This series of images of comet C/2012 S1 (ISON) was taken by the Medium-Resolution Imager of NASA’s Deep Impact spacecraft over a 36-hour period on Jan. 17 and 18, 2013. At the time, the spacecraft was 493 million miles (793 million kilometers) from the comet.
Image credit:

NASA/JPL-Caltech/UMD

An animation depicting the trajectory of asteroid 2012 DA14 as it travels within the Earth-moon system on February 15, 2013.

*2012 DA14 is a near-Earth asteroid with an estimated diameter of about 45 meters (148 ft) and an estimated mass of about 130,000 metric tons. It was discovered on February 23, 2012, by the OAM Observatory, La Sagra in Spain  seven days after passing 0.0174 AU (2,600,000 km; 1,620,000 mi) from Earth on February 16. Calculations show that on February 15, 2013, the distance between the asteroid and Earth will be 0.000228 AU (34,100 km; 21,200 mi). The 2013 passage of 2012 DA14 by Earth is a record close approach for a known object of this size.

(*Source Wikipedia)

The further away you look, the further back in time you see. Astronomers use this fact to study the evolution of the Universe by looking at nearby and more distant galaxies and comparing their features. Hubble is particularly well suited for this type of work because of its extremely high resolution and its position above the blurring effects of the earth’s atmosphere. This has allowed it to detect many of the most distant galaxies known, as well as making detailed images of faraway objects.

Comparing galaxies in the distant past with those around us today, astronomers have noticed that the nearby galaxies are far quieter and calmer than their distant brethren, seen earlier in their lives. Nearby galaxies (although not the Milky Way) are often large, elliptical galaxies with little or no ongoing star formation, and their stars tend to be elderly and red in color. These galaxies, in astronomers’ language, are “red and dead.”

This is not so for galaxies further away, which typically show more vigorous star birth.

The reason for this appears to be that as the Universe has aged, galaxies have often collided and merged together, and these events disrupt gas clouds within them. A merger will usually be a trigger for such intense star formation that the supply of gas is used up, and no more star formation occurs afterwards. The merged elliptical galaxy then creeps into old age, getting redder as its stars get older. This is expected to happen to the Milky Way when it merges with the nearby Andromeda Galaxy, some four billion years from now.

The galaxy in this image, catalogued as 2MASX J09442693+0429569, marks a transitional phase in this process as young, star-forming galaxies settle to become massive, red and dead galaxies.

The galaxy has tail-like features extending from it, typical of a galaxy that has recently undergone a merger. Studying the properties of the light from this galaxy, astronomers see no sign of ongoing star formation; in other words, the merger triggered an event which has used up all the gas. However, the observations suggest that star formation was strong until the very recent past, and has ceased only within the last billion years. This image therefore shows a snapshot of the moment star formation stopped forever in a galaxy.

A version of this image was entered into the Hidden Treasures image processing competition by contestant Nick Rose.

ESA/Hubble & NASA