scholarly journals Alternative standard frequencies for interstellar communication

2017 ◽  
Vol 18 (3) ◽  
pp. 209-210
Author(s):  
C. Sivaram ◽  
Kenath Arun ◽  
O. V. Kiren
Keyword(s):  
Neutral Hydrogen ◽  
Hydrogen Line ◽  
Hyperfine Transition ◽  
Standard Scale ◽  
Radio Signals ◽  
Interstellar Communication ◽  
Pioneer 10

AbstractThe 21 cm hydrogen line is considered a favourable frequency by the SETI programme in their search for signals from potential extraterrestrial (ET) civilizations. The Pioneer plaque, attached to the Pioneer 10 and Pioneer 11 spacecraft, portrays the hyperfine transition of neutral hydrogen and used the wavelength as a standard scale of measurement. Although this line would be universally recognized and is a suitable wavelength to look for radio signals from ETs, the presence of ubiquitous radiation from galactic hydrogen could make searches a little difficult. In this paper, we suggest several alternate standard frequencies, which are free of interference from atomic or molecular sources and is independent of any bias.

scholarly journals Probing the high-z IGM with the hyperfine transition of 3He+

2020 ◽  
Vol 497 (1) ◽  
pp. 572-580 ◽  
Author(s):  
Shivan Khullar ◽  
Qingbo Ma ◽  
Philipp Busch ◽  
Benedetta Ciardi ◽  
Marius B Eide ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Signal To Noise Ratio ◽  
Neutral Hydrogen ◽  
Noise Power ◽  
Large Collection ◽  
X Ray ◽  
Hyperfine Transition ◽  
The One ◽  
X Ray Binaries ◽  
Insight Into

ABSTRACT The hyperfine transition of 3He+ at 3.5 cm has been thought as a probe of the high-z IGM, since it offers a unique insight into the evolution of the helium component of the gas, as well as potentially give an independent constraint on the 21 cm signal from neutral hydrogen. In this paper, we use radiative transfer simulations of reionization driven by sources such as stars, X-ray binaries, accreting black holes and shock heated interstellar medium, and simulations of a high-z quasar to characterize the signal and analyse its prospects of detection. We find that the peak of the signal lies in the range ∼1–50 μK for both environments, but while around the quasar it is always in emission, in the case of cosmic reionization a brief period of absorption is expected. As the evolution of He ii is determined by stars, we find that it is not possible to distinguish reionization histories driven by more energetic sources. On the other hand, while a bright QSO produces a signal in 21 cm that is very similar to the one from a large collection of galaxies, its signature in 3.5 cm is very peculiar and could be a powerful probe to identify the presence of the QSO. We analyse the prospects of the signal’s detectability using SKA1-mid as our reference telescope. We find that the noise power spectrum dominates over the power spectrum of the signal, although a modest signal-to-noise ratio can be obtained when the wavenumber bin width and the survey volume are sufficiently large.

scholarly journals Sensitive Search for HI in E and SO galaxies

1983 ◽  
Vol 100 ◽  
pp. 305-306
Author(s):  
Norbert Thonnard
Keyword(s):  
Neutral Hydrogen ◽  
Optical Image ◽  
Type I ◽  
Hydrogen Line ◽  
Upper Limit

Do elliptical and SO galaxies in which type I supernovae (SNI) were detected contain more gas than those without SNI detections? Thirteen E and SO galaxies in the Virgo and Pegasus I clusters, seven with SNI detections and six without, were mapped well beyond the optical image at the 21-cm neutral hydrogen line. No HI was detected. In Virgo, the upper limit to MMI/LB is between 0.0005 and 0.0024.

The recognition of extraterrestrial intelligence

1975 ◽  
Vol 189 (1095) ◽  
pp. 143-153 ◽  
Keyword(s):  
Prime Numbers ◽  
Microwave Spectrum ◽  
Nearby Star ◽  
Auto Correlation ◽  
The Earth ◽  
Clear Sign ◽  
Radio Signals ◽  
Correlation Techniques ◽  
Difficult Subjects ◽  
Pioneer 10

A necessary but not sufficient condition for the recognition of extra-­terrestrial intelligence is a significant departure from thermodynamic equilibrium. This can be discerned clearly in the inverse problem of the detection of terrestrial intelligence from a distance. Photography of the Earth in reflected sunlight reveals no clear sign of life until 100 m resolution is achieved, at which point the agricultural and urban reworking of the Earth’s surface in rectangular arrays first becomes obvious. This pattern is however detectable only over interplanetary distances. Mars exhibits no such patterns. The departure from radiative equilibrium - represented by radio, television and radar technology - in the microwave spectrum of the Earth is by contrast easily detectable over inter­stellar distances. Even with a technology no more advanced than our own, a civilization on a planet of a nearby star could easily determine, by auto-correlation techniques, the artificiality of these radio signals. Intentional interstellar radio messages should be detected and decrypted far more readily. Possible message contents for interstellar discourse of a modulated signal at any accessible frequency include (1) m -dimensional imagery represented by the transmission of numbers which are the products of m prime numbers; and (2) the use of a common mathematics, physics or astronomy to convey a range of information on more difficult subjects. The only direct attempts to date to communicate with extra­-terrestrial intelligence - the plaques aboard the Pioneer 10 and 11 space­-craft - are discussed briefly.

scholarly journals Hydrogen Content of Young Stellar Clusters. I. Methods of Observation and Reduction

1973 ◽  
Vol 26 (6) ◽  
pp. 829 ◽  
Author(s):  
HM Tovmassian
Keyword(s):  
Radio Telescope ◽  
Hydrogen Content ◽  
Data Reduction ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
Continuum Emission ◽  
Stellar Clusters ◽  
Hydrogen Line ◽  
Galactic Clusters

