What are constellations?

The entire sky (half of which is above the horizon at any moment) is divided into 88 constellations. The constellations and their borders have nothing to do with science. The stars in a particular constellation are not necessarily related to one another, nor are they even near each other in space. The constellations recognized by astronomers in the northern sky come from ancient Greek and Roman mythological star-pictures. The southern constellations were named by the first Western mariners to explore southern waters. Other cultures have their own constellation patterns, which do not necessarily match "classical" ones. Constellations cover much too broad an area of space to be imaged by the Hubble Space Telescope (HST), and there really is no reason for HST to photograph constellation patterns even if it could be done.

Has Hubble found planets around other stars?

Astronomers believe that there is little chance of finding new planets in our own solar system, and the Hubble Space Telescope (HST) has not been involved in any searches. However, the search for planets around other stars is very active, and HST is involved. Not even HST has directly seen planets around other stars, but it can detect indirect evidence.

Find out more from other sources:

How is the color of a star cluster linked to its age?

Measuring a star cluster’s color yields information about its age. A newly formed cluster of stars contains stars of all colors, but it appears blue because its hot, blue stars outshine all the others. These blue stars are relatively short-lived compared to the cluster’s dimmer, redder stars. The blue stars die off over a period of a few hundred million years, but the redder stars continue to shine for billions of years. Therefore, as a star cluster ages, its color gradually shifts from blue to red. The oldest, reddest star clusters we have found are over 10 billion years old.

What are globular star clusters?

A globular star cluster is a collection of up to a million stars that all share the same origin. The globular clusters associated with our Milky Way galaxy are typically composed of old stars, greater than 10 billion years old. But Hubble pictures of other galaxies sometimes reveal globular-like clusters containing young stars that are less than 50 million years old.

What is a supernova, and what can it tell us about the universe?

A supernova is the explosive death of a star, which unleashes a burst of light through the cosmos. Supernovas happen in two different ways:

  • When massive stars run out of fresh nuclear fuel, there is no more pressure to sustain them against their own weight. The central part of such a star then collapses. The outer layers of the star fall in on the core and then rebound in a tremendous explosion.
  • Matter piling up on the compressed core of an already-dead star, known as a white dwarf, can reach sufficient density to trigger a thermonuclear explosion.

These violent deaths occur about once a century in a typical spiral galaxy like our Milky Way. Every 200-300 years we discover a supernova that happens to be bright and close enough to be visible to the unaided eye. The last supernova seen in our galaxy was discovered in 1604. When visible to the eye they appear in the sky as a "new" (Latin: "nova") star. A supernova observed in the "nearby" Large Magellanic Cloud (an irregular galaxy outside of our Milky Way galaxy) in 1987 was the first one visible to the unaided eye since 1604. The Hubble Space Telescope (HST) was not yet in orbit when the explosion was observed, but HST has made dramatic observations of the expanding gaseous remains of that star. Although supernovas are rare in our galaxy, there are many galaxies, and HST has observed stellar explosions elsewhere in the universe.

Supernovas blaze so brightly that they can be seen at distances of up to 10 billion light years. Light from these distant supernovas can tell us how the behavior of the universe has changed during the several billion years of the light’s journey to Earth.

Find out more from HubbleSite:

Can I get a star named after someone I know?

The International Astronomical Union is the only sanctioned body that has the authority to name celestial bodies. Any names that you or any commercial enterprise should care to attach to a celestial body would not be recognized, nor would they be used by the astronomical community in technical journals, etc. Naming conventions for both solar system and deep space objects are strictly adhered to.

For more information on this subject, you can go to the International Astronomical Union Web site at:

HubbleSite and STScI are not responsible for content found outside of hubblesite.org and stsci.edu

Return to question list for Stars and Star Clusters

Return to FAQ home