On the first Tuesday of each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.
This is reprinted by permission form the Oklahoman and newsok.com.
Astronomers currently know of 3726 confirmed planets beyond our solar system. The Kepler space telescope found the bulk of them, and 4496 more Kepler candidate exoplanets await confirmation. Now, two new instruments are set to boost those numbers considerably.
Kepler’s successor is the Transiting Exoplanet Survey Satellite (TESS) which launched last month. Like Kepler, TESS will continuously stare at a large number of stars, watching intently for slight drops in the stars brightness as an orbiting planet passes in front of, or transits, any of them. TESS plans on watching far more stars than Kepler did, so it should be far more successful at finding them.
The discovery process used by Kepler and TESS can only be done in space. The change in brightness as a planet passes in front of its parent star is miniscule, at most only one percent of the star’s brightness. If you have ever look at stars in the night sky from the surface of Earth, you know they twinkle or change in brightness. A star’s twinkling changes the apparent brightness of a star by well more than one percent. That flickering is caused by turbulence in our atmosphere.
In space, stars don’t twinkle as there are no molecules of atmospheric gases interfering with the view. A dedicated space telescope can easily track such tiny changes in a star’s brightness. There are other processes that can cause a star to dim a bit. Sunspots come and go on our sun’s surface all the time, which causes its light output to vary. Some stars are inherently variable. But all the other known ways a star’s brightness can change have a different pattern than a planet transiting a star. Kepler’s and TESS’s software filters light changes of the wrong pattern. And you can’t argue with Kepler’s track record.
The other new piece of equipment goes by the acronym DARKNESS (the DARK-speckle Near-infrared Energy-resolved Superconducting Spectrophotometer). Astronomers love cute acronyms for their projects, even if it is sometimes a stretch. DARKNESS uses a new type of camera with a new imaging technique to actually photograph the planets directly.
This is no easy task. Trying to see a planet close to a star is like trying to see a firefly next to a giant spotlight. The ability to resolve these two objects so close together and so different in brightness is beyond the capability of the semiconductor-based cameras used in all telescopes until now. This is the same technology used by the Hubble Space Telescope, Kepler, Tess and your cell phone. Fine for selfies, but not for seeing a firefly next to a spotlight.
DARKNESS uses superconducting technology for vast improvement in resolution. “When a single photon with the energy of more than 1 electron volt hits a semiconductor detector, it frees one electron," said physicist Ben Mazin from the University of California, Santa Barbara, who led the team developing the camera. "In a superconducting detector, it frees something like 5,000 or 10,000 electrons. And since there are many more electrons to measure, we can do things that you can't do with the semiconductor detector."
DARKNESS will have a capability currently not available. "It actually takes a picture of the star and the planet," said Mazin. "You can [even] get a spectrum of the planet, but it's extremely technically challenging." The ability to get a spectrum means we can decipher the makeup of the planet’s atmosphere and see if it contains certain constituents, like oxygen or methane, which indicate the presence of life.
DARKNESS or TESS may soon find Earth 2.0.