NASA Latest Images ( from 15-Dec-2015 to 28-Dec-2015 )

Star Streams and the Whale Galaxy
Image Credit & Copyright: R Jay Gabany (Blackbird Observatory)
Collaboration: David Martínez-Delgado (University of Heidelberg), et al.

Explanation: NGC 4631 is a spiral galaxy found only 25 million light-years away, toward the well-trained northern constellation Canes Venatici. Seen egde-on, the galaxy is similar in size to the Milky Way. Its distorted wedge shape suggests to some a cosmic herring and to others its popular moniker, The Whale Galaxy. The large galaxy's small, remarkably bright elliptical companion NGC 4627 lies just above its dusty yellowish core, but also identifiable are recently discovered, faint dwarf galaxies within the halo of NGC 4631. In fact, the faint extended features below (and above) NGC 4631 are now recognized as tidal star streams. The star streams are remnants of a dwarf satellite galaxy disrupted by repeated encounters with the Whale that began about 3.5 billion years ago. Even in nearby galaxies, the presence of tidal star streams is predicted by cosmological models of galaxy formation, including the formation of our own Milky Way.

Falcon 9 First Stage Landing
Video Credit: SpaceX

Explanation: The booster has landed. Spaceflight took a step toward the less expensive last week when the first stage of a Falcon 9 rocket set down on a landing pad not far from its Florida launch. Previously, most rocket stages remained unrecovered -- with the significant exception of the Space Shuttles landing on a runway and their solid rocket boosters being fished back from the sea. The landing occurred while the Falcon 9 second stage continued up to launch several communications satellites into low Earth orbit. The controlled landing, produced by SpaceX, was the first of its kind, but followed a booster landing last month by Blue Origin that did not involve launching satellites. Boeing and SpaceX were selected last year by NASA to launch future astronauts to the International Space Station. The pictured rocket booster will be analyzed for wear and reusability, but then is scheduled to be retired. 

Doomed Star Eta Carinae
Image Credit: J. Morse (Arizona State U.), K. Davidson (U. Minnesota) et al., WFPC2, HST, NASA

Explanation: Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This featured image, taken in 1996, brought out new details in the unusual nebula that surrounds this rogue star. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained.

To Scale: The Solar System
Video Credit & Copyright: Wylie Overstreet and Alex Gorosh

Explanation: Want to build a scale model Solar System? A blue marble 1.4 centimeters (about half an inch) across would be a good choice for a scale model Earth. Since the Sun is 109 times the diameter of Earth, a 1.5 meter diameter balloon could represent the Sun. But the distance between the Earth and Sun, 150 million kilometers, would translate to just under 180 meters (590 feet) at the same scale. That would mean the completed project, including the orbits of the outer planets, is probably not going to fit in your backyard. Still, you might find enough room on a dry lakebed. Check out this video for an inspirational road trip through the Solar System to scale. 

SN Refsdal: The First Predicted Supernova Image
Image Credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

Explanation: It's back. Never before has an observed supernova been predicted. The unique astronomical event occurred in the field of galaxy cluster MACS J1149.5+2223. Most bright spots in the featured image are galaxies in this cluster. The actual supernova, dubbed Supernova Refsdal, occurred just once far across the universe and well behind this massive galaxy cluster. Gravity caused the cluster to act as a massive gravitational lens, splitting the image of Supernova Refsdal into multiple bright images. One of these images arrived at Earth about ten years ago, likely in the upper red circle, and was missed. Four more bright images peaked in April in the lowest red circle, spread around a massive galaxy in the cluster as the first Einstein Cross supernova. But there was more. Analyses revealed that a sixth bright supernova image was likely still on its way to Earth and likely to arrive within the next year. Earlier this month -- right on schedule -- this sixth bright image was recovered, in the middle red circle, as predicted. Studying image sequences like this help humanity to understand how matter is distributed in galaxies and clusters, how fast the universe expands, and how massive stars explode.

A Dark Earth with a Red Sprite
Image Credit: ISS, Expedition 31 Crew, NASA

Explanation: There is something very unusual in this picture of the Earth -- can you find it? A fleeting phenomenon once thought to be only a legend has been newly caught if you know just where to look. The featured image was taken from the orbiting International Space Station (ISS) in late April and shows familiar ISS solar panels on the far left and part of a robotic arm to the far right. The rarely imaged phenomenon is known as a red sprite and it can be seen, albeit faintly, just over the bright area on the image right. This bright area and the red sprite are different types of lightning, with the white flash the more typical type. Although sprites have been reported anecdotally for as long as 300 years, they were first caught on film in 1989 -- by accident. Much remains unknown about sprites including how they occur, their effect on the atmospheric global electric circuit, and if they are somehow related to other upper atmospheric lightning phenomena such as blue jets or terrestrial gamma flashes.

Herbig-Haro 24
Image Credit: NASA, ESA, Hubble Heritage (STScI / AURA) / Hubble-Europe Collaboration
Acknowledgment: D. Padgett (GSFC), T. Megeath (University of Toledo), B. Reipurth (University of Hawaii)

Explanation: This might look like a double-bladed lightsaber, but these two cosmic jets actually beam outward from a newborn star in a galaxy near you. Constructed from Hubble Space Telescope image data, the stunning scene spans about half a light-year across Herbig-Haro 24 (HH 24), some 1,300 light-years or 400 parsecs away in the stellar nurseries of the Orion B molecular cloud complex. Hidden from direct view, HH 24's central protostar is surrounded by cold dust and gas flattened into a rotating accretion disk. As material from the disk falls toward the young stellar object it heats up. Opposing jets are blasted out along the system's rotation axis. Cutting through the region's interstellar matter, the narrow, energetic jets produce a series of glowing shock fronts along their path.

The Horsehead Nebula
Image Credit & Copyright: José Jiménez Priego

Explanation: The Horsehead Nebula is one of the most famous nebulae on the sky. It is visible as the dark indentation to the red emission nebula in the center of the above photograph. The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright red emission nebula. Like clouds in Earth's atmosphere, this cosmic cloud has assumed a recognizable shape by chance. After many thousands of years, the internal motions of the cloud will surely alter its appearance. The emission nebula's red color is caused by electrons recombining with protons to form hydrogen atoms. On the image left is the Flame Nebula, an orange-tinged nebula that also contains filaments of dark dust. Just to the lower left of the Horsehead nebula featured picture is a blueish reflection nebulae that preferentially reflects the blue light from nearby stars.

Source- NASA