all Paul Ho stories

Structure in dust around Vega may be signature of planet

70652986 — Mon, 26 Mar 2007 05:18:03 -0400

Vega, located 25 light years away in the constellation Lyra, is the brightest star in the summer sky. Observations of Vega in 1983 with the Infrared Astronomy Satellite provided the first evidence for large dust particles around another star, probably debris related to the formation of planets. This discovery likely inspired Carl Sagan to place the alien listening post at Vega in his novel Contact. In January 2001, astronomers David Wilner, Matt Holman, Paul Ho and Marc Kuchner of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., announced that features observed in the dust swirling around the nearby star Vega may be the signatures of an unseen planet in an eccentric orbit around the star. The report was presented at a meeting of the American Astronomical Society in Washington, D.C. This work was supported by the Smithsonian Astrophysical Observatory and a grant from NASA's Origin of Solar Systems Program.

Young star may be belching spheres of gas, astronomers say

70652986 — Mon, 26 Mar 2007 05:13:39 -0400

Observations by astronomers of a young star in the constellation Cepheus, more than 2000 lights-years away, suggest that it is repeatedly belching spheres of gas. Current theories about how young stars shed matter would not have predicted such eruptions. In order to remain stable while accumulating matter, young stars have to throw off some of the infalling material to avoid "spinning up" so fast they would break apart, according to those theories. But that infalling matter forms a thin spinning disk around the core of the new star, and material is ejected in twin "jets" perpendicular to the plane of the disk. Therefore, jets are expected, while spheres of gas are not.

Streamers of gas feed beast at center of our galaxy

70652986 — Mon, 26 Mar 2007 05:09:40 -0400

Astronomers have long known that a supermassive black hole, more than 2 million times more massive than our Sun, lies at the center of the Milky Way Galaxy some 27,000 light-years from Earth. A point-like source of radio emission called Sagittarius A* (pronounced "A-star") marks the location of this black hole. Now researchers Robin S. McGary and Paul T. P. Ho of the Harvard-Smithsonian Center for Astrophysics report that narrow "streamers" of ammonia gas appear to be flowing from giant clouds of gas toward the center of the galaxy. These findings, presented Jan. 12, 2000, at the American Astronomical Society meeting, could pinpoint the source of the black hole's gluttonous diet. The black hole is surrounded by a ring of dust and gas orbiting Sagittarius A* (Sgr A*) at a radius of about 6.5 light-years from the black hole. This "circum-nuclear disk" revolves around the black hole at a velocity of 110 km/s. Gas and dust are stripped from the disk by the strong gravitational pull of the black hole and spiral towards Sgr A*.