When the Hubble Space Telescope photographed the globular star cluster NGC 6752 (located 13,000 light-years away in our Milky Way’s halo), the image revealed a never-before-seen dwarf galaxy cataloged as Bedin 1 located far behind the cluster’s crowded stellar population. The galaxy is only 30 million light-years away but had not been noticed before. It’s classified as a dwarf spheroidal galaxy because it measures only around 3,000 light-years at its greatest extent. Because it’s so small, it’s roughly a thousand times dimmer than the Milky Way.
Because it’s very old, 13 billion years, and relatively isolated, it’s seen hardly any interaction with other galaxies It’s the astronomical equivalent of a living fossil from the early universe.
This composite image above shows the location of Bedin 1 behind the globular cluster NGC 6752. The lower image of the complete cluster is a ground-based observation from the Digitized Sky Survey 2. The upper right image shows the full field of view of the Hubble Space Telescope. The upper left image highlights the region containing the galaxy Bedin 1.
Image Credits: NASA / ESA / DSS / STScI
The North America Nebula (aka NGC 7000) is an emission nebula in the constellation Cygnus, close to Deneb, the bright star at the tail of the Swan. The nebula appears large (about 4X the area of the Moon) but very dim in the sky. It can’t be seen with the naked eye but is visible with good binoculars with a dark sky.
These four images show how the appearance of the North America nebula can change dramatically using different combinations of visible and infrared observations from the Digitized Sky Survey and the Spitzer Space Telescope. The visible-light view (upper left) shows an obvious similarity to the North America continent. The image highlights the east coast and and Gulf of Mexico. (The pink region in the right of the frame is the Pelican nebula.) The view at upper right includes both visible and infrared observations. In the bottom two images, only infrared light seen by Spitzer is shown—data from the infrared array camera is on the left and data from both the infrared array camera and the multi-band imaging photometer, which sees longer wavelengths, is on the right. These pictures show detail not seen in visible light because infrared light can penetrate dust which visible light cannot. Dusty, dark clouds in the visible image become transparent in infrared.
Image Credit: NASA
Video Credit: ESA / Digitized Sky Survey / Nick Risinger (skysurvey.org)
Here are the views seen by four different observatories looking in toward the galactic core. At the very center, a cluster with a half-million-or-so stars surrounds the Milky Way’s central supermassive black hole, which is about 4 million times the mass of our sun. The galaxy’s nucleus (marked) is home to the central, supermassive black hole called Sagittarius A*.
Image Credits: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Acknowledgment: T. Do, A.Ghez (UCLA),V. Bajaj (STScI)