Chart assignment
Charts to read and discuss
Read each chart, then answer its questions. Every chart shows its source and date; open it for a table of the numbers and the data to download.
Chart 1 of 3 · Space
How many planets outside our solar system are discovered each year?
The interactive chart needs JavaScript. The numbers are on the chart's page.
Astronomers confirmed 246 new planets around other stars in 2025. The first were found in 1992, and the count leaped in 2014 and 2016 (872 and 1,504), when NASA's Kepler team confirmed hundreds of its candidates at once. The archive counts a planet in the year its discovery was published and keeps adding late confirmations, so recent years can still rise.
Questions to discuss
- In one sentence of your own, what does this chart show?
- Find the biggest change or difference in the chart. What might explain it?
- Who collected these numbers, and how recent are they? What else would you want to know before drawing a conclusion?
Source: NASA Exoplanet Archive, Planetary Systems Composite Data (Public domain (NASA data); this research has made use of the NASA Exoplanet Archive, operated by Caltech under contract with NASA) · Data as of Dec 31, 2025
Open the chart and its numbersChart 2 of 3 · Climate
How much has the US warmed since 1895?
The interactive chart needs JavaScript. The numbers are on the chart's page.
The contiguous US averaged 54.6°F in 2025. The warmest year since records began in 1895 was 2024, at 55.5°F. Through 2025, the dashed trend line, the straight line that best fits every year, rose about 0.18°F a decade, or 2.3°F since 1895, and warming had sped up to about 0.5°F a decade since 1970. Alaska and Hawaii aren't included.
How to read this chart
Each point is one year's average temperature across the lower 48 states, in degrees Fahrenheit. The axis doesn't start at zero, so a small rise looks steep: read the numbers on the axis, not the height of the line. The dashed line is the trend, the straight line that best fits every year; single years bounce above and below it.
Questions to discuss
- Find the warmest and coolest years on the chart. How many degrees apart are they?
- Why might one year be much cooler than the year before, even while the trend line keeps rising?
- The axis doesn't start at zero here, but bar charts always do. Why is that fair for temperatures but not for bars?
Source: NOAA National Centers for Environmental Information, Climate at a Glance (Public domain (U.S. government work)) · Data as of Dec 31, 2025
Open the chart and its numbersChart 3 of 3 · Crime
Is violent crime in the U.S. going up or down?
The interactive chart needs JavaScript. The numbers are on the chart's page.
Down, over the long run. Police reported about 329 violent crimes per 100,000 people in 2025, about 59% below the 1991 peak of about 798, and the lowest since at least 1985. The rate rose in 2020 and 2022, then fell in 2023, 2024 and 2025. In 2021 the FBI stopped taking its old summary reports and accepted only its newer, more detailed system (NIBRS); many police departments hadn't switched yet, so agencies covering only about 77% of Americans reported, against 88 to 98% in other years, and 2021's number is less certain. Rates count only the agencies that reported, so they differ a little from the FBI's national estimates, and the FBI widened its definition of rape in 2013.
How to read this chart
Each point is the number of violent crimes police reported for every 100,000 Americans that year. The line starts at zero, so its height shows the true size. In 2021 the FBI changed how it collects reports and fewer police departments sent numbers, so that year is less certain than the others.
Questions to discuss
- Find the year with the highest rate. About how much lower is the rate in the latest year?
- Many people say they think crime is rising. How could that belief and this chart both seem true to different people?
- Why might a change in how crimes are counted, like the one in 2021, make one year hard to compare with the rest?
Source: FBI Crime Data Explorer, Uniform Crime Reporting Program (Public domain (U.S. government work); source FBI Uniform Crime Reporting Program) · Data as of Dec 31, 2025
Open the chart and its numbersTeachers: make your own chart assignment, or change this one. Free, no account needed.