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1.
Nature ; 601(7891): 49-52, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34987214

RESUMO

Magnetic fields have an important role in the evolution of interstellar medium and star formation1,2. As the only direct probe of interstellar field strength, credible Zeeman measurements remain sparse owing to the lack of suitable Zeeman probes, particularly for cold, molecular gas3. Here we report the detection of a magnetic field of +3.8 ± 0.3 microgauss through the H I narrow self-absorption (HINSA)4,5 towards L15446,7-a well-studied prototypical prestellar core in an early transition between starless and protostellar phases8-10 characterized by a high central number density11 and a low central temperature12. A combined analysis of the Zeeman measurements of quasar H I absorption, H I emission, OH emission and HINSA reveals a coherent magnetic field from the atomic cold neutral medium (CNM) to the molecular envelope. The molecular envelope traced by the HINSA is found to be magnetically supercritical, with a field strength comparable to that of the surrounding diffuse, magnetically subcritical CNM despite a large increase in density. The reduction of the magnetic flux relative to the mass, which is necessary for star formation, thus seems to have already happened during the transition from the diffuse CNM to the molecular gas traced by the HINSA. This is earlier than envisioned in the classical picture where magnetically supercritical cores capable of collapsing into stars form out of magnetically subcritical envelopes13,14.

2.
Science ; 268(5219): 1879-83, 1995 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-11536723

RESUMO

Jupiter's nonthermal microwave emission, as measured by a global network of 11 radio telescopes, increased dramatically during the Shoemaker-Levy 9 impacts. The increase was wavelength-dependent, varying from approximately 10 percent at 70 to 90 centimeters to approximately 45 percent at 6 and 36 centimeters. The radio spectrum hardened (flattened toward shorter wavelengths) considerably during the week of impacts and continued to harden afterward. After the week of cometary impacts, the flux density began to subside at all wavelengths and was still declining 3 months later. Very Large Array and Australia Telescope images of the brightness distribution showed the enhancement to be localized in longitude and concentrated near the magnetic equator. The evidence therefore suggests that the increase in flux density was caused by a change in the resident particle population, for example, through an energization or spatial redistribution of the emitting particles.


Assuntos
Elétrons , Júpiter , Meteoroides , Micro-Ondas , Fenômenos Astronômicos , Astronomia , Poeira Cósmica , Interações de Partículas Elementares , Análise Espectral
3.
Nature ; 226(5245): 529-31, 1970 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-16057371

RESUMO

This paper reports further detailed measurements of strong radio pulses from the pulsar NP 0532 in the Crab nebula, recorded at Arecibo.

4.
Nature ; 225(5232): 527-8, 1970 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-16056588
5.
Nature ; 228(5276): 1074, 1970 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-16058787
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