What is the name of the new exoplanet discovered by NASA Transiting Exoplanet Survey Satellite (TESS)?

Introduction / Context:
This question belongs to the space science and current affairs segment. NASA Transiting Exoplanet Survey Satellite, abbreviated as TESS, is a space telescope designed to search for planets outside the solar system by monitoring the brightness of nearby stars. When TESS identifies a new exoplanet, astronomers assign a specific designation to it, which often becomes the subject of exam questions.

Given Data / Assumptions:

• The discovery is attributed to NASA TESS mission.
• The options are similar looking alphanumeric codes representing possible planet designations.
• Only one of these codes matches the official name of the discovered exoplanet.

Concept / Approach:
Exoplanet names usually follow a pattern linked to their host star. In this case, the star designation is HD 21749 and the planet is named HD21749b. The letter suffix often indicates the order of discovery around that star. The distractor options modify or remove parts of the code, so careful attention to the exact format is required to avoid mistakes.

Step-by-Step Solution:
Step 1: Recognise that TESS discoveries typically have designations starting with a catalog name such as HD followed by digits and a letter. Step 2: Examine each option to see which one fits this format correctly. Step 3: Identify HD21749b as the correct combination of catalog star number and planet suffix. Step 4: Notice that D21749b and H21749b are missing letters or use incorrect ones, and 21749b lacks the HD prefix. Step 5: Select HD21749b as the correct official designation.

Verification / Alternative check:
Space news articles describing TESS discoveries mention that HD21749b is a sub Neptune exoplanet orbiting a nearby star. The full name includes both the HD catalog prefix and the lower case letter b. The other codes do not appear in official mission documentation or astronomy databases, which confirms that HD21749b is the correct label.

Why Other Options Are Wrong:
D21749b: Missing the initial H, so it does not match the actual star catalog name.
H21749b: Drops the letter D, which again makes the designation incorrect.
21749b: Omits the HD prefix entirely, so it is not the standard astronomical naming format.

Common Pitfalls:
Candidates may quickly glance at the options and misread the letters, especially when they appear in a crowded question paper. Since the codes look very similar, not paying close attention to each character can lead to incorrect selection. Developing the habit of reading technical codes carefully is important for space science questions of this kind.

Final Answer:
The new exoplanet discovered by NASA TESS is named HD21749b.