A Glimpse of the Andromeda Galaxy, Horsehead Nebula and Venus

Observatory / Course Archives / ASTR 110 Fall 2019 / DeVries

Andromeda Galaxy

The picture above displays the Andromeda Galaxy, the cool kids call it M31. From the Rehoboth telescope, the picture was taken. In order to create the picture, it was necessary to “mosaic together an array of overlapping fields;” 98 feilds to be exact. The image was viewed through three filters: green, red, and blue. Thanks to Jess Vriesema, Melissa Haegert, and Dan Van Noord, the picture of the Andromeda Galaxy can be enjoyed .

As a spiral galaxy, M31 has distinct features. These features include a yellow bulge, blue arms, dust lanes and an emission nebula. Why are the parts of the galaxy different colors? In the bulge, mostly old stars are found. Old stars are not as hot, thus they have a more yellow color to them. In contrast, the spiral arms are blue. The blue color of the arms demonstrate the high temperature of the young stars located within them; old stars can be found in the arms as well. Within the galaxy, about thirty other galaxies can be found. M31's core holds a double nucleus. According to the Hubble Space Telescope, one of the nuclei is brighter than the other; this brightness may be a result of cosmic cannibalism. Just like a hungry Pac-Man, the stellar concentration may have “eaten” another galaxy, thus becoming more bright.

With the naked eye, the Andromeda Galaxy can be seen. M31 is the largest galaxy within the Milky Way Galaxy. However, these galaxies may not always remain distinct. Though Hubble Space Telescope (HST) observation of M31’s motion from 2002 to 2010, NASA has concluded that in approximately 4 billion years, the Andromeda Galaxy will pass through the Milky Way Galaxy. After the galaxies have made contact, they will spend about 2 billion years trying to reunite, eventually forming a single galaxy.

Horsehead Nebula

Barnard 33 resembles the head of a horse, thus, it is cleverly referred to as “The Horsehead Nebula.” The Horsehead Nebula is located in the dense Orion B molecular cloud. 1,550 light years is the distance of the nebula. While the distance across Barnard 33 is great, the best chance to view it in the sky is in January. Speaking of visibility, Travis Rector took the picture above with a 0.9 meter telescope provided by the National Science Foundation. The picture was taken at the National Optical Astronomy Observatory in the Kitt Peak National Observatory, which is close to Tucson, Arizona.

Within the nebula, the head appears dark due its dust and gas blocking the star’s light behind it. This thick blanket of dust and gas has a pinkish color from the hydrogen gas behind the nebula. Signma Orionis then ionizes the gas from behind the nebula. At its core, the diffuse dark nebula is the perfect place for star formation. The Horsehead Nebula is also rotating. Rotation of the nebula is the result of the centrifugal force which moved the horses mane and nose further from the neck. With the fast pace of 4 million years, the neck will complete one turn.

Venus

From June 4, 1998, the picture above conveys the surface view of the planet Venus. The image is the product of NASA via a radar investigation from the Magellan Mission. Centered at 180 degrees east longitude, the spacecraft captured approximately 98% of Venus, with a resolution of 100m, and 3 kilometers of effective resolution. Combined with images from an Arecibo radar, the composite image was created to highlight the details of Venus’ surface. In addition, the image is color coded to distinguish elevation.

Known as Earth’s sister planet, Venus has many similarities and differences to Earth. Similarly, the Earth and Venus both are terrestrial planets, with the interior structure of an iron core, rocky molten mantle, and silicate crust. Nevertheless, siblings are bound to have differences. Venus has no moons. Also, the length of one day on Venus is 2802.0 hours. Due to this slow rotation, Venus has a very weak magnetosphere. Not only is the rotation of Venus slow, but it opposite from most planets. This east to west rotation is similar to only Uranus. The “renegade rotation” of Venus was most likely caused by a collision with an asteroid or comet.

Venus has other distinct features. Thankfully, Venus and Earth do not have the same atmospheric composition. With its atmosphere being around 96% carbon dioxide, it traps heat like a greenhouse. Due to this greenhouse effect, the temperature can reach 471 degrees Kelvin; and yes, that is hot enough to melt lead. Venus also has 90% of Earth's gravity, which would crush any human standing on the planet. Lastly, Venus is very bright. This brightness is due to the fact that like the moon, Venus reflects most of the sunlight that reaches its surface.