What is astrometry? what is astrometry? measuring the positions of stars on the sky using metric units for distance (e. g. meters rather than light years) measuring distances to stars measuring the velocities of stars via the doppler effect searching for planets around stars

Explanation:

It is a branch of astronomy wherein measurements of the positions and movements of celestial bodies are precisely are made.  

For the measurement, minute wobbling of the position of the body is detected. When the shift is detected periodically, the astronomers  come to know that the star is orbited by a planet.  

Also, basic data about the properties of the stars can be collected using this method.

1 a

2 b

3 b

4 d

5 d

6 d

explanation:

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.