Spotting the Firefly: The Exoplanet Imaging Contrast Quiz

If a star is a massive fusion reactor and a planet only reflects a tiny fraction of that light, then the star will be significantly more luminous; if the ratio of brightness is extreme (like 1,000,000,000 to 1), then the star’s glare acts like a searchlight that hides the "firefly" planet.

If contrast in this context refers to light levels, and if stars generate light while planets mostly reflect it, then the term describes the difference in luminosity or magnitude rather than physical diameter.

If two objects are far apart in the sky, they are easy to separate; if they are close together, and if one is vastly brighter than the other, then the bright light spills over and hides the dimmer object.

If a telescope captures light from a star system, and if the star is billions of times brighter than the planet, then the star's photons will flood the detector; if the detector is flooded, it cannot distinguish the few photons coming from the faint planet.

If a star is very far away, its light is faint; if the planet is too close to the star's image, they blur together; if the atmosphere distorts light, it creates a "halo" around the star that masks the planet.

If the star's glare is the primary obstacle, then removing that light from the image is necessary; if a coronagraph acts as an internal mask to block the star, then the faint light of the planet can finally be seen.

If contrast represents the "gap" or ratio between two things, and if the star is much brighter than the planet, then high contrast means a massive difference; if there is a massive difference, the brighter object makes the dimmer one much harder to see.

If light is composed of particles called photons, and if we are comparing how much light we receive from each source, then we are calculating the ratio of photons collected from the star versus the planet.

If planets are hot from their formation, and if hot objects emit thermal radiation in the infrared, then the planet is "brighter" in those wavelengths; if the star is relatively less dominant in the infrared, then the contrast ratio improves.

If light waves pass through a circular opening (the telescope), they spread out into a pattern; if this pattern covers a wide area, then the star's light will physically overlap the location where the planet is supposed to be.

If the atmosphere contains water vapor and turbulence that blurs and blocks light, then placing a telescope above as much atmosphere as possible (on a mountain) or entirely above it (in space) reduces the glare and "noise" in the image.

If an Earth-like planet is billions of times dimmer than its star, then the contrast ratio is closer to 10^9 to 1 or 10^10 to 1; therefore, a 10 to 1 ratio is far too low to be accurate.

If light reflects off a mirror that isn't perfectly smooth, the light scatters into tiny dots called speckles; if these speckles look like faint planets, they create "noise" that confuses the observer.

If a starshade is a separate spacecraft miles away from the telescope, and if it is positioned to cast a shadow over the telescope's opening, then it blocks the starlight before it can scatter inside the instrument, revealing the planet.

If a planet is young, it is still contracting and releasing heat; if it is hot, it glows in the infrared; if the planet is glowing while the star is the same, then the contrast ratio is smaller, making the planet easier to detect.

If a contrast ratio is expressed as "X to 1," then the first number represents the brightness of the star relative to the second number representing the planet; therefore, 1,000,000 to 1 means the star provides 1 million photons for every 1 from the planet.

If the atmosphere distorts starlight in real-time, then a computer-controlled deformable mirror can change its shape to cancel out those distortions; if the distortions are removed, the star's image becomes sharper and the planet becomes easier to see.

If resolution depends on the diameter of the telescope (aperture), then a larger mirror is needed to distinguish a planet that is very close to its star; if the mirror is too small, the two objects will blend into one dot.

If the biggest problem in direct imaging is the bright star next to the planet, and if a rogue planet has no host star, then there is no glare to block; if there is no glare, then we only need a sensitive enough telescope to see the planet's faint glow.

If a planet is small (less surface area), it reflects very few photons; if it is close to a bright star, it is lost in the glare; if the star is millions of times brighter, it masks any signal from the planet.