Seeing Further Trivia Quiz

Answer: IceCube

IceCube is one of the most impressive particle detectors ever built. Located near the South Pole, it consists of columns of photon detectors on strings sunk deep into the ice. These detectors can spot light produced anywhere within a cubic kilometer of ice! Ancient and unadulterated, the ice makes a magnificently transparent target for neutrinos, which - in their rare interactions - produce additional particles and telltale signatures in light. Using the detector data, scientists can then reconstruct the energy and direction of the original neutrino. Construction was completed in 2010.

Neutrinos from outer space make excellent astrophysical messengers: they interact very rarely and they don't feel magnetic fields, so they point back to their original source. IceCube particularly targets very high-energy neutrinos, which carry information about the source of cosmic rays.

Answer: COBE

COBE, the Cosmic Background Explorer, was a satellite with infrared and microwave detection abilities that flew from 1989 to 1993. Its purpose was to study the cosmic microwave background, relic radiation from just 380,000 years after the Big Bang. These photons were created with high energy, reflecting the high ambient temperatures at the time, but the expansion of the universe since cooled them to the microwave range.

COBE established that this radiation has a nearly perfect blackbody spectrum, as expected for a thermal source. The satellite was also able to detect anisotropies - directional variations in temperature - echoing the tiny density fluctuations that seeded the later formation of galaxies and clusters. Its success was followed up by the even more sophisticated WMAP and Planck satellites, complementing ground- and balloon-based telescopes.

Answer: LIGO

Gravitational waves, a consequence of general relativity, stretch and strain space-time as they pass through a region. The Laser Interferometer Gravitational-Wave Observatory - LIGO to its friends - is designed to detect that strain. LIGO uses laser light to very precisely compare the lengths of two perpendicular 4-km flight paths, via a method called interferometry that exploits the wave nature of light. Gravitational waves change the length of one arm versus the other in an oscillatory way characteristic of how the waves were created, for example by merging black holes or neutron stars.

LIGO is a tremendous scientific and technical achievement, capable of detecting length changes down to one part in 10^21 at its two sites (Hanford, Washington, and Livingston, Louisiana, both in the U.S.). On September 14, 2015, LIGO detected its first-ever gravitational wave, the echo of a black-hole merger more than a billion light-years away. Since that time, another gravitational-wave observatory, VIRGO near Pisa, Italy, has come online, and more gravitational waves have been detected. 2015 marks the start of a new era of astronomy.

Answer: Hubble

The Hubble Space Telescope, placed in orbit in 1990, is a tremendously versatile device. After an initial Space-Shuttle servicing mission corrected a manufacturing flaw, it has been able to take incredibly detailed, high-resolution images of faraway objects, unhindered by the atmospheric turbulence that so affects telescopes on the ground. Its infrared and ultraviolet capabilities enrich the picture: photons at those wavelengths are easily absorbed in air, making ground-based measurements impossible.

Hubble has made magnificent images of other bodies in our solar system; helped pin down the existence of black holes at the cores of galaxies; established the age of the universe; and revealed that the expansion of the universe is accelerating. Truly, it's a telescope for all scales.

Answer: New Horizons

New Horizons is a probe, launched in 2006, that flew by Pluto in 2015 - passing only 12,500 km (7,800 mi) away from the dwarf planet. The New Horizons measurements were a bonanza for Plutonian geology; for the first time, astronomers could determine that the surface of Pluto is almost pure nitrogen ice, and could study the varied terrain of the planet. It is now hypothesized that Pluto's rocky core is surrounded by a thick mantle of water ice - and possibly some liquid water near the boundary with the core.

In a rather sweet footnote, scientists used some of New Horizons' tight mass allowance to include 30 g (1 oz) of the ashes of Clyde Tombaugh, who discovered Pluto in 1930.

