As we zoom into the very core of the Galactic Center, our field of view shrinks to a mere 5 arcseconds (one thousandth of a degree). At radio wavelengths, the brightest feature of this region is the point like cheap jerseys from china radio source Sagittarius A (pronounced « Sag A star »). This source is a compact object, and approximately one Astronomical Unit (1 AU is about 93 million miles) in size, which is much smaller than our solar system (Neptune is 2.8 billion miles from the Sun). At near infrared wavelengths, this point source in the radio is not clearly seen. Astronomers have seen pulsation near the radio position of Sgr A in the near infrared, which they attribute to this radio source flaring.
In the past 20 years, astronomers have collected enough evidence through the observed motions of gas and stars to convince ourselves that something very massive lurks at the center of our galaxy. The first dynamical evidence came from the motions of the ionized gas streamers of the mini spiral orbiting Sgr A. Using the velocities of the gas estimated from the Doppler shift of spectral lines, astronomers estimated that a mass of six million solar masses must lie within 10 arcseconds of Sgr A. This did not explicitly prove the existence of a black hole since that amount of matter could be accounted for by a high density of stars within such a large volume.
Since 1995, high resolution near infrared studies have observed a compact cluster of early type stars surrounding the radio position of Sgr A. These stars have very large proper motions (they are moving across the sky very quickly) considering their 24 million light year distance from the Earth. The two main groups devoted to tracking these stars include Andrea Ghez and others at UCLA, who use the 10 m Keck telescope on Mauna Kea, Hawaii, and Reinhard Genzel and Andreas Eckart who use the 8 m VLT telescopes in Chile. Both groups take advantage of the high spatial resolution and sensitivity of these large telescopes to track the positions of the stars within the cluster using near infrared images collected once or twice a year.
Despite the large diameters of the Keck and VLT telescopes, air turbulence in the Earth’s atmosphere blurs the images taken at the telescopes. The atmosphere has a lot of wholesale jerseys china molecules that are colliding into each other and getting heated up. On really hot days, we can see the heat waves coming up off the ground, or if you look at a flame, you can see the heat influencing the air around it. This is what happens in our atmosphere. In order to correct for it, astronmers are now using Adaptive Optics (AO) systems, which increases the sensitivity of observations. AO systems use a deformable mirror that mimics the shape of the incoming lightwave and corrects for the atmospheric turbulence before the data is recorded.
Very accurate stellar positions can be estimated in order to keep track of the motions of the stars in the compact central cluster, which are zipping around Sgr A at speeds up to 3 million miles per hour! Using Kepler’s laws of motion, the orbital velocities and the positions of the bright stars an be used to wholesale nfl jerseys estimate the mass that must be contained within their orbits. The resulting enclosed mass is 4.6 0.7 X 10^6 solar masses 4.6 million times the mass of our Sun! This large mass cheap jerseys free shipping combined with the minute size of Sgr A in radio emission suggests taht the stars must be swiftly circling around a supermassive black hole.
An active galactic nucleus (Cen A). There is a lot of activity at long wavelengths and short,
energetic wavelengths. This is completely different than our galactic nucleus, Sgr A.
Sgr A may have been more energetic in the past. Credit: NASA
Recent observations of nearby galaxies reveal that such supermassive black holes are not unique to the MIlky Way. The formation of such a large black hole and how it affects the evolution of its host galaxy are not well understood. In the case of Sgr A, there is a mysterious absence of the high energy emission (X rays and UV radiation) often observed from active galactic nuclei.Articles Connexes：
OFF, 4th Annual CANADIAN, Juried Painting Competition, raising funds for art based programs for people living with Alzheimer’s. Judges include CJAD 800’s Andrew Carter. $25. Katie Liberta 514 867 3745 or email: subject tickets. Oct. 16: An Evening Of Poetry With Darren Bifford And Talya Rubin And Two Special Guest Poets, raising funds for Of The Causes of Wonderful Things, a solo theatre work at Theatre La Chapelle in early November. Dominique. $20. Includes a mixed drink cheap Michael kors with homemade Replica Christian Louboutin sugar syrups made from garden grown ingredients and Christian Louboutin Online Store a raffle ticket. 17: Exprience ADN Urban Ball, for the Fondation du Centre hospitalier Universit de Montral (CHUM). Organized by the DNA Committee the future of the Fondation du CHUM. Theme: A Futuristic Evening, inspired by the miracle of research. $150. Oct. 17:Les Amis Du Parc Meadowbrook Rock vs. Disco Dance Party, raising funds for, and celebrating, 25 years of cheap Michael Kors Outlet protecting this important green space. $25. Oct. 17: Annual Trafalgar Ross Lecture, supporting the Trafalgar Ross
Baltimore Sports Blitz It time to talk about Chris Tillman. The Orioles Opening Day starter, who retired four batters and was charged with seven runs all earned in giving back a seven run lead and taxing the bullpen in Sunday 13 9 win http://www.inspirativni.tv/cheap-jerseys-cheap-nike-jerseys-free-shipping-1ah64-wholesale-jerseys-from-china/ over http://soltrite.com/ Toronto, has taken such a clear step back from last year late season form that even his biggest apologists might soon acknowledge even a small bit of concern. Can you imagine Ray Lewis as a wrestler? No, not that kind of wrestler. I’m http://www.tacinelli.it/?p=5942 talking about the feud starting, piledriver http://www.lastekaraoke.ee/?p=1019 ing, leather vest http://foosh.ca/sale-2/cheap-jerseys-wholesale-jerseys-free-6th716-wholesale-jerseys-from-china/ wearing kind of wrestler. Of course you can imagine Ray http://www.longarabrush.com.au/ Lewis as a wrestler. Antoine Bethea xl women jersey His pregame "squirrel" dance might as well have http://www.lafollettewines.com/blog/?p=442 been an audition tape for WWE. He spoke as http://www.blanketstories.net/cheap-jerseys-cheap-jerseys-from-china-free-7fw939-wholesale-jerseys-from-china/ if Vince McMahon was spoonfeeding him lines, then lacing the words with 5 http://roelhosting.com/wp/?p=230 Hour Energy. So when. Michael Oher says Blind Side has hurt his NFL career Mike Preston wasn’t blindsided http://aprenderbolsa.com/?p=866 by Michael Oher’s actions Baltimore Sun sports columnist Mike Preston talks about http://aksoyasansor.net/ergo-baby-carrier-video-instruction-holocaust-heroes.html former Ravens offensive lineman http://www.tpww.net/ Michael