Galaxies contain how many stars

While Hubble is unable to see the very first galaxies, it can track the development of galaxies over much of cosmic time. The series of Hubble Deep Field images and other deep surveys have uncovered galaxies at many different distances out in the universe, and therefore at many different times in their development.

Farther galaxies, seen earlier in time, have less developed structure. Nearer galaxies, seen later in time, grow to resemble the familiar galaxy shapes we see in the local universe. The Building Blocks of the Universe. On This Page. Types of Galaxies. What Kinds of Galaxies Are There? This graphic compares illustrations of the three main types of galaxies top with actual photos of galaxies bottom that fit the categories.

Credit: A. Feild STScI. Dark Matter. What Is Dark Matter? This detailed view of our galactic next-door neighbor, the Andromeda galaxy, contains over million resolved stars and thousands of star clusterss. The panorama sweeps from the galaxy's central bulge across lanes of stars and dust to the sparser outer disk.

Dalcanton, B. Williams, and L. The Bullet Cluster was formed after the collision of two large clusters of galaxies. Hot gas detected by Chandra in X-rays is seen as two pink clumps in the image and contains most of the "normal," or baryonic, matter in the two clusters.

The bullet-shaped clump on the right is the hot gas from one cluster, which passed through the hot gas from the other larger cluster during the collision. An optical image from the Hubble and Magellan telescopes shows the galaxies in orange and white. The blue areas in this image depict where astronomers find most of the mass in the clusters. Most of the matter in the clusters blue is clearly separate from the normal matter pink , giving direct evidence that nearly all of the matter in the clusters is dark.

Markevitch et al. Clowe et al. Galaxy Collisions. Can Galaxies Collide? This celestial firestorm is the blazing wreckage of a collision between two spiral galaxies that began a few hundred million years ago. The smashup has pulled dark dust into long strands stretching across the galaxies. It has also compressed huge clouds of gas and dust, igniting a rash of new star formation within the galaxies. This illustration depicts the night sky in 3. At this point, Andromeda fills the field of view and the Milky Way begins to show distortion due to the pull of Andromeda.

Levay and R. Hallas, and A. With this simple calculation you get something like 10 22 to 10 24 stars in the Universe. This is only a rough number, as obviously not all galaxies are the same, just like on a beach the depth of sand will not be the same in different places.

No one would try to count stars individually, instead we measure integrated quantities like the number and luminosity of galaxies.

ESA's infrared space observatory Herschel has made an important contribution by 'counting' galaxies in the infrared, and measuring their luminosity in this range — something never before attempted. Knowing how fast stars form can bring more certainty to calculations. Herschel has also charted the formation rate of stars throughout cosmic history. If you can estimate the rate at which stars have formed, you will be able to estimate how many stars there are in the Universe today.

In , an image from the Hubble Space Telescope HST suggested that star formation had reached a peak at roughly seven thousand million years ago. Recently, however, astronomers have thought again. The Hubble Deep Field image was taken at optical wavelengths and there is now some evidence that a lot of early star formation was hidden by thick dust clouds. Dust clouds block the stars from view and convert their light into infrared radiation, making them invisible to the HST. Kornreich cautioned this would be very hard to speak about generally, but said that one difference could be looking at elliptical galaxies vs.

Elliptical galaxies tend to have more K- and M-type red dwarf stars than spiral galaxies. Because elliptical galaxies are older, they will have less gas because that was blown away during their evolution. Once a galaxy's mass is determined, the other tricky thing is figuring out how much of that mass is made of stars.

Most of the mass will be made up of dark matter , a type of matter that emits no light but which is believed to make up most of the mass of the universe. With much of the remaining "stuff" in the galaxy made up of diffuse gas and dust, Kornreich estimated that about 3 percent of the galaxy's mass will be made up of stars, but that could vary.

Further, the size of the stars itself can greatly vary from something that is the size of our sun, to something dozens of times smaller or bigger. The number of stars is approximately ….

So is there any way to figure out how many stars are for sure? In the end, it comes down to an estimate. In one calculation, the Milky Way has a mass of about billion solar masses, so it is easiest to translate that to billion stars.

This accounts for the stars that would be bigger or smaller than our sun, and averages them out. However, the mass is tough to calculate — other estimates have said the galaxy has a mass of between billion and billion solar masses. ESA says Gaia will map 1 percent of the stellar content in the Milky Way , which puts the estimate of the total stars in our galaxy at billion. Gaia's goal is to make the best-ever three-dimensional map of the Milky Way. The caveat, Kornreich said, is that these numbers are approximations.

More advanced models can make the approximation more accurate, but it would be very difficult to count the stars one by one and tell you for sure how many are in the galaxy.

If you want to try and capture the Milky Way yourself, we have guides to the best cameras for astrophotography and the best lenses for astrophotography , to help you see as much of the system as possible. Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community space.

Elizabeth Howell is a contributing writer for Space. She is the author or co-author of several books on space exploration.