Related Experiment Video
Updated: Jul 12, 2026
11:38
Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment
Published on: December 3, 2019
Deceleration of interstellar hydrogen at the heliospheric interface
Science (New York, N.Y.)
|May 21, 1993
Summary
Neutral hydrogen from the local interstellar cloud slows down at the solar system
Area of Science:
- Astronomy and Astrophysics
- Interstellar Medium
- Heliospheric Physics
Background:
- High-resolution stellar spectra reveal absorption lines from the local interstellar cloud.
- This cloud moves at 26 km/s relative to the Sun, aligning with the interstellar wind.
- Previous measurements indicated differing velocities for neutral hydrogen and helium within the solar system.
Purpose of the Study:
- To investigate the velocities of neutral hydrogen and helium from the local interstellar cloud within the solar system.
- To determine the interaction of interstellar material with the heliospheric interface.
- To constrain the density of the interstellar plasma and the location of the heliospheric shock.
Main Methods:
- Analysis of high-resolution spectra from nearby stars to study interstellar cloud material.
- Utilizing data from the Ulysses spacecraft for neutral helium drift measurements.
- Employing the Hubble Space Telescope's High-Resolution Spectrograph for new hydrogen emission line measurements.
Main Results:
- Neutral helium from the local interstellar cloud drifts at 26 km/s, consistent with the interstellar wind.
- Neutral hydrogen from the same cloud is decelerated to 20 km/s.
- This deceleration is attributed to charge-exchange with interstellar protons at the heliospheric interface.
Conclusions:
- Neutral hydrogen atoms are preferentially slowed by interactions with the heliospheric plasma.
- Neutral helium is unaffected by the plasma, indicating selective interaction.
- The observed deceleration implies an interstellar plasma density of 0.06–0.10 cm⁻³, placing the heliospheric shock within 100 AU of the Sun.
Related Concept Videos
01:19Escape Velocities of Gases
To escape the Earth's gravity, an object near the top of the atmosphere at an altitude of 100 km must travel away from Earth at 11.1 km/s. This speed is called the escape velocity. The temperature at which gas molecules attain the rms speed, which is equal to the escape velocity, can be estimated by using the equation for the average kinetic energy of the gas molecules. According to the kinetic theory of gas, the average kinetic energy of the gas molecules is proportional to its temperature.
03:40Hess's Law
There are two ways to determine the amount of heat involved in a chemical change: measure it experimentally, or calculate it from other experimentally determined enthalpy changes. Some reactions are difficult, if not impossible, to investigate and make accurate measurements for experimentally. And even when a reaction is not hard to perform or measure, it is convenient to be able to determine the heat involved in a reaction without having to perform an experiment.
01:21Schwarzschild Radius and Event Horizon
No object with a finite mass can travel faster than the speed of light in a vacuum. This fact has an interesting consequence in the domain of extremely high gravitational fields.
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape velocity with the...
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape velocity with the...
01:23IR Spectrum Peak Broadening: Hydrogen Bonding
The vibrational frequency of a bond is directly proportional to its bond strength. As a result, stronger bonds vibrate at higher frequencies, while weaker bonds vibrate at lower frequencies. The stretching vibration of the strong O–H bond in alcohols and phenols (very dilute solution or gas phase) appears as a sharp peak at 3600–3650 cm−1.
However, the extent of hydrogen bonding influences the observed stretching frequency and band broadening. Intermolecular or intramolecular hydrogen bonding...
However, the extent of hydrogen bonding influences the observed stretching frequency and band broadening. Intermolecular or intramolecular hydrogen bonding...
00:26Hydrogen Bonds
Hydrogen BondsHydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, and has a partial negative charge. The other is a hydrogen atom that has bonded with another electronegative atom and has a partial positive charge.Hydrogen Bonds Control the World!Because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom, such as oxygen or nitrogen, electrons in the bond are...
01:04Hydrogen Bonds
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another polar molecule, such as water (H2O), hydrogen fluoride (HF), or ammonia (NH3). The huge electronegativity difference between the H atom (2.1) and the atom to which it is bonded (4.0 for an F atom, 3.5 for an O atom, or 3.0 for an N atom), combined with the very small size of an H atom...