A supermassive black hole sits within this cloud of gas and dust at the center of our Milky Way galaxy. One of NuSTAR’s first goals will be to image this black hole in detail. NASA/CXC/MIT/F. Baganoff, R. Shcherbakov et al.

The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) was NASA’s first Small Explorer mission, launched in 1992. SAMPEX studied charged particles, including galactic cosmic rays and energetic particles coming from coronal mass ejections — explosions emanating from the sun’s surface, like the one in this image. These particles influence conditions on Earth, so the mission was designed to measure their abundances and determine their influence on atmospheric chemistry. SAMPEX finished its mission in 2004. NASA/SOHO

The Fast Auroral Snapshot Explorer (FAST) captured high data rate snapshots of auroras around the Earth’s poles. It was launched in 1996 and completed its mission in 2009. FAST was designed to study the smallest scale dynamics of space plasmas and the way that charged particles interact with the Earth’s magnetic field. This image shows the southern aurora seen from the space shuttle in 1991. Earth Sciences and Image Analysis Laboratory, Johnson Space Center

The Transition Region and Coronal Explorer (TRACE) took a deep, long look at the sun, focusing on the 3-D magnetic structures that emerge from its surface layer, the photosphere. Launched in 1998, TRACE observed the dynamics of coronal loops — giant filaments of plasma protruding into the solar atmosphere. Data from the spacecraft has helped astronomers model this turbulent region of the sun. It made its last science images in 2010. NASA/TRACE

Launched in 1998, the Submillimeter Wave Astronomy Satellite (SWAS) helped give astronomers a better understanding of star formation by looking at the composition of interstellar clouds, such as this dark globule in the constellation Cepheus. SWAS searched for different molecules, including oxygen and carbon monoxide, and detected water in almost every cloud it looked at, suggesting that the molecule is important in cooling clouds enough to allow them to collapse and form stars. The spacecraft diligently observed the sky until 2004, when it was deactivated. It was briefly brought back online the next year for three months to help observe the effects of NASA’s Deep Impact probe, which shot a projectile at comet Tempel 1. NASA/JPL-Caltech/W. Reach [SSC/Caltech]

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) takes high-resolution images of hard x-rays and gamma rays emitted from the sun during a solar flare. Much of the energy released during a solar flare goes into accelerating charged protons and electrons to very high energies but the details are not well understood. RHESSI, launched in 2002, works to pinpoint exactly where and how the charged particles are getting accelerated from on the solar surface. In this image, from NASA’s STEREO B satellite, a solar flare heats up mysteriously for a second time after cooling down. NASA/STEREO B

The Galaxy Evolution Explorer (GALEX) has studied tens of thousands of galaxies over about 10 billion years of cosmic history. Launched in 2003, GALEX looks in ultraviolet light to map out the rate of star formation in galaxies and their distances from Earth. In May, GALEX operations and funding were transferred to Caltech – which had previously been a partner with NASA on the project – the first time the agency has made such an agreement with a university. In this image, the telescope has spotted a runaway star plowing through the depths of space at 204,000 mph, shedding its own atmosphere to form a dusty shell. NASA/JPL-Caltech

Launched in 2007, the aim of Aeronomy of Ice in the Mesosphere (AIM) is to study mysterious and ephemeral icy clouds that float at the edge of the atmosphere above Earth’s poles. These clouds occur 50 miles above the ground, far higher than any other cloud, and can be seen hanging over Europe and North American in this image. They were first observed in the 1800s and seem to have become more common in recent years. AIM measures the thermal and chemical properties of the environment around these clouds to understand the conditions that give rise them and whether they are related in any way to climate change. NASA/AIM

Peering at the very edge of our solar system, the Interstellar Boundary Explorer (IBEX) has continually astounded astronomers. The mission, launched in 2008, investigates how the solar wind — a flow of charged particles coming from the sun — interacts with surrounding gas and dust in our galaxy. IBEX’s first surprise came when it found that neutral atoms generated when these two flows meet form a narrow ribbon two to three times brighter than anything else in the sky. Astronomers were also amazed to discover that the solar wind does not produce a “bow shock,” such as the one seen around a distant star in this image, when it hits the interstellar medium. The findings suggests that the sun travels more slowly through the galaxy than previously predicted. NASA/Hubble space telescope

Scheduled to launch in December, the Interface Region Imaging Spectrograph (IRIS) will trace the flow of energy and plasma between the sun’s upper layers and atmosphere, known as the corona. A long standing problem in solar astrophysics is explaining exactly why the corona is millions of degrees, while the surface of the sun is merely thousands of degrees. The layer between the surface and corona, known as the chromosphere, is difficult to image directly, but this is what IRIS will focus on. Hinode JAXA/NASA