A human hand-shaped figure will be seen in space and this will herald the coming of Hz. Mahdi (As).
... AT THAT TIME [OF THE APPEARANCE OF HAZRAT MAHDI (AS)] A HAND WILL BE SEEN REVEALING ITSELF FROM THE SKY... (Al-Muttaqi al-Hindi, Al-Burhan fi Alamat al-Mahdi Akhir az-Zaman, p. 51)
... Asma bint Umays says: THE PORTENT OF THAT DAY [THE COMING OF HAZRAT MAHDI (AS)] IS A HAND EXTENDING FROM THE SKY AND PEOPLE TURNING TO LOOK AT IT. (Al-Muttaqi al-Hindi, Al-Burhan fi Alamat al-Mahdi Akhir az-Zaman, p. 69)
This hadith mentions one of the signs of Mahdi’s coming, ‘the hand extending from the sky’. An image taken by Chandra Observatory of NASA showed a vast stellar formation cluster looking like a hand grabbing another stellar formation. This hand-shaped figure was named by NASA ‘the Hand of God’.
The news report reads as follows:
(CNN) — New photographs released by NASA have captured images of a vast stellar formation resembling a human hand reaching across space. The image, taken by NASA's space-based Chandra Observatory telescope, shows an X-ray nebula 150 light years across. It shows what appear to be ghostly blue fingers -- thumb and pinky clearly discernible from index, ring and middle digits -- reaching into a sparkling cloud of fiery red.
(April, 15, 2009, CNN ; http://edition.cnn.com/2009/TECH/space/04/14/space.hand/index.html)
This hand reaching across the sky, just as described in the hadith, heralds the coming of Hz. Mahdi (as), that he is on duty and the time for his recognition by people is coming close (Allah knows the truth).
The hadith says ‘PEOPLE TURNING TO LOOK AT IT’, and thus miraculously informs
us today from 1,400 years ago about the ‘cosmic nature’ of this incident by indicating that it will attract the attention of the astronomers who constantly ‘look’, ‘watch’ and ‘observe’.
THE HADITH WHICH SAYS “A HAND WILL EXTEND FROM THE SKY, AND TELL PEOPLE ‘THIS IS MAHDI (AS), FOLLOW HIM’,” REFERS TO THE HAND OF HZ.MAHDI (AS) SEEN ON TV AND INTERNET.
From Qaza’ah. He said: ... A VOICE WILL BE HEARD FROM THE SKY, SAYING, “THE SAINT OF ALLAH IS A COMPANION OF A SUCH. [Referring Hazrat Mahdi (as)] Asma bint Umays said: THE SIGN OF THAT DAY IS A HAND REACHING FROM THE SKY AND PEOPLE STARING AT IT CONSTANTLY.
... ... AT THAT TIME A HAND WILL BE SEEN REVEALING ITSELF FROM THE SKY......
Conflict and disputes will persist until A HAND APPEARS FROM THE SKY and a voice cries “Hazrat Mahdi (as) is your amir.” THE SIGN OF THAT DAY: A HAND WILL EXTEND FROM THE SKY and people will look at and see it.
According to the hadiths, before the emergence of Hz. Mahdi (as), one sign that will introduce Hz. Mahdi (as) to people will be ‘the hand extending from the sky’. People ‘will see this hand, look at it’. With this hand extending from the sky, people will be said ‘this is the saint of Allah, Hz. Mahdi (as). This hand that will speak to people will actually be the voice of Hz. Mahdi (as). Hz. Mahdi (as) will not claim to be Mahdi, however, as the person that knows about Hz. Mahdi (as) the most, he will explain Hz. Mahdi (as) on TV and internet.
Again according to the hadiths, Hz. Mahdi (as) will be clearly seen by the people through TV and internet, and people will be able to see the hand of Hz. Mahdi (as) all the time. Also, we can understand again from the hadiths, that just like the hands of the Prophet Moses (as), the hand of Hz. Mahdi (as) will be very beautiful and that he will use his hands frequently which will therefore be constantly seen by people.
I seek refuge in Allah from the accursed satan:
And he [the Prophet Moses (as)] drew out his hand and there it was, pure white to those who looked. (Surat al-A’raf, 198)
In another hadith, it is said that Hz. Mahdi (as) will use his hands when he is speaking, and when he emphasizes something, he will move his hands and people will be able to see these movements:
”HE WILL STRIKE HIS LEFT KNEE WITH HIS RIGHT HAND when he speaks slowly and steadily.
It appears from all these indications that “a hand being seen by people” is another important sign enabling them to recognize Hazrat Mahdi (as).
 (Hadith interpreted by Jalaluddin Al-Suyuti, Al-Muttaqi al-Hindi, Al-Burhan fi Alamat al-Mahdi Akhir az-Zaman, p. 69)
 (Celalettin Suyutinin Tasnifinden Hadisler, Ahir Zaman Mehdisinin Alametleri, Ali Bin Hüsameddin El Muttaki, s. 51)
 ((Al-Muttaqi al-Hindi, Al-Burhan fi Alamat al-Mahdi Akhir az-Zaman, p. 53)
 (Al-Barzanji, Al-Isha'ah li-ashrat al-sa'ah, p. 174)