Consider the following pairs: Objects in space-Description 1) Cepheids -Giant clouds of dust and gas in space 2) Nebulae -Stars which brighten and dim periodically [2023]

Consider the following pairs:

Objects in space	Description
Cepheids	Giant clouds of dust and gas in space
Nebulae	Stars which brighten and dim periodically
Pulsars	Neutron stars that are formed when massive stars run out of fuel and collapse

How many of the above pairs are correctly matched?

Only one
Only two
All three
None

Explanation

Pair 1 is incorrect

Cepheids, also called Cepheid Variables, are stars which brigthen and dim periodically. This behaviour allows them to be used as cosmic yardsticks out to distances of a few tens of millions of light-years.
Cepheids are reasonably abundant and very bright. Astronomers can identify them not only in our Galaxy but also in other nearby galaxies. They are very special variable stars because their period (the time they take to brighten, dim and brighten again) is regular (that is, does not change with time), and a uniform function of their brightness. That is, there is a relation between the period and brightness such that once the period is known, the brightness can be inferred.

Additional Information

To understand Cepheid Variables better, look at the example given below:
Using two of the world’s most powerful space telescopes — NASA’s Hubble and ESA’s Gaia — astronomers have made the most precise measurements to date of the universe’s expansion rate.
This is calculated by gauging the distances between nearby galaxies using special types of stars called Cepheid variables as cosmic yardsticks. By comparing their intrinsic brightness as measured by Hubble with their apparent brightness as seen from Earth, scientists can calculate their distances. Gaia further refines this yardstick by geometrically measuring the distances to Cepheid variables within our Milky Way galaxy.
This allowed astronomers to more precisely calibrate the distances to Cepheids that are seen in outside galaxies.

Astronomical diagram illustrating Hubble and Gaia telescopes measuring Cepheid variable stars to determine cosmic distances. It features labeled telescopes, a dotted circular boundary, and galaxies, highlighting the method of distance measurement between Earth and distant stars

Pair 2 is incorrect

Outlined below are the steps involved in a star’s evolution, from its formation in a nebula to its death as a white dwarf or a neutron star.
- Nebula: a cloud of gas (mostly hydrogen and helium) and dust in space. Nebulae are the birthplaces of stars.
- Protostar: an early stage of a star formation where nuclear fusion is yet to begin.
- T Tauri Star: a young star still undergoing gravitational contraction; it represents an intermediate stage between a Protostar & a low-mass main sequence star.
- Main Sequence Star: E.g., Sun – full of life (nuclear fusion at the core is in full swing).
- Red Giant (in case of a small star) and Red Supergiant (in case of a large star).
- Planetary Nebula (in case of a small star) and Supernova (in case of a large star).
- White dwarf (in case of a small star) and Neutron Star or Black Hole (in case of a large star).

Diagram illustrating stellar evolution stages from protostar to final outcomes, including neutron star, black hole, and white dwarf. It features labeled color-coded illustrations of nebula, protostar, large and small stars, red supergiant, red giant, supernova, planetary nebula, and white dwarf, with explanatory text on nuclear fusion processes, star size effects, and triggers for supernova events

Pair 3 is correct

Neutron stars are formed when a massive star runs out of fuel and collapses. The very central region of the star – the core – collapses, crushing together every proton and electron into a neutron.
If the core of the collapsing star is between about 1 and 3 solar masses, these newly-created neutrons can stop the collapse, leaving behind a neutron star. (Stars with higher masses will continue to collapse into stellar-mass black holes.)
Most neutron stars are observed as pulsars. Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds.
Pulsars have very strong magnetic fields, which funnel jets of particles out along the two magnetic poles.

Answer: (a) Only one; Difficulty Level: Medium

2023, PYQs