AFAIK, Rig veda says, every star is related to a God and hence everyday is special day(festival) to worship a specific god, what are those stars and to which god does they relate to?
There are 27 Star ( Nakshatra ).
Ashvinī Bharanī Kṛttikā Rohinī Mrigashīra Ārdrā Punarvasu Pushya Ashlesha (nakshatra) Maghā Pūrva Phalgunī (Pubbha) Uttara Phalgunī (Uttara) Hasta Chitrā Svātī Vishākhā Anurādhā Jyeshtha Mūla Pūrva Ashādhā Uttara Ashādhā Shravana Dhanistha Shatabhisha Pūrva Bhādrapadā Uttara Bhādrapadā Revatī
You can say all these are देवता (devta) but not god (bhagwan).
To know more Nakshatra.
I find the answer by Saurabh Chandra Patel incomplete. Some of the Nakshatras are named after Devatas etc. For example, the Ashwini twins are considered as Devatas. Although, most of the Nakshatras are not e.g, Mula, Purva Ashadha, Hasta etc. Hasta means hand, Mula means root and these are not Devatas in itself.
In Jyotisha, most Nakshatras are considered to be associated with presiding deities. This can be considered as the relatoionship between these stars and the Gods. In addition to that, they are ruled by different planets which are also considered Gods.
This list provides the name of the Nakshatra followed by the presiding deity followed by the ruling planet (in some cases, only the ruling planet is mentioned):
Ashvini * Ketu
Bharani * Shukra * Venus
Krittika * Surya * Sun
Rohini * Brahmi * Chandra * Soma
Mrigashirsha * Mangala
Arudra * Rahu
Punarvasu * Yamaka * Guru
Pushyami * Sidhya * Shani * Saturn
Azlesa * Naga * Budha * Mercury
Magha * Pitri * Ketu
Purva-phalguni * Yoni* Shukra * Venus
Uttara-phalguni * Aryamna * Surya
Hasta * Savitra * Chandra * Somana
Chitra * Tvastri * Mangala
Swati * Vayu Arcturus * Rahu
Bishaja * Vishaka * Radha * Guru
Anuradha * Maitra * Shani * Saturn
Jyestha * Ketta * Budha * Mercury
Mula * Alakshmi * Ketu
Purvazadha * Apah * Shukra * Venus
Uttara-azadha * Vaizva * Surya
Shravana * Hari * Chandra * Somana
Dhaniztha * Sravishtha * Mangala
Shatavishaka * Shatatakara * Rahu
Purva-bhadra-pada * Prosthapada Pegasus * Guru
Uttara-bhadra-pada * Ahira-budhnaya * Shani * Saturn
Revati * Pushan * Budha * Mercury
Taken from the website of Barbara Pijan Lama: http://www.barbarapijan.com/bpa/Nakshatra_radical/nakshatra_main_page.htm