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Artist's illustration of a gamma-ray burst. Credit: Aurore Simonnet/Sonoma State University, NASA Education & Public Outreach
Among all electromagnetic waves, gamma rays have the shortest wavelengths (less than 0.01 nm), highest frequencies (around 1019 Hz), and, consequently, the highest energies (at least 100 keV). They’re even more energetic compared to their more popular cousins, X-rays.
Most of the gamma radiation observed on the surface of the Earth come from radioactive substances. Due to the wave-particle duality of matter, gamma rays (which are actually electromagnetic waves) are also known as gamma particles. These particles, released during a transition of a radioactive nucleus from a more excited state to a lesser one, bear the energy difference between the two states.
These energy differences are very large, typical of the energies exhibited during interactions in the nucleus. As a consequence, the gamma particles carrying this released energy are very much capable of wreaking havoc on atoms they collide with, rendering the atoms ionized. Thus, like X-rays, gamma rays are considered ionizing radiation.
Gamma particles are actually photons. That means they have zero mass. Despite this, they carry a lot of momentum. Classical physics tells us that this cannot be possible. However, because of the extremely high speeds that these gamma particles have the moment they are released from the nucleus, relativistic effects have to be considered.
One consequence of which is the ability to acquire momentum despite having zero mass. That is why these massless gamma particles can still collide and dislodge loosely attached atom members like electrons. This is precisely the reason why gamma rays, like X-rays, are harmful to the body. You can protect yourself from them though. Gamma rays can be stopped by high density shielding materials like lead. Reminds you of Superman’s weakness, kryptonite, doesn’t it?
In astronomy, gamma rays play an important role in scientists’ understanding of the goings on in galaxies far far away. Gamma ray detection has to be performed at high altitudes since much of what enters the Earth’s atmosphere is dissipated through collisions with particles found there.
The detection of gamma rays coming from outer space confirms the presence of cataclysmic events like supernova explosions. Hence, it is safe to conclude that the events that take place in other parts of the Universe are characterized by high-energy explosions, collisions, and the like.
Through these extremely high-energy electromagnetic waves, we have learned a lot about many of the entities that we have never seen like supernovae, black holes, neutron stars, pulsars, and other unidentified sources.
You can read more about gamma rays here in Universe Today. Want to learn more about the solved mystery of gamma ray distribution in the Milky Way? We’ve also written about how ‘dark’ gamma-ray bursts has shed light on star formation.
There’s more about it at NASA. Here are a couple of sources there:
Here are two episodes at Astronomy Cast that you might want to check out as well:
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