Astronomers used a computer and data about the star AB Doradus to make this picture. This is what the star might look like. Can you see some starspots on AB Doradus?
Click on image for full size
Image courtesy A. Cameron, M. Jardine and K. Wood, University of St Andrews.
You may have heard of sunspots that sometimes dot the "surface" of
the nearest star, our Sun. Well, other stars have spots too. They are called starspots and are relatively
cool, dark regions on the visible "surfaces" of some stars.
formation is apparently a result of the tangling of the Sun's
magnetic fields due to the Sun's rotation.
The powerful magnetic
fields on other stars are also thought to generate starspots.
The Sun is roughly 5 billion years old and rotates once every 25 days. Most
of the stars upon which starspots have been "observed" are young and rotate rapidly. The star AB
Doradus has rotational period of just 12.4 hours (it spins nearly 50 time faster
than the Sun!) and is only 30 million years old. Another spotted star, EK Draconis,
turns once every 2.7 days and is 100 million years old.
Astronomers have even observed starspots on binary star systems (double stars). This is especially the case for
binaries which orbit very close to each other, and may result from interactions
between the two stars. The binary system VW Cephei is a remarkable case; spots
cover some 66% of the surface area of one partner and 55% of the other, and
both stars appear to have large spots at their poles.
One active red
giant star, HD 12545, has a HUGE starspot. The single spot covers
11% of the entire surface area of the giant star, which has a radius 11.4 times
the size of our Sun. This gigantic elliptical spot covers an area 10,000 times bigger than the largest
sunspots observed on the Sun.
Stars are so far away that their images, even in the largest telescopes, are
much too small for us to directly view starspots. Astronomers have to "observe" starspots indirectly? Please use the button bar at the top of the page to read more about these techniques at the Advanced level of text.
Just as the number and locations of sunspots vary over the course of the sunspot
cycle, some astronomers are beginning to study similar variations in
starspot counts and locations on certain stars.
Shop Windows to the Universe Science Store!
The Summer 2010 issue of The Earth Scientist
, available in our online store
, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.
You might also be interested in:
Sunspots are dark, planet-sized regions that appear on the "surface" of the Sun. Sunspots are "dark" because they are colder than the areas around them. A large sunspot might have a temperature of about...more
Most of the energy we receive from the Sun is the visible (white) light emitted from the photosphere. The photosphere is one of the coolest regions of the Sun (6000 K), so only a small fraction (0.1%)...more
The Sun has a very large and very complex magnetic field. The magnetic field at an average place on the Sun is around 1 Gauss, about twice as strong as the average field on the surface of Earth (around...more
The force of magnetism causes material to point along the direction the magnetic force points. As shown in the diagram to the left, the force of magnetism is illustrated by lines, which represent the force....more
You may have heard of sunspots that sometimes dot the "surface" of the nearest star, our Sun. Well, other stars have spots too. They are called starspots and are relatively cool, dark regions on the visible...more
Astronomers use a special term to talk about the brightness of stars. The term is "magnitude". The magnitude scale was invented by the ancient Greeks around 150 B.C. The Greeks put the stars they could...more
Because of the rotation of the Earth and its orbit around the Sun, we divide the stars and constellations into two groups. Some stars and constellations never rise nor set, and they are called circumpolar....more