Peculiar Galaxies of Arp 273
This week’s photo, from NASA, we see two galaxies experiencing a close encounter:
The spiky stars in the foreground of this sharp cosmic portrait are well within our own Milky Way Galaxy. The two eye-catching galaxies lie far beyond the Milky Way, at a distance of over 300 million light-years. Their distorted appearance is due to gravitational tides as the pair engage in close encounters. Cataloged as Arp 273 (also as UGC 1810), the galaxies do look peculiar, but interacting galaxies are now understood to be common in the universe. In fact, the nearby large spiral Andromeda Galaxy is known to be some 2 million light-years away and approaching the Milky Way. Arp 273 may offer an analog of their far future encounter. Repeated galaxy encounters on a cosmic timescale can ultimately result in a merger into a single galaxy of stars. From our perspective, the bright cores of the Arp 273 galaxies are separated by only a little over 100,000 light-years. The release of this stunning vista celebrates the 21st anniversary of the Hubble Space Telescope in orbit.
With all the talk of gravitational waves and black holes recently, I thought this was an interesting specimen. See the original here.
Ah, everyone’s favorite planet! Fresh from the Cassini mission, this picture shows the sheer immensity of the sixth planet orbiting Sol. To give you an idea of how big it is, look in the lower right-hand corner and you will notice one of its moons, Tethys. To give you some reference point, our own moon is only about 3 times as large as Tethys. You could fit 763 Earths inside Saturn itself.
From JPL/NASA: This view looks toward the sunlit side of the rings from about 8 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on March 7, 2015 using a spectral filter that preferentially admits wavelengths of near-infrared light centered at 752 nanometers.
Tethys has been brightened by a factor of 2 to increase its visibility.
The view was acquired at a distance of approximately 1.6 million miles (2.6 million kilometers) from Saturn. Image scale is 10 miles (16 kilometers) per pixel. Tethys is slightly closer at 1.5 million miles (2.4 million kilometers) away, for an image scale of 9 miles (14 kilometers) per pixel.
(If you were a subscriber to The Road Goes Ever On, from walkingamdg.wordpress.com, things may look a bit different. Don’t worry, I’m simply redesigning the site a bit, including adding a new custom address: BelievingAstronomer.com, with a focus on faith, science, literature, reflections, with news and reviews thrown in from time to time. A longer post will be added this weekend, as I am currently on retreat and this post is simply a pre-scheduled item that I set up at the end of December. Feel free to tell me what you think!)
From time to time, I will post interesting pictures from astronomy and cosmology, although expect a few surprises too… I’m talking science fiction, faith, or other branches of human knowledge that relate to this enterprise. This week, however, we look at the solar system. In fact, we look at how mind-bogglingly huge our solar system is through NASA’s own APOD, which, incidentally, has brought us a video rather than a picture. Enjoy!
From NASA: Want to build a scale model Solar System? A blue marble 1.4 centimeters (about half an inch) across would be a good choice for a scale model Earth. Since the Sun is 109 times the diameter of Earth, a 1.5 meter diameter balloon could represent the Sun. But the distance between the Earth and Sun, 150 million kilometers, would translate to just under 180 meters (590 feet) at the same scale. That would mean the completed project, including the orbits of the outer planets, is probably not going to fit in your backyard. Still, you might find enough room on a dry lakebed. Check out this video for an inspirational road trip through the Solar System to scale.