Sunspots are dark because they are much cooler than the surrounding portions of the sun, according to Cool Cosmos, a joint project by the National Aeronautic and Space Administration’s Jet Propulsion Laboratory and California Institute of Technology’s Infrared Processing and Analyses Center. These sunspots usually have temperatures of approximately 6,300 degrees Fahrenheit, while the surrounding portions of the sun are approximately 10,000 degrees Fahrenheit.Know More
As explained on SpaceWeather.com, scientists count and catalog these planet-sized cool spots. According to the Marshall Space Flight Center, the abundance of sunspots varies in time. During the late 17th century and early 18th century, sunspot activity was very low. Concurrently, with this reduction in solar spot frequency, the Earth’s temperature dropped significantly. This period is often referred to as the “little ice age,” as many rivers and snowfields remained frozen longer than normal. There is some evidence that similar cool periods occurred in the more distant past as well.
According to Windows to the Universe from the National Earth Science Teachers Association, the sun’s magnetic field causes the sunspots. Once formed, the sunspots may last as briefly as a few hours or as long as a few months. Sunspots typically fluctuate through an 11-year cycle. Even though sunspots appear dark against the surface of the sun, the areas are still almost as bright as the full moon, and if moved away from the sun, they would be luminous.Learn more about Stellar Astronomy
The largest identified star in the known universe is VY Canis Majoris, a hypergiant of the constellation Canis Major, calculated to be more than 1,540 times larger than the sun. YV Canis Majoris is situated 5,000 light years away from earth and is probably far from the largest star in the galaxy.Full Answer >
Most stars cannot be seen during daylight hours because light from the sun is brighter than the relatively faint light from the other stars. This is largely a result of the Earth's atmosphere scattering the sun's light so that every point in the sky seems brighter than distant stars.Full Answer >
Betelgeuse is 4,000 degrees Fahrenheit cooler than the sun, measuring an effective temperature of 6,000 degrees Fahrenheit compared to the sun's 10,000 degrees Fahrenheit. Despite its lower temperature, Betelgeuse's diameter of 600 million miles is around 700 times the diameter of the sun.Full Answer >
Stars vary in size from less than 8 percent of the size of the sun to those with diameters of more than 1,800 times that of the sun. In terms of mass, stars must have enough mass to support the nuclear chain reaction that takes place in the core of a star, which is about 10 percent of the sun’s mass. There is also a limit to how massive starts can grow, and scientists suspect that the limit is about 150 times the mass of the sun.Full Answer >