Life in Space: The Habitable Planets Quiz

Olivia Seitz

What is an exoplanet?

The most promising planets outside our solar system are exoplanets. These planets benefit from the warmth and protection of a nearby star.

When was the first exoplanet discovered?

Didier Queloz and Michel Mayor, from Switzerland, discovered the first exoplanet in 1995. They named it 51 Pegasi b.

Roughly how many planets are in our galaxy?

Each star in the Milky Way has an average of 1.6 planets orbiting it. This number could easily change as new information comes to light.

As of early 2017, how many exoplanet discoveries have been confirmed by NASA?

Almost three and a half thousand exoplanets have been discovered, and there will certainly be more to come! Not all of these planets fit our criteria for supporting life, though.

In February 2017, NASA announced the discovery of how many Earth-sized planets orbiting the same star?

In a rare and exciting find, scientists pinpointed the location of seven planets orbiting the same star. They're all roughly the same size as Earth, making it more likely that they can support life.

What is the name of the star that has seven Earth-sized planets orbiting it?

TRAPPIST-1 is a dwarf star, approximately 40 light-years from Earth. Three of the planets orbiting it are in its "habitable zone."

What do scientists know about the planets in TRAPPIST-1's habitable zone?

While we can't know details about the planets' surfaces, all three observations are likely true. Because TRAPPIST-1 is so much cooler than our own sun, scientists almost didn't investigate the area!

How many more years will TRAPPIST-1 be alive after Earth's sun goes out?

Another reason the discovery is so exciting is that TRAPPIST-1 should long outlive our own sun. If we can develop a sustainable method of space travel, the new system could be on our short list for colonization.

What would the night sky look like on a TRAPPIST-1 planet?

Anyone standing on the surface of TRAPPIST-1f, for example, would see the surface of the neighboring planets the same way we can see the moon. Since the planets are larger than the moon, they'd appear even closer and larger in the night sky!

How long would a year be on TRAPPIST-1f's surface?

Because the planets around TRAPPIST-1 are so close to their star, their years are extremely short compared to Earth's years. TRAPPIST-1f, the middle of the three hopefully habitable planets in the system, still only has a nine-day year.

Which method is used by astronomers to locate exoplanets?

One useful strategy is the transit method, in which scientists track the light from a star to determine if a celestial body is ever blocking the light. When a planet passes between its star and Earth, changes in the star's luminosity give clues as to the planet's size.

Which phenomenon is observed when scientists use radial velocity to confirm the presence of an exoplanet?

If a star is orbited by a planet, the pull of the planet affects the star's position. The result is a star that "wobbles" in place!

What do scientists look for when using gravitational microlensing to find exoplanets?

The gravity of nearby planets can bend the path light takes in between the star that emits it and the instrumentation that receives it. Scientists are able to look at how that path changes to determine if there are exoplanets around the star!

What is Drake's equation?

Frank Drake, an astronomer, wanted to estimate how many planets in our galaxy could give rise to intelligent life. The equation, written in 1961, was one of the earliest attempts at an estimate.

Which of the following is a factor included in Drake's equation?

Drake's equation attempts to take into account the factors necessary for a civilization to develop, such as the suitability of the planet and the chance that life develops.

Which of the following factors from Drake's equation can we reasonably estimate?

Many of the factors for Drake's equation cannot be estimated accurately, since there is no data that we can use to refine our estimations! Only the beginning conditions - such as star birth rate and estimating how many planets could support life - are within our reach.

What is true about a star's habitable zone?

Not every star has a habitable zone, let alone a stable planet in its orbit. A safe orbital distance can vary greatly; for Proxima b, the right distance is a mere 4.7 million miles; for Earth, it's 93 million miles.

Which of the following is important for the habitability of a planet?

To be habitable, planets need to be properly shielded from radiation. They also need to have days with reasonable lengths; otherwise, areas of the planet would be alternately too cold and too hot.

Which satellite is primarily responsible for exoplanet discoveries?

Kepler is the main source of data used to discover exoplanets. It was launched into orbit in 2009.

How many stars is Kepler capable of scanning at once?

