Universe Today

Image credit: Hubble

Astronomers have discovered a new object far past the orbit of Pluto. Dubbed Quaoar, the object is 1,200 km across (approximately 1/10th the size of the Earth), and orbits the sun once every 288 years. Although the object is half the size of the Pluto, it probably won’t be considered a new planet ? even Pluto’s planetness is hotly debated. Ironically, Quaoar was caught in images taken as far back as 20 years ago; astronomers just didn’t realize what they were looking at.

NASA’s Hubble Space Telescope has measured the largest object discovered in the solar system since the discovery of Pluto 72 years ago.

Approximately half the size of Pluto, the icy world 2002 LM60, dubbed “Quaoar” (pronounced kwa-whar) by its discoverers, is the farthest object in the solar system ever to be resolved by a telescope. It was initially detected by a ground-based telescope, as simply a dot of light, until astronomers aimed the powerful Hubble telescope at it.

Quaoar is about 4 billion miles away from Earth, well over a billion miles farther away than Pluto. Unlike Pluto, its orbit around the Sun is very circular, even more so than most of the planetary-class bodies in the solar system.

Although smaller than Pluto, Quaoar is greater in volume than all the asteroids combined (though probably only one-third the mass of the asteroid belt, because it’s icy rather than rocky). Quaoar’s composition is theorized to be largely ices mixed with rock, not unlike that of a comet, though 100 million times greater in volume.

This finding yields important new insights into the origin and dynamics of the planets, and the mysterious population of bodies dwelling in the solar system’s final frontier: the elusive, icy Kuiper belt beyond Neptune.

Michael Brown and Chadwick Trujillo of Caltech are reporting the findings today at the 34th annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Birmingham, Ala.

Earlier this year, Trujillo and Brown used the Palomar Oschin Schmidt telescope to discover Quaoar as an 18.5-magnitude object creeping across the summer constellation Ophiuchus (it’s less than 1/10,000th the brightness of the faintest star seen by the human eye). Brown had to do follow-up observations using Hubble’s new Advanced Camera for Surveys on July 5 and August 1, 2002, to measure the object’s true angular size of 40 milliarcseconds, corresponding to a diameter of about 800 miles (1300 kilometers). Only Hubble has the sharpness needed to actually resolve the disk of the distant world, leading to the first-ever direct measurement of the true size of a Kuiper belt object (KBO).

Like Pluto, Quaoar dwells in the Kuiper belt, an icy debris field of comet-like bodies extending 7 billion miles beyond Neptune’s orbit. Over the past decade more than 500 icy worlds have been found in the Kuiper belt. With a few exceptions all have been significantly smaller than Pluto.

Previous record holders are a KBO called Varuna, and an object called 2002 AW197, each approximately 540 miles across (900 kilometers). Unlike Hubble’s direct observations, these diameters are deduced from measuring the objects’ temperatures and calculating a size based on assumptions about the KBOs’ reflectivity, so the uncertainty in true size is much greater.

This latest large KBO is too new to have been officially named by the International Astronomical Union. Trujillo and Brown have proposed naming it after a creation god of the Tongva native American tribe, the original inhabitants of the Los Angeles basin. According to legend, Quaoar, “came down from heaven; and, after reducing chaos to order, laid out the world on the back of seven giants. He then created the lower animals, and then mankind.”

Quaoar’s “icy dwarf” cousin, Pluto, was discovered in 1930 in the course of a 15-year search for trans-Neptunian planets. It wasn’t realized until much later that Pluto actually was the largest of the known Kuiper belt objects. The Kuiper belt wasn’t theorized until 1950, after comet orbits provided telltale evidence of a vast nesting ground for comets just beyond Neptune. The first recognized Kuiper belt objects were not discovered until the early 1990s. This new object is by far the “biggest fish” astronomers have snagged in KBO surveys. Brown predicts that within a few years even larger KBOs will be found, and Hubble will be invaluable for follow-up observations to pin down sizes.

