Question

1. if objects cannot be seen from earth with optical telescopes, how are astronomers able to study them?
2. explain how the new, globular cluster was spotted.
3. compare observations using infrared radiation and observations that rely on visible light

Explanation:

Question 1

Astronomers use non - optical telescopes (like radio, infrared, X - ray, etc.) or space - based telescopes (e.g., Hubble) to study objects not visible with optical telescopes from Earth. These telescopes detect different types of electromagnetic radiation emitted by celestial objects. For example, radio telescopes detect radio waves, which can pass through interstellar dust that blocks visible light.

Globular clusters were likely spotted using advanced telescopes (optical or non - optical like infrared) that can detect the light (or other electromagnetic radiation) from the stars within them. Astronomers analyze the light's properties (e.g., intensity, spectrum) to identify the cluster. Also, techniques like astrometry (measuring star positions) and photometry (measuring star brightness) help in detecting the clustered stars' pattern.

• Visible Light Observations: Depend on light in the visible spectrum (400 - 700 nm). Good for seeing stars/objects with strong visible emission, but blocked by interstellar dust/gas. Shows surface details of objects (e.g., Sun's surface).
• Infrared Radiation Observations: Detects longer - wavelength (700 nm - 1 mm) radiation. Can penetrate interstellar dust/gas, so useful for seeing objects behind dust (e.g., star - forming regions). Detects cooler objects (e.g., brown dwarfs, dust clouds) that emit little visible light.
• Comparison: Visible light shows surface details of hot, unobscured objects; infrared shows obscured/cool objects and penetrates dust. Infrared has lower spatial resolution than visible in some cases, but reveals hidden structures.

Answer:

Astronomers use non - optical telescopes (e.g., radio, infrared, X - ray telescopes) or space - based telescopes (like Hubble) that detect other forms of electromagnetic radiation (e.g., radio waves, infrared, X - rays) emitted by celestial objects. These radiations can pass through interstellar matter that blocks visible light, allowing study of such objects.

Question 2