Tour of the Universe!

Transcription

1 Tour of the Universe!

2 Andromeda: M31 (NGC 224, the famous Andromeda Galaxy) is the nearest large galaxy to our own Milky Way galaxy. It is so bright that it is easily seen by naked eye as a faint fuzzy patch of light in the northern part of Andromeda. It forms part of the Local Group of galaxies along with our Milky Way, its satellite galaxies, and M33. Of all members of the Local Group M31 is considered to have the closest external resemblance to the Milky Way, thus it is often referred to as a 'sibling galaxy'. Also seen in this photograph are M31's satellite galaxies M110 (below) and M32 (above) - in this respect it is also similar to the Milky Way, with M110 corresponding to the Large Magellanic Cloud and M32 corresponding to the Small Magellanic Cloud. M31 is an 'island universe' - a gigantic collection of billions of stars estimated to be 2.54 million light years distant. It has been observed since ancient times and was first catalogued as long ago as 905 AD. The common name of M31 derives from Charles Messier's entry # 31 in his famous Messier catalogue in August 1764.

3 Centaurus A: Centaurus A, also known as NGC 5128, is a prominent galaxy in the constellation of Centaurus. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its type (spiral galaxy or a giant elliptical galaxy and distance (10-16 million light-years). NGC 5128 is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the fifth brightest in the sky, making it an ideal amateur astronomy target, although the galaxy is only visible from low northern latitudes and the southern hemisphere.

4 NGC-1427A: THE IMPENDING DESTRUCTION OF NGC 1427A What happens when a galaxy falls in with the wrong crowd? The irregular galaxy NGC 1427A is a spectacular example of the resulting stellar rumble. Under the gravitational grasp of a large gang of galaxies, called the Fornax cluster, the small bluish galaxy is plunging headlong into the group at 600 km/sec or nearly 400 mi/sec. NGC 1427A, which is located some 62 million light-years away from Earth in the direction of the constellation Fornax, shows numerous hot, blue stars in this newly released image obtained by the Hubble Space Telescope. These blue stars have been formed very recently, showing that star formation is occurring extensively throughout the galaxy. As the galaxy rams into the center of the Fornax cluster located off the image to the upper left the galaxy becomes distorted, forming an arrowhead in the direction of its high-velocity motion. Galaxy clusters, like the Fornax cluster, contain hundreds or even thousands of individual galaxies. Within the Fornax cluster, there is a considerable amount of gas lying between the galaxies. When the gas within NGC 1427A collides with the Fornax gas, it is compressed to the point that it starts to collapse under its own gravity. This leads to formation of the myriad of new stars seen across NGC 1427A. The tidal forces of nearby galaxies in the cluster may also play a role in triggering star formation on such a massive scale. NGC 1427A will not survive long as an identifiable galaxy passing through the cluster. Within the next billion years, it will be completely disrupted, spilling its stars and remaining gas into intergalactic space within the Fornax cluster.

5 M-87: The heart of the galaxy known as M87 is a place of unimaginable violence. A black hole up to seven billion times as massive as the Sun sits at the galaxy's center -- one of the most massive black holes ever measured. As gas spirals into the black hole, it's heated to millions of degrees, so it produces enormous amounts of X-rays. Some of the hot gas around the black hole shoots back into the galaxy in powerful jets that span thousands of light-years. M87 is at the center of the Virgo Cluster, a collection of thousands of galaxies that move through space together. It is a giant elliptical galaxy, so it's shaped like a fat, fuzzy watermelon. M87's diameter is only a little bigger than the Milky Way's, but because the galaxy is thicker than the thin disk of the Milky Way, it encompasses a much larger volume. As a result, M87 contains many more stars and is perhaps 10 times as massive as the Milky Way.

6 Sombrero Galaxy: Some of the defining features of the Sombrero Galaxy are its bright nucleus, large central bulge, and a prominent dust lane in its disk. The galaxy is seen nearly edge on, and so it has the appearance of a Sombrero hat. Since the galaxy has an apparent magnitude of +9.0, it s easily visible in amateur telescopes; but too dim to see with the unaided eye. The dark dust lane that you can see in the Hubble image is a symmetric ring that encloses the bulge of the galaxy. Astronomers have detected that it mostly contains hydrogen gas and dust. The bulk of star formation that occurs in the Sombrero Galaxy is happening within this ring.

7 Whirlpool Galaxy: The Whirlpool Galaxy is also known as Messier 51a, and it s one of the most familiar galaxies. If you ve seen a picture of a galaxy captured by the Hubble Space Telescope, chances are you were looking at the Whirlpool Galaxy. That s because this galaxy, located about 23 million light-years away in the constellation Canes Venatici, is aligned almost perfect face on. We have beautiful view of the Whirlpool Galaxy s entire structure, from its spiral arms to its dense galactic core. The Whirlpool Galaxy is fascinating for another reason as well. It has a companion galaxy to one side called NGC The two galaxies interact through gravity, and this gives astronomers a chance to study what happens when galaxies collide. Astronomers have calculated that the Whirlpool Galaxy measures about 38,000 light-years across, with a mass of about 160 million times the mass of the Sun. This makes the galaxy smaller and less massive than our own Milky Way. You can see the Whirlpool galaxy with a good pair of binoculars, or a small backyard telescope; although, you ll want a bigger telescope to see the spiral structure and detect the companion galaxy NGC To find the Whirlpool Galaxy, located the easternmost star in the Big Dipper. Then go about 3.5 degrees to the southeast. On a dark night you should be able to see a fuzzy spot where the galaxy is. Astronomers think that NGC 5195 first passed through the main disk of the Whirlpool Galaxy about 500 to 600 million years ago, and then made another disk crossing about 50 to 100 million years ago.