Lawrence Berkeley Laboratory is a step closer to unravelling the mystery of dark energy. The lab's vision for a space mission made NASA's short list today.
The lab is leading an international team of about 140 scientists at 14 different institutions, including UC Berkeley and the Stanford Linear Accelerator Centre, to design a space telescope and camera to capture images of distant supernovae. These exploding stars may give clues to the enigmatic dark energy that makes up more than three quarters of the universe but about which almost nothing is known. Berkeley Lab has been working on designing the SuperNova/Acceleration Probe, or SNAP, almost since physicist Saul Perlmutter discovered dark energy in 1998. By measuring how light from exploding stars is stretched as it travels toward earth, Perlmutter calculated that the expansion of the universe was speeding up rather than slowing down as most scientists believed. The reason for this unexpected acceleration is some sort of force that overwhelms the universe's gravitational pull. Because it is so mysterious, this force was dubbed dark energy. Perlmutter recently won two prestigious international awards for his discovery, the Shaw Prize in Astronomy and the Feltrinelli International Prize in the Physical and Mathematical Sciences. The next step is to find out exactly what this stuff is, and Perlmutter and physicist Michael Levi are hoping their probe will be the one to do that. The design includes a powerful telescope and a digital camera with nearly a billion pixels. The Department of Energy has invested nearly $9 million in the SNAP project since 2003 and is a cosponsor, along with NASA, of the dark energy mission.
"There are still many hurdles for us to clear on the NASA side" - Michael Levi.
Two other teams will compete for the chance to launch their concept into space, one led by Johns Hopkins University and another by the National Optical Astronomy Observatory. NASA has allocated $2 million to be divided by the three teams to take their designs to the next level where they are basically ready to be built for launch and the cost for each can be estimated. The space agency will decide in 2009 whether or not to go ahead with whichever dark energy proposal is chosen.
"We are hopeful that given the impact of the science NASA will support this mission, but they have a lot on their plate. We are still hoping for a launch at the end of 2013" - Michael Levi.
Title: Snapping Supernovae at z>1.7 Authors: Greg Aldering, Alex G. Kim, Marek Kowalski, Eric V. Linder, Saul Perlmutter
Researchers examine the utility of very high redshift Type Ia supernovae for cosmology and systematic uncertainty control. Next generation space surveys such as the Supernova/Acceleration Probe (SNAP) will obtain thousands of supernovae at z>1.7, beyond the design redshift for which the supernovae will be exquisitely characterised. They find that any z≥2 standard candles' use for cosmological parameter estimation is quite modest and subject to pitfalls; we examine gravitational lensing, redshift calibration, and contamination effects in some detail. The very high redshift supernovae - both thermonuclear and core collapse - will provide copious interesting information on star formation, environment, and evolution. However, the new observational systematics that must be faced, as well as the limited expansion of SN-parameter space afforded, does not point to high value for 1.7<z<3 SNe Ia in controlling evolutionary systematics relative to what SNAP can already achieve at z<1.7. Synergy with observations from JWST and thirty meter class telescopes afford rich opportunities for advances throughout astrophysics.