Searchlights in a Dark Universe

New missions to find what’s hidden.

Hubble mirrors.jpg
Inspecting the James Webb Space Telescope’s test mirrors.

NASA’s astrophysics division had good reason to celebrate the new year. At the end of December, Congress passed a federal budget that gave astrophysics a 6.7 percent bump in funding. About half of that goes to the James Webb Space Telescope (JWST), which remains on track to launch in October 2018. The powerful infrared telescope will have many uses, but perhaps the most tantalizing is its potential to see the very first stars that formed some 13.5 billion years ago. Such observations could give scientists a better understanding of how events unfolded in the early universe.

The budget increase also allows NASA to fire the starting gun on the next major space telescope that will follow JWST. The agency was allocated $90 million to start the formulation phase on the Wide-Field Infrared Survey Telescope, or WFIRST. The project will use one of the two 2.4-meter mirror telescopes donated by the National Reconnaissance Office in 2011 to conduct, among other observations, surveys that measure the rate of the universe’s expansion. The discovery in 1998 that this expansion was accelerating led scientists to conclude that some kind of “dark energy” was exerting an influence on the expanding matter. But the nature of dark energy, which accounts for about 70 percent of the universe, remains a mystery. According to a national Dark Energy Task Force, more precise measurements of the rate of the universe’s expansion and determining whether that rate has evolved over time will provide scientists two clues to how dark energy behaves. The survey telescope will also provide an additional clue by measuring the growth rate of structure, which is suppressed during the periods when dark energy dominates. WFIRST could launch as early as 2024, and would spend the next two to three years completing its first surveys.

The European Space Agency is developing a similar telescope as part of Cosmic Visions, a ten-year program of missions that began last year. Euclid will be a 1.2-meter space telescope designed to conduct surveys similar to WFIRST’s, and to probe the mysteries of dark matter by observing mass distribution in galaxies. Having passed a key design review last month, construction of the telescope will get under way this year, with the goal to launch it in 2020.  

China also has a dog in the hunt for dark matter, with the December launch of the Dark Matter Particle Explorer, or DAMPE, which will search for indirect evidence by measuring high-energy electrons and protons. The Japanese Space Agency’s ASTRO-H spacecraft will launch in February to observe high-energy X-rays coming from black holes and supernova remnants, among other sources. There are many links between dark matter theory and X-ray observations: One theory is that certain particles giving off so little light that they can’t be seen will, when they decay, produce X-rays with a certain energy. ESA’s XMM-Newton mission, which has had several extensions since it began observing in 2000, found such X-ray emitters, a group of scientists announced last September. This may be the final year for the ESA X-ray observatory, but it’s still functioning well and could get another two-year extension, which would leave astronomers another tool for investigating the dark matter problem.

Meanwhile, the search for gravitational waves will continue in 2016. Many ground-based observatories are already searching for them (rumors began swirling again in January that researchers at LIGO, a pair of observatories in Washington state and Louisiana, have an announcement in the works), and Europe’s LISA Pathfinder, which launched in late 2015, will soon reach its observing  station at the L1 libration point between Earth and the sun. LISA Pathfinder is an engineering test mission that will tell astronomers if it’s possible to conduct the kinds of precise measurements necessary to detect gravitational waves from space.    

Finally, the Neutron Star Interior Composition Explorer, or NICER, will launch in late 2016 to the International Space Station, where it will join other science instruments attached to the station’s exterior, like the Alpha Magnetic Spectrometer, the dark matter and cosmic ray hunter installed in 2011.

The search for newly identified phenomena like dark energy is a long game, and scientists can’t predict just how long it might take to solve fundamental mysteries about the nature of the universe. But in 2016, they’ll at least have a few new tools.

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