The answer is found in proper analysis of Gayathri Mantra.
Gayathri Mantra contains the seed of everything around and within us.
We all know of Gayathri Devi as source of Gayathri Mantra. But not many know of Vishwakarma, the male counterpart of Gayathri Devi. It appears the current teachings/teachers of today have omitted this other half required to complete the Gayathri Mantra.
Vishwakarma here is not the shilpy which is what you will get by google search. Vishwakarma here is the Brahman.
The gayathri mantra we know today is just the most basic (kindergarten) meter (akshara).
Akshara means algebra :)
Om Bhur Bhuvah Svah is not Gayathri.
It is kavach.
Tat Savitur Varenyam
Bhargo Devasya Dheemahi
Deeyo yona prachodayat .. is Gayathri
Gayathri Devi is energy. Vishwakarma Brahma is structure. Knowing how to channel energy is how you and me are here breathing. The lokas (worlds) you refer to is not what it is meant to be; forgivable blunder.
Pick up any (Shruti) text, loka is not refered to as planets which we all have come to understand. The correct sanskrit word is Patala. Patalas that are off spring from Vishwakarma Brahma are called Nakshatra.
So what is the meaning of Loka? The closest english word is "consciousness".
Western science do not accept the concept of consciousness. It is a para-science known as psychology. Until Jung lobbied for his research, the best cure for a mentally unstable person was lobotomy ( a surgical procedure of removing a part of your brain to cut off all sensory perception). This was the "science" that was practiced till 1980's.
"Consciousness" in sanskritic-meaning-english-reverse-translation would mean "Aura".
Aura is the energy field that is on the external of the body functioning as a cover (Kavach). The etymology of the english word "Cover" is a loan from the sanskrit word "Kavach".
How does Aura come about? It is emitted from the respective Chakras ( also refuted by western science)
How to emit Aura from Chakras? Through Gayatri Mantra upasana.
So, lokas means aura that is manifested from the chakras.
There are countless galaxies and universes mentioned in scriptures (Shruti), which today proved true, so Gayathri Mantra's reference is definitely not just about 7 planets. Also there are 9 planets that has effect on the human body according to Jyotish, one of the Vedanga.
So the above pointers further negates any remote reference that Gayathri Mantras reference of lokas means planets.
What it means is the 7 layers of aura which is being broadcasted from the sahasra chakra in harmony with the rest of the chakras. The surya namaskar is an activator of the pineal glad which produces ojas of which you put into vibratory motion in sandhyavandhan using Gayathri.
By the way, one anga of Gayathri Mantra upasana is Suryanamaskar. This is the Surya reference that the Gayatri Mantra gives. The Surya that is an activator of the ojas.
So just because it mentions Surya, one cannot conclude that the rest of the sloka would double-mean references to planets.
Western science has understood this recently, embraced rather, and have built the Particle Accelerator (CERN), where a matter (atom) is excited by energy (Surya for the human body) and let to exhaust itself by "dancing" around a given trajectory [chakras (lokas) in human body] and then to fuse itself in the process with electrons (ojas with Gayatri Mantra) so as to produce anti-matter ( Shakti ~ Gayatri Mata )
Of course CERN is unsuccessful, as no mantra (vibration) in certain fixed patterns (algebra) was used. While every initiated Hindu goes through this cycle every morning in Suryanamaskar followed by Sandhyavandan.
Thus, matter is Gayatri Devi and anti matter is Vishwakarma Brahma; proven millenias ago. This is the upadesh that is revealed in Gayatri Vidya by a proper Guru ( a handful exist).
This truth is further embodied in the Sri Chakra, the physical manifestation of the Gayathri. When it is manifested in 3 dimensional as the Meru, it is completed as perfect, as the 7 layers of "loka", consciousness is establised.
The white man Macaulfie is responsible for this mistranslation of loka to patala, from which all current modern literature on this subject has been based on. He linked bharata-vasara to bhu loka. This science is taught in Srimad Bhagavatam by Sri Vishwakarma's son to Brihaspati.
Further proof: in the sankalpa stanza one can find "bharata vasara" mentioned. This is the correct patala (i.e. Earth). The names of the rest of the patalas can be found in the same Srimad Bhagavatam.
To gain deeper understanding how Gayathri is manifested, one has to seek Purusha Suktam [i.e. the vigyan (science) of cause: creation, preservation and destruction]
Advancing into the subject; there are 11 akshara variations. The secret starts off with the first akshara seque.