Kepler's range is limited by its position and the sensitivity of its equipment. It won't be able to scan even close to the billions of stars in our galaxy.

As of February of 2017, how many exoplanets have been confirmed as potentially habitable?

Most exoplanets are a bust when it comes to comfortable living conditions. Fortunately, a lab at the University of Puerto Rico keeps a live count at the Habitable Exoplanets Catalog.

Of the known potentially habitable planets, what size is most common?

Thirty-one of the planets discovered are actually larger than Earth (but no larger than Neptune). Only eighteen are Earth-sized, and none are significantly smaller than Earth.

What is the estimated cost of the Kepler mission?

Launching the Kepler and analyzing the incoming data doesn't come cheap, as they say. The mission, to find potentially habitable exoplanets, cost about six hundred million dollars.

Why is planet Upsilon Andromedae b uninhabitable?

One half of Upsilon Andromeda b is a frozen wasteland, and the other half is a blazing inferno. One researcher described trying to travel from one side to the other as "equivalent to leaping into a volcano."

How can researchers determine if a planet is largely inhabited?

A planet with vegetation and extensive life shows different patterns of light absorption on the surface than uninhabited planets. In addition, the chemistry of the atmosphere is affected by gasses like carbon dioxide.

What was exciting about the discovery of Kepler-452b?

Kepler-452b was announced in July 2015 as the planet most similar to Earth that had yet been found. Its orbit produces a 385-day year, only twenty days longer than our own.

How does Kepler-452b compare in size with Earth?

Kepler-452b is 60% larger than Earth, meaning the gravitational force would take some adjustment for anyone trying to settle on the planet. The amount of sunshine, on the other hand, would be about the same.

How many years of data were needed to confirm information about Kepler-452b?

Putting together information about the planet and confirming everything took four years' worth of observation. Since the planet only crosses in front of the star once every year, getting data from the transit method takes a while.

How close is the nearest potentially habitable planet?

In terms of space travel, 4.25 light-years is surprisingly close! The honor of "closest potentially habitable planet" belongs to Proxima Centauri b.

What is the climate probably like on Proxima Centauri b?

While it mostly fits the criteria for being habitable, Proxima Centauri b is unlikely to have life, due to the deadly radiation it was exposed to from its sun, a red dwarf.

What would prevent us from living on 55 Cancri e, a planet estimated to be about 1/3 diamond?

While the thought of harvesting diamonds from this planet would make any entrepreneur giddy with glee, the living conditions would not be feasible. The high surface temperature and super short years (equivalent to only eighteen Earth hours) are just a few problems we'd need to overcome.

When was the first potentially habitable Earth-sized planet discovered?

The discovery of Kepler-186f was announced in 2014, to the great excitement of the scientific community. The planet is only about 10% larger than Earth, making it one of the closest to Earth's size.

What happens when a planet is significantly larger than Earth?

Scientists have found that most planets larger than 1.5x Earth's size tend to be more gaseous. The thicker atmosphere makes it more difficult for life to survive.

What does it mean if a planet is "tidally locked"?

The TRAPPIST-1 planets, for example, are tidally locked. This happens when the orbital period equals the rotational period. Our moon is also tidally locked, to Earth.

When does NASA plan to launch the James Webb Space Telescope, to further the search for habitable planets?

The James Webb Space Telescope is set to launch in 2018. It will provide additional insight into the nature of discovered exoplanets, along with adding to the list of discoveries. It may be able to gather key atmospheric data about potentially habitable planets.

Explore More Quizzes

Image: shutterstock

About This Quiz

Is there a home for humans beyond Earth? Learn about new worlds beyond our solar system that could support life as we know it when you take this quiz!

About HowStuffWorks Play

How much do you know about dinosaurs? What is an octane rating? And how do you use a proper noun? Lucky for you, HowStuffWorks Play is here to help. Our award-winning website offers reliable, easy-to-understand explanations about how the world works. From fun quizzes that bring joy to your day, to compelling photography and fascinating lists, HowStuffWorks Play offers something for everyone. Sometimes we explain how stuff works, other times, we ask you, but we’re always exploring in the name of fun! Because learning is fun, so stick with us!