Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
Does Enceladus have underground oceans that could support life? The discovery of jets spewing water vapor and ice was detected by the Saturn-orbiting Cassini spacecraft in 2005. The origin of the water feeding the jets, however, was originally unknown. Since discovery, evidence has been accumulating that Enceladus has a deep underground sea, warmed by tidal flexing. Pictured here, the textured surface of Enceladus is visible in the foreground, while rows of plumes rise from ice fractures in the distance. These jets are made more visible by the Sun angle and the encroaching shadow of night. A recent fly-through has found evidence that a plume — and so surely the underlying sea — is rich in molecular hydrogen, a viable food source for microbes that could potentially be living there.
Image Credit & Copyright: Stephanie Ziyi Ye
A scene in high contrast this thoughtful night skyscape is a modern composition inspired by M. C. Escher’s lithograph Phosphorescent Sea. In it, bright familiar stars of Orion the Hunter and Aldebaran, eye of Taurus the Bull, hang in clear dark skies above a distant horizon. Below, faintly luminous edges trace an otherworldly constellation of patterns in mineral-crusted mud along the Uyuni Salt Flat of southwest Bolivia. The remains of an ancient lake, the Uyuni Salt Flat, Salar de Uyuni, is planet Earth’s largest salt flat, located on the Bolivian Altiplano at an altitude of about 3,600 meters. Escher’s 1933 lithograph also featured familiar stars in planet Earth’s night, framing The Plough or Big Dipper above waves breaking on a more northern shore.
Although galaxy formation and evolution are still far from being fully understood, the conditions we see within certain galaxies — such as so-called starburst galaxies — can tell us a lot about how they have evolved over time. Starburst galaxies contain a region (or many regions) where stars are forming at such a breakneck rate that the galaxy is eating up its gas supply faster than it can be replenished!
NGC 4536 is such a galaxy, captured here in beautiful detail by the Hubble’s Wide Field Camera 3 (WFC3). Located roughly 50 million light-years away in the constellation of Virgo (The Virgin), it is a hub of extreme star formation. There are several different factors that can lead to such an ideal environment in which stars can form at such a rapid rate. Crucially, there has to be a sufficiently massive supply of gas. This might be acquired in a number of ways — for example by passing very close to another galaxy, in a full-blown galactic collision, or as a result of some event that forces lots of gas into a relatively small space.
Star formation leaves a few tell-tale fingerprints, so astronomers can tell where stars have been born. We know that starburst regions are rich in gas. Young stars in these extreme environments often live fast and die young, burning extremely hot and exhausting their gas supplies fairly quickly. These stars also emit huge amounts of intense ultraviolet light, which blasts the electrons off any atoms of hydrogen lurking nearby (a process called ionization), leaving behind often colorful clouds of ionized hydrogen (known in astronomer-speak as HII regions).
Credit: ESA/Hubble & NASA
Text Credit: European Space Agency
NASA scientists are releasing new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet. This composite image, one of three new full-hemisphere views, provides a view of the Americas at night. The clouds and sun glint — added here for aesthetic effect — are derived from MODIS instrument land surface and cloud cover products.
In the years since the 2011 launch of the NASA-NOAA Suomi National Polar-orbiting Partnership (NPP) satellite, a research team led by Earth scientist Miguel Román of NASA’s Goddard Space Flight Center has been analyzing night lights data and developing new software and algorithms to make night lights imagery clearer, more accurate and readily available. They are now on the verge of providing daily, high-definition views of Earth at night, and are targeting the release of such data to the science community later this year.
Today they are releasing a new global composite map of night lights as observed in 2016, as well as a revised version of the 2012 map. The NASA group has examined the different ways that light is radiated, scattered and reflected by land, atmospheric and ocean surfaces. The principal challenge in nighttime satellite imaging is accounting for the phases of the moon, which constantly varies the amount of light shining on Earth, though in predictable ways. Likewise, seasonal vegetation, clouds, aerosols, snow and ice cover, and even faint atmospheric emissions (such as airglow and auroras) change the way light is observed in different parts of the world.
Feature: New Night Lights Maps Open Up Possible Real-Time Applications
NASA Earth Observatory’s “Night Lights” website
Image Credit & Copyright: Jens Hackmann
This was supposed to be a shot of trees in front of a setting Sun. Sometimes, though, the unexpected can be photogenic. During some planning shots, a man walking his dog unexpected crossed the ridge. The result was so striking that, after cropping, it became the main shot. The reason the Sun appears so large is that the image was taken from about a kilometer away through a telephoto lens. Scattering of blue light by the Earth’s atmosphere makes the bottom of the Sun appear slightly more red that the top. Also, if you look closely at the Sun, just above the man’s head, a large group of sunspots is visible. The image was taken just last week in Bad Mergentheim, Germany.
Image Credit & Copyright: A. Dimai, (Col Druscie Obs.), AAC
Comet Hale-Bopp, the Great Comet of 1997, became much brighter than any surrounding stars. It was seen even over bright city lights. Away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d’Ampezzo, Italy. Comet Hale-Bopp’s blue ion tail, consisting of ions from the comet’s nucleus, is pushed out by the solar wind. The white dust tail is composed of larger particles of dust from the nucleus driven by the pressure of sunlight, that orbit behind the comet. Comet Hale-Bopp (C/1995 O1) remained visible to the unaided eye for 18 months — longer than any other comet in recorded history. This year marks the 20th anniversary of Comet Hale-Bopp’s last trip to the inner Solar System. The large comet is next expected to return around the year 4385.
This image, taken by the JunoCam imager on NASA’s Juno spacecraft, highlights a feature on Jupiter where multiple atmospheric conditions appear to collide.
This publicly selected target is called “STB Spectre.” The ghostly bluish streak across the right half of the image is a long-lived storm, one of the few structures perceptible in these whitened latitudes where the south temperate belt of Jupiter would normally be. The egg-shaped spot on the lower left is where incoming small dark spots make a hairpin turn.
The image was taken on March 27, 2017, at 2:06 a.m. PDT (5:06 a.m. EDT), as the Juno spacecraft performed a close flyby of Jupiter. When the image was taken, the spacecraft was 7,900 miles (12,700 kilometers) from the planet.
The image was processed by Roman Tkachenko, and the description is from John Rogers, the citizen scientist who identified the point of interest.
Credit & Copyright: Leonardo Julio (Astronomia Pampeana)
The silhouette of an intriguing dark nebula inhabits this cosmic scene. Lynds’ Dark Nebula (LDN) 1622 appears below center against a faint background of glowing hydrogen gas only easily seen in long telescopic exposures of the region. LDN 1622 lies near the plane of our Milky Way Galaxy, close on the sky to Barnard’s Loop – a large cloud surrounding the rich complex of emission nebulae found in the Belt and Sword of Orion. Arcs along a segment of Barnard’s loop stretch across the top of the frame. But the obscuring dust of LDN 1622 is thought to be much closer than Orion’s more famous nebulae, perhaps only 500 light-years away. At that distance, this 1 degree wide field of view would span less than 10 light-years.
Expedition 50 Flight Engineer Thomas Pesquet of the European Space Agency (ESA) photographed brightly glowing auroras from his vantage point aboard the International Space Station on March 27, 2017. Pesquet wrote, “The view at night recently has been simply magnificent: few clouds, intense auroras. I can’t look away from the windows.”
The dancing lights of the aurora provide stunning views, but also capture the imagination of scientists who study incoming energy and particles from the sun. Aurora are one effect of such energetic particles, which can speed out from the sun both in a steady stream called the solar wind and due to giant eruptions known as coronal mass ejections or CMEs.
