Light and the Universe

Observatory / Course Archives / ASTR 110 Fall 2019 / Henson

TrEs-2b

Imagine a planet darker than coal, the darkest substance on earth; a planet that reflects only 0.1% of the light that hits it. That planet is TrEs-2b, the darkest known exoplanet. However, this doesn't mean it fades into the background. The nature of "darkness" relates to how much light it absorbs rather than how much it reflects, and TrEs-2b orbits so close to its sun, absorbs so much light that the planet glows thermally, emitting a low red light like an ember. TrEs-2b's composition mimics that of Jupiter in that it too is a gas giant, but TrEs-2b falls under a specific type of gas giants called "hot jupiters". These planets are characterized by their close proximity to their stars and a high surface temperature. TrEs-2b's surface temperature is estimated to be around 1800 degrees Fahrenheit. It is typical for hot jupiters, like TrEs-2b, to be dark, yet the cause for this phenomenon is unknown. Current theory suggests that surface temperatures characteristic of these planets prohibits the formation of light-reflecting clouds and causes light-absorbing molecules like potassium and sodium to vaporize and spread into the atmosphere. The catch is that there shouldn’t be this much potassium or sodium to make TrES-2b as dark as it is, and so the mystery continues.

Messier 83

Moving to the other end of the spectrum, Messier83 (M83) is bursting with light. Literally. The spiral galaxy has around 300 recorded supernovae, six of which formed just within the last 100 years. M83 is one of the brightest spiral galaxies, which makes sense considering all the action going on within its barred arms. Images of the galaxy show concentrations of dust spiraling out, mixing with an array of different colors; the yellow hue in the middle of the structure indicate the presence of older stars, and the ruby-red bursts on the outer edge are clouds of hydrogen gas. The glowing ultraviolet and radio waves indicate the birth of new stars ionizing, somethink M83 is quite good at and known for, causing the pink-ruby glow.

Bernard 68

One of the first things one might notice about this nebula is the fact that it is not bright and colorful like the popular understanding. In fact, Barnard 68 (B68) is called a dark nebula, also called an absorption nebula. B68 is composed of hydrogen, helium, and interstellar dust particles, the latter being the reason we cannot see through the cloud.These dust particles obscure visibile light wavelengths, especially in the coldest and densest part of the cloud, which is typically the core. B68's interior is around 16K. While there are difficulties presented by the cold core of the nebula, infrared technology allows us to be able to see the stars behind it, which is how we found B68; despite it's lack of luminosity, we know B68 exists because it is in an area that is densly populated by stars. In fact, the nebula is on the verge of becoming one such star. It's edges are well-defined, which is unusual for a dark cloud nebulae, and indicates its impending gravitational collapse.

References:

"A galaxy with two hearts." Hubble Space Telescope. <https://www.spacetelescope.org/news/heic1403/>

Aguilar, David A. and Pulliam, Christine. "Alien World is Blacker than Coal." Harvard and Smithsonian Center for Astrophysics. <https://www.cfa.harvard.edu/news/2011-21>.

"An Infrared Portrait of the Barred Spiral Galaxy Messier 83." European Southern Obervatory. <https://www.eso.org/public/usa/news/eso0136/>

"A Thousand-Ruby Galaxy." European Southern Observatory. <https://www.eso.org/public/usa/news/eso0825/>

"Dark Nebula". University of Oregon. <http://abyss.uoregon.edu/~js/glossary/dark_nebula.html>.

ESO. "Thousand-Ruby Galaxy: Pinwheel Shines in The Darkness." ScienceDaily. <https://www.sciencedaily.com/releases/2008/09/080902104901.htm>

Garner, Rob. "Messier 83 (The Southern Pinwheel)." NASA. <https://www.nasa.gov/feature/goddard/2017/messier-83-the-southern-pinwheel>

Kelly, Morgan. "'Darkest' world enlightens astronomers about mysterious light-gobbling planet." Princeton University. <https://www.princeton.edu/news/2011/09/26/darkest-world-enlightens-astronomers-about-mysterious-light-gobbling-planet>.

Lemonick, Michael D. "Blackest Planet in the Universe: How Astronomers Discovered a Dark, Glowing 'Hot Jupiter'." Time. <http://content.time.com/time/health/article/0,8599,2089304,00.html>.

Pellerin, Bill. "Shallow Sky Object of the Month: Barnard 68 - Dark Nebula". Houston Astronomical Society. <https://www.astronomyhouston.org/newsletters/guidestar/shallow-sky-object-month-barnard-68-dark-nebula>.

"Secrets of a Dark Cloud." European Southern Observatory. <https://www.eso.org/public/usa/news/eso9934/>.

Wikipedia, "Barnard 68". <https://en.wikipedia.org/wiki/Barnard_68>.

Wikipedia, "Dark Nebula". <https://en.wikipedia.org/wiki/Dark_nebula>.

Wikipedia, "Hot Jupiter". <https://en.wikipedia.org/wiki/Hot_Jupiter>

Wikipedia, "TrEs-2b". <https://en.wikipedia.org/wiki/TrES-2b>