Astr111 Photography Projects, Spring 2007

Spiral Galaxy (M95), Jordan Vanderpol

This is a picture of the spiral galaxy Messier Object 95, or M95. It was first discovered by the French Astronomer Pierre Mechain on march 20, 1781. This galaxy, along with M96 and M105, is located in the Leo I group. A spiral galaxy is a group of millions or billions of stars that have a central, dense area with spiraling arms. The arms of these galaxies are typically where new stars are formed and the middle area or bulge is where the older, brighter stars in the galaxy are located. This particular galaxy was a key project of the Hubble Space Telescope in helping to determine Hubble's constant. The universe is expanding and galaxies are moving away from the earth in all directions. Using the Hubble telescope, scientists pointed it at individual stars within M95 and measured their Cepheid variables to discover these stars' absolute luminosity. With this measurement (E) and also by measuring the flux (F), astronomers could determine the distance with the equation F = E / 4π(d^2), where 'd' is the distance of the galaxy. By knowing the distance and velocity of its movement (derived from the Doppler-shift equation), V = dH could be rearranged to V/d = H, making the discovery of Hubble's constant possible, proving that the universe is expanding.

Spiral galaxies can be either a "normal spiral" or a less common "barred spiral," meaning that the center of a barred spiral galaxy has an elongated center, resembling the shape of a bar running through the middle. In this picture, the 'bar' can be easily recognized when looking at the elongated center of the photo. M95 is 38 million light-years from the earth, with the linear size being approximately 55,600 light-years

References:
Frommert, Hartmut and Kronberg, Christine. "NGC 3351." http://www.seds.org/messier/m/m095.html

Zoom Astronomy Glossary. http://www.enchantedlearning.com/subjects/astronomy/stars/galaxy/spiral.shtml

TheSky Software

Professor Molnar

Additional links:

http://www.seds.org/messier/Mdes/dm095.html

http://www.noao.edu/outreach/aop/observers/m95.html