Objection 1. It would seem that it was unfitting that Christ should work miracles in the heavenly bodies. For, as Dionysius says (Div. Nom. iv), "it beseems Divine providence not to destroy, but to preserve, nature." Now, the heavenly bodies are by nature incorruptible and unchangeable, as is proved De Coelo i. Therefore it was unfitting that Christ should cause any change in the order of the heavenly bodies.
Objection 2. Further, the course of time is marked out by the movement of the heavenly bodies, according to Genesis 1:14: "Let there be lights made in the firmament of heaven... and let them be for signs, and for seasons, and for days and years." Consequently if the movement of the heavenly bodies be changed, the distinction and order of the seasons is changed. But there is no report of this having been perceived by astronomers, "who gaze at the stars and observe the months," as it is written (Isaiah 47:13). Therefore it seems that Christ did not work any change in the movements of the heavenly bodies.
Objection 3. Further, it was more fitting that Christ should work miracles in life and when teaching, than in death: both because, as it is written (2 Corinthians 13:4), "He was crucified through weakness, yet He liveth by the power of God," by which He worked miracles; and because His miracles were in confirmation of His doctrine. But there is no record of Christ having worked any miracles in the heavenly bodies during His lifetime: nay, more; when the Pharisees asked Him to give "a sign from heaven," He refused, as Matthew relates (12,16). Therefore it seems that neither in His death should He have worked any miracles in the heavenly bodies.
On the contrary, It is written (Luke 23:44-45): "There was darkness over all the earth until the ninth hour; and the sun was darkened."
I answer that, As stated above (Question 43, Article 4) it behooved Christ's miracles to be a sufficient proof of His Godhead. Now this is not so sufficiently proved by changes wrought in the lower bodies, which changes can be brought about by other causes, as it is by changes wrought in the course of the heavenly bodies, which have been established by God alone in an unchangeable order. This is what Dionysius says in his epistle to Polycarp: "We must recognize that no alteration can take place in the order end movement of the heavens that is not caused by Him who made all and changes all by His word." Therefore it was fitting that Christ should work miracles even in the heavenly bodies.
Reply to Objection 1. Just as it is natural to the lower bodies to be moved by the heavenly bodies, which are higher in the order of nature, so is it natural to any creature whatsoever to be changed by God, according to His will. Hence Augustine says (Contra Faust. xxvi; quoted by the gloss on Romans 11:24: "Contrary to nature thou wert grafted," etc.): "God, the Creator and Author of all natures, does nothing contrary to nature: for whatsoever He does in each thing, that is its nature." Consequently the nature of a heavenly body is not destroyed when God changes its course: but it would be if the change were due to any other cause.
Reply to Objection 2. The order of the seasons was not disturbed by the miracle worked by Christ. For, according to some, this gloom or darkening of the sun, which occurred at the time of Christ's passion, was caused by the sun withdrawing its rays, without any change in the movement of the heavenly bodies, which measures the duration of the seasons. Hence Jerome says on Matthew 27:45: "It seems as though the 'greater light' withdrew its rays, lest it should look on its Lord hanging on the Cross, or bestow its radiancy on the impious blasphemers." And this withdrawal of the rays is not to be understood as though it were in the sun's power to send forth or withdraw its rays: for it sheds its light, not from choice, but by nature, as Dionysius says (Div. Nom. iv). But the sun is said to withdraw its rays in so far as the Divine power caused the sun's rays not to reach the earth. On the other hand, Origen says this was caused by clouds coming between (the earth and the sun). Hence on Matthew 27:45 he says: "We must therefore suppose that many large and very dense clouds were massed together over Jerusalem and the land of Judea; so that it was exceedingly dark from the sixth to the ninth hour. Hence I am of opinion that, just as the other signs which occurred at the time of the Passion"--namely, "the rending of the veil, the quaking of the earth," etc.--"took place in Jerusalem only, so this also:... or if anyone prefer, it may be extended to the whole of Judea," since it is said that "'there was darkness over the whole earth,' which expression refers to the land of Judea, as may be gathered from 1 Kings 18:10, where Abdias says to Elias: 'As the Lord thy God liveth, there is no nation or kingdom whither my lord hath not sent to seek thee': which shows that they sought him among the nations in the neighborhood of Judea."
