Comet Lovejoy cruises by the Large Magellanic Cloud, the largest, brightest satellite galaxy of the Milky Way, on January 13. Credit: Rob Kaufman
Lovejoy, the little comet that beat the odds and survived its swing around the sun last month, still shows a sleek cometary form, but it’s barely visible anymore with the naked eye. Amateur astronomers like to joke that they saw an object at the threshold of visibility using a technique called “averted imagination”, a reference to averted vision, which really can help you see a faint object more clearly by not staring straight at it.
Comet Lovejoy’s tail still shows up in long time exposure photos as a long, wispy streak. Depending on the darkness of the sky and lens used, amateurs have recorded tails lengths of between 20 and 37 degrees this week. The comet continues heading northward in the coming days and will finally become visible a week from now for residents in the far southern U.S. in places like Tucson, New Orleans and Key West. On January 22 at 9 p.m. it will be just 5 degrees high due south in the constellation Pictor the Painter’s Easel from southern Arizona. Hopefully, we’ll still be able to see some of it with binoculars without having to use averted imagination. For a recent NASA update on Lovejoy, click HERE.
A computer simulation of superheated plasma swirling around the black hole at the center of our galaxy. The dark shadow at center is what astronomers hope to finally see. Image by Scott Noble/RIT
Astronomers and physicists from around the world will gather in Tucson, Arizona on January 18 for a conference on the first coordinated endeavor to spy a black hole using the Event Horizon Telescope. Although there’s lots of circumstantial evidence for black holes, no one’s ever seen or photographed one. Despite their enormous masses, most are quite small. The dark shadow of a typical black hole, called the event horizon, measures only about 20 miles in diameter. Larger ones called supermassive black holes contain millions of solar masses and lurk in the centers of many galaxies including the Milky Way. Those can be up to a billion miles across or about the distance of Saturn from the sun. The one in our galaxy contains about 2.6 million times the mass of the sun and is estimated to be no more than 93 million miles across or nearly equal that of Earth’s distance from the sun.
The UA Submillimeter Telescope on Mt. Graham is one of the many radio telescopes forming the Earth-sized Event Horizon Telescope. Credit: Dave Harvey/UA Steward Observatory
Even a 93-million-mile wide shadow is a small thing when seen from Earth’s vantage point 26,000 light years from the galactic center. It’s been likened to spotting a grapefruit on the moon. To see something that small, you need a gigantic telescope. That’s why the new Event Horizon”telescope” will be a combination of 50 existing radio telescopes around the globe to form one monster virtual scope the size of Earth. Utterly cool idea. Data from each instrument will be carefully combined in a central processing center to create the images. Radio was chosen over optical telescopes because radio waves can penetrate the dust and other star gunk between us and the galactic center.
According the University of Arizona press release, participating in the project are the Submillimeter Telescope on Mt. Graham in Arizona, telescopes on Mauna Kea in Hawaii and the Combined Array for Reasearch in Millimeter-wave Astronomy in California. The global array will include several radio telescopes in Europe, a 10-meter dish at the South Pole and potentially a 15-meter antenna atop a 15,000-foot peak in Mexico.
The supermassive black hole in the center of our galaxy is the target of the Event Horizon Telescope. Two views of the Milky Way are shown: face-on from above and edge-on from the side. The solar system is some 26,000 light years from the center.
The Milky Way’s black hole is an ideal candidate because it’s large and relatively close by. Although there are bigger black holes out there, they’re in other galaxies and much too far away. Of course, scientists want to do more than just take a picture. They hope to study the hot, glowing matter swirling around the hole right up until it disappears at the event horizon. Dust and stars that stray near a black hole can end up like water going down your bathtub drain. The material is heated to incandescence through friction as its swirls its way to oblivion. They’d also like to know if the prediction made by Einstein’s Relativity Theory that the event horizon is circular is correct.
It’s an exciting project and I’ll bet you’re as eager as I am to see the first photo of a black hole.