Original Source: Hubble News Release

What is the biggest telescope in the world?

Image credit: NASA

A team of astronomers have taken the highest resolution mid-infrared picture ever taken of the center of our Milky Way galaxy. The image is so detailed, you can actually see dust swirling around the giant black hole located at the centre of the galaxy. The camera, called the Mid-Infrared Large-Well Imager, or Mirlin, is attached to the enormous Keck observatory in Hawaii.

The highest resolution mid-infrared picture ever taken of the center of our Milky Way galaxy reveals details about dust swirling into the black hole that dominates the region.

The image was taken by a team led by Dr. Mark Morris of the University of California, Los Angeles, at the Keck II telescope in Hawaii, with an infrared camera built at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The camera, called the Mid-Infrared Large-Well Imager, or Mirlin, used three different infrared wavelengths to build the color composite image available online at http://irastro.jpl.nasa.gov/GalCen/galcen.html.

The mid-infrared part of the electromagnetic spectrum comprises the wavelengths at which room temperature objects glow most brightly. Everything on Earth, including the telescope, the astronomers, and even the atmosphere, emits a bright glow in the mid-infrared. Seeing celestial objects though this glow is like trying to see stars during daylight; special techniques are needed to tease the stars from this glow to build a recognizable picture.

Near the center of the image, but not apparent at these wavelengths, is a black hole three million times heavier than our Sun. Its gravitational pull, so powerful that not even light can escape from its surface, affects the motion of dust, gas and even stars, throughout the region.

A veil of dust absorbs the visible light emitted by most of the stars near the Galactic Center. The light warms the dust, which then radiates in the infrared and becomes visible to the mid-infrared camera.

The image shows this dusty material spiraling toward the black hole, most notably the stream of gas and dust called the Northern Arm. When this material eventually falls into the black hole, it will release energy that affects everything in its vicinity. This event, which astronomers are certain has happened many times in the history of the Milky Way, may trigger the formation of a new generation of stars by causing other nearby dust clouds to collapse, or it may actually inhibit the formation of new stars if the released energy destroys those clouds. Either way, the black hole continues to grow larger as new material falls into it.

Astronomers know that the stars in this image are all very luminous, because less luminous stars appear very faint to a mid-infrared camera. A massive star nearing the last stages of its life, the red supergiant IRS7, is visible in this image as the smallish, bright spot just above the center. IRS7 is simply so luminous — more than 100,000 times as bright as our Sun — that we can see its starlight directly.

The “mini-cavity” in the center is a bubble that has apparently been evacuated of dust and gas. A star located at the center of the mini-cavity (not visible in this image) apparently blows this bubble with its powerful stellar wind. The “bullet” is a mysterious, fast-moving feature pointing roughly away from the mini-cavity, just below and to the right of the center. It may be a jet composed of gas and dust.

Other members of the Mirlin imaging team, along with Morris, are Dr. Andrea Ghez, Dr. Eric Becklin and Angelle Tanner of UCLA; Drs. Michael Ressler and Michael Werner of JPL; and Dr. Angela Cotera Hulet of the Arizona State University, Tempe, Ariz. The camera was built at JPL by Ressler and Werner. Operation of Mirlin is supported by a grant from NASA’s Office of Space Science, Washington, D.C. Some findings based on this image have been published in the Astrophysical Journal.

Studying processes in the center of our own galaxy may teach astronomers more about much more active, more distant galactic nuclei — objects like quasars and Seyfert galaxies, which are the most violent places known in the universe. More information about both the center of our Milky Way and the centers of other galaxies may be obtained with future instruments that have higher resolution and greater sensitivity.

For example, NASA is planning a similar infrared camera, the Mid-Infrared Instrument, one of three instruments that will fly aboard the James Webb Space Telescope, launching in 2010. This camera will achieve resolution roughly equivalent to the Keck images, but because it will orbit above the warm glow emitted by Earth’s atmosphere, it will be 1,000 times more sensitive. Using this instrument, astronomers will be able to study the centers of galaxies all the way to the edge of the observable universe.