On this point, however, credence is to be given rather to Dionysius, who is an eyewitness as to this having occurred by the moon eclipsing the sun. For he says (Ep. ad Polycarp): "Without any doubt we saw the moon encroach on the sun," he being in Egypt at the time, as he says in the same letter. And in this he points out four miracles. The first is that the natural eclipse of the sun by interposition of the moon never takes place except when the sun and moon are in conjunction. But then the sun and moon were in opposition, it being the fifteenth day, since it was the Jewish Passover. Wherefore he says: "For it was not the time of conjunction."--The second miracle is that whereas at the sixth hour the moon was seen, together with the sun, in the middle of the heavens, in the evening it was seen to be in its place, i.e. in the east, opposite the sun. Wherefore he says: "Again we saw it," i.e. the moon, "return supernaturally into opposition with the sun," so as to be diametrically opposite, having withdrawn from the sun "at the ninth hour," when the darkness ceased, "until evening." From this it is clear that the wonted course of the seasons was not disturbed, because the Divine power caused the moon both to approach the sun supernaturally at an unwonted season, and to withdraw from the sun and return to its proper place according to the season. The third miracle was that the eclipse of the sun naturally always begins in that part of the sun which is to the west and spreads towards the east: and this is because the moon's proper movement from west to east is more rapid than that of the sun, and consequently the moon, coming up from the west, overtakes the sun and passes it on its eastward course. But in this case the moon had already passed the sun, and was distant from it by the length of half the heavenly circle, being opposite to it: consequently it had to return eastwards towards the sun, so as to come into apparent contact with it from the east, and continue in a westerly direction. This is what he refers to when he says: "Moreover, we saw the eclipse begin to the east and spread towards the western edge of the sun," for it was a total eclipse, "and afterwards pass away." The fourth miracle consisted in this, that in a natural eclipse that part of the sun which is first eclipsed is the first to reappear (because the moon, coming in front of the sun, by its natural movement passes on to the east, so as to come away first from the western portion of the sun, which was the first part to be eclipsed), whereas in this case the moon, while returning miraculously from the east to the west, did not pass the sun so as to be to the west of it: but having reached the western edge of the sun returned towards the east: so that the last portion of the sun to be eclipsed was the first to reappear. Consequently the eclipse began towards the east, whereas the sun began to reappear towards the west. And to this he refers by saying: "Again we observed that the occultation and emersion did not begin from the same point," i.e. on the same side of the sun, "but on opposite sides."
Chrysostom adds a fifth miracle (Hom. lxxxviii in Matth.), saying that "the darkness in this case lasted for three hours, whereas an eclipse of the sun lasts but a short time, for it is soon over, as those know who have seen one." Hence we are given to understand that the moon was stationary below the sun, except we prefer to say that the duration of the darkness was measured from the first moment of occultation of the sun to the moment when the sun had completely emerged from the eclipse.
But, as Origen says (on Matthew 27:45), "against this the children of this world object: How is it such a phenomenal occurrence is not related by any writer, whether Greek or barbarian?" And he says that someone of the name of Phlegon "relates in his chronicles that this took place during the reign of Tiberius Caesar, but he does not say that it occurred at the full moon." It may be, therefore, that because it was not the time for an eclipse, the various astronomers living then throughout the world were not on the look-out for one, and that they ascribed this darkness to some disturbance of the atmosphere. But in Egypt, where clouds are few on account of the tranquillity of the air, Dionysius and his companions were considerably astonished so as to make the aforesaid observations about this darkness.
Reply to Objection 3. Then, above all, was there need for miraculous proof of Christ's Godhead, when the weakness of human nature was most apparent in Him. Hence it was that at His birth a new star appeared in the heavens. Wherefore Maximus says (Serm. de Nativ. viii): "If thou disdain the manger, raise thine eyes a little and gaze on the new star in the heavens, proclaiming to the world the birth of our Lord." But in His Passion yet greater weakness appeared in His manhood. Therefore there was need for yet greater miracles in the greater lights of the world. And, as Chrysostom says (Hom. lxxxviii in Matth.): "This is the sign which He promised to them who sought for one saying: 'An evil and adulterous generation seeketh a sign; and a sign shall not be given it, but the sign of Jonah the prophet,' referring to His Cross... and Resurrection... For it was much more wonderful that this should happen when He was crucified than when He was walking on earth."
Source: Summa Theologica (New Advent)