When worlds collide

This exercise is a part of Educator Guide: Analyzing Images and an Exoplanet Collision Afterglow / View Guide
Illustration showing a donut-shaped cloud of vaporized rock and water in orange and red hues with a large rocky piece of debris in the foreground and a star in the background
The collision of two exoplanets may have left behind a donut-shaped cloud of vaporized rock and water (illustrated), which cast an infrared glow visible to telescopes.Mark Garlick

Directions for teachers:

To engage students before reading the article, have them view the video “Watch an animation of what happens when exoplanets collide | Science News.” Then have students answer the “Before Reading” questions as a full class warmup in class or for homework.

Now ask students to read the online Science News article “In a first, astronomers spot the afterglow of an exoplanet collision” Afterward, have them answer the “During Reading” questions. As an optional extension for deeper assessment on scientific claims made from exoplanet data, have students discuss the “After Reading” questions or even complete this expansion activity about the hunt for exoplanets. This article also appears in the November 18 issue of Science News. Science News Explores offers another version of the same article written at a middle school reading level.

Directions for students:

Watch this video and answer the “Before Reading” questions either as a class or individually. Then read the online Science News article “In a first, astronomers spot the afterglow of an exoplanet collision” and answer the following questions as directed by your teacher.

Before Reading

1. Watch this video and explain what happens in the animation. (Ignore the graphs on the righthand side for now.)

The animation shows two planets colliding, producing a burst of white light. The planets appear to turn into one, larger purple blob that elongates into an eclipse during its orbit.

2. The two graphs on the righthand side of the video show how two kinds of light — infrared and visible light — would appear to us from Earth. Watch the video again and focus on the change in visible light. Notice that it remains consistent until a certain point. What causes the dip in visible light?

Visible light dips when the collided planets block the star’s light from Earth.

3. Now watch the video yet again, this time focusing on the infrared light graph. What event causes the spike in infrared light?

Infrared light spikes when the planetary collision occurs.

4. At the point when visible light dips, what’s happening with the infrared light?

At the point when visible light dips, the infrared light drops only slightly.

5. Imagine you are on a distant exoplanet looking at our sun through a high-powered telescope. To you it looks like a bright star. Your telescope can detect very faint dips in the sun’s brightness. You notice these dips occur regularly, almost as though something around the star occasionally blocks the light. What is a possible explanation for these dips in brightness? If you measured the frequency and duration of these dips, what might you infer from that data?

Answers will vary. You may infer the existence of an exoplanet that passes before the star, blocking some light. From measuring the frequency and duration of those dips, one might conclude details about the orbit of that exoplanet, such as its orbital period.

During Reading

1. How many light-years away from Earth did the collision of exoplanets occur that’s described in this article?

The collision occurred approximately 1,800 light-years from Earth.

2. Scientists have discovered evidence of exoplanet collisions before. What about this particular observation makes it unique?

This observation is unique because it’s the first-time scientists have seen smoldering remains of exoplanetary collisions.

3. What was Matthew Kenworthy searching for when he made his surprising discovery? What type of data would have indicated the presence of such objects?

Matthew Kenworthy was searching for rings around exoplanets. Stars with unusual flickering might indicate the presence of a planet with rings that periodically block the star’s light.

4. What first caught Kenworthy’s eye about the star ASASSN-21qj? Upon further inspection, Kenworthy noticed the something unusual about the visible and infrared light from the star. Describe what he observed.

Kenworthy noticed the light of ASASSN-21qj dimming repeatedly. Upon further inspection, he noticed the star fading in visible light but increasing in infrared.

5. What did scientists learn in studying the data from NASA’s WISE telescope?

Scientists realized the strong uptick in infrared light started about 900 days before the visible light began to dim.

6. What “single event” might explain the periodic blocking of ASASSN-21qj’s visible light?

Debris from the collision of two large planets could have spread out while in orbit around the star, occasionally blocking visible light that reaches Earth.

7. What is a second potential explanation for the data that involves two separate events?

Another possible explanation is that two small, rocky planets collided. Then, the leftover dust warmed up over time, and began to glow with infrared light.

After Reading

1. In this article, Philip Carter says, “As far as I’m aware, no one’s claimed this before.” To what claim is Carter referring? Describe the evidence the scientists used to support their claim.

Philip Carter refers to claims that scientists have found smoldering remains of a collision between two exoplanets. Scientists used the infrared and visible light data from telescopes to support their claim.

2. In this study, two potential explanations could both explain the data. Kenworthy describes one of these as being “really, really, really unlikely.” What was it about that explanation that made Kenworthy find it so unlikely? To what extent do you agree or disagree with his conclusion? Explain your answer.

The explanation that called for two separate events was considered improbable by Kenworthy because it depended on two unlikely events occurring at close to the same time. Answers will vary regarding whether the student agrees or disagrees with the conclusion.

3. Consider the explanation that scientists in this article consider most probable. What might scientists do to increase their confidence in this explanation? What additional data might they need or seek?

Scientists consider the “single event” explanation most probable. They can increase confidence in this explanation by continuing to watch the area and gather evidence that might hint at the formation of new planets from the rubble.