Sun
12 questions tagged Sun — spanning every one of the seven Ws.
How many Earths could fit inside the Sun?
About 1.3 million Earths could fit inside the Sun by volume.
What is the heliosphere?
The heliosphere is the vast bubble of charged particles and magnetic field blown out by the Sun, surrounding the entire Solar System.
What is a geomagnetic storm?
A geomagnetic storm is a major disturbance of Earth's magnetic field caused by bursts of charged particles from the Sun.
Why does the Sun look larger than other stars even though it is just a star?
The Sun appears bigger because it is far closer to Earth than any other star. Its actual diameter is similar to other stars, but distance changes how large it looks in the sky.
What is a coronal mass ejection?
A coronal mass ejection, or CME, is a huge cloud of charged particles thrown out from the Sun. If aimed at Earth, it can trigger geomagnetic storms and auroras.
When did the first spacecraft reach the Sun’s vicinity and begin solar orbit studies?
Parker Solar Probe launched in 2018 and began its series of close solar encounters soon after, becoming the closest-ever mission to the Sun.
Whose mission first detected the solar wind close to the Sun?
NASA’s Parker Solar Probe, launched in 2018, made the first close in-situ measurements of the solar wind near the Sun. It has flown closer to the Sun than any previous spacecraft.
How long does sunlight take to reach Earth?
Sunlight takes about 8 minutes and 20 seconds to reach Earth, travelling roughly 150 million kilometres at the speed of light.
What is solar wind?
Solar wind is a stream of charged particles constantly flowing outward from the Sun’s outer atmosphere.
Why is the Sun’s corona visible only during a total solar eclipse?
The corona is millions of times fainter than the Sun’s surface, so the bright photosphere normally overwhelms it.
Why is the Sun's outer atmosphere hotter than its surface?
The corona is heated by magnetic processes, not by direct sunlight, and can reach temperatures of over 1 million degrees Celsius.
Why is the Sun considered to be in the middle of the Solar System?
The Sun contains about 99.8% of the Solar System's total mass, so its gravity dominates the motion of everything else. That makes it the natural centre of the system.