WHAT'S NEW SINCE PUBLICATION:
Stars and Stellar Evolution

It appears that isolated stellar-mass black holes have been detected, using the Hubble Space Telescope. The detections were made by observing the effects of gravitational lensing on distant background stars and announced at the January 2000 meeting of the American Astronomical Society. The Space Telescope Science Institute provided a press release on January 13, 2000.
Thanks to spectacular new images and other data from spacecraft such as Yohkoh, TRACE, Ulysses, and SOHO, along with ground-based observations, we are gaining new insights into the nature of the Sun, including solar oscillations, magnetic fields (MHD), flares, prominences, and other solar activity.

The spectacular image shown above may not be material ejected from the luminous star Eta Carinae. According to a result published in the Astrophysical Journal Letters, 505, L131-133, October 1, 1998, Lamers, Livio, Panagia, and Walborn argue that the nebula is more chemically advanced (metal-rich) than the central star. It appears that Eta Carinae may be part of a binary star system with a period of 5.5 years. The unseen companion must be more evolved than Eta Carinae itself.
Evidence is growing that a new class of ultra-strong magnetic field stars, magnetars, may exist. These stars may possess field strengths of >10¹⁴ G. One possible candidate for a magnetar is SGR 1900 +14, which sent a stream of gamma rays through the Solar System on August 27, 1998. The activity was detected by several space craft, including Ulysses. See Science News, September 12, 1998.

A new spectral class (L) has been recently been suggested that would extend the well-known spectral classification scheme, OBAFGKM (see An Introduction to Modern Astrophysics, p. 223). Using the Keck II Telescope, stars cooler than class M have been discovered with atmospheres containing appreciable quantities of iron hydride and chromium hydride. To date, ten of these very cool, very low-mass stars have been detected (and are distinct from brown dwarfs). If the new class becomes established, the classification scheme would then be OBAFGKML (with the possible mnemonic: "Oh be a Fine Girl/Guy, Kiss My Lips"). See Science News, July 4, 1998.

Neutrino oscillations have been verified at the Super-Kamiokande laboratory in Japan and were announced June 5, 1998 at the Neutrino '98 Conference in Takayama, Japan. These results imply a small but non-zero rest mass for neutrinos (estimated to be 0.07 +/- 0.04 eV). This discovery could have profound implications for the solution of the solar neutrino problem (discussed in Section 11.1), the mechanisms for supernova production, dark matter, and the predominance of matter over anti-matter in the universe. For more information see http://www.phys.hawaii.edu/~superk; see also Sky and Telescope, September, 1998, p. 19.

At least one solar flare (occurring on July 9, 1996) has been observed to generate a sunquake. The observation was made using the Solar and Heliospheric Observatory (SOHO) and published in the May 28, 1998 issue of Nature.

On December 14, 1997, a gamma-ray burst was detected that appears to have released 100 times more energy than a supernova explosion. On May 5, 1998 a radio burst was detected from a different part of the sky that also suggests a supernova explosion with 100 times more energy than is typical. Dubbed "hypernovae," these events might represent the link between supernovae and gamma-ray bursts. It may be that typical supernovae yield neutron stars, while hypernovae produce black holes. For more information, see Science News, May 9, 1998 and May 23, 1998; see also Sky and Telescope, September, 1998, p. 24.

The infrared camera, NICMOS, on board the Hubble Space Telescope, may have imaged an extrasolar protoplanet for the first time. Located in the constellation of Taurus, the planet appears to be escaping from a newborn binary star system. Given the low luminosity of the object, it is unlikely to be a dim star, but a planet having a mass of several Jupiters. The announcement of the detection was released on May 28, 1998.

Tornados have been discovered on the surface of the Sun by the SOHO spacecraft. The announcement was made on April 28, 1998. These solar tornadoes, which can be larger than the entire earth, are likely to provide important information about the solar wind and the solar corona.

Another Sun-observing spacecraft, NASA's Transition Region and Coronal Explorer (TRACE) , was launched on April 1, 1998 and is returning spectacular images, including this FeIX line image of a solar prominence, released on April 22, 1998.

In April 1998, the Space Telescope Science Institute announced that Hubble has recently identified a very young, hot white dwarf that was formed from a 7.6 solar mass progenitor. This places a new lower limit on the mass of main-sequence stars that will form white dwarfs rather than detonating as a supernovae. The white dwarf was discovered in the stellar cluster NGC 1818, which is a member of the Large Magellanic Cloud. Details of the discovery are scheduled to be published in the Astrophysical Journal Letters.

The Solar and Heliospheric Observatory (SOHO) has detected tens of thousands of magnetic field bundles that connect the visible "surface" of the Sun to the corona. This "magnetic carpet" appears to be responsible for transporting the energy into the corona that is necessary to maintain its >10⁶ K temperature. (See: Science News, November 8, 1997; Physics Today, March 1998, pp. 19-21.)

SOHO has also detected "plasma rivers" or "jet streams" below the surface of the Sun. These fluid flows are likely associated with the solar cycle. (See Scientific American.)

Recent evidence argues against an inverse correlation between sunspot number and the number of neutrinos received from the Sun (discussed in Section 11.3, pp. 429-430). The July 29, 1996 issue of Physics News Update contains the announcement of an article by Y. Fukuda et al. in Physical Review Letters, 26 August 1996. Further information on this topic can be found in an article by Guenther Walther in Physical Review Letters, 08 December 1997.

The latest information about the immediate surroundings of the Crab pulsar (Section 15.7, p. 616) may be found at the Space Telescope Science Institute. The right-hand frame of this image shows wisps that move away from the pulsar with a speed of 0.5c. The pulsar itself is the left of the pair of stars near the center of the frame. This view was obtained by the HST and was released in May 1996. [Courtesy of Jeff Hester and Paul Scowen (Arizona State University), and NASA.]

The existence of a brown dwarf has been confirmed. Gliese 229B has a mass of between 20 and 50 Jupiter masses (the lower limit for nuclear fusion is about 80 Jupiter masses). It was discovered by Tadashi Nakajima (Caltech) and colleagues at Mount Palomar and confirmed by the Hubble Space Telescope. This discovery makes the comment in footnote 6 of Chapter 20 (p. 826) out of date! (Refs: Sky and Telescope, January 1996, p. 11, and June 1996, p. 24.)

An image of new-born stars emerging from globules in the Eagle Nebula (M16) was obtained by the Hubble Space Telescope and released to the public in November 1995. The EGGs (evaporating gaseous globules) of M16 are located in Serpens, approximately 2000 pc away. For background on the interstellar medium, star formation, and HII regions, see Chapter 12. [Courtesy of Jeff Hester and Paul Scowen (Arizona State University), and NASA.]

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Last modified September 12, 2005.