NGC628, the extended object in the picture above, is a spiral galaxy. Spiral galaxies appear as flat, white discs with a yellow colored bulge at their center. They're filled with cool gas and dust, and have beautiful spiral arms extending outward. The spiral arms contain clusters of hot, short-lived stars. More hot stars populate the regions between the arms, and are also filled with a large amount of atomic gas and interstellar dust. The spiral arms are actually density waves that propagate through the disc. The density waves move through the disc, compacting the gas and material within, causing many stars to form. The radius of spiral galaxies can extend over 100,000 light years. NGC628 was discovered in 1780 by a French astronomer, Pierre Méchain. An interesting fact is it was one of 14 spiral galaxies discovered before 1850.
Many of the features of spiral galaxies can be seen in this picture of NGC628. It's yellow center is the bulge of the galaxy, and the arms make up the disc. In the picture, NGC628 has clear and distinct arms in a very nice spirals around the bulge. This is a great example, a sort of grand design galaxy, as not all spiral galaxies show such perfect spirals. The bluish color comes from the formation of young, bright stars as the density waves move through the galaxy. The red tint is a result of hydrogen in the galaxy. As the density waves move through it, the hydrogen is heated up by the compression and creation of stars. This causes the hydrogen to give off a red glow. With an estimated distance of 35,000,000 light years, we find a maximum angular size of approximately 4.8 arcminutes, which corresponds to a linear size of 2,931,937 light years. This shows that NGC628 is truly a massive galaxy. It is almost 30 times as large as the Milky Way, our own galaxy, which is estimated to be about 100,000 light years across.
Bennett, Jeffrey, Megan Donahue, Nicholas Schneider, and Mark Voit. The Essential Cosmic Perspective. 2ndnd ed. San Fransisco: Addison Wesley, 2003. Print.
|Right Ascension (J2000)||1:36|
|Filters used||B (Blue), C (Clear), R (Red), V (Green)|
|Exposure time per filter||B, V, R, and C: (60s x 5)|
|Date observed||November 18, 2011|