A big tool flies in space.
It looks for new worlds. It looks at many stars. This helps us find planets like Earth. It was a great helper.
Do you like the stars?
A special tool flies in space.
It looks for new worlds. It looks at many stars. When a planet moves in front of a star, the star gets a little dim. This tells us a planet is there. The tool found thousands of these planets.
It worked for nine years. Then, it ran out of fuel. Now, the tool is retired.
It helped us learn so much about space.
NASA launched the Kepler space telescope in 2009. Its big job was to find planets like Earth. These planets orbit other stars. We call these distant worlds exoplanets.
Kepler used a tool called a photometer. A photometer measures how bright a light is. The telescope watched about 150,000 stars. It looked for a tiny dip in starlight. This dip happens when an exoplanet crosses in front of a star.
Finding these worlds was not always easy. Two of its four reaction wheels failed. Reaction wheels are parts that help the ship point. Because of this, NASA started a new plan called K2. This plan let Kepler find planets around smaller stars.
Kepler was a great planet hunter. It found 2,778 confirmed planets. Some of these are rocky and in the habitable zone. The habitable zone is the area where life might exist.
Kepler worked for nine and a half years. In 2018, it ran out of fuel. NASA retired the telescope that same day.
The Kepler space telescope was a special tool built to find worlds like our own. NASA launched this spacecraft in 2009 to hunt for Earth-sized exoplanets. These are planets that orbit stars far away from our solar system. The mission aimed to see how many of the billions of stars in the Milky Way have such planets. It also looked for planets in habitable zones. These are areas where conditions might be just right for life.
Kepler worked by watching the brightness of many stars. It used a scientific tool called a photometer to do this. The photometer looked at about 150,000 stars in a fixed part of the sky. When a planet passes in front of its star, the star looks a little dimmer. This is called a transit. Kepler looked for this periodic dimming to find new worlds. The telescope could only see planets if they crossed their stars edge-on from our view.
Building and running the mission was a big job for many people. The project was part of NASA's Discovery Program. NASA's Jet Propulsion Laboratory managed the construction and early work. Ball Aerospace helped develop the flight system for the spacecraft. The principal investigator for the mission was William J. Borucki. In 2006, the launch was delayed because of budget and fiscal problems. During that time, engineers changed the antenna design to save money.
Kepler faced some hard times during its journey through space. It used four reaction wheels to help it point at the stars. One wheel stopped turning in July 2012. Then, a second wheel failed in May 2013. This made it very hard to collect science data. NASA responded by starting a new plan called the K2 mission. This extension allowed Kepler to find planets around smaller, dimmer red dwarfs.
By the time it finished, Kepler had found many amazing things. It observed 530,506 stars during its life. As of June 2023, it had detected 2,778 confirmed planets. Some of these, like Kepler-452b, are almost the same size as Earth. Scientists even estimated there could be 40 billion rocky planets in habitable zones in our galaxy. Kepler officially retired on October 30, 2018. It ran out of fuel after nine and a half years of service.
The Kepler space telescope was a sophisticated NASA mission designed to find Earth-sized exoplanets. An exoplanet is a planet that orbits a star outside our own solar system. Kepler aimed to discover planets within habitable zones, which are regions where conditions might allow life. It also sought to estimate how many of the billions of stars in the Milky Way possess such worlds.
The spacecraft was named after the famous astronomer Johannes Kepler. Its principal investigator was William J. Borucki. The mission was part of NASA's Discovery Program for low-cost science missions.
To find these distant worlds, Kepler used a specialized scientific instrument called a photometer. This device continually monitored the brightness of approximately 150,000 main sequence stars. The telescope looked for a process called a transit. A transit occurs when an exoplanet crosses in front of its host star from our perspective. This event causes a periodic dimming of the star's light. Kepler could only detect planets whose orbits were seen edge-on from Earth.
This method allowed scientists to detect very small changes in light.
Kepler's hardware was incredibly advanced for its time. The telescope featured a Schmidt camera with a large primary mirror. This mirror was made of ultra-low expansion glass by Corning. It was designed to be very light, weighing only 14% of a solid mirror. The camera's focal plane consisted of forty-two CCDs, which are light-sensitive sensors. Together, these sensors provided a total resolution of 94.6 megapixels.
This made it the largest camera system ever launched into space at that time. The array was cooled by heat pipes connected to an external radiator.
Managing the spacecraft required complex orbital mechanics. Kepler was placed into an Earth-trailing heliocentric orbit. This means it orbits the Sun and slowly falls behind Earth. It travels about 16 million miles further from Earth each year.
This orbit helps avoid sunlight and gravitational interference from Earth. The spacecraft was three-axis stabilized to keep it steady. It used fine-guidance sensors, reaction wheels, and hydrazine thrusters to maintain its orientation.
History shows that the mission faced several technical challenges. The initial planned lifetime was only three and a half years. However, the mission was extended because of noise in the data. In July 2012, one of the four reaction wheels used for pointing failed. A second wheel failed on May 11, 2013. This failure disabled the collection of science data and threatened the mission.
NASA responded by creating the K2 mission, or "Second Light." This allowed Kepler to use its remaining two wheels and thrusters to hunt for planets around smaller red dwarfs.
The scientific impact of Kepler was massive. By January 2015, it had confirmed 1,013 exoplanets in about 440 star systems. On January 6, 2015, NASA announced the 1,000th confirmed exoplanet discovery. Some notable finds include Kepler-438b, Kepler-442b, and Kepler-452b. These three planets are almost Earth-size and likely rocky.
Astronomers estimated there could be as many as 40 billion rocky Earth-size planets in habitable zones in the Milky Way. Specifically, about 11 billion might orbit Sun-like stars.
Throughout its service, Kepler observed a total of 530,506 stars. As of June 16, 2023, it had detected 2,778 confirmed planets. The mission also provided data to help understand supernovae. These are massive astronomical events that scientists studied using Kepler's light curves.
After nine and a half years of operation, the spacecraft ran out of fuel. NASA announced its retirement on October 30, 2018. The telescope was shut down the same day. A newer mission, TESS, was launched in 2018 to continue this important search.
Where will your curiosity go next?
🖼️ Images & Media (25)
+ 13 more
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.