Bakersfield Night Sky – March 7, 2015
By Nick Strobel
In a couple of weeks the William M Thomas Planetarium at Bakersfield College will be showing the ever-popular "Black Holes". The first part of show covers the formation of black holes from the deaths of massive stars. The black holes that form in this way have masses several times to perhaps a few tens of times the mass of the Sun. These are "stellar mass" black holes because they have masses that are the same as big stars. The last part of the show covers the supermassive black holes at the centers of galaxies. These black holes have masses from a few MILLION times the mass of the Sun to several BILLION times the mass of the Sun. One of the mysteries about the supermassive black holes is how they formed.
One possibility favored by most astronomers is that the supermassive black holes formed from the growth of much smaller stellar mass black holes over a long time. The compact, dense black holes would have tended to spiral in toward the galaxy centers through a process called "dynamical friction". Stellar mass black holes would merge to form a larger black hole. Also, stars and gas clouds getting very close to a black hole at a galaxy's center would have been torn apart and at least part of their material would have been dumped into the black hole, increasing the black hole's mass, and, therefore, its gravity.
The feeding of the black hole at a galaxy's center is enhanced when galaxies merge together. These mergers would have been more common in the early universe when the galaxies were closer together and more prone to "bump" into each other. The galaxy collisions would have dumped even more gas and dust into the galaxy centers. The big black holes at the galaxy centers would spiral into each other and merge. Given enough time, it's easy to see how a supermassive black hole can form from the "tiny" seed of a stellar mass black hole.
Given enough time. Time seems to be the problem in one of the astronomy news items making the rounds. The quasar J010013.02+28022.5 (usually shortened to J0100+2802) has a supermassive black hole that is 12 or 13 billion times the mass of the Sun. Quasars are super-active galaxies that generate up to thousands of times the energy of an entire ordinary galaxy in the volume of something the size of our solar system. If Pluto's orbit was the size of a quarter coin, the Milky Way would be the size of the western United States. The energy of the quasars is coming from the hot gas spiraling into the supermassive black hole before it crosses the black hole's event horizon.
The quasar J0100+2802 is very distant so we are seeing it as it was long ago, 12.8 billion years ago to be more precise. The universe started expanding about 13.8 billion years ago and it was too dense, hot and violent to make stars at that time. Recent results from the Planck mission are indicating that it took about 500 million to 600 million years for conditions to calm down enough to easily form stars. Those stars are the ones that would form the stellar mass black holes that would be the seeds of the supermassive black holes. Doing some arithmetic one sees that J0100+2802's huge black hole was able to grow so massive in just 400 million years. That's uncomfortably small for the stellar mass black hole seed idea.
Another idea being looked at more seriously now is the one that has large clumps of gas collapsing directly down to black holes of a thousand to ten thousand times the mass of the Sun without forming stars at all. That idea is still in the beginning stages of development so a lot more work needs to be done on it. Also, more more work will be done on the quasar and other very distant quasars with overly large supermassive black holes as well as nailing down the time when stars first began to form before we have to throw out the stellar mass black hole seed idea. Finding the time when the stars first began to form in the young universe will probably have to wait for observations with the James Webb Space Telescope, scheduled to launch in late 2018.
Closer to home is a news item that has captured some of my students' interest. That's the large plumes that have appeared at the edge of Mars images. If the plumes are real martian features, they would be 120 to 150 miles above Mars's surface. Perhaps they are very high clouds catching the sunlight just right to make them visible. However, ice or dust particles shouldn't exist this high above the surface. Now, before we get too excited about the discovery of a new process, we need to rule out other less fantastic possibilities. One possibility is ordinary height clouds forming over a region that is higher in elevation than the area at the sunrise terminator boundary. This would artificially inflate the altitude of the clouds because we would be using the wrong reference for the height calculations.
Another possibility is that the sharpening technique used to create the images from ground-based amateur telescopes may be producing artifacts. Observers who observed the plumes under poorer sky conditions produced images with more significant plumes than those who observed under very stable air conditions ("good seeing"). That fact raises warning bells in my mind about the reality of the plumes but since the Hubble Space Telescope has seen high altitude clouds, including one set of images in mid-1997 with a plume similar to ones making the news today, the plumes are probably real. The resolution of this puzzle requires, you guessed it, more data.
At home, we won't be able solve this puzzle in March 2015. Mars is now getting dimmer and less noticeable as it sinks into the evening twilight in the west after sunset. You're probably going to need binoculars to pick it out now. Above it is very bright Venus. Venus continues to climb up farther from the Sun on our sky. Venus is now setting about 2.5 hours after sunset but by the end of March, that time interval will increase to 3 hours.
Jupiter is well above the eastern horizon at sunset and it will be about halfway up in the east-southeast when the evening twilight is gone. It will be the brightest object in the eastern sky after sunset, so you can't miss it if there are no clouds in the way. The first star chart below shows the sky at 9 PM with the bright winter constellation Orion and the bright spring constellation Leo on either side of the meridian due south. The bright star in the middle of the southern sky will be Procyon at one end of Canis Minor, the little dog (or puppy). At about midnight Saturn will rise just above the head of Scorpius. A Waning Gibbous Moon will be next to Saturn on March 12th as shown in the second star chart below. Eight days later (on March 20th), the New Moon will cover up the Sun for observers in the North Atlantic and Arctic Oceans. The total solar eclipse will start in the north Atlantic Ocean south of Greenland. The path of totality will loop to just east of Iceland and then to north of Norway and Siberia. Totality will last up to 2 and 3/4 minutes.
Several hours later at 3:45 pm PDT marks with official start of spring for us in the Northern Hemisphere. The Sun will be north of the projection of the Earth's equator onto the sky, the Celestial Equator on the following days. Oh, by the way, "PDT" means Pacific Daylight (savings) Time that begins tomorrow morning. Spring your clocks forward one hour!
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com