Answer: Chandra

The Chandra X-ray Observatory satellite, named after Nobel laureate Subrahmanyan Chandrasekhar, was launched into Earth orbit in 1999. Astrophysical X-rays are important complements to visible light, giving an entirely different perspective on stars, galaxies, black holes and other interesting objects. You can't build an X-ray observatory on Earth, though, because the atmosphere badly scrambles the signal in that wavelength range. Chandra and other X-ray telescopes - such as Suzaku and XMM-Newton - must therefore be built for space.

Chandra is a fantastic, solid instrument for X-day astronomers, and has yielded new discoveries on everything from main-sequence stars to black holes to dark matter.

Answer: Kepler

The Kepler observatory was a Sun-orbiting spacecraft that flew from 2009 to 2018; its mission ended after its fuel ran out. Kepler's job was to search for planets outside our solar system by continuously measuring the brightness of hundreds of thousands of stars in the Milky Way. If a star is orbited by a planet, and that orbit brings the planet between the star and Kepler, then the telescope would note a telltale dimming of the star's light every time the planet completes a revolution. To put this into perspective, each transit of Earth reduces the Sun's apparent brightness by only about one hundredth of one percent! Nevertheless, Kepler identified more than 3000 exoplanets, including almost 400 around the same size as Earth. The first exoplanet around a Sun-like star was only discovered in 1995, so this represents an incredible leap for the field.

Kepler's successor is the TESS mission.

Answer: Fermi LAT

The Fermi Gamma-ray Space Telescope is a satellite placed in low-Earth orbit in 2008, and outfitted with several instruments to detect gamma rays - the highest-energy photons in the spectrum. The flagship instrument is the Large Area Telescope (LAT), which allows systematic surveys of wide swaths of sky. A separate instrument monitors lower-energy gamma rays to detect gamma-ray bursts.

Gamma rays yield information about some of the strangest and most dynamic environments in the universe: pulsars, supernova remnants, black holes actively accreting material in galactic cores, and other sources yet undetermined. Ground-based telescopes like VERITAS and HESS complement Fermi data for a thriving astronomical niche.

Answer: Alpha Magnetic Spectrometer

Cosmic rays are high-energy massive particles originating outside our solar system, and often outside our galaxy! They fly through space continually; when a cosmic ray strikes our atmosphere, the resulting showers of particles can be detected relatively easily. (It's a great undergraduate lab project.) The precise origins of these particles are still mysterious, and pinning down their composition - ie, what percentage are protons versus other atomic nuclei or even antimatter - is an important step in this investigation.

The Alpha Magnetic Spectrometer, or AMS, is a particle detector mounted on the International Space Station and designed to measure the antimatter fraction of cosmic rays. It's been taking data since 2011, and has found that the antimatter fraction varies with the energy of the cosmic ray. AMS data complements measurements by PAMELA, a satellite that operated 2006-2016.

Answer: Cryogenic Dark Matter Search

WIMPs are hypothesized particles, predicted by supersymmetric theory, that might make up the dark matter in the universe. Astronomers and particle physicists would really like to know whether they do! There are a few ways to search for it. You could look for indirect evidence, for example light created by WIMP annihilation in the centers of galaxies; gamma-ray telescopes are the right tool for that. You could try to make them in a particle collider, and teams of scientists at the Large Hadron Collider are scanning their data to see whether that's happened. Or, you could try to detect existing dark-matter WIMPs streaming through the universe (and, therefore, through your laboratory). That's where the Cryogenic Dark Matter Search (CDMS) and its counterparts -- LUX, XENON, LZ, and others -- come in.

If WIMPs exist, then they should occasionally scatter from regular nuclei via the weak force. That gives the nuclei a little bounce, or recoil. A carefully designed detector can spot that energy transfer to the nucleus. The trick is to get a large target -- that is, lots and lots of nuclei, since this interaction would be very rare even if it occurs --, a very sensitive detector, and very low backgrounds, which such experiments achieve by moving deep underground (to avoid cosmic rays) and screening their detector materials to ensure low intrinsic radioactivity.

The SuperCDMS experiment uses ultra-cold semiconductor detectors (germanium nuclei) at the bottom of the Soudan Mine in Minnesota, in the U.S. It began taking data in 2012.