Which radio telescope array was recently used by astronomers to discover approximately 300000 new galaxies in a large sky survey of the universe?

Introduction / Context:
Astronomy often appears in general knowledge questions, particularly when major discoveries are made about our universe. One such discovery involved the identification of around 300000 previously unknown galaxies using a powerful radio telescope array. This question asks you to identify which telescope or observatory was responsible for that discovery, with options representing several famous astronomical instruments.

Given Data / Assumptions:

• The discovery was of approximately 300000 new galaxies.
• The observation was carried out using a radio telescope array, not an optical or purely space based observatory.
• The options are LOFAR, Gemini Observatory, Chandra X-ray Observatory, and Kepler Space Telescope.
• We assume the question refers to a widely reported sky survey that mapped low frequency radio emissions from distant galaxies.

Concept / Approach:
LOFAR, which stands for Low Frequency Array, is a large network of radio telescopes spread across several European countries. It is designed to observe the universe at low radio frequencies, revealing phenomena such as distant galaxies and cosmic structures that are difficult to detect at other wavelengths. The discovery of roughly 300000 new galaxies was attributed to LOFAR's sensitive sky survey. In contrast, Gemini is an optical/infrared observatory, Chandra focuses on X rays, and Kepler was dedicated to exoplanet searches. The correct approach is to associate the large number of newly discovered galaxies in the radio band with LOFAR.

Step-by-Step Solution:
Step 1: Note that the question refers to a discovery made using a radio telescope array, which narrows the field.Step 2: Recognise that LOFAR is specifically a low frequency radio telescope network, whereas Gemini and Kepler work primarily in optical/infrared, and Chandra in X rays.Step 3: Recall news reports describing how LOFAR mapped the sky and identified around 300000 new galaxies based on their radio emissions.Step 4: Compare this information with the options and confirm that LOFAR fits the description exactly.Step 5: Select LOFAR as the correct answer.

Verification / Alternative check:
Verification can be done by remembering that LOFAR's surveys are often presented as revealing a “radio universe” full of previously unseen galaxies. Kepler, by contrast, is famous for discovering exoplanets by observing dips in starlight, not for cataloguing galaxies. The Gemini Observatory provides high resolution images of specific objects rather than conducting massive low frequency surveys, and Chandra focuses on high energy phenomena like black holes and supernova remnants. This confirms that LOFAR is the instrument used to discover roughly 300000 new galaxies in the reported survey.

Why Other Options Are Wrong:
Option B (Gemini Observatory) is incorrect because, although it is a powerful optical/infrared facility, it was not the telescope responsible for this specific radio galaxy survey. Option C (Chandra X-ray Observatory) studies X ray sources such as black holes and hot gas, not low frequency radio emissions used to find these galaxies. Option D (Kepler Space Telescope) concentrated on detecting planets around other stars, not on mapping galaxies on a large scale.

Common Pitfalls:
Some candidates may recognise Gemini, Chandra, or Kepler as famous names in astronomy and choose them without considering the wavelength and survey type mentioned in the question. Another pitfall is to overlook the clue that this was a “radio telescope array,” which strongly points to LOFAR. A careful reading of the question and basic familiarity with what each observatory does will lead you to the correct option.

Final Answer:
The correct answer is LOFAR, the Low Frequency Array radio telescope network that helped discover around 300000 new galaxies.