in sulphuric acid. By imaging the clouds with the Sun directly behind the Venus Express spacecraft, scientists hoped to spot a glory in order to determine important characteristics of the cloud droplets.
They were successful. The glory in the images here was seen at the Venus cloud tops, 70 km above the planet’s surface, on 24 July 2011. It is 1200 km wide as seen from the spacecraft, 6000 km away.
From these observations, the cloud particles are estimated to be 1.2 micrometres across, roughly a fiftieth of the width of a human hair.
The fact that the glory is 1200 km wide means that the particles at the cloud tops are uniform on this scale at least.
The variations of brightness of the rings of the observed glory is different than that expected from clouds of only sulphuric acid mixed with water, suggesting that other chemistry may be at play.
One idea is that the cause is the “UV-absorber”, an unknown atmospheric component responsible for mysterious dark markings seen in the cloud tops of Venus at ultraviolet wavelengths. More investigation is needed to draw a firm conclusion.
Image credit: ESA/MPS/DLR/IDA
Astrophotography from 1908 — 1919
I can’t even describe how much respect I have for early astronomers.
Image courtesy: Yerkes Observatory, Royal Observatory of Greenwich, Mount Wilson Observatory
You say you love me.
But I wonder if it’ll last,
Like a zealous comet
That moves too fast
Just to evaporate
Into the void,
All hopes and dreams
You ask for a key
To my secret desires.
But a daring meteor
Of stone and fire
Most likely burns up
As it gets close.
Would you finally reach me
If it was you I chose?
You swear to be around,
That we’ll never be apart.
But how long will you stay
And watch over my heart?
Don’t be an asteroid
Wandering at a distance.
What good would it do—
A far persistence?
If the Sun and the Moon
Ceased to light your way,
Nights consumed by darkness
That swallows your days,
If tomorrow your eyes
Should stop seeing me,
Would you just pass me by
Like some space debris?
An interstellar butterfly
They say the flap of a butterfly’s wings can set off a tornado on the other side of the world. But what happens when a butterfly flaps its wings in the depths of space?
This cosmic butterfly is a nebula known as AFGL 4104, or Roberts 22. Caused by a star that is nearing the end of its life and has shrugged off its outer layers, the nebula emerges as a cosmic chrysalis to produce this striking sight. Studies of the lobes of Roberts 22 have shown an amazingly complex structure, with countless intersecting loops and filaments.
A butterfly’s life span is counted in weeks; although on a much longer timescale, this stage of life for Roberts 22 is also transient. It is currently a preplanetary nebula, a short-lived phase that begins once a dying star has pushed much of the material in its outer layers into space, and ends once this stellar remnant becomes hot enough to ionise the surrounding gas clouds and make them glow. About 400 years ago, the star at the centre of Roberts 22 shed its outer shells, which raced outwards to form this butterfly. The central star will soon be hot enough to ionise the surrounding gas, and it will evolve into a fully fledged planetary nebula.
Image credit: NASA, ESA, and R. Sahai (Jet Propulsion Laboratory)
Gamma rays from galactic center dark matter?
What is creating the gamma rays at the center of our Galaxy? Excitement is building that one answer is elusive dark matter. Over the past few years the orbiting Fermi Gamma-ray Space Telescope has been imaging our Galaxy’s center in gamma-rays. Repeated detailed analyses indicate that the region surrounding the Galactic center seems too bright to be accounted by known gamma-ray sources. A raw image of the Galactic Center region in gamma-rays is shown above on the left, while the image on the right has all known sources subtracted — leaving an unexpected excess. An exciting hypothetical model that seems to fit the excess involves a type of dark matter known as WIMPs, which may be colliding with themselves to create the detected gamma-rays. This hypothesis is controversial, however, and debate and more detailed investigations are ongoing. Finding the nature of dark matter is one of the great quests of modern science, as previously this unusual type of cosmologically pervasive matter has shown itself only through gravitation.
Image credit: T. Daylan et al., Fermi Space Telescope, NASA
On 20 January, ESA’s Rosetta spacecraft emerged from a 31-month hibernation on the final leg of its 10-year journey to comet 67P/Churyumov–Gerasimenko. Just like the spacecraft, the mission’s target is also now emerging from hibernation.
For the last few months, the comet has been behind the Sun from our vantage point on Earth. But in late February, the Very Large Telescope of the European Southern Observatory in Chile resumed observations – its last look was on 5 October 2013.
The image presented here was taken on the night of the 27 February (09:30 GMT on 28 February). The image on the left was created by stacking individual exposures to show the background stars. These were then shifted to compensate for the motion of the comet, which appears as a small dot right on top of one of the stars (at the centre of the circle). The image on the right shows the comet when the star trails have been subtracted.
The observatory is collaborating with ESA to monitor the four kilometre-wide comet from the ground to help refine Rosetta’s navigation and to make assessments of the comet’s activity prior to the spacecraft’s arrival in August.
The comet is about 50% brighter than when it was last observed. Although it is also now nearer to Earth, it has brightened faster than expected for an inactive comet of this size, suggesting that its icy nucleus has started to evaporate as it moves gradually closer to the Sun.
The comet travels around the Sun between the orbits of Jupiter and Earth; its closest approach to the Sun, in August 2015, is at a distance of 185 million kilometres.
Rosetta will be the first mission to make continuous measurements at close-quarters of how a comet’s activity changes as it journeys around the Sun.
Image credit & copyright: ESO/C. Snodgrass (Max Planck Institute for Solar System Research, Germany) & O. Hainaut (ESO)
Twinkle, twinkle little Earth
Venus, Mars, and other planets can appear as “evening stars in our skies, depending on your location and the time of year. On January 31, 2014, Earth played the same role for an earthling on Mars. NASA’s Curiosity rover turned its Mast Camera toward the horizon and snapped this photo of home.
Earth is just barely visible (image top-center-left), just above the dim glow of twilight near the Martian landscape. The image was captured about 80 minutes after sundown on the rover’s 529th day, or sol, on the red planet.
Curiosity and Mars were about 160 million kilometers (99 million miles) from Earth at the time, and the Big Blue Marble or Pale Blue Dot looked more like a faint white speck in this view. However, a human observer with normal vision, if standing on Mars, could easily see Earth and its moon as two distinct “evening stars.”
Image credit: NASA/JPL-Caltech/MSSS/TAMU
A hole in Mars
What created this unusual hole in Mars? The hole was discovered by chance in 2011 on images of the dusty slopes of Mars’ Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. Why there is a circular crater surrounding this hole remains a topic of speculation, as is the full extent of the underlying cavern. Holes such as this are of particular interest because their interior caves are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.
Image credit: NASA, JPL, U. Arizona
Redshifted is a star
When it’s moving away.
A slight change in wavelength
Discloses the star’s sway.
Its light frequency
Decreases as it goes—
An unsophisticated mind
Doubting what it shows.
And in a blink of an eye
Its light shifts toward blue,
Fluctuating in the spectrum.
Which one is more true?
What does it mean,
This radial velocity
That changes back and forth?
Is it ferocity
Of distance and desertion,
The saying good-bye,
Or an indication of the returning
Of that bright star thereby?
The presence of an object
To the naive one is unknown,
That pulls the strings of gravity
Without its body shown.
So she continues to wonder
As he snubs her and smiles,
Far from knowing the truth
Behind what his eyes beguile.