JPL, in conjunction with a consortium of European countries and the European Space Agency, is developing the Mid-Infrared Instrument. The James Webb Space Telescope is managed by the Goddard Space Flight Center, Greenbelt, Md.

JPL is a division of the California Institute of Technology in Pasadena.

Original Source: NASA/JPL News Release

An amateur astronomer has discovered what could be a new object orbiting the Earth; maybe it’s a recently captured space rock, or maybe it’s just a remnant from the Apollo program. Whatever it is, the object, dubbed J002E2, seems to orbit the Earth every 50-days in a wide orbit. If it turns out to be natural, the object will become the Earth’s 3rd moon (and you only thought we had one), after Cruithne which was discovered in 1986 in a long erratic orbit. (BBC News Story)

Image credit: SWRI

Although the Kuiper Belt, a region of icy objects located past the orbit of Neptune, was only discovered in 1992, it’s already presented a host of mysteries. One mystery is why an unusually large number of these objects have small satellites orbiting them – 8 out of the 500 objects discovered so far have had satellites. The high number brings into question the traditional theory that they’re caused by collisions.

The Kuiper Belt region of the solar system, which stretches from just past Neptune to beyond the farthest reaches of Pluto?s orbit, was only discovered in 1992, but continues to reveal new knowledge into the formation processes of the planets. Now, in a paper to be published in the October issue of The Astronomical Journal, a Southwest Research Institute? (SwRI?) scientist reveals a new mystery about Kuiper Belt Objects (KBOs).

The study examined the formation of KBO satellites, which have been observed only since 2001 and continue to be discovered around an unexpectedly large number of the more than 500 known KBOs.

?In just over a year since the first satellite of a KBO was found, scientists have discovered a total of seven KBO satellites. Surprisingly, observations by both ground-based telescopes and the Hubble Space Telescope have indicated that, in many cases, the KBO satellites are as large or nearly as large as the KBOs around which they orbit,? says Dr. S. Alan Stern, director of the SwRI Space Studies Department. ?That so many binary or quasi-binary KBOs exist came as a real surprise to the research community.?

The focus of Stern?s work was not observational in nature, but rather it sought to understand how such large KBO-satellite pairs could form. The standard model for large satellite formation is based on collisions between an interloping body and the parent object around which the satellite orbits. This model has successfully explained binary systems around asteroids and the Pluto-Charon system, and also has direct relevance to the formation of the Earth-moon system.

Stern?s findings call into question the formation of KBO satellites by standard collisional processes. Collisions of the magnitude required, Stern found, appear to be energetically improbable, given the number and masses of potential impactors in both the ancient (more massive) and modern day (eroded) Kuiper Belts.

This likely implies one of two alternatives: Either KBO satellites were not formed by collisions, as has been commonly assumed, or the surface reflectivities (which help determine size) of KBOs with satellites, or the reflectivity of the satellites themselves, have been significantly underestimated.

?If the surfaces of KBOs with satellites, or the satellites themselves, are more reflective than previously thought,? says Stern, ?these objects would be smaller and less massive, and would therefore require smaller, less energetic impacts to create the satellite systems we see.?

NASA?s new Space Infrared Telescope Facility (SIRTF), set for launch early next year, will help resolve these two alternatives, Stern says, by directly measuring the reflectivities and sizes of numerous KBOs, including those with satellites.

In addition to this work, Stern serves as principal investigator of the NASA New Horizons mission to Pluto and the Kuiper Belt. Expected to launch in January 2006, this spacecraft will make the first ever flyby reconnaissance of the Pluto and Charon system and then go on to explore KBOs as it leaves the solar system. New Horizons is the only NASA mission planned to study Kuiper Belt Objects at close range.

The NASA Origins of Solar Systems program provided funding for this research.

Original Source: SWRI News Release