Observations of 16 open galactic clusters in their continuum emission and at the neutral hydrogen line have been made with the Parkes 64 m radio telescope in an attempt to determine the total amount of hydrogen gas associated with them. In this, the first of a series of five papers, the observing procedure and the method of data reduction are described.

scholarly journals Contribution to the study of the distribution of neutral hydrogen in the region 230° ≤ lII ≤ 280°

1970 ◽  
Vol 38 ◽  
pp. 157-163
Author(s):  
D. Goniadzki ◽  
A. Jech
Keyword(s):  
Radio Astronomy ◽  
Neutral Hydrogen ◽  
Hydrogen Line ◽  
Sky Survey

A sky survey of the 21 cm hydrogen line has been made with the 100-foot Radiotelescope of the I.A.R.-C.I.W. Radio Astronomy Station in the region 230° ≤ lII ≤ 280°, −15° ≤ bII ≤ −3°.We study the distribution of the local hydrogen and that in the Orion, Intermediate and Perseus arms. We find a new structure that starts at lII = 265°. We also study the concentrations which lie far below the plane; some of them seem to be related to Lindblad's G arm.

scholarly journals High-resolution observations of the galactic centre at 1420 Mc/s in the continuum and in the neutral hydrogen line

1964 ◽  
Vol 20 ◽  
pp. 191-195
Author(s):  
N. F. Ryzhkov ◽  
T. M. Egorova ◽  
I. V. Gossachinsky ◽  
N. V. Bystrova
Keyword(s):  
Neutral Hydrogen ◽  
Continuum Emission ◽  
Galactic Centre ◽  
Hydrogen Line ◽  
Sagittarius A ◽  
The Mean ◽  
The Right ◽  
Right Ascension ◽  
Large Pulkovo Radio Telescope ◽  
The Continuum

The large Pulkovo radio telescope has a beamwidth of 7 min of arc in R.A. at a frequency of 1420 Mc/s. The continuum emission from the source Sagittarius A was measured with a bandwidth of 5 Mc/s. The mean drift curve is shown in Figure 1. It can be separated into components according to Drake (1959) as indicated in the figure. The galactic ridge is also shown. The right ascension, the antenna temperature, the observed angular diameter, and the flux density of each component are given in Table 1. The errors given in the table can be somewhat higher in the case of components 2 and 3 because of the difficulties of separating them. The calibration of the antenna and receiver was made using the flux densities of the sources IAU 19N4A, 05N2A, 05S0A, and 18S1A according to Westerhout (1958) with the corrections given by Altenhoff et al. (1960). The atmospheric extinction at λ = 21 cm was taken from these works as well.

scholarly journals 21 Cm Hydrogen-Line Survey Of The Large Magellanic Cloud Ii. Distribution And Motions Of Neutral Hydrogen

1966 ◽  
Vol 19 (3) ◽  
pp. 343 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Neutral Hydrogen ◽  
Hii Regions ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Radial Velocities ◽  
Hydrogen Line ◽  
Ob Stars ◽  
Mean Diameter ◽  
Line Survey

The 21 cm hydrogen-line data from a survey of the Large Magellanic Oloud with a 14',5 aerial beam have been simplified into distributions of intensities and radial velocities at profile peaks. Fifty-two large HI complexes of mean diameter 575 pc, density I hydrogen atom per cm3, and mass 4 X 106M o have been delineated. The study of the correlation between optically visible Population I components, such as HII regions and supergiant OB stars, and the neutral hydrogen has been greatly extended.

scholarly journals A Low Resolution Hydrogen-line Survey of the Magellanic System. II. Interpretation of Results

1963 ◽  
Vol 16 (4) ◽  
pp. 570 ◽  
Author(s):  
JV Hindman ◽  
FJ Kerr ◽  
RX McGee
Keyword(s):  
Neutral Hydrogen ◽  
Magellanic Clouds ◽  
Wide Area ◽  
Hydrogen Line ◽  
Low Resolution ◽  
Double Peaks ◽  
Line Survey ◽  
System 1 ◽  
Small Cloud ◽  
Magellanic System

A low resolution (202) survey of the neutral hydrogen in the Magellanic Clouds has produced two important additions to our knowledge of the system. (1) A bridge of gas between the Small and Large Cloud has been mapped. (2) The Small Cloud profiles show double peaks over a wide area, suggesting the possibility of two substantially separate masses of gas.

scholarly journals Conformal Cosmology and the Pioneer Anomaly

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Gabriele U. Varieschi
Keyword(s):  
Cosmological Parameters ◽  
Hubble Constant ◽  
Conformal Gravity ◽  
Conformal Cosmology ◽  
Pioneer Anomaly ◽  
Radio Signals ◽  
Anomalous Acceleration ◽  
Near Future ◽  
Pioneer 10

We review the fundamental results of a new cosmological model, based on conformal gravity, and apply them to the analysis of the early data of the Pioneer anomaly. We show that our conformal cosmology can naturally explain the anomalous acceleration of the Pioneer 10 and 11 spacecrafts, in terms of a local blueshift region extending around the solar system and therefore affecting the frequencies of the navigational radio signals exchanged between Earth and the spacecraft. By using our model, we explain the numerical coincidence between the value of the anomalous acceleration and the Hubble constant at the present epoch and also confirm our previous determination of the cosmological parameters γ∼10−28 cm−1 and δ~10-4–10-5. New Pioneer data are expected to be publicly available in the near future, which might enable more precise evaluations of these parameters.

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