Astronomers!

[gmat_perfect]

An international team of astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter, the solar system's largest planet.

(A) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter
(B) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres that are at an estimated 5 to 15 times Jupiter's mass
(C) astronomers is working at telescopes in the Canary Islands and Spain, having detected at least 18 huge gas spheres that are estimated at 5 to 15 times the mass of Jupiter
(D) astronomers, working at telescopes in the Canary Islands and Spain, and has detected at least 18 huge gas spheres estimated at 5 to 15 times the mass of Jupiter
(E) astronomers, working at telescopes in the Canary Islands and Spain, has detected at least 18 huge gas spheres they have estimated as being 5 to 15 times Jupiter's mass

[spoiler]OA:A[/spoiler]

[kvcpk]

Jupiter should be in the end of the underlined portion.
B,E out.
In C, "having detected atleast" is wrong.

An internation team of astronomers, and has detected
is wrong in D.

pick A

[reply2spg]

I am not sure what question you have, but this is one another simple question. Answer is A.

Non-underlined part 'the solar system's largest planet' should modify Jupitor. B and E are out.
C - red part looks awkward
D - red part is not correct.

That leaves only A

An international team of astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter, the solar system's largest planet.

(A) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter
(B) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres that are at an estimated 5 to 15 times Jupiter's mass
(C) astronomers is working at telescopes in the Canary Islands and Spain, having detected at least 18 huge gas spheres that are estimated at 5 to 15 times the mass of Jupiter
(D) astronomers, working at telescopes in the Canary Islands and Spain, and has detected at least 18 huge gas spheres estimated at 5 to 15 times the mass of Jupiter
(E) astronomers, working at telescopes in the Canary Islands and Spain, has detected at least 18 huge gas spheres they have estimated as being 5 to 15 times Jupiter's mass

[spoiler]OA:A[/spoiler]

[Haaress]

An international team of astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter, the solar system's largest planet.

The question focuses on Subj - verb and Modifier.

A team ......has
Jupiter, the solar system's largest planet.

Only A has the correct S-V as well as the correct modifier.

(A) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter
(B) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres that are at an estimated 5 to 15 times Jupiter's mass
(C) astronomers is working at telescopes in the Canary Islands and Spain, having detected at least 18 huge gas spheres that are estimated at 5 to 15 times the mass of Jupiter
(D) astronomers, working at telescopes in the Canary Islands and Spain, and has detected at least 18 huge gas spheres estimated at 5 to 15 times the mass of Jupiter
(E) astronomers, working at telescopes in the Canary Islands and Spain, has detected at least 18 huge gas spheres they have estimated as being 5 to 15 times Jupiter's mass

[reply2spg]

I am not sure what question you have, but this is one another simple question. Answer is A.

Non-underlined part 'the solar system's largest planet' should modify Jupitor. B and E are out.
C - red part looks awkward
D - red part is not correct.

That leaves only A

An international team of astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter, the solar system's largest planet.

(A) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter
(B) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres that are at an estimated 5 to 15 times Jupiter's mass
(C) astronomers is working at telescopes in the Canary Islands and Spain, having detected at least 18 huge gas spheres that are estimated at 5 to 15 times the mass of Jupiter
(D) astronomers, working at telescopes in the Canary Islands and Spain, and has detected at least 18 huge gas spheres estimated at 5 to 15 times the mass of Jupiter
(E) astronomers, working at telescopes in the Canary Islands and Spain, has detected at least 18 huge gas spheres they have estimated as being 5 to 15 times Jupiter's mass

[spoiler]OA:A[/spoiler]

[loveusonu]

Clear A.
But no question is simple, keep asking!!

A great idea is always generated from a simple brain!

[blaster]

An international team of astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter, the solar system's largest planet.

(A) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter
(B) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres that are at an estimated 5 to 15 times Jupiter's mass
(C) astronomers is working at telescopes in the Canary Islands and Spain, having detected at least 18 huge gas spheres that are estimated at 5 to 15 times the mass of Jupiter
(D) astronomers, working at telescopes in the Canary Islands and Spain, and has detected at least 18 huge gas spheres estimated at 5 to 15 times the mass of Jupiter
(E) astronomers, working at telescopes in the Canary Islands and Spain, has detected at least 18 huge gas spheres they have estimated as being 5 to 15 times Jupiter's mass

[spoiler]OA:A[/spoiler]

Jupiter must modify the last part of sentence. That's why eliminating BE .
In C astronomers is working is not correct
In D astronomers, who is working is much better that in choice,in my opinion. also sentence not correctly conjuncted between each other.That's why i eliminated it
so only A remains.

[gmat_perfect]

Thanks buddies.

[nikhilkatira]

IDIOM "estimated to be "

only A remains