Current Events in Astronomy
| January 2002 | Archives |
| THE SKY AFTER DARK |
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| The eastern night sky in January offers an exceptional view of stars and planets. View from Seattle, Washington, around 6:00 P.M. on January 15. Image created with Starry Night Backyardtm. |
Information about upcoming celestial events can be found at the sites listed below.
Discovering the Universe 5th edition: Chapter 1, "Discovering the Night Sky"
| PLANETS AND MOONS |
E x t r a s o l a r P l a n e t s
| Protostellar disk Lynds 1157, located about 1300 light years from Earth in the constellation Cepheus. The multicolored area shows a dust disk surrounding a newborn star. The red-orange area at the center represents the brightest region, which contains the young star. It is surrounded by the cooler, dusty disk, which appears as yellow, green, and blue. The white lines trace the radio wave emission of methanol, which comes only from the outer parts of the disk. A warm shock occurs in that zone when the cloud material moves in toward the star and meets up with the outer surface of the disk. NASA-JPL. |
Shock zone found where planets are formed. NASA-JPL; January 8, 2002. Using the Owens Valley Radio Observatory Millimeter Array, a team of astronomers has gathered evidence that a shock is created when material falls in toward a dust disk around a growing star. Dusty disks around stars, called protostellar disks, form from gas and dust in interstellar clouds. The disks grow as they accumulate material falling in from the parent cloud. Where the cloud material meets the disk, astronomers had predicted that a warm shock would occur. This new discovery confirms that prediction. Scientists believe dust particles in these disks clump together to form small rocks and, eventually, planets and comets. Protostellar disks are planetary construction zones. Over the past several years, astronomers have discovered planets orbiting dozens of other stars. The key mystery waiting to be solved is whether any extrasolar planet may have conditions suitable for life, and if so, whether life exists there.
| Two giant clumps of dust in the ring surrounding Vega may be signatures of an unseen planet orbiting the star. Observations at millimeter wavelengths indicate that infalling dust is trapped in dynamical resonances by the gravitational influence of a planetary body. Such effects may offer an additional method of detecting and studying extrasolar planets. David Wilner and David Aguilar, Harvard-Smithsonian Center for Astrophysics. |
Structure in dust around Vega may be signature of planet. Harvard-Smithsonian Center for Astrophysics; January 8, 2002. 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. 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. In our solar system, dust particles created by asteroid collisions and the evaporation of comets spiral in toward the Sun. The gravity of the planets affects the distribution of these dust particles. The Earth, for example, traps dust in a series of dynamical resonances that produce a ring of enhanced density along the Earth's orbit. When viewed from afar, the signatures of extrasolar planets imprinted on circumstellar dust may be the most conspicuous evidence of their existence besides their gravitational influence on their central stars. The dust clouds are much easier to detect than the planets because of their much larger surface area. The gravitational effects of extrasolar planets on circumstellar dust may provide another way to infer the existence and orbital properties of extrasolar planets.
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C o m e t s
| Comet Machholz 1 seen close to the Sun by SOHO on January 8, 2002. The mask in the LASCO coronagraph hides the bright Sun, the size of which is shown by the inner ring. SOHO/ESA/NASA. |
SOHO's private view of sunbathing comet. European Space Agency; January 8, 2002. The Solar and Heliospheric Observatory (SOHO) recently captured a view of Comet Machholz 1 on its closest approach to the Sun (18 million kilometers). This unusual comet, reputed to flare up a lot, is in an orbit that brings it back to the solar vicinity every 63 months. The LASCO coronagraph on SOHO, designed for viewing outbursts from the Sun, uses a mask to block the bright rays from the visible surface. It monitors a large volume of surrounding space, and as a result it became the most prolific discoverer of comets in the history of astronomy. Most of them are small sungrazing comets that burn up completely in the Sun's hot atmosphere. Machholz 1 is a more robust, but puzzling, comet. No one is sure of the reason for its frequent outbursts.
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| STARS AND STELLAR EVOLUTION |
T h e S u n
| Three views of a spectacular coronal mass ejection on January 4. From left to right: Extreme-UV Imaging Telescope (EIT), Large Angle and Spectrometric Coronagraph (LASCO) C2, and LASCO C3. SOHO/ESA/NASA. |
SOHO Hot Shot: A Fiery CME. Solar and Heliosphere Observatory (SOHO); January 4, 2002. Another spectacular coronal mass ejection (CME) took off from the Sun in the early hours of January 4, starting off as a filament eruption seen by the Extreme-ultraviolet Imaging Telescope (EIT). The complexity and structure of the CME as it passed through the Large Angle and Spectrometric Coronagraph (LASCO) C2 and C3 fields of view amazed even experienced solar physicists at the SOHO operations center. Although the center of the CME was directed almost a full 90 degrees away from the Sun-Earth connection line, it still appeared as a (weak) full halo event, opening up the possibility of a small impact on Earth's space weather. However, no clear effect was recorded.
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S t a r B i r t h
| Hubble image of Thackeray's globules (dark nebulae) in star-forming region IC 2944. IC 2944 is located about 1500 light-years away, in the constellation Centaurus. STScI/AURA. |
Thackeray's Globules in IC 2944. Space Telescope Science Institute; January 3, 2002. Dark nebulae known as Bok globules appear in this image taken with the Hubble Space Telescope. These dense, opaque dust clouds are silhouetted against nearby bright stars in the busy star-forming region IC 2944. Astronomer A. D. Thackeray first spied the globules in IC 2944 in 1950. Globules like these have been known since Dutch-American astronomer Bart Bok first drew attention to them in 1947. But astronomers still know very little about their origin and nature, except that they are generally associated with large hydrogen-emitting star-forming regions, called HII regions because of the glowing light of the hydrogen gas. IC 2944 is filled with gas and dust that is illuminated and heated by a loose cluster of massive stars. These stars are much hotter and much more massive than our Sun. The remarkable resolution offered by the Hubble Space Telescope has allowed astronomers to study the intricate structure of these globules for the first time. The globules appear to be heavily fractured, as if major forces were tearing them apart. When radio astronomers observed the faint hiss of molecules within the globules, they realized that the globules are actually in constant, churning motion. This motion may be caused by the powerful ultraviolet radiation from the luminous, massive stars, which also heat up the gas in the HII region, causing it to expand and stream against the globules, ultimately destroying them.
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| Left: Infrared image of the Pillars of Creation at the center of the Eagle Nebula. ESO. Right: The famous Hubble image of the pillars in visible light. STScI/AURA. The pillars themselves are less prominent in the IR view than in the visible-light image because near-infrared light penetrates the thinner parts of the gas and dust clouds and only the heads remain opaque. |
The Eagle's EGGs: VLT looks for young stars in the famous Pillars of Creation. European Southern Observatory; December 21, 2001. Through imaging at infrared wavelengths, evidence has been found for recent star formation in the Pillars of Creation in the Eagle Nebula (also known as Messier 16), made famous when the Hubble Space Telescope obtained spectacular visible-wavelength images of this object in 1995. Those huge pillars of gas and dust are being sculpted and illuminated by bright and powerful high-mass stars in the nearby young stellar cluster NGC 6611. The Hubble astronomers suggested that perhaps even younger stars were forming inside. Using the ISAAC instrument on the Very Large Telescope (VLT) 8.2-meter ANTU telescope at the ESO Paranal Observatory, European astronomers have now made a wide-field infrared image of the Messier 16 region with excellent spatial resolution, enabling them to penetrate the obscuring dust and search for light from newly born stars. Two of the three pillars are seen to have very young, relatively massive stars in their tips. Another dozen or so lower mass stars seem to be associated with the small "evaporating gaseous globules (EGGs)" that the Hubble astronomers had discovered scattered over the surface of the pillars.
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| GALAXIES AND COSMOLOGY |
O u r G a l a x y
| This 400 by 900 light-year mosaic of several Chandra images of the central region of our Milky Way galaxy reveals hundreds of white dwarf stars, neutron stars, and black holes bathed in an incandescent fog of multimillion-degree gas. The supermassive black hole at the center of the Galaxy is located inside the bright white patch in the center of the image. The colors indicate X-ray energy bands: red (low), green (medium), and blue (high). NASA/UMass/D.Wang et al. |
Chandra takes in the bright lights, big city of the Milky Way. Chandra X-Ray Observatory; January 9, 2002. NASA's Chandra X-ray Observatory has made a stunning, high-energy panorama of the central regions of our Milky Way galaxy. The new Chandra images provide a new perspective on how the turbulent galactic center region affects the evolution of the galaxy as a whole. An analysis of the X-ray data showed that the temperature of the gas does not have to be 100 million degrees Celsius, as previously thought. Rather, a relatively mild 10 million degrees will do. This hot gas appears to be escaping from the center into the rest of the galaxy. The outflow of gas, chemically enriched from the frequent destruction of stars, will distribute these elements into the galactic suburbs. Because it is only about 25,000 light years from Earth, the center of our galaxy provides an excellent laboratory to learn about the cores of other galaxies.
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