Gallery: Space Photos of the Week: Hubble Spots a Big Blue Bubble
<a href="http://www.nasa.gov/feature/goddard/2016/hubble-sees-a-star-inflating-a-giant-bubble"> NASA, ESA, and the Hubble Heritage Team</a>01SPoW-April21-03.jpg
Just in time for the 26th anniversary of Hubble's launch on April 24, 1990, the telescope has photographed an enormous, balloon-like bubble being blown into space by a super-hot, massive star. Astronomers trained the iconic telescope on this colorful feature, called the Bubble Nebula, or NGC 7635. The bubble is 7 light-years across — about one-and-a-half times the distance from our sun to its nearest stellar neighbor, Alpha Centauri.
<a href="http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20358">NASA</a>02SPoW-April21-06.jpg
Craters with bright material on dwarf planet Ceres shine in new images from NASA's Dawn mission. In its lowest-altitude mapping orbit, Dawn has provided scientists with spectacular views of the dwarf planet. Haulani Crater shows evidence of landslides from its crater rim. Smooth material and a central ridge stand out on its floor. An enhanced false-color view allows scientists to gain insight into materials and how they relate to surface morphology.
<a href="http://www.nasa.gov/feature/pluto-s-halo-craters">NASA/JHUAPL/SwRI</a>03SPoW-April21-08.jpg
A photo of Pluto’s ‘halo’ craters spotted by New Horizons. The upper image – in black and white – sports several dozen “haloed” craters. The largest crater, at bottom-right, measures about 30 miles across. The craters’ bright walls and rims stand out from their dark floors and surrounding terrain, creating the halo effect. In the lower image, composition data from New Horizons’ Ralph/Linear Etalon Imaging Spectral Array indicate a connection between the bright halos and distribution of methane ice, shown in false color as purple. The floors and terrain between craters show signs of water ice, colored in blue. Exactly why the bright methane ice settles on these crater rims and walls is a mystery; also puzzling is why this same effect doesn’t occur broadly across Pluto.
<a href="https://www.spacetelescope.org/images/potw1616a/">ESA/Hubble & NASA</a>04SPoW-April21-07.jpg
At first sight, NGC 4111 looks like a fairly uneventful galaxy, but there are unusual features that suggest it is not such a peaceful place. Running through its centre, at right angles to the thin disc, is a series of filaments, silhouetted against the bright core of the galaxy. These are made of dust, and astronomers think they are associated with a ring of material encircling the galaxy’s core. Since it is not aligned with the galaxy’s main disc, it is possible that this polar ring of gas and dust is actually the remains of a smaller galaxy that was swallowed up by NGC 4111 long ago.
<a href="http://www.nasa.gov/image-feature/jpl/pia18366/y-marks-the-spot">NASA/JPL-Caltech/Space Science Institute</a>05SPoW-April21-05.jpg
A sinuous feature snakes northward from Enceladus' south pole like a giant tentacle. This feature, which stretches from the terminator near center, toward upper left, is actually tectonic in nature, created by stresses in Enceladus' icy shell. Geologists call features like these on Enceladus "Y-shaped discontinuities." These are thought to arise when surface material attempts to push northward, compressing or displacing existing ice along the way. Such features are also believed to be relatively young based on their lack of impact craters – a reminder of how surprisingly geologically active Enceladus is.
<a href="http://www.nasa.gov/mission_pages/chandra/comets-ison-panstarrs.html"> X-ray: NASA/CXC/Univ. of CT/B.Snios et al, Optical: DSS, Damian Peach</a>06SPoW-April21-01.jpg
Astronomers used Chandra to observe Comet ISON and Comet PanSTARRS in 2013, when these comets were relatively close to the Earth. The graphic shows the comets in optical images taken by an astrophotographer, with insets showing the X-ray images from Chandra. The X-ray emission is produced when a wind of particles from the Sun – the solar wind – strikes the comet’s atmosphere. The Chandra data was used to estimate the composition of the solar wind, including the amount of carbon and nitrogen, finding values that agree with independent measurements.
