at great speeds

[joham]

This image was taken by the European Space Agency's Faint-Object Camera aboard HST. It shows the very center of a nearby binary (double) star system, known to astronomers as R Aquarii, where one star has recently undergone an outburst. This has thrust hot gas into space at great speeds, up to hundreds of thousands of kilometers per hour, which can be seen streaming away.

This sentence is taken from the COCA. My question is why the plural 'speeds' is used here. We always have 'at great/high/top/high speed' in our dictionaries.

Could I ask native speakers to help me please? Thank you in advance.

[David L.]

speed (= velocity) is a constant rate of movement.

The gas is moving at rates of "up to hundreds of thousands of kilometers per hour" - that is, the gas is not moving at a constant speed. The velocity (speed) varies for some reason, and they are indicating that by using the plural "speeds".

Is the COCA you refer to :Comprehensive Outcomes of Cognitive Assessment and one of the tests they have?

[joham]

speed (= velocity) is a constant rate of movement.

The gas is moving at rates of "up to hundreds of thousands of kilometers per hour" - that is, the gas is not moving at a constant speed. The velocity (speed) varies for some reason, and they are indicating that by using the plural "speeds".

Is the COCA you refer to :Comprehensive Outcomes of Cognitive Assessment and one of the tests they have?

Thank you, David. I got it. To your question:
No. It's Mark Davies' THE CORPUS OF CONTEMPORARY AMERICAN ENGLISH (COCA)