As to your question whether the power of Bahá’u’lláh extends over our solar system and to higher worlds: while the Revelation of Bahá’u’lláh, it should be noted, is primarily for this planet, yet the spirit animating it is all-embracing, and the scope therefore cannot be restricted or defined.
(Shoghi Effendi, Lights of Guidance, p. 481)
As you rightly state, Bahá’u’ll‘ah affirms that every fixed star has its planets, and every planet its own creatures. The House of Justice states however, that it has not discovered anything in the Bahá’í Writings which would indicate the degree of progress such creatures may have attained. Obviously, as creatures of earth have managed to construct space probes and send them into outer space, it can be believed that creatures on other planets may have succeeded in doing likewise.
Regarding the attitude Bahá’ís should take toward unidentified flying objects, the House of Justice points out that they fall in the category of subjects open to scientific investigation, and as such, may be of interest to some, but not necessarily to everyone. In any case, Bahá’ís have a fundamental obligation at this stage of the development of the earth’s people, that is, the responsibility of spreading the unifying Message of Bahá’u’ll‘ah.
(From a letter dated 11 January 1982 written on behalf of the Universal House of Justice to an individual believer)
 See The World Order of Bahá’u’ll‘ah: Selected Letters (Wilmette: Bahá’í Publishing Trust, 1991), pp. 170-186.
(The Universal House of Justice, 1996 Aug 06, Sabeans, UFOs, Alien Abduction and Genetic Engineering)
Mr. Garcia refers to a book entitled Abduction, written by a Harvard psychiatrist, Dr. John Mack, which posits that ... alien beings of a vastly superior intelligence, who are possibly from other planets or dimensions, or from our own distant future, have been conducting genetic experiments on unwilling humans to produce a crossbreed between humans and aliens (reportedly to repopulate our planet with a more peaceful species after we destroy ourselves).
Mr. Garcia comments on the popularity of this topic and mentions that a number of Bahá’ís claim to have had experiences similar to those associated with abduction by aliens. He requests guidance concerning how to respond to such matters.
The Bahá’í Teachings do not deal specifically with the subjects of alien abduction and genetic engineering. The following extracts concerning unidentified flying objects might be of assistance to Mr. Garcia:
There is nothing in the Teachings about spaceships; and the Guardian does not feel this is a subject on which he can offer the friends any advice whatsoever. Indeed, to be frank, he is so busy with the work of the Cause that he seldom has time to devote much thought to speculation of this nature, however fascinating it may be.
(From a letter dated 15 February 1957 written on behalf of Shoghi Effendi to several believers)