A new study from the SETI Institute shows that alien signals may be harder to find. However, the reason is not that they are missing. Instead, the signals can become scrambled by their own stars. Turbulentturbulent/ˈtɜːrbjələnt/L2混乱的；动荡的；狂暴的moving in a very rough, violent, or uncontrolled way plasmaplasma/ˈplæzmə/L2等离子体a gas-like state of matter made of charged particles, found in stars and lightning and stellar storms spread the signal across a wider range of frequenciesfrequencies/ˈfriːkwənsiz/L2频率（复数）the number of times a wave (like a radio wave) repeats in one second. This happens before the signals even leave the star system, so alien messages may have already reached Earth without us noticing.
Also, researchers studied radio signals from spacecraftspacecraftL1Kapal luar angkasaa craft capable of traveling in outer space in our solar system. They measured how plasma from the Sun can change narrow signals. Then they used this data to predict the effect around other stars. The researchers used data from solar system probes to calibratecalibrate/ˈkælɪbreɪt/L2校准；标定to check and adjust a measuring instrument so that it gives accurate results their measurements. 'If a signal gets broadened by its own star's environment, it can slip below our detection thresholds,' said Dr. Vishal Gajjar, lead author.
M-dwarf stars are the most common stars in the Milky Way. They make up about 75% of all stars. These stars are especially likely to broadenbroaden/ˈbrɔːdən/L2加宽；扩大to make something wider or more spread out alien signals. Scientists now have a better way to predict which stars might hide alien signals, as the study provides a new framework for estimating signal broadening. As a result, future searches should look for wider signals, not just very narrow ones.
