The distance between starts is usually measured in
a. light-years
b. kilometers
c. astronomical units
d. miles

physical properties used to measure stars include
a. mass
b. brightness
c. size
d. all of the above

an h-r diagram
a. is a map of the positions of the stars
b. graphs stars according to their size and distance
c. lists every known star
d. graphs a sample of stars according to surface temperature an absolute brightness

the apparent change in position of an object with respect to a distant background is
a. light-year
b. parallax
c. luminosity
d. absorption

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases . this process does not change the mass number.

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as -decay. in this the mass number remains same.

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

momentum of soft ball three times less than